Plasmodium falciparum sequesters in vital organs, and this is also the species responsible for the vast majority of malaria-related deaths. Autopsy studies of fatal malaria cases show convincing correlations between extent of sequestration in the brain and coma as a presenting symptom [We are grateful for Ian Clark's suggestions  in resposymptom . Direct symptom . Both ar


Severe falciparum malaria in children was studied as part of the characterization of the Kassena-Nankana District Ghana for future malaria vaccine trials. Children aged 6–59 months with diagnosis suggestive of acute disease were characterized using the standard WHO definition for severe malaria.Of the total children screened, 45.2% (868/1921) satisfied the criteria for severe malaria. Estimated incidence of severe malaria was 3.4% (range: 0.4–8.3%) cases per year. The disease incidence was seasonal: 560 cases per year, of which 70.4% occurred during the wet season (June-October). The main manifestations were severe anaemia (36.5%); prolonged or multiple convulsions (21.6%); respiratory distress (24.4%) and cerebral malaria (5.4%). Others were hyperpyrexia (11.1%); hyperparasitaemia (18.5%); hyperlactaemia (33.4%); and hypoglycaemia (3.2%). The frequency of severe anaemia was 39.8% in children of six to 24 months of age and 25.9% in children of 25–60 months of age. More children (8.7%) in the 25–60 months age group had cerebral malaria compared with 4.4% in the 6–24 months age group. The overall case fatality ratio was 3.5%. Cerebral malaria and hyperlactataemia were the significant risk factors associated with death. Severe anaemia, though a major presentation, was not significantly associated with risk of death.Severe malaria is a frequent and seasonal childhood disease in northern Ghana and maybe an adequate endpoint for future malaria vaccine trials. Plasmodium falciparum with more than one million deaths each year. About 60% of the clinical episodes and more than 80% of the deaths occur in young children in Africa, south of the Sahara, where malaria accounts for 25–35% of all outpatients visits, 20–45% of hospital admissions and 15–35% of hospital deaths  aging below 24 months of age  had a positive parasitaemia and, of these, 61.8% (868/1405) satisfied the criteria for severe In all, 47 (5.4%) of the children had cerebral malaria (Blantyre coma score < 3), the frequency of cerebral malaria in the 25–60 months old was 8.7%  compared to 4.4%  in 6–24 months olds. Proportions of boys and girls with cerebral malaria were similar (5% (23/490) vs. 6% (24/378). Fewer children with cerebral malaria had severe anaemia compared to those without cerebral malaria (28%(13/47) vs. 37% (302/816). Again a higher proportion of children with cerebralmalaria had higher respiratory distress than those without (70.2% vs. 21.3%). The mean of haemoglobin, serum lactate and blood glucose among cerebral malaria patients were 7.0 g/dl, 8.5 mmol/l, and 6.2 mmol/l, respectively. The total case fatality ratio among children with cerebral malaria was 29.8% (14/47).This was the most frequent manifestation, 36.5% 315/863), and was more prevalent in males than females [40.2% vs. 31.6%], in 6–24 month olds than 25–60 olds [39.8 vs. 25.9], Figure 5/863, anAbout 24% 212/868) of the participants presented with respiratory distress. Children with respiratory distress were likely to be younger , and had higher geometric mean parasite density , hyperlactataemia 33.4% (249/746), hyperparasitaemia 18.5% (161/868) and hypoglycaemia 3.2% (24/761).The overall study case fatality ratio was 3.5 (30/868). The ratio was similar in males and females (3.3% vs. 3.7%) and in 6–24 and 25–59 month's olds (3.3 vs. 3.9%). Their baseline presentations were: cerebral malaria 46.7% (14/30), severe anaemia 36.7% (11/30), respiratory distress 60%(18/30) and hyperlactataemia 61.5(16/26). Bivariate analysis  and 560 severe malaria cases giving an overall incidence of 0.034 cases per year. The incidence was highest in the age group, 6–11 months and lowest in the 48–59 month old  were enrolled in June-October (the high transmission season) and 29.4%(166/560) in November-May (low transmission season). The highest number of cases, 127 (22.7%) were enrolled in September and the lowest, 6 (1.1%) in April  being children between 6–24 months old, with a significant decreasing trend towards increasing age Figure . As in oThe overall case fatality ratio in this study was 3.5%; this was similar by gender (3.3% vs. 3.7%) and by the age groups (3.3% vs. 3.9%). The independent prognostic indicators were cerebral malaria and hyperlactataemia confirming the fact that in severe malaria, neurological involvement and metabolic dysfunction are the factors that are most associated with poor outcome ,28. SeveFurther significant seasonal variation of severe malaria was recorded over the period. The highest prevalence occurred in the months of July to December (during the rainy season). The observed pattern points to the fact that increase in vector breeding following the raining season is responsible for the upsurge in the malarial cases and supports an earlier transmission studies . In malaMajor conclusions can be drawn from this study. First, severe malaria in the area occurs frequently in the first 30 months of life, the predominant feature being severe anaemia. Most of the severe malaria occurs in the high transmission and short period, which suggest that the area can effectively support intervention studies including vaccine trials in the prevailing short, but intensive, transmission season.AO, KK, WR, FN: conception and design, and data acquisition, analysis and interpretation. Manuscript drafting and revision for the intellectual content.FA, FA, AT: conception and design, and acquisition and interpretation of data.PA, AA, NM, AH: acquisition and interpretation of data, and manuscript preparation.


Blood group O has been significantly associated with increased placental malaria infection in primiparae and reduced risk of infection in multiparae in the Gambia, an area with markedly seasonal malaria transmission. This study analyses the association between ABO blood group phenotypes in relation to placental malaria pathology and birth outcomes in southern Malawi, an area with perennial malaria transmission.A cross-sectional study of 647 mother/child pairs delivering in Montfort Hospital, Chikwawa District between February-June 2004 and January-July 2005 was undertaken. Maternal peripheral and cord blood samples were obtained at delivery. Placental tissue was obtained and malaria histology classified as active, past or no malaria infection. Birth anthropometry was recorded. ABO blood group was measured by agglutination.In primiparae, blood group O was significantly associated with increased risk of active placental infection  and an increased foetal-placental weight ratio compared to non-O phenotypes  In multiparae blood group O was significantly associated with less frequent active placental infection , and a higher newborn ponderal index compared to non-O phenotypes . In multivariate regression parity was independently associated with increased risk of placental malaria (active andpast infection) in primiparae with blood group O (p = 0.034) and reduced risk in multiparae with the same phenotype (p = 0.015).Parity related susceptibility to placental malaria is associated with the mothers ABO phenotype. This interaction influences foetal and placental growth and could be an important modifying factor for pregnancy outcomes. The biological explanation could relate to sialic acid dependent placental membrane differences which vary with ABO blood group. In a previous analysis we reported for the first time an association between the ABO blood group phenotypes, placental malaria and pregnancy birth outcomes . Blood gP. falciparum infection with its associated complications is determined partly by host genetic factors, which include various haemoglobinopathies and red cell enzyme deficiencies . For this reason and in view of the likelihood of other confounding factors, it is of interest that the effects on the fetal-placental weight ratios were comparable across the two studies. This supports the conclusion that the ABO histo-blood group antigens are of critical importance in the pathophysiology of placental malaria.The practical implications of these findings relate not only to the recognition of particular mother-child risk groups, but also to the potential influence of these red cell antigens for both parasite replication and the immune response to malaria.


The main objective of this study was to assess the quality of home malaria management with pre-packaged chloroquine in two areas in the Moramanga district of Madagascar. The knowledge, attitude and practices of care providers in terms of home treatment options were evaluated and compared. The availability of treatment options by studying retailers and community-based service providers was also investigated.A cross-sectional investigation in two communities, in the hamlets and villages located close to carers, retailers, community-based service providers and primary health centres was carried out.Carers in the two districts were equally well aware of the use of pre-packaged chloroquine. Their first response to the onset of fever was to treat children with this antimalarial drug at home. The dose administered and treatment compliance were entirely satisfactory (100%) with pre-packaged chloroquine and rarely satisfactory (1.6% to 4.5%) with non pre-packaged chloroquine. In cases of treatment failure, the carers took patients to health centres. Chloroquine was supplied principally by private pharmacies and travelling salesmen selling unpackaged chloroquine tablets. Non pre-packaged chloroquine was the most common drug used at health centres. The frequency of positive rapid malaria tests (P = 0.01) was significantly higher in children treated with non pre-packaged chloroquine (38%) than in children treated with pre-packaged chloroquine (1.3%).Home malaria management should be improved in Madagascar. Efforts should focus on communication, the training of community-based service providers, access to pre-packaged drugs and the gradual withdrawal of pre-packaged chloroquine and its replacement by pre-packaged artemisinin-based combination therapies. Official data show a reported 2,114,400 cases of suspected malaria in 2003 . About 740,000 of these cases occurred in children under the age of five years [Malaria, known locally as "ve years . Thus, pve years . A stron®) was introduced privately by an NGO called "Population Service International" and sold at an affordable price of US $0.025. Since March 2005, another form of pre-packaged chloroquine, Ody Tazomoka®, has been freely distributed at primary public health facilities. Both presentations of pre-packaged chloroquine are available for children from six to 11 months of age (three tablets of 75 mg) and for children from 12 to 59 months of age (three tablets of 150 mg) . This decision followed a major malaria outbreak in the mid-1980s, with the widespread distribution of chloroquine (in the form of unpackaged 100 mg tablets). HMM was advocated as part of the National Malaria Control Programme (NMCP) in 1998. In November 2003, pre-packaged . The knowledge, attitude and practices of caregivers in terms of home treatment options (non pre-packaged and pre-packaged chloroquine) were first evaluated and compared, at community level, by interviewing carers, and at primary health centre level, by interviewing the parents or guardians of children under the age of five years consulting for fever. The malaria burden among these children was also evaluated by rapid testing. The availability of treatment options in these two areas, by studying retailers and community-based service providers was also investigated.This survey was conducted between April and June 2005, in two communities in the eastern foothills of the highlands of Madagascar: Ambohibary, a periurban community, and Lakato, a remote rural community , with 15,831 inhabitants, living in 10 villages, with 44 hamlets. There is one "level two" primary health centre  and two "level one" primary health centres (CSB1: "centre de santé de base niveau 1" managed by a nurse). The prevalence of malaria in children under five years of age in this district has been estimated at 30%, with peaks in April-May and September-October .Lakato , is located in a remote area 40 kilometres away from the national road connecting Antananarivo, the capital of Madagascar, to Toamasina, the main harbour on the east coast. This area is poorly accessible, especially at the beginning of the study period (rainy season), and can only be reached by poor-quality tracks. It covers an area of 702 km2 , with 16,557 inhabitants living in nine villages with 50 hamlets. It has one level 2 primary health centre and two level 1 primary health centres. The prevalence of malaria in children under five years of age in this district has been estimated at 27%, with a peak in April-May .Ambohibary  is located in a periurban area seven kilometres from the urban centre of Moramanga. It covers an area of 729 kmA cross-sectional investigation in the two communities, focusing on carers, drug sellers and community-based service providers and primary health centres in the hamlets and villages was carried out.® and Ody Tazomoka®). If the carers said that they had used pre-packaged chloroquine, they were asked to indicate the presentation used: PaluStop® or Ody Tazomoka®. The investigator also checked whether insecticide-impregnated bed nets were used.A two-level cluster sampling for the investigation of carers was used. A questionnaire was designed to collect data on knowledge, attitudes, practices and beliefs (KAPB) relating to malaria. This questionnaire was tested on 21 carers, to determine the frequency of knowledge relating to HMM. The minimum sample size required for the carer investigation was estimated at 392 . Four hundred twenty carers (30 clusters of 14 carers) were finally included. All villages were informed one day before the investigation, by the head of the district. Each interviewer worked with a guide, who introduced him at each village. On the day of the investigation, the objectives of the study were explained to the children's carers before the interview. Carers were included in the study after they provided written informed consent. During the investigation, the interviewers were provided with questionnaires and pre-packaged chloroquine  to confirm the diagnosis of malaria and checked that the questionnaire had been completed correctly. The results of the rapid tests for malaria were communicated to the head of the primary health centre.At primary health centres (three in Ambohibary and three in Lakato), all children under the age of five, clinically suspected of malaria (fever and recent history of fever) were enrolled and their parents or guardians were interviewed after they had provided written informed consent. Questionnaires were completed by health workers. The investigator carried out a rapid diagnostic test . Chi-squared tests were used to assess the significant of differences between proportions. For continuous data, the significance of differences was assessed using Student's The study was carried out in 27 hamlets and villages (13 in Ambohibary and 14 in Lakato). At the community level, 420 carers (196 in Ambohibary and 224 in Lakato), 10 community-based service providers (6 in Ambohibary and 4 in Lakato) and 32 retailers (22 in Ambohibary and 10 in Lakato) were interviewed. At primary health centre level, 341 patients attended health centres (109 in Ambohibary and 232 in Lakato), of which 207 children under the age of five, clinically suspected of malaria, were enrolled in the study (60 in Ambohibary and 147 in Lakato).-6): 90.6% farmers in Lakato and 54.6% farmers in Ambohibary, with 19.4% craftsmen in Ambohibary and 0.4% in Lakato. Educational status profiles also differed significantly between Ambohibary and Lakato (P = 0.00005): no formal education (15.3% in Ambohibary and 42% in Lakato), primary education (51.5% in Ambohibary and 39.3% in Lakato), and secondary or further education (33.1% in Ambohibary and 18.8% in Lakato). The distance from the hamlet or village to the nearest health centre also differed significantly (P < 10-6) between Ambohibary and Lakato  of carers were married, or cohabited with a partner, the remaining carers being single, divorced, separated or widowed. The mean number of children under the age of five years looked after by an individual carer was significantly higher in Lakato (1.6) than in Ambohibary (1.4) (P = 0.0026). Significant differences were also found between the two districts in terms of professional activity . In most cases, the plant concerned was gathered, prepared and administered directly by the carer. The reasons for administering antimalarial drugs at home, according to carers, differed slightly between the two areas: (i) in Ambohibary, the first reason given by carers was that they already had such drugs at home (46.8% non pre-packaged chloroquine and 53.2% pre-packaged chloroquine), the second reason was that they had enough money to pay for a consultation with a health worker and the third reason was that the health centre was too far away; (ii) in Lakato, the two most important reasons given by carers were that they already had drugs at home (42.8% non pre-packaged chloroquine and 57.2% pre-packaged chloroquine), and the health centre being too far away. The third reason given was that there were often no health workers at the health centre. Regardless of the location, it was observed that the further the distance between the village and the health centre, the more likely the carer was to use antimalarial drugs at home . Conversely, the frequentation of health centres decreased with distance from the village, from 34% to 13% in Ambohibary and from 17% to 3% in Lakato.The management of uncomplicated childhood fever by carers in Ambohibary and Lakato is detailed in Table ® or Ody Tazomoka® )and rarely satisfactory (1.6% to 4.5%) with non pre-packaged chloroquine treatment. The carers took a mean time of 3.5 days (3.7 in Ambohibary and 3.3 in Lakato) to evaluate the efficacy of treatment. In case of treatment failure , the carers in both communities took the patient to a health centre.In both areas, the dose administered and treatment compliance were entirely satisfactory (100%) with pre-packaged chloroquine treatment . A single tablet of 100 mg non pre-packaged chloroquine was sold at the same price as an entire box of pre-packaged chloroquine (full treatment for a child under five). Chloroquine often seemed to be in short supply in both areas.®). This brand of chloroquine has been available for 12 months in Ambohibary and 10 months in Lakato.Four retailers and salesmen in Ambohibary (18%) and two retailers in Lakato (20%) sold pre-packaged chloroquine  and by only one such service provider in Lakato (25%). This drug only became available a few weeks before the start of the study.Ody TazomokaOf the 207 children under five years of age seen at health centres (60 in Ambohibary and 147 in Lakato), 50% were initially treated at home in Ambohibary and 27.2% in Lakato. The mean time between the onset of fever and consultation at a health centre was two days in Ambohibary (0 to 6 days) and three days in Lakato (0 to 14 days).In both areas, non pre-packaged chloroquine was the drug most frequently used for treatment at home (53.7% in Ambohibary and 50.8% in Lakato). Pre-packaged chloroquine was used less frequently (19.6% in Ambohibary and 10.4% in Lakato). Of the 70 children treated with chloroquine at home, 55 were treated with non pre-packaged chloroquine and 15, with pre-packaged chloroquine. Rapid tests for malaria were positive in 40% of cases in Ambohibary and 45% of cases in Lakato. The frequency of positive rapid tests for malaria (P = 0.01) was significantly higher for children treated with non pre-packaged chloroquine  than for children treated with pre-packaged chloroquine .The success of health interventions such as HMM requires communities to have detailed knowledge of perceived health problems . These hThis study was carried out in two areas with different socio-demographic profiles, representative of the current situation in Madagascar. In these two areas, most of the carers were mothers, as reported in other areas of Madagascar  and in AIn the two areas studied, mothers faced with a case of suspected malaria in one of their children chose first to administer antimalarial drugs at home, seeking care for their child at a health facility only in case of treatment failure. This shows that mothers have the potential to manage malarial fever correctly at home and to consult health workers. These positive attitudes and practices should be reinforced during health interventions, to decrease severe morbidity and mortality from childhood malaria by improving case management. However, even in Ambohibary, where the mothers knew that malaria was transmitted by mosquitoes, only one third of the children slept under insecticide-impregnated bed nets. Although many mothers were aware of pre-packaged chloroquine (69.9% in Lakato and 76.1% in Ambohibary) only half of them used it, often because they had the drug in an non-packaged form at home. This was the case in the periurban area of Ambohibary, where the flow of information about HMM strategy and the supply of pre-packaged chloroquine are easy to establish. In this area, either information about the HMM strategy was not transmitted by health workers due to a lack of motivation, or carers chose not to use the free pre-packed chloroquine because they thought that it was not effective. In the remote area of Lakato, the main reason for not using pre-packaged chloroquine was the time lag to the release of free pre-packaged chloroquine, because of a lack of co-ordination between the communities and the headquarters of the district health authority.homapak", because it was neatly and attractively packaged. A decrease in the efficacy of chloroquine against P. falciparum has recently been recorded in several areas [Chloroquine was introduced into Madagascar in 1945 and is the antimalarial drug best known to the Malagasy people ,19. As pal areas ,23. BaseHowever, if pre-packaged drugs are to be used, efforts are required: (i) to ensure effective communication, favouring correct care-seeking behaviour and appropriate and effective HMM for the treatment of febrile illness. Particular attention should be paid to stressing the link between mosquitoes and malaria for less literate carers, and the importance of prompt and complete treatment with pre-packaged drugs; (ii) to train community-based service providers, to ensure that they have the necessary skills and knowledge to manage febrile illness or malaria. This training could take place within the commercial sector, but might then have to be based on a limited curriculum, dictated by the amount of time that trainers are willing to spend without compromising their own businesses; (iii) to supervise and monitor implementation activities at the community and health facility levels.AR, MR and DMe were involved in all stages of this study. PM, JLS and LR were involved in the design of the study. BR participated in the coordination of the field work. DMa helped to compose the manuscript and gave constructive advice.


Over the course of human history, hundreds of thousands of genetic mutations have arisen in the global population. The most harmful ones usually disappear—by affecting an individual's “fitness,” i. e., the ability to reproduce, the mutations are lost before carriers can pass them on to their children—whereas most mutations are maintained in the population in low frequencies. Some mutations, however, can give the carrier such a large survival advantage that the mutations become positively selected for, leading to their presence in high frequencies in some populations.Blood disorders are a good example of this selection process. The sickle cell mutation, for example, is a mutation of the β-globin gene that can cause severe anemia in people who inherit two mutated genes. People with just one mutated hemoglobin (Hb) S gene, however, can be highly protected against malaria. And in Africa, where malaria is one of the biggest killers, up to 40% of people are believed to carry one of the sickle genes.+-thalassemia . Despite the well-known beneficial effect of α+-thalassemia against malaria, scientists know little about how exactly the α+-thalassemias result in this protection, and whether they protect against all forms of the disease.The thalassemias are also inherited blood disorders that result from mutations in either the α-globin or β-globin genes. α-thalassemias are now the most common genetic disorders of human beings, and this is thought to be because of their protective effect against malaria. People usually have four α-globin genes, two on each Chromosome 16. In Africa, however, a common deletion can remove one of these genes from either chromosome or from both chromosomes; individuals with three or two α-globin genes remaining have anemia, which is more severe the fewer α-globin genes are present but is not life-threatening. This condition, in which at most one α-globin gene is missing from each chromosome, is known as αPLoS Medicine, Thomas Williams, Sammy Wambua, and colleagues—researchers from Kenya and Oxford—investigated the effect of α+-thalassemia on malaria and other childhood diseases, such as gastroenteritis, in two groups of children in Kenya. The first group comprised children younger than five years old, recruited between September 1998 and August 2001, 301 of whom were analyzed in the study (the mild disease cohort). The second group comprised 2,104 children recruited at birth between May 1992 and April 1995 (the birth cohort). All children analyzed were typed for both HbS and α+-thalassemia.In a new study in+-thalassemia (either with one or two α-globin genes lost) was associated with significant reductions in the rate of admission to hospital with malaria (with or without signs of severity) and severe malaria. Both homozygous individuals  and heterozygote individuals  had much lower rates of severe malaria anemia than normal children.Williams and colleagues found that α+-thalassemia had no effect on symptomless parasitemia . And although the occurrence of uncomplicated malaria was lower in both those heterozygous and those homozygous for α+-thalassemia compared with normal children, this drop in incidence was not statistically significant.However, α+-thalassemia and the occurrence of nonmalarial illnesses. There were, however, two exceptions. In the birth cohort, fewer heterozygous infants than normal children were admitted to hospital with severe anemia. In the mild disease cohort, both heterozygous and homozygous children had a lower frequency of lower respiratory tract infections than normal children—although, this was not seen in the other cohort.In general, there were no links between α+-thalassemia might increase the frequency of uncomplicated malaria. The authors say this might partly be explained by the fact that, unlike Kenya, in Vanuatu two species of malaria,P. vivax andP. falciparum, both cause disease at similar frequencies. Furthermore, there may be major genetic differences in both human and parasite populations between these regions.These findings appear to contradict previous results from a study conducted by the same group in the Pacific islands of Vanuatu that showed αWhether the mutation has a protective effect against other diseases is still unresolved. The authors maintain that such an effect is plausible—indeed, the protection from lower respiratory tract infections in some children was of a similar magnitude to that for malaria. The authors have also previously recorded protection against nonmalarial diseases in Papua New Guinea.These findings have important implications for researchers looking for “antimalarial” genes and for those searching for potential vaccine candidates: they will need to use a carefully focused approach that differentiates between uncomplicated, or symptomless, disease and the complicated, or severe, form.


The current malaria control strategy of WHO centres on early diagnosis and prompt treatment using effective drugs. Children with severe malaria are often brought late to health facilities and traditional health practitioners are said to be the main cause of treatment delay. In the context of the Rectal Artesunate Project in Tanzania, the role of traditional healers in the management of severe malaria in children was studied.A community cross-sectional study was conducted in Kilosa and Handeni Districts, involving four villages selected on the basis of existing statistics on the number of traditional health practitioners involved in the management of severe malaria. A total of 41 traditional health practitioners were selected using the snowballing technique, whereby in-depth interviews were used to collect information. Eight Focus Group Discussions (FGDs) involving traditional health practitioners, caregivers and community leaders were carried out in each district.degedege, a prominent feature in severe malaria, to biomedically-defined malaria. The majority of mothers (75%) considered degedege to be caused by evil spirits.Home management of fever involving sponging or washing with warm water at the household level, was widely practiced by caregivers. One important finding was that traditional health practitioners and mothers were not linking the local illness termed degedege, which was believed to be caused by evil spirits. Treatment seeking was, therefore, a complex process and mothers would consult traditional health practitioners and modern health care providers, back and forth. Referrals to health facilities increased during the Rectal Artesunate Project, whereby project staff facilitated the process after traditional medical care with the provision of suppositories. This finding is challenging the common view that traditional healers are an important factor of delay for malaria treatment, they actually play a pivotal role by giving "bio-medically accepted first aid" which leads to reduction in body temperature hence increasing chances of survival for the child. Increasing the collaboration between traditional healers and modern health care providers was shown to improve the management of severe malaria in the studied areas.The healing process was therefore organized in stages and failure to abide to the procedure could lead to relapse of Traditional health care is not necessarily a significant impediment or a delaying factor in the treatment of severe malaria. There is a need to foster training on the management of severe cases, periodically involving both traditional health practitioners and health workers to identify modalities of better collaboration. Malaria is a major public health problem in Tanzania with about 16 million cases being reported annually in a population of 34.5 million . MalariaPlasmodium are transmitted to humans through the bite of female mosquitoes belonging to the genus Anopheles. The disease is also known to be associated with fever, headache, chills, shivering, loss of appetite, vomiting, general body weakness and joint pains. Such a biomedical conceptual framework has continuously been challenged when the perspectives of the people in a community are concerned. In the socio-cultural context, traditional beliefs are the basis for the local definitions of health problems occurring in the community as to whether they are due to natural causes, spirits or bewitchment. Thus, treatment seeking for childhood malaria depends very much on the manifestations of the disease in which the conception of natural or unnatural disease will be derived. Such a local body of knowledge, developed as an interplay between biomedical and traditional beliefs and logics, has been reported to guide people in deciding on treatment routes, i.e. whether to consult traditional healers or health facilities or both systems at the same time [Biomedically, malaria is a well-defined disease, in which parasites of the genus ame time .malaria ya kawaida) and 'cerebral malaria' characterized by convulsions (degedege) [In recent years, great emphasis has been placed in investigating socio-cultural factors that influence health-seeking behaviour for malaria and cause delay in attending health facilities . An ethnegedege) . Actuallegedege) ,13.In Tanzania, as in most sub-Saharan Africa, prompt case diagnosis and effective treatment is the main control strategy for malaria. The government has made deliberate and successful efforts to make health care services accessible to the majority of rural communities. However, this does not guarantee that all patients utilize the services when they fall ill. Since malaria may present in different forms like convulsions, altered consciousness and coma, community perception of underlying causes may differ. Consequently, many patients with these conditions turn to traditional healers prior to seeking modern health care resulting in delay in receiving effective treatment.The Rectal Artesunate Project, which is currently taking place in Kilosa and Handeni districts in Tanzania, aims to identify and assist children with severe malaria, including convulsions and coma, in their referral to hospital where proper, equitable and adequate treatment is available. Therefore, it was thought necessary to find ways to identify patients with such conditions at an early stage and provide them with effective treatment. The exploratory study was planned to collect baseline information, which would be used as a basis for an intervention to find out ways of involving traditional healers in the management of severe malaria in children. A set of key topics regarding treatment seeking and management of severe malaria was investigated in the study areas. These are:Community knowledge about malaria: local definition, causes, symptoms, and more specifically, whether people link the symptoms and manifestations to malaria;• Treatment-seeking: biomedical, traditional beliefs and logics which guide treatment-seeking paths;• Mode of acquisition of traditional healing knowledge: spirits, apprenticeship• Traditional management of severe malaria: home management, traditional healers management, referral system;• Collaboration of traditional healers and Rectal Artesunate Project: willingness to collaborate, collaboration areas.• The study area comprises the districts of Kilosa in the Morogoro region of south-eastern and Handeni in the Tanga region of north-eastern Tanzania. The specific setting for this study is in a stable perennial malaria transmission belt. A multi-stage sampling procedure was used. The study districts were stratified into two strata. The stratification takes into account the geographical reasons namely northern and southern zones. Stratification also took into account the main ethnic divisions of the Kilosa district namely Sagara, Kaguru and Vidunda, and Zigua for the Handeni District. Each stratum was mapped to determine the number of traditional health practitioners.A two-stage cluster sampling was conducted to select a sample of villages to be studied. The first stage involved a purposeful selection of one ward from each stratum in collaboration with Council Health Management Team (CHMT) members, taking into account the statistical number of traditional healers in the district. In stage two, two villages were randomly selected from the wards. Initially, traditional healers were identified, through key informants including local authorities, health workers from local health facilities, schoolteachers and elders in the community. A snowballing technique was employed to identify healers who, in turn, identified others. Sampling included traditional healers dealing with malaria case management. In a situation where the number was too large, a few were selected. More attention was given to traditional healers and Traditional Birth Attendants (TBAs) who treat among other diseases malaria/febrile illnesses to children five years of age and below. Mothers/caregivers of children under five years were selected in collaboration with health workers and TBAs in a situation where births occurred at home.Qualitative approaches including in-depth interviews and focus group interviews were applied to explore and describe management patterns of severe malaria in the study communities. In-depth interviews were conducted with the traditional healers and mothers/caregivers to get an insight on their knowledge of malaria, symptoms and health-seeking behaviour. Two focus group discussions (FGDs), one with traditional healers and another one with mothers/caregivers, 'significant others' and community elders were carried out in each village. These discussions aimed at getting views on childhood malaria and health seeking behaviour, local terminologies for mild and severe malaria and community views regarding the Rectal Artesunate Project in the area. FGD participants were usually selected on the basis of shared experiences and interests, knowledge of the subject under investigation and willingness to participate in the discussions . ParticiSince most of data collected was qualitative in nature, text analysis software  was used. The codes permitted compilation of text segments of interest for thematic analysis. The STATA 7.0 (Stata Group) was used for analysis of quantitative information.A standard explanation and introduction was given out to each individual on the benefits of participating in the study before informed consent was sought. Individuals were asked whether they had any questions and whether they agreed to take part in the study. The study used qualitative methods (interviews and discussions) with minimal risks to the participants. Confidentiality of all study participants was assured. Ethics clearance was obtained from Medical Research Co-ordinating Committee (MRCC) of the National Institute for Medical Research (NIMR), Tanzania.The socio-demographic profiles of the study groups are summarized in Table The mode of acquisition of the traditional healing practice described by the interviewed healers fall into four major paths:1. Training through apprenticeship2. Inheritance from member of the family3. Dreamed instructions from the ancestral spirits4. Falling sick and become a healer on recoveryMost of the traditional healers interviewed (31 out of 41), indicated to have passed through a combination of routes 1, 2 and 3. All of the 31 were raised in families with traditional healers, who involved them in the healing process and they were familiar with the profession at the time they started to practice on their own . All rep"I experienced unknown illness which took away my senses, then I ran away into the forest and lived in a cave for three years. After that duration, I came back into the village as a horrible creature with long hairs, nails and a stinking body. My relatives ran away and some of the courageous ones got hold of me and took me directly to one traditional healer for divination. The outcome of divination indicated that the ancestral spirits have already completed their training on me to become a healer, thus instructing my relatives to cut my hairs and nails and thereafter the traditional healer conducted a series of rituals on me. After that my senses came back and I have become a traditional healer for over 40 years now!"A similar account was reported by Geissler et al  in a shoThe long time duration of practice ranging from 10 to 61 years in the surveyed traditional healers indicates their long-term experience in dealing with community health problems and the corresponding trust the people have bestowed upon them.malaria ya kawaida), severe malaria  and convulsions (degedege). Symptoms of "malaria ya kawaida" mentioned were ordinary fever, chills, body weakness, loss of appetite and vomiting, whereas; "malaria kali" was identified with high fever, shivering, loss of appetite, child becoming very weak and sleeping all the time; while "degedege" identified with high fever, loss of appetite, vomiting, rigid body and un-coordinated movements of the limbs and eyes.The results show that the two studied communities held good biomedical knowledge of febrile illnesses. Mothers identified three distinct types of febrile illnesses as mild malaria , from Kilosa, substantiated further on the motivation to send convulsing children to traditional healers first, as injections were considered fatal for such condition as used in modern system."It is because of fear and mistrust of Western medicine treatment which is carried out by use of injections, mothers decide to send convulsed children to traditional healers as possible survival is predictable compared to hospital treatment. I know if I take my convulsed child to hospital they may inject him and this practice is known to kill children. On this background, I avoid hospital treatment for degedege and what I normally do is to send the convulsed child to the traditional healer for treatment and then after that, send the child to hospital for check up and treatment of malaria fever".A Ward Executive Officer (WEO) explaining his experience in the area further explains;"Mothers traditionally believe that degedege is caused by bad spirits. Based on this belief, they send convulsing children to traditional healers for treatment first and then to hospital".milieu in which people live. Generally, mothers would consult different healing resources at the same time starting with traditional healers and then modern care, back and forth.The above accounts show that, in the study areas, treatment seeking for children suffering from malaria is a complex process, being a function of socio-cultural mavi ya tembo' 8% and smearing herbs on the child body (10%). Others said they do nothing at home, instead resort to either traditional healers or health facilities 58% (N = 84). This is also indicated in other studies in Tanzania [The most common way practiced by mothers for treating a convulsing child at home included sponging or washing by cold water believed to reduce the temperature 22% (N = 84), placing the febrile child under bed and urinating on him/her especially in Kilosa District 12% (N = 84), elephant dung smoke infusion 'Tanzania , which smama kumkujolea mtoto wake', which is believed to lower the temperature of the child, thus serving as 'First Aid'.One way of managing a child suffering from mild or severe malaria at home by mothers involved a mother urinating on the child 'It follows, therefore, that home management of a mild or severe case of malaria is a common practice, and it is only after the observation of the outcome that a child is taken to another medical resource i.e. traditional healers or nearby health facility. The findings of this study indicate that mild or severe cases could be associated with various causes and establishing and negotiating diagnoses involved different types of specialists as well as what has been referred to as 'Therapy Management Group (TMG)' . In manyTraditional healers identified at least five stages through which a child suffering from severe malaria must pass during the healing process. It must be pointed out, however, that not all the healers would necessarily pass through the 5 stages, but the stages of diagnosis and treatment were considered paramount. Although there were some variations from one healer to another, generally the process involved the following stages:This entailed warm welcome of the mother to the compound and greetings according to the local culture. At this session, the mother is required to explain the ailment of the child, when the ailment started and the steps taken by the mother so far to address it.mwingajini', sponging by using warm water and, in some cases, the mother of the child urinating on her child, 'mama kumkojolea mtoto wake', in which the child is positioned under the bed and the mother over the bed, after the mattress has been removed.This was a necessary second step involving certain forms of homecare, including bathing the child using grounded local herbs "kupiga kengele' or reading the Quoran. The outcome of divination was to identify appropriate treatment or solution of the problem. It appeared that in five cases the mother needed to be treated first, so as to prepare for a smooth healing for the baby, in the belief that evil spirits possessing the mother are causing illness to her child. One 76-year old female, traditional healer in Mswaki, Handeni, who has 30 years of experience, expressed it this way:This stage involved several forms with the objectives of finding out the exact causes of the situation in hand. Most healers were herbalists-cum-diviners. Divination was done by ringing the bell '"I must first of all find out if the mother is bewitched by evil spirits- that may cause the child illness, especially if the mother was not 'cleansed' from the spirits. Thereafter, I treat the child. In so doing I ensure that the bad spirits will not harm the child again through the mother."The above account indicates, therefore, that diagnosis of the problem goes beyond the current problem afflicting the child to a broader societal causes of ailment especially if there is suspicion that evil sprits may be the root cause, as shown in other studies.Ocimum suave), Mhasu, Mlwati, Mlama, Mkongodeka, Unganyiki, Mkwaju (Tamarindus indica), Bhangi (Cannabis sativa), Mlingo, Mvungaliza, Mdimbogo, Mbolo, Mkunde Kitimbilikwima (Senna auriculata), Lufyambo, Mhofya, Mningajini (Cassia abbreviata), Mnungu , Mninga (Pterocarpus angolensis), Mzizima, Mfiwi, Mbaazi (Vigna unguiculata), Mkwambekwambe, Mtunduru, Kibwamsongera, Fuzifuzi, Mhuwangulu, Turatura (Solanum incanum), Vitunguu Swaumu (Allium spp), Mwaraka, Kitako cha Nge, Msalaka (Saraka Indica), Lwenya, Msekela, Ngurukila, Mfunguo and Mkulagembe. These herbs were grounded and at times boiled then administered while using cold or boiled water. Some were given to the mother of child to be administered at home for three to five days. Generally, the treatment ranged from two to seven hours for healers who do not hospitalise the patients, and two to five days for those who do.The treatment procedure followed the divination or diagnostic process, where specific medicine or treatment would be known. The most common local herbs mentioned were katula mpama, kivumbasa  agreed they refer cases of malaria to health facilities. Only 15% of the healers admitted that referrals were done to other healers on conditions such as casting out of demons and changing of the colour of the child, which necessitated referral to nearby facility. It is worth noting the existence of healers who specialized in casting demons- these received clients from other healers in the study area.degedege' again. A study in Kilombero district in Tanzania [waganga' was taken after several visits to hospitals and because they were sceptical about having received the correct examination or the correct treatment.It also emerged that referrals to health facilities increased with the introduction of Rectal Artesunate Project, whereby the project aides facilitated referral after provision of a suppository. With regard to who decided on when and where the child is to be referred to, it emerged both from mothers and healers interviewed, that the mothers would consult the healer and that a mutual agreement was reached. In a situation where there was no mutual agreement, it sometimes happened that the mother would take the decision herself and take her child to the health facility. Close to a three quarter of mothers interviewed said that they would prefer referral to a heath facility, compared to referral to another healer, in a situation of worsening condition of the child. It has to be noted that the referral to the facility did not indicate that the mother would not come back to the healer again – there was movement from the healer to health facility, back and forth, even when the condition of the baby showed improvement. Revisiting healers was mainly done with the purpose of cleansing the child from contracting 'Tanzania  concludeAll the traditional healers interviewed (N = 41) said they were aware of the Rectal Artesunate Project and admitted to have collaborated with the project staff in one way or another since 2000. Project staff constantly visited the healers and, in collaboration with project aides recruited in the areas, they helped manage severe cases of malaria. It also emerged that the project aides were well known and respected persons in their communities and many women with children suspected with malaria turned to them, either directly or through healers.However, some healers complained of project aides robbing them of their clients who used to visit them: these now go to the project aides directly, thereby bypassing the healers. In addition, the healers felt that the project aides had more recognition  and monetary motivation . They requested for some form of recognition, as the project gets some of its clients through them. Majority of the healers (85%) were willing to collaborate with the Rectal Artesunate Project in reducing morbidity and mortality of malaria among children in the studied areas. They identified possible ways to enhance the existing collaboration Table .degedege (convulsions) as a serious childhood condition, caused by evil spirits, which attacks a child in conjunction with malaria. Mothers related mild malaria to mosquito bites, whilst degedege, though acknowledged as being a serious childhood condition, was not recognized as possible outcome of malaria infection. The local interpretation of malaria and related complications are reflected to the logic of actions and treatment-seeking behaviours followed for a sick child. In view of the fact that severe forms of malaria are linked to supernatural causes, a traditional healer is considered more appropriate for treating a convulsing child. Similar findings have been reported elsewhere [degedege.Qualitative data have indicated that people in the study areas have integrated conceptions derived from biomedicine into their local knowledge and practice. It is evident that most of interviewed mothers possess a good knowledge in recognizing mild malaria, which is consistent with the biomedical definition of mild malaria. Most mothers perceived lsewhere  whereby,lsewhere ,22,23. Mdegedege to biomedically-defined malaria, they affirmed that, when convulsion occurs in a child, malaria is its usual companion. On this realization, they refer their patients to health facilities for malaria treatment immediately after arresting the spirits causing the convulsion. Furthermore, with the introduction of the Rectal Artesunate Project in the study areas, traditional health practitioners were provided with a nearby health service for referring their patients, hence an increase of the number of referrals from traditional healers. None of the other studies on degedege [Although traditional health practitioners participating in this study were not linking degedege ,8,23,24 There are healers in almost every village and they represent the most numerous health care providers in Tanzania, with an estimated 1: 350 healer per population , as compSome of the barriers to smooth collaboration between biomedical health personnel and healers include:• Natural competition for prestige and patientsReluctance of biomedical personnel to cooperate with healers, because of a genuine concern that their practice may harm the patients, which may not always be true.• Negative attitude by most biomedical towards traditional health practices, by branding it as witchcraft.• Government officials and biomedical staff having little or no knowledge of the actual healing practices of traditional healers.One of the key recommendations from this study is to enhance collaboration by focusing on improving the capacity of traditional healers to assist their patients on referral and on decreasing possibly harmful traditional practices. More operational research is needed to clarify the best approaches to make such a collaboration possible.The introduction of Rectal Artesunate Project in the study areas is a positive step towards collaboration between modern and traditional health practices in the management of malaria in children. The collaboration in the Rectal Artesunate Project area has convinced the community that dual health services are possible and represent a positive step towards early referral and prompt treatment, hence, reducing morbidity and mortality. The involvement of traditional healers has improved management of severe malaria by introducing the new paradigm that, after convulsions in a child, medical care for malaria is necessary, before convulsion-preventive rituals can be carried out. The introduction of artesunate suppositories was acceptable to traditional healers and improved referrals. The study has gone some way to remove the blame from traditional healers accused in delaying access of sick children to prompt medical care.E A Makundi obtained funding, contributed to the study conception, design, fieldwork, data analysis, interpretation and drafting, revision and final approval of the manuscript. H Malebo contributed to data analysis, data interpretation, revision and final approval of the manuscript. P Mhame participated in data collection, data analysis, reviewed draft of the report and approved the final version. A Y Kitua contributed to study conception, design, drafting the first version, revision and approval of final version. M Warsame obtained funding, contributed to the study conception, design, data interpretation and drafting, revision and final approval of the manuscript.The author(s) declare that they have no competing interests.


No two brain diseases would seem to be more different than Alzheimer disease (AD) and fragile X syndrome (FXS). AD affects the old, while FXS occurs in childhood. AD affects about 4 million Americans of both sexes, while FXS affects fewer than 50,000, primarily boys. And while the cause of most cases of AD is unknown, the gene responsible for virtually every case of FXS has been known for over a decade.Despite these dissimilarities, the two diseases may be more closely linked than expected. A new study by Cara Westmark and James Malter shows that the protein whose absence causes FXS is a key translation regulator of a protein implicated in AD.AD, the most common neurodegenerative disease, is characterized by death of neurons throughout the brain. A prominent feature of brain degeneration in most cases is the appearance of amyloid plaques. These sticky clumps are largely made of a protein fragment called beta-amyloid (Aβ). Aβ is cleaved off of a larger protein, amyloid precursor protein (APP), whose precise function is unknown but which is believed to be involved in synapse formation during development. After APP messenger RNA (mRNA) is synthesized, a fraction of it remains quiescent until the neuron is excited by the neurotransmitter glutamate. When that occurs, APP synthesis rapidly spikes upward.fmr-1 gene, already containing multiple repeats of the nucleotides cytosine-guanine-guanine, expands to more than 200 repeats. This inhibits transcription of the gene. The gene is on the X chromosome, meaning boys only have one copy. When the mutated and silenced form is the only copy, the result is FXS, which causes—in addition to mental retardation—autistic-like behavior, seizures, and a group of abnormal physical traits. The fmr-1 gene encodes a protein called FMRP, whose normal role is to bind mRNA and repress its translation. To date, over 500 mRNA targets of FMRP have been identified, many of which may be involved with synaptic function.FXS, the most common cause of inherited mental retardation, occurs when a section of the FMRP binds with its target mRNAs at sites rich in guanine, especially those whose RNA can fold into a cage-like structure called a guanine quartet (G-quartet). Therefore, the authors began their search for likely FMRP targets by focusing on genes with these sequence characteristics. Their database searches revealed that APP contains such a sequence, which suggested it might be regulated by FMRP. To show that FMRP actually binds to APP mRNA, they isolated synaptoneurosomes, which contain pre- and post-synaptic vesicles, from the mouse brain and treated them with antibodies against FMRP. When the antibodies were isolated, the researchers found they had captured not only FMRP, but also APP mRNA, indicating the two were physically linked together, at least indirectly.fmr-1 gene (“knockout” mice) expressed APP, but only normal mice increased expression in response to DHPG, which stimulates the glutamate receptor. Thus, it appears that FMRP regulates APP production in some manner. The results were not due to any effect of FMRP on APP mRNA stability, the authors found. Instead, as expected, FMRP repressed APP translation. To show this, the authors treated stimulated synaptoneurosomes with anti-FMRP antibodies. Unlike in resting synaptoneurosomes, in which APP mRNA is isolated along with FMRP, in stimulated synaptoneurosomes, the APP mRNA was not captured, indicating it had dislodged. Presumably, this rapid dissociation of the two is the first step in the stimulus-dependent synthesis of APP.They next used neurons in culture to examine the effect of FMRP on the expression of APP. They found that both normal mice and mice missing the To determine whether FMRP binds directly to APP mRNA, and not to some other intermediary, the authors digested the FMRP–mRNA complex with RNAse, which digests exposed RNA while passing over the region bound by protein. Their results showed that the two did bind directly with each other, but to their surprise, the FMRP bound a guanine-rich region near, but not identical with, the G-quartet region.fmr-1 knockout mice, which make no FMRP, contain up to 2.8-fold more Aβ than those of normal mice, in keeping with the loss of translational repression. The significance of this result for FXS patients is unknown. It suggests patients may be at risk for increased amyloid deposits, but very few aged brains from FXS patients have been analyzed, and no deposits have been observed in younger brains. Intriguingly, relatives of FXS patients with only moderately expanded fmr-1 genes are at risk for developing a late-onset syndrome of dementia and movement disorder (fragile X tremor/ataxia syndrome). Whether this is a direct result of decreased APP repression is unknown as of yet.Finally, the authors showed that the brains of Taken together, these results indicate a close relationship between FMRP and APP, with FMRP regulating the normal excitation-dependent expression of APP. Given APP’s probable role in synaptic development, it seems likely that its dysregulation may be a key step in the development of mental retardation in FXS. How, or whether, this relationship also plays a part in AD is much less certain. Nonetheless, given APP’s role in plaque formation, further understanding of how APP is created is likely to lead to new insights into how levels of Aβ are controlled, and from that, perhaps even how those levels might be reduced.


Plasmodium cause many hundreds of millions of cases of malaria worldwide optimism that in the future effective vaccination will join the current strategies of preventive and therapeutic uses of antimalarials, and of reduction in human–vector contact, as part of the global malaria control toolkit.Parasites of the genus P. falciparum [P. falciparum and P. vivax that have advanced to clinical trials in recent years are targeted against two distinct stages of the parasite life cycle. The first is the sporozoite, which is injected by the bite of a mosquito into the human host as a haploid, free-living unicellular form, and which seeks out the liver, where it invades a hepatocyte and undergoes intracellular multiplication. Among key target antigens at this stage are thrombospondin-related adhesive protein (TRAP), liver-stage antigen 1 (LSA-1) and circumsporozoite protein (CSP). The most successful malaria vaccine to date, the recombinant protein RTS,S administered with the adjuvant AS02A, afforded sustained protection to ~30% of children under five years of age in a large proof-of-principle Phase II trial in Mozambique [The complex life cycle of the malaria parasite, a protozoan of the phylum Apicomplexa, requires a sophisticated array of proteins. These are encoded by a genome of 23 Mb distributed across 14 chromosomes in CSP: Circumsporozoite protein, a candidate sporozoite vaccine antigen; primary component of the RTS,S vaccineHaplotype: Literally a “haploid genotype.” As used in this article, refers to a particular combination of linked polymorphisms occurring in a particular parasite cloneLSA-1: Liver-stage antigen 1; candidate liver-stage vaccine antigenMerozoite: Free-living parasite that emerges from infected hepatocytes and invades erythrocytes to initiate disease-causing blood-stage malaria; replication in erythrocytes releases further merozoites every 48–72 hoursMSP-1: Merozoite surface protein 1; a large multi-domain protein associated with the merozoite apical complex; cleaved by specific proteases during erythrocyte invasion19:MSP-1 Carboxyl-terminal domain of MSP-1 retained on the merozoite surface after proteolytic cleavage; quite conserved in sequence, and shown to elicit protective immune responses in a number of studies; a leading candidate blood-stage antigenSporozoite: Free-living malaria parasite stage injected into vertebrate host by mosquito bite; invades hepatocytesTRAP: Thrombospondin-related adhesive protein, a candidate sporozoite/liver stage vaccine antigen19. As a prime target of natural immune responses in malaria-exposed populations, MSP-1 is a polymorphic antigen, and many variants can occur in a single parasite population. Therefore, there is a risk that MSP-1 vaccine-elicited immune responses may be variant specific, and thus not provide protection against all parasite genotypes encountered within a given population. The MSP-119 portion of the molecule is relatively conserved, but does contain six polymorphic amino acid residues that may contribute to immune evasion by the parasite.A second major class of malaria vaccines targets the blood stage of the life cycle. This intraerythrocytic stage of infection is responsible for the syndrome of clinical symptoms familiar to us as malaria. Free-living merozoites in the blood, before invading a host erythrocyte, present the immune system with a number of potential immunogens. Among these, merozoite surface protein 1 (MSP-1) is considered one of the most promising vaccine targets, and a number of candidate MSP-1 vaccines are currently in the development pipeline. Many of these are based on the 19 kDa polypeptide at the carboxyl terminus of the MSP-1 protein, MSP-1PLoS Medicine, Shannon Takala and colleagues present a detailed longitudinal analysis of polymorphisms in the msp-1 genes of parasite isolates taken from a cohort of a broad age range in Bandiagara [n = 2,309) from a random selection of 100 cohort participants across three age strata were analysed through three malaria transmission seasons from 1999 to 2001. This group of 100 individuals provided a staggering 1,375 parasite-positive events during this time, and these isolates were analysed for msp-1 polymorphisms by pyrosequencing. The authors use the data to present an analysis of the population-level dynamics of 14 different haplotypes encoding MSP-119. The study provides novel and important information on three levels.Renewed interest in the testing of malaria vaccines at a number of clinical trial sites in sub-Saharan Africa has lead to development of the infrastructure and expertise required for Phase II and Phase III studies of vaccine safety, immunogenicity, and efficacy. One of these sites is at Bandiagara, Mali, where malaria transmission is intense but highly seasonal. In this month's ndiagara . Monthly19 population and demonstrate dynamic fluctuations over the three-year study. These data can inform vaccine design, by indicating that either of two dominant haplotypes  occur in about 80% of infections overall. In contrast, the haplotype ETSSRL, found in the 3D7 laboratory clone of P. falciparum, and the basis of one leading MSP-1 vaccine, FMP1/AS02A, occurred in only 16% of infections. Thus, if vaccine-elicited immunity is sequence anti-MSP-119 specific, a vaccine targeting either or both of the more prevalent haplotypes might be more effective in this population. Interestingly, the 3D7 haplotype ETSSRL, and two other haplotypes, appeared to be significantly more common in asymptomatic infections, a result largely accounted for in multivariate modelling by an association with lower parasite densities. This raises the intriguing possibility that specific MSP-119 haplotypes may contribute to reduced virulence, but as Takkala et al. point out, this possibility requires further investigation in other endemic areas, and with a broader genome-wide analysis of parasite polymorphism.First, Takkala and colleagues are able to measure the prevalence of haplotypes in the different MSP-119 haplotypes, on the average number of parasite clones in each infection, and on the relative proportion of parasite-positive individuals who had symptomatic malaria, as opposed to asymptomatic infection, in each age group. Such “baseline” knowledge of parasite population dynamics, collected in the absence of a vaccine intervention, is crucial to any future analysis of postintervention data.Second, it was found that the seasonality of malaria transmission in Mali has a profound effect on the prevalence of some MSP-119 haplotypes elicit sequence-specific immunity. For a given surveillance interval in which two infections occurred in the same patient, infection with a haplotype differing in amino acid sequence at residue 1691, 1700, or 1716 was significantly associated with risk of clinical malaria in the latter episode. This finding suggests that there is some level of haplotype-specific immunity, and may also mean that only a subset of the possible MSP-119 sequence combinations needs to be covered by a vaccine in order to counteract the effect of polymorphism at these residues.Third, careful analyses of sequential isolates collected from individual patients provide new evidence that some MSP-119 vaccine trials. Confirmation in other endemic settings is required to verify the evidence that certain residues in this antigen may be particularly important in eliciting sequence-specific protection, and that particular haplotypes are associated with lower parasite densities. Nevertheless, this study provides ample warning that analysis of antigen diversity in the target parasite population should not only be gathered as part of postintervention evaluation in vaccine trials [The data presented by Takkala et al., gathered in the absence of any intervention with a vaccine, demonstrate the potential impact that parasite population diversity could have on the outcome of MSP-1e trials , but sho


Temperature, rainfall and humidity have been widely associated with the dynamics of malaria vector population and, therefore, with spread of the disease. However, at the local scale, there is a lack of a systematic quantification of the effect of these factors on malaria transmission. Further, most attempts to quantify this effect are based on proxy meteorological data acquired from satellites or interpolated from a different scale. This has led to controversies about the contribution of climate change to malaria transmission risk among others. Our study addresses the original question of relating meteorological factors measured at the local scale with malaria infection, using data collected at the same time and scale.676 children (6–59 months) were selected randomly from three ecologically different sites . During weekly home visits between December 1, 2003, and November 30, 2004, fieldworkers tested children with fever for clinical malaria. They also collected data on possible confounders monthly. Digital meteorological stations measured ambient temperature, humidity, and rainfall in each site. Logistic regression was used to estimate the risk of clinical malaria given the previous month's meteorological conditions.The overall incidence of clinical malaria over the study period was 1.07 episodes per child. Meteorological factors were associated with clinical malaria with mean temperature having the largest effect.Temperature was the best predictor for clinical malaria among children under five. A systematic measurement of local temperature through ground stations and integration of such data in the routine health information system could support assessment of malaria transmission risk at the district level for well-targeted control efforts. Meteorological factors are important drivers of malaria transmission. Temperature, rainfall and humidity have been associated with the dynamics of malaria vector population and, therefore; with spread of the disease. Ambient temperature plays a major role in the life cycle of the malaria vector. The development of the parasite within the mosquito (sporogonic cycle) is dependent on temperature. The sporogonic cycle takes about 9 to 10 days at temperatures of 28°C, but stops at temperatures below 16°C . The daiSeveral field studies have reported the impact of ambient temperature on malaria outcomes. -10. In SRainfall provides breeding sites for mosquitoes to lay their eggs, and ensures a suitable relative humidity of at least 50 to 60% to prolong mosquito survival. Relative humidity below 60% shortens the life span of the mosquitoes. The onset of the rainy season was associated with an increase in vector abundance ,12. The Despite consistently reported evidence that meteorological factors affect malaria transmission, conflicting opinions persist about their relative importance. Shanks and colleagues  could noThe purpose of the current study was to estimate the effects of temperature, rainfall, and relative humidity on the incidence of clinical malaria, by examining data on these meteorological factors and laboratory-confirmed cases of clinical malaria. A binary-response logistic regression model with fractional polynomial (FP) transformations was used to assess these effects. The FP approach allowed us to explore better the nature of the relationships between these meteorological parameters and the risk of clinical malaria. This is because presumed linearity of these relationships is not justified -3.The study was conducted in the town of Nouna and the villages of Cissé and Goni. These three sites are part of the Nouna Demographic Surveillance Systems (DSS) area , which iChildren were selected at each site by cluster sampling of households, using a sampling frame produced from the DSS database. The sample size was set to detect inter-site differences in clinical malaria incidence of at least 10%, with 80% power and 95% confidence, and accounting for 15% loss to follow up. Children were involved after getting informed consent from their parents. In total, 676 children , aged 6 to 59 months, took part in the study. The Nouna ethical committee approved the study.Three trained interviewers, one based at each site, visited each child at home every week. At each visit, they measured the child's axillary temperature and collected a blood film (by finger prick) from any child who was febrile (axillary temperature > = 37.5 C). In addition, interviewers collected information on bed net use and housing conditions. Blood films were read in the Laboratory of the Nouna Health Research Centre. Details on the clinical malaria detection procedure are provided elsewhere . The outFor purposes of this study, incidence was defined as the number of clinical malaria episodes detected per 1000 units of person time bearing in mind that some illness episodes which occurred between visits may have been missed.For ethical reasons, children with fever were treated presumptively with cholorquine (CQ) according to the then national treatment guidelines for malaria. When fever persisted for two days or other symptoms surfaced, the interviewers immediately referred the child to the nearest health centre. The project covered all related costs.Rainfall, temperature, and humidity were measured on the ground using meteorological units installed at each of the three sites. Each meteorological unit consisted of a Digital Datalogger , to which three sensors  were connected Figure . FollowiH1(X) = Xp, where p takes eight possible values: -2, -1, -0.5, 0, 0.5, 1, 2, 3. The linear model is represented by X1, and X0 represents the logarithm of X. The transformation can be either first or second-degree [A conventional binary outcome logistic regression model was used to assess the effects of mean, minimum, and maximum temperatures (T°C), relative humidity (RH), and amount of rainfall (Pmm) of the previous month on clinical malaria rates among study participants. The interaction terms  were included in the model to control for the high correlation of the three individual variables. Other covariates included in the model were site of the study; sex; age; use of bed net; type of house; presence of a well; presence of a farm ; presence of animals; and presence of a mosquito breeding site within a 30-metre radius of a participant's house. As the temperature, rainfall and relative humidity are continuous variables and their relationships with clinical malaria might not be linear, multivariate FP procedures ,22 were d-degree ,22.For the simplest model, the one with one continuous variable (e.g. temperature) and one binary variable , the logistic regression model using the first-degree FP isib is the predicted probability of a child testing positive for clinical malaria at a temperature i, and for bed net use b (yes or no); H1 (X) is the functional form to which the co-variable X is transformed; β1 its coefficient; and γ is the coefficient of the co-variable; Wb, the use of a bed net. The rate ratio for the first-degree PF transformation is given by the formula:... Where πn is the number of possible powers (8), and k the number of powers in each combination (2); thenSecond-degree transformation uses a combination of two powers from the list of eight. In total, 36 combinations are possible. This is calculated as follows:1(X) and H2(X) are the respective functions to which co-variable X is transformed...where, HThe rate ratio for the second-degree FP is given by the formula:® software [x(0) were defined. These are mean temperature = 27°C, the value at which clinical malaria risk peaked; rainfall = 164 mm, the highest value observed; and relative humidity = 60%, the minimum value required for malaria vector survival.All the models were run and fit using STATA software . The outTable During the one-year follow up, 20 children (3.0% of 676) left the cohort, either because of death (11) or migration out of the study sites (9). Although 52 home visits were planned for each child, on average, each child was seen for 45.4 times, because children were not always present at each visit. In total 594.9 person-years (PYs) were observed.The three sites presented a similar pattern of meteorological conditions Figure , 4, 5. RThe mean daily temperature variation in a month, expressed by standard deviation, was high in March for all sites . From March onwards, at all sites, this variation decreased in all sites to achieve its smallest value in December, which was 0.7 and 1.1 in Goni and Nouna, respectively. An unusual small variation was observed in Cissé in October (0.1).Over the study period, 1274 episodes of fever were observed; thus, an incidence of 2.1 episodes per PY (1274 episodes/594.9 PYs), which was similar in all sites . Out of 1274 fever episodes, 635 had parasiteamia and were therefore considered as cases of clinical malaria, giving an incidence of 1.1 episodes per PY. Nouna had the lowest incidence of 0.8 per PY. In Cissé and Goni, the incidence was 1.2 and 1.3 per PY, respectively.Table Table Although other variables were included in the model for adjustment purposes, their estimates are not shown in Table The effects of meteorological parameters on clinical malaria expressed in rate ratios (RR) are presented in Figure Mean temperature ranged from 21°C to 34°C. The relationship between mean temperature and clinical malaria incidence displayed a bell-shape curve Figure . The risThe effect of rainfall on clinical malaria risk was observed only for values above 100 mm Figure . Below tRelative humidity observed in the field ranged between 15% and 80%. The clinical malaria risk increased with an increase in relative humidity, but not linearly  life cycle could explain these results. Indeed, the sporogonic cycle (the development of the parasite within the vector) is shorter (9–10 days) at 28°C and longer (about 100 days) at temperatures below 20°C [Anopheles gambiae is about 21 days. At high temperatures, vector survival decreases and temperatures of 40°C will result in zero vector survival. Craig and colleagues [Mean temperature alone was a strong predictor of clinical malaria rates among the children in our sample. Its relationship with clinical malaria was bell-shaped such that the risk was lowest at low and high temperatures. The infection risk was highest at temperatures around 27°C. There is no direct biological link between human infection and ambient temperature. However, the temperature-dependence of the horter 9–0 days atlow 20°C . Therefolleagues ,26,7,9.Cumulative rainfall from the previous month had a positive effect on clinical malaria rates as well. Several other studies reported similar results ,6,9,10. The individual effect of relative humidity on risk of clinical malaria, compared to temperature and rainfall, has been reported less often in the literature. Mean relative humidity of the previous month had a positive effect on malaria incidence. The effect was greater than that of rainfall. This is in line with the findings of Bi and colleagues . To accoThe study was performed only for one year; thus, it cannot claim to be representative of all years. In fact, rainfall and humidity were both below the average of the last 10 years , but average temperatures were similar. Clinical data from several years (at least three years) of observation would have been ideal; but this was not feasible, given the costs involved in collecting the malaria infection data. In addition, the reported malaria incidence was not significantly different from that reported in a study conducted in the preceding year. Without a catastrophic event (like flooding or drought), the effect of meteorological variables on malaria infection should not change much from one year to another.In such a semi-immune population, malaria may be transient. Therefore, weekly visits may not be sensitive enough to capture all the episodes. Infection acquired between visits could have been treated and cured and therefore missed. Indeed, Snow and colleagues reported a sensitivity of 74% of weekly visits in capturing clinical malaria episodes compared to daily visits . In thisThe findings of this study confirm that meteorological conditions have a significant influence on clinical malaria rates among children under-five years old. Although several individual meteorological parameters have an impact on clinical malaria incidence, mean temperature is the best predictor and the main driving force, at least in the region. This is also observed in other regions. For example in the highlands region the preventing factor for malaria transmission is the low temperature because of the high altitude. Changes in ecological settings because of climate change are to be expected in this sub-Saharan region, especially the rain patterns. These changes may modify local mosquito microhabitats and affect transmission widely. A health information system including systematic monitoring of temperature and rainfall could yield an early warning system to support malaria control efforts at district level.The author(s) declare that they have no competing interests.YY designed and implemented the study. He performed the statistical analysis and drafted the manuscript. VL took part in statistical analysis, writing of the manuscript and interpretation of the findings. SS supervised the fieldwork and contributed in the writing. RS participated in the design, implementation, and writing of the manuscript. All authors read and approved the final manuscriptThe pre-publication history for this paper can be accessed here:


Pregnant women are more susceptible to malaria, which is associated with serious adverse effects on pregnancy. The presentation of malaria during pregnancy varies according to the level of transmission in the area. Our study aimed to demonstrate the prevalence and risk factors for malaria  among pregnant women of eastern Sudan, which is characterized by unstable malaria transmission.Plasmodium falciparum malaria were investigated in 744 pregnant Sudanese women attending the antenatal clinic of New Haifa Teaching Hospital, eastern Sudan, during October 2003-April 2004.The prevalence and possible risk factors for P. falciparum malaria, 18(17.6%) of these were severe cases (jaundice and severe anaemia). Univariate and multivariate analysis showed that, age and parity were not associated with malaria. Women who attended the antenatal clinic in the third trimester were at highest risk for malaria .A total 102 (13.7%) had Women with malaria had significantly lower mean haemoglobin . A significantly lower haemoglobin was observed in those with severe falciparum malaria compared to non-severe form .P. falciparum malaria is common in pregnant women attending antenatal care and that anaemia is an important complication. Preventive measures (chemoprophylaxis and insecticide-treated bednets) may be beneficial in this area for all women irrespective of age or parity.The results suggest that  Pregnant women are more susceptible to malaria, which causes serious adverse effects including abortion, low birth weight and maternal anaemia. It is the leading cause maternal mortality in Sudan -7.The presentation of malaria during pregnancy varies according to the pre-existing immunity of the mother. Women living in areas of low transmission have little immunity to malaria which can cause severe syndromes, such as cerebral malaria and pulmonary oedema. In contrast, those who live in areas of stable malaria transmission enjoy greater immunity and experience fewer symptoms during episodes of malaria, although they commonly develop severe anaemia as consequence of the infection ,2,5,8,9.P. falciparum malaria transmission is unstable in the eastern region [P. falciparum malaria in pregnant women from eastern Sudan.Understanding the epidemiology of malaria during pregnancy provides important insight into relevant immunological processes and facilitates decision on control strategies. Although there are extensive studies in highly endemic African countries ,6,10-12,n region . The stuPregnant women attending antenatal clinic (booking visit) of the New Haifa Teaching Hospital, eastern Sudan, during the period October 2003-May 2004 were approached to participate in the study. After verbal consent, questionnaires were administered requesting demographic informations on age, parity, gestational age and history of maternal illness. Gestational age was calculated from the last menstrual period and confirmed by ultrasound, when clinically indicated. Physical examination was completed to identify signs of severe malaria  and alsoThick and thin blood films were prepared from capillary blood, stained with Giemsa and 100 oil immersion fields were examined. Parasite density was determined by counting parasites and 200 leucocytes, assuming each woman has 6,000 leucocytes/μl. All the slides were double-checked blindly.The haemoglobin concentration was estimated by the haematic acid method  in the fThe study received ethical clearance from the Research Board of the Faculty of Medicine, University of Khartoum.t-test, ANOVA, X2 and Fisher's exact tests as appropriate. P < 0.05 was regarded as significant. Multivariate logistic regression was performed with malaria as the dependent variable, using age, parity and gestation as independent variables. These variables were categorized and used as follows: median age, ≤ 25 years versus >25 years); gravidae as primigravidae, secundigravidae, multigravidae (3–5)or grandmultigravidae >5; gestation as first (< 14 weeks), second (14–28 weeks) and third (> 28 weeks) trimester.Data were entered in a computer using SPSS for windows. Comparisons between means and percentages were done by Students' A total of 744 pregnant women attended the antenatal clinic of New Haifa Teaching Hospital during the study, 29.5% were primigravidae.P. falciparum, 18(17.6%) of these were severe cases (jaundice and severe anaemia). Malaria prevalence and intensity (parasite count) were not significantly different amongst the different gravidity sub-groups (P > 0.05). The highest prevalence (18.3%) occurred in grandmultigravidae and the highest intensity  was observed in primigravidae (Table Table Mean (SD) age  and parity  were not significantly different between infected and non-infected women. Two of 18 (11.1%), 29 of 290 (10%) and 71 of 436 (16.3%) women were infected in the first, second and third trimester respectively (P = 0.05).Univariate and multivariate analysis indicated that, age and parity were not significantly associated with malaria infection. The third trimester was significantly associated with malaria infection . A lower haemoglobin also occurred in women with severe malaria .P. falciparum malaria during pregnancy in an area of New Haifa, which is characterized by unstable transmission [This study investigated the morbidity pattern of smission . The malsmission , malariasmission -12. Sevesmission  and diffsmission .The study showed no significant association between malaria and parity, which is also reported from other areas and locations with intense malaria transmission ,12,18. Iet al have also reported no significant association between malaria infection and maternal age [In contrast to the previous observations -12, age rnal age .et al reported the first trimester as the main risk period [Women who attended the antenatal clinic in the third trimester had about a 1.5-fold higher risk of malaria parasitaemia. This is in line with some observations, although several studies report the second and early third trimesters as the time of peak prevalence ,4,10-12.k period .The mean haemoglobin was significantly lower in women with malaria infection and significantly lower in severe cases. Reduction of haemoglobin has been reported in areas of unstable transmission in Thailand and in Ethiopia, as well as in areas with stable transmission ,6. RegarP. falciparum malaria is considerable in pregnant women in this part of Sudan and severe cases do occur. Preventive measures (chemoprophylaxis and insecticide-treated bednets) may be beneficial in this area for all women irrespective of their age or parity.The results suggest that prevalence of IA carried out the study and participated in the statistical analysis and procedures, AHK participated in the statistical analysis, MIE coordinated and participated in the design of the study, statistical analysis and the drafting of the manuscript. All the authors read and approved the final version.


Standard methods for defining clinical malaria in intervention trials in endemic areas do not guarantee that efficacy estimates will be unbiased, and do not indicate whether the intervention has its effect by modifying the force of infection, the parasite density, or the risk of pathology at given parasite density.Three different sets, each of 500 Phase IIb or III malaria vaccine trials were simulated corresponding to each of a pre-erythrocytic, blood stage, and anti-disease vaccine, each in a population with 80% prevalence of patent malaria infection. Simulations considered only the primary effects of vaccination in a homogeneous trial population. The relationships between morbidity and parasite density and the performance of different case definitions for clinical malaria were analysed using conventional likelihood ratio tests to compare incidence of episodes defined using parasite density cut-offs. Bayesian latent class models were used to compare the overall frequencies of clinical malaria episodes in analyses that did not use diagnostic cut-offs.The different simulated interventions led to different relationships between clinical symptoms and parasite densities. Consequently, the operating characteristics of parasitaemia cut-offs in general differ between vaccine and placebo arms of the simulated trials, leading to different patterns of bias in efficacy estimates depending on the type of intervention effect. Efficacy was underestimated when low parasitaemia cut-offs were used but the efficacy of an asexual blood stage vaccine was overestimated when a high parasitaemia cut-off was used. The power of a trial may be maximal using case definitions that are associated with substantial bias in efficacy.Secondary analyses of the data of malaria intervention trials should consider the relationship between clinical symptoms and parasite density, and attempt to estimate overall numbers of clinical episodes and the degree of bias of the primary efficacy measure. Such analyses would help to clarify whether the effect of an intervention corresponds to that anticipated on the basis of the parasite stage that is targeted, and would highlight whether the primary measure of efficacy results from unexpected behaviour in the parasitological and clinical data used to estimate it. Plasmodium falciparum parasites, without these causing any acute illness. It follows that the presence of parasites in a sick person does not necessarily mean that malaria is the cause of the illness. In field trials of novel interventions, estimates of efficacy need to be made using case definitions with high specificity. Otherwise efficacy will be underestimated.In endemic settings malaria usually presents with rather non-specific symptoms, such as fever, and not all sick individuals with malaria parasites are really suffering from clinical malaria. This is because most of the population may be infected with The greater the parasite density in the blood the more reasonable it is to assume that an illness is caused by malaria, so a case definition for clinical malaria for use in a trial can be obtained by defining a parasite density cut-off specific for the surveillance mechanism of choice . The sensitivity and specificity of different parasite density cut-offs can be obtained by modeling the excess risk of fever as a function of parasite density ,2, whereThis approach has been endorsed by the WHO Study Group on Measures of Malaria Vaccine Efficacy for obtaining case definitions for use in pivotal trials of malaria vaccine . EfficacApplying such an algorithm though does not guarantee that efficacy estimates will be unbiased, and does not provide an interpretation of how a vaccine is acting. As secondary objectives of malaria vaccine trials, investigators should be interested also in drawing inferences about whether the vaccine acts in accordance with its design and how it interacts with natural immunity. This paper uses simulations of trials to consider the theoretical performance of this method for different kinds of vaccines, and suggests a range of additional exploratory analyses that can be carried out in order to better understand vaccine action. The simulations consider the likely effects of different kinds of vaccines but the same approach is applicable to the analysis of the clinical impact of any effective intervention against malaria.P. falciparum malaria, a distribution of parasite densities in the population, θc(x), (in the absence of vaccine or in a placebo group) as shown in the thick line Figure Phase IIb or III malaria vaccine trials were simulated assuming the study population to comprise children with an 80% prevalence of Vaccine A: (Pre-erythrocytic vaccine). This vaccine reduces the force of infection by 50%. For simplicity, this is assumed to be reflected in a 50% reduction in the proportion of individuals who are infected across the whole range of parasite densities, and a random sample of 50% of the clinical malaria episodes are assumed to be averted.Vaccine B: . This vaccine reduces parasite densities by 50%, but does not affect the number of individuals who are infected, or the parasite densities at which they become ill.Vaccine C: (Anti-disease vaccine). This vaccine is assumed to have no effect on parasite densities but to lead to an increase in the parasite density at which clinical malaria occurs.For each of these models of vaccination 500 simulated trials were run. Each simulated trial had a standard design with (i) an equal number of placebo and vaccine recipients; (ii) a total of 100 parasitological slides in each arm used to estimate the effect on the parasite density distribution in the population, and (iii) a standardised clinical surveillance to detect fever cases, with a total of 100 cases expected in unvaccinated individuals.Datasets were constructed from these simulations using 19 categories of parasite density. The community parasitaemia data were generated by defining multinomial probabilities for each of the 19 categories based on the data of Figure θc(x), the parasite density distribution in the community  the density in sick individuals  is the parasite density distribution in patients with clinical malaria and λ is the malaria attributable fraction. θs(0), θc(0) are then the frequencies of the uninfected (aparasitaemic) classes, and the relative risk of given parasite density x in sick individuals relative to controls  is the malaria attributable proportion of clinical cases at x, equal to:where s Figure  is givenθm(x). The sensitivity of a cut-off X is then given by:Figure Figure  and the To compare the efficacy in averting clinical episodes that might be estimated in the simulated trials two distinct analyses of all 500 sets of simulated trials were carried out:V(X)/IP(X) in the 500 simulated trials, where where IV(X) is the number of simulated cases in vaccinees, with parasite density>X; and IP(X) is the number of simulated cases in the placebo arm  = IP(X) (significance level α = 0.05).The power of these analyses was then estimated by determining the proportion of the sample of 500 simulated trials that gave significant efficacy as assessed using using binomial likelihood ratio tests (two sided) of the null hypothesis Iθc(x).2. The second analysis sought to estimate the number of clinical malaria cases in each arm of each of the 500 simulated trials, by assigning a probability to each fever case, as a function of parasite density, rather than by using a dichotomous classification. These probabilities were estimated using a latent class model ,11 as prThe parasite density distributions in the community Figure  vary as The distributions of parasite densities in the clinical cases differ among the three vaccines Figure . For allThese differences in parasite density distributions lead in turn to different relationships between incidence of disease and the community parasite density distribution, depending on the action of the vaccine Figure , and henSimilarly, and as a direct consequence of the curves shown in Figure The relative frequencies of malaria cases at different parasite densities Figure  show simIntegration of the curves in Figure x, corresponding to high specificity, the mean efficacy estimate  for vaccines A and C approaches the true efficacy, while for vaccine B (where specificity in the vaccine arm is higher than in the placebo arm) the efficacy is overestimated. The proportion of trials giving statistically significant results /IP(x) where IV(x) is the incidence of cases at or above cut-off (x) in the vaccine arm, and IP(x) the corresponding incidence in the placebo arm. Assuming the specificity (ψ) of the diagnostic cut-off to be the same in both arms then an estimate of E adjusted for the effects of the imperfect case definition is:Analyses of trial data using such parasitaemia cut-offs have generally not quantified the bias that remains. The true efficacy is defined as λ is the attributable fraction in the placebo arm. A potential improvement in efficacy estimates is to thus to estimate λ, and ψ and to use E. If ψ is sufficiently close to unity, then the difference between these two estimates is small.where x , though it should not be so if the assumptions underlying its estimation are correct. The non-linear logistic regression model most widely used for defining the parasitaemia cut-off[Exploratory analyses of the behaviour of a cut-off. This asIt is evident from Figure The most satisfactory alternative to using a single cut-off would probably be to estimate the total number of clinical malaria cases in each arm of the trial by assigning a probability to each fever case, rather than classifying each case dichotomously as above, or below, cut-off. This approach has not so far been used in analyses of clinical trials though it has been proposed as an alternative to the arbitrary choice of a cut-off . It has Such secondary analyses using latent class models, or considering the whole range of possible parasite density cut-offs will also help to identify possible biases in efficacy estimates made using single case definitions, at the same time as analysing the kind of protection. Where multi-centre trials give heterogeneous efficacy estimates, it will be important to examine whether this can be accounted for by differential bias in the primary outcome measurements.In a real trial the reduction in proportion of individuals infected varies over the trial period, depending on the time course of incidence, patterns of treatment with anti-malarial drugs, and on the variation between individuals in exposure to vectors and responses to vaccination. These factors significantly complicate the analysis of relationships between infection and morbidity because, strictly speaking, the comparison should always be between contemporaneous data. This problem is particularly acute if parasites are cleared at the start of the trial, leading to complicated dynamics of infection and disease during the trial follow-up period. The present simulations do not address the implications of sub-patent parasitaemia. This especially complicates analysis of effects of asexual blood stage vaccines because reduction of parasite densities differentially inflates the proportion of false-negative blood slides in vaccinated individuals.It follows that the analyses illustrated in this paper represent considerable simplifications of those that might be carried out in a real trial, where these complicating factors need to be taken into account. Nevertheless, when feasible, it would be logical to carry out secondary analyses corresponding to the different panels in Figure