Formerly known as the Malaysian hunter gatherers, the Negrito Orang Asli (OA) were heavily dependent on the forest for sustenance and early studies indicated high prevalence of intestinal parasitism. Initiation of a redevelopment program in the 1970s aimed to demarginalize the OA was expected to reduce soil transmitted helminth (STH) infections. Gradually, the OA were relocated to new resettlement areas at the peripheries. The aim of this study was to compare STH infections between Negritos who are still living in the inland jungle with those living in resettlements. A total of 416 Negrito participants were grouped into two categories of communities based on location; Inland Jungle Villages (IJV); and Resettlement Plan Scheme (RPS). Iodine wet mount, formalin-ether sedimentation, modified Trichrome and modified Ziehl-Neelsen staining and Kato-Katz methods were performed on stool samples. A questionnaire was used to collect information regarding demographic, socioeconomic, environmental and hygiene behaviors. Prevalence of STH was significantly higher in IJV (91. 3%) versus RPS (83. 1%) (P = 0. 02). However, the percentage of individuals with severe intensity of Trichuris trichiura infections was significantly higher in the RPS (17. 2%) compared to IJV (6. 5%) (P = 0. 01). Severe Ascaris lumbricoides infection was observed at 20. 0% amongst RPS Negritos and 15. 0% amongst IJV (P = 0. 41). Whilst for hookworm infection, both prevalence and individuals with moderate to severe infections were higher in the IJV (26. 2%, 41. 0%) versus RPS (18. 7%, 24. 0%) (P values = 0. 08,0. 09), accordingly. The prevalence other intestinal parasitic infections (e. g. Entamoeba sp. , Blastocystis and flukes) was also higher in IJV versus RPS. Apart from poor hygienic behaviors as significant risk factors in both communities, low socio-economic status was highly associated with STH infections in RPS (P<0. 001) but not significantly associated in IJV. The findings showed that ex situ development plan by RPS has not profoundly contributed to the STH reduction among the OA. Conversely, burden rate of T. trichiura infections increased due to their extreme poverty and poor hygienic behaviors. Here, we are suggesting biannual mass albendazole intervention (triple dose regimens in RPS, but a single dose in IJV) and community empowerment to both communities. For a long-term and better uptake, these strategies must be done together with the community input and participation, respecting their traditional customs and accompanied by recruitment of more OA people in the health-care taskforce.
Cultural, socio-economic and environmental changes affect the pattern of diseases and health persistence within a population [1]. According to palaeoparasitology history, intestinal parasites, particularly soil-transmitted helminths (STH) had co-evolved together with humans since the very beginning, as was proven by the discovery of the parasites in an ancient fecal sample [2]. As time passed, the colonization of intestinal parasites has declined tremendously in certain parts of the world, greatly influenced by the rapid improvement of socio-economic status and sanitation standards, as seen in developed nations [3]. In contrast, however, owing to the lack of proper sanitation and good hygiene practice, intestinal parasitic infections (IPI) are still afflicting a majority of the deprived and underserved peoples, for example the indigenous populations in low- and middle-income countries [4,5]. In Malaysia, the Orang Asli (OA) indigenous (which means the ‘original people’ or ‘the first people) population has experienced a state of transition between hunter-gatherer lifestyles with strong adherence with the tropical rain forest towards modernity. The transition took place since the initiation of a redevelopment program among OA communities in 1970s by the Malaysian government, with the aim to demarginalize the OA [6,7]. The program was primarily conducted by improving existing OA villages (in situ development) and initiating resettlement plans (Rancangan Pengumpulan Semula or RPS) (ex situ development). Under the RPS program, the OA were regrouped and relocated to new resettlements at the peripheries or near township areas with the aim to improve their health by having better access to health-care facilities, increasing their socio-economic status and education opportunities. Basic facilities such as housing, electricity and water supply, and schools were provided. Customary cultures such as foraging, hunting and subsistence cropping were gradually replaced by cash crop agriculture (e. g. palm oil or rubber plantations). These RPS communities consequently developed a closer contact with other mainstream communities (e. g. the Malay community) [6,7]. In 2011, the fraction of the OA communities that have been relocated under the RPS program was 63. 0% [8,9]. On the other hand, some tribes of OA still live and remain in the inland within the forest areas (37. 0%) and still prefer the foraging and gathering lifestyles despite provision of basic infrastructure in their villages (in situ development) [7,9]. While the transition towards modernity by the rapid growth of socio-economic advancement has shown significant reduction of STH in the general population, such improvement is negligible among the OA communities [10,11], since STH infections are still highly endemic [12–14]. Given these contrasting findings, the pre-assumptive idea that demarginalization and redevelopment among OA lead to a better standard of living and consequently facilitate the reduction of intestinal parasitism among this community need to be reevaluated [10,15]. While most of the prevalence studies highlighted low household income and sanitary behavior as the significant risk factors for STH infections among OA [12,16,17], very few focused on the effect of demarginalization and resettlement on the infections. Therefore, our ultimate objective is to address the latter aspect, which could be achieved primarily by comparing the findings from two different OA communities from similar tribes which have different environment and ecological settings. In the present study, from three OA tribes; Senoi, Proto-Malay (or Aboriginal-Malay) and Negrito [18,19], the Negrito was chosen as our study population based on three aspects; the tribe is the earliest inhabitants in Peninsular Malaysia (~50,000 years ago) [20], have the least population (~5000) currently and are known as hunter gatherers [19]. Moreover, except for a few reports available on the Negritos, the majority of the STH infection studies were conducted mainly among other tribes, namely the Senoi and Proto-Malay due to their larger population sizes [16,21,22]. Given these factors, we believed the Negritos provide a good model in determining how transition towards demarginalization influences the pattern of STH infections that traditionally inflict them [21]. Here, we report a finding pertaining on the current pattern of intestinal parasitism, STH infection intensity and associated risk factors by comparing the Negritos who are still living in the inland jungle (in situ improvement) and those who have undergone resettlement (RPS ex situ development) at the peripheries of towns.
This study received ethical approval from both the Ethics Committee of the Universiti Teknologi MARA (reference no: 600- IRMI (5/1/6) and National Medical Research Register (NMRR), Ministry of Health, Malaysia (NMRR-17-3055-37252 (IIR). Permission to conduct the study was obtained from the Department of Orang Asli Development (JAKOA) [Reference no: JAKOA/pp. 30. 052J1d9 (29) ]. A cross-sectional survey with a convenient, snowball sampling method was carried out from May 2016 to April 2017 in eight villages comprising all six Negrito sub-tribes; Jahai, Bateq, Kintak, Lanoh, Kensiu and Mendriq. The villages were selected based on the list of Negrito villages permitted by JAKOA, by further invitations from headman of the tribes, and after agreement and willingness of participation by each headman and members of their village. These villages are all located in the northern states of Peninsular Malaysia (S1A Fig). Prior to sample collection, visits and meetings were conducted at the selected villages. A short briefing was held before each sampling session, during which the purpose and method of the study were clearly informed to prospective participants. Those who agreed to participate either signed or thumb-printed informed consents, witnessed by the accompanying JAKOA officer (s). Permission and consent via signature from legal representatives were obtained for participants below 12 years old. Participants were informed of their rights to withdraw from the study at any time without prior notice. For the purpose of comparison, the villages were grouped into two categories based on location and types of development; ‘Inland Jungle Villages (IJV) of in situ improvement’ (S1B Fig) and ‘Resettlement Plan Scheme (Rancangan Pengumpulan Semula or RPS) of ex situ development’ (S1C Fig). The IJV community refers to the group of Negritos staying in inland tropical rain forest (as in the case of Lanoh, Kintak and some groups of Batek and Jahai) with some still practicing hunting and gathering lifestyles. Each village has a population size from as low as 50 to as high as 300 individuals and were not easily accessible, except by boat and four-wheel-drive vehicles. Despite being officially recognized by the government, the villages lacked basic facilities, some lacking electricity due to their very remote locations. Because contact with outsiders was minimal, their transition towards demarginalization is regarded as slow. Meanwhile, the RPS community is defined as groups of Negritos which have gathered and relocated into designated settlements at the peripheries of towns (these Kensiu, the Mendriq and some groups of Batek and Jahai) by JAKOA. Each resettlement has a population size of between 170 and 450 people. Their locations are near the road, easily accessible and their communities are provided with better housing, piped water supply, electricity, education and health-care facilities. Their transition towards assimilation and demarginalization with mainstream populations within the country is faster. A detailed summary of the sub-tribes and villages included in this study is shown in Table 1. The sample size for this study was determined according to the formula by Wang and Chow [23]. The calculation was performed using PS Power and Sample Size Calculation Software for two proportions with the following parameters; 5% level of significance at 95% confidence interval, 80% power of study and anticipated STH infection prevalence as follows: 81. 3% among RPS [16] and 96. 5% among IJV Negritos [21]. By adjusting for 25% attrition rate, the minimum number of participants required in this study was estimated at 160 (80 participants from each population category). We managed to voluntarily recruit a total of 430 Negritos in this study. However, only 416 of these (representing approximately 8. 3% of the entire Negrito population in Malaysia) which had paired stool samples and datasets were included in the analyses (Table 1). Out of the 416 participants, 149 (35. 8%) Negritos were categorized under IJV and the remaining 267 (64. 2%) belonged to RPS. Interviews were conducted by two trained research assistants in the Malay language based on a pretested questionnaire. The questions were mainly on participants’ demographic data (i. e. sub-tribes, age, gender and number of family members), socio-economic and educational status (i. e. household monthly income, occupational status and level of education), general sanitation and environmental conditions, which include source of water supply and availability of latrine system (pour/flush toilet or pit latrine). The source of water supply was categorized into treated (government piped water) and untreated (river, lakes, mountain water, etc.). Other questions were on behavioral risks (personal hygiene) such as habit of washing hands after defecation or after playing/in contact with soil, indiscriminate defecation (preference to defecate anywhere without any specific location or latrine, usually in the bushes or near the river), and closer contact (own or always playing) with domestic animals (commonly dogs and cats). Finally, we also asked about their previous history of anti-helminthic treatment; whether they have taken any anti-helminthic drug (prescribed by medical personnel or during a deworming program) or none at all during their entire life. For young children, the information was collected by interviewing their parents or guardians in their home setting. Those with a history of antibiotic or anti-helminthic treatment in the previous 3 months before the commencement of the study were excluded from this study. Pre-labelled capped stool containers were given to the participants a day before stool sample collection along with instruction on correct placement of their stool into the containers. Stool samples were collected without age discrimination, the following morning between 8 and 11 am. Each stool sample was divided into three aliquots [fresh, 10% formalin (only a few drops of formalin so that the samples do not became liquefied), and 2. 5% potassium dichromate], sealed with zip-locked plastic bag, kept in cool boxes during transportation, transferred to a laboratory in the Institute for Medical Molecular Biotechnology (IMMB), Universiti Teknologi MARA within 6 to 12 hours of duration and stored at 4 °C before examination. The laboratory examination was conducted using different methods as soon as possible upon the arrival of samples to the laboratory. The samples were first processed using a standard direct wet smear and formalin–ether sedimentation [25] to detect the presence of ova or cyst in the stool samples. A modified Kato–Katz method was then applied to quantify the burden of STH infections within 4 hours of reaching the laboratory. Duplicate 41. 7 mg Kato–Katz thick smears were prepared from each fresh and formalin-fixed sample (the preservative was discarded first), and were read twice after 15 minutes by two different technologists. The corresponding results were compared and in cases of significant inconsistencies (positive vs. negative and/or difference in egg counts of more than 20%), the slides were re-examined. The total number of eggs was multiplied by a factor of 24 (number of eggs × 24) to produce the number of eggs per gram (epg) of feces. The lower limits of moderate and heavy infections were 5,000 and 50,000 epg for A. lumbricoides; 1,000 and 10,000 epg for T. trichiura; and 2,000 and 4,000 epg for hookworm [26,27]. Modified Wheatley Trichrome (according to manufacturer’s protocols—Thermo Scientific Remel Trichrome Stain Kit) and modified acid-fast staining techniques (adapted from CDC DPDx stool specimens—staining procedure) were also incorporated in this study to facilitate detection and provide accurate identification of intestinal protozoa. Stool samples were considered positive if the intestinal parasites were detected by any of these methods. Data were double-entered, cross-checked and merged into a single data set in a Microsoft Office Excel 2010 document. Statistical analysis was performed using IBM SPSS version 20 (SPSS, Chicago, IL, USA). Demographic data, socio-economic, environmental and behavioral factors were treated as categorical variables. For the number of family members, we categorized them into <7 members and >7 members as it was generally common among OA to have large family sizes. Monthly household income was categorized into ~ <USD 125 and >USD 125 because more than half of the studied populations have a gross monthly income of less than USD 125. Descriptive statistical analyses were performed to obtain a clear understanding of the population. Frequency, percentages (rate), measures of central tendency (means, medians and other percentiles) and dispersion (standard deviations, ranges) were computed to describe the characteristics of the studied population. Shapiro–Wilk statistic coupled visual diagrams (Q–Q Plots and histogram) were used for assessing the normality of the scores. P-value of more than 0. 05 indicates normality. For normally distributed data, arithmetic means with standard deviations (SD) or standard error of the mean (SE) were presented. For data not normally distributed, medians with data range (interquartile, IQR) were used. Pearson’s chi-squared test (χ2) or Fisher’s exact test were used to determine the independence between categorical independent variables and the outcome. The same test was used to measure the association of STH infections with the test variables. An independent t test was calculated by analyzing means from two independent continuous variables. For STH risk measurements, odds ratio (OR) and 95% confidence interval (CI) were analyzed by univariate logistic regression analysis. All variables with P-value less than 0. 25 in univariate analysis were accepted for further multivariate (backward stepwise) logistic regression [28]. Model fitness was determined by the Hosmer–Lemeshow statistic. A P-value of less than 0. 05 (P < 0. 05) was taken as significant.
A total of 416 Negritos (149 IJV and 267 RPS) participated in this study with ages ranging from 2 to 64 years old. By age groups, the majority of the respondents (47. 1%) were primary school children aged between 7 and 12 years old. The gender ratio was 1: 1. Table 2 shows the demographic profiles, socio-economic, environmental conditions and behavior characteristics in our general studied participants and according to the categories (IJV versus RPS). With regards to the IJV Negritos, even though their locations are far from the township areas, they had significantly better socio-economic status (40. 9% with a household income >USD 125) compared with those living in the RPS community (29. 6%). However, about 20. 4% children were not enrolled in school with only some parents sending their young children to the provided boarding school for OA children due to distance factor. In terms of hygiene behavior, walking barefoot was common and they also preferred to defecate indiscriminately (open defecation without any specific locations or at any designated latrines) mainly at the river and bushes. Moreover, about 50. 3% had previously never taken or been prescribed with any anti-helminthic treatment (AHT). Despite better development in the RPS community, the majority of the houses did not have electricity supply due to their inability to settle outstanding bills. Similar situations were seen with their piped water supplies. As a consequence, rivers (54. 7%) remained the main source of water supply, especially for bathing and washing. A single latrine was commonly available in the RPS community, but the facility was not fully utilized because most of them still preferred to defecate indiscriminately as practiced in IJV. Education attainment was better in RPS, with most children being enrolled in school. However, not many of their adolescents continued or completed secondary school. Regarding drug treatment, they were highly exposed, with 74. 9% having taken at least one dosage of AHT due to easier access to health-care facilities and periodic visits by medical personnel. Of the 416 participants, the overall prevalence of IPIs was 87. 0%, with 358 (86. 1%) found to be infected with at least a single species of STH and 106 (25. 5%) with at least one species of intestinal protozoa (Table 3). By community categories, the prevalence of STH infections was found to be significantly higher in the IJV community compared to RPS (P = 0. 02). The most dominant STH species was T. trichiura (IJV: 72. 5%; RPS: 71. 9%), followed by A. lumbricoides (IJV: 40. 3%; RPS: 44. 9%) and hookworm (IJV: 26. 2%; RPS: 18. 7%). The prevalence of polyparasitism (having more than one type of infection) was slightly higher in the IJV community than in the RPS community but not significant. The percentage of participants positive with Entamoeba sp. , Blastocystis sp. and other types of parasites (flukes, tapeworms, unidentified eggs and cysts) was greater in IJV (P = 0. 01) indicating higher diversity of parasitic infections among the IJV community. Our findings showed that Negritos who live in IJV had 2. 1 times greater risks (95% CI: 1. 1,4. 1; P = 0. 02) to be infected with STH than RPS. We then compared the associations between STH infections with demographic, socio-economic and environmental circumstances, and personal hygiene behavior variables (Table 5). In the IJV community, univariate analysis indicated significant association between children aged <12 years old (P = 0. 03), persons who defecated indiscriminately (commonly at the bushes) (P = 0. 04), walking barefoot (P = 0. 003) and had close contact with domestic animals (P = 0. 002) with the presence of STH. Meanwhile in RPS, the Negritos with low household monthly income (<USD 125) had 3. 9 times greater risks (P <0. 001) to be infected with STH. Other significant risk factors in RPS communities were related to poor sewage disposal system (P = 0. 01) and bad hygiene behaviors, such as not washing hands after playing or contact with soil (P<0. 001), not washing fruits and vegetables before eating (P = 0. 03) and closer contact with animals (P< 0. 001). Table 6 shows the result of further multivariate models for final significant predictors for STH infections in both the IJV and RPS communities. For the IJV community, only three factors; closer contact with animals, indiscriminate defecation, and walking barefooted (P values: 0. 01,0. 03 and 0. 04, accordingly) which were all grouped under poor hygiene behaviors, remained as the significant predictors. Goodness-of-fit by the Hosmer–Lemeshow test indicated the model fits the data well (χ2 = 2. 20; df = 4, P = 0. 69). With regards to RPS community, from eleven variables, five factors were retained; low monthly income of less than USD 125 (P < 0. 001), improper sewage disposal (P = 0. 03), poor hygiene behavior of not washing hands after playing with soil (P = 0. 01), indiscriminate defection (0. 04) and those with a closer contact with animals (or have domestic animals in their household) (P < 0. 001) had a higher prevalence rate of STH than their counterparts with STH infections (Hosmer–Lemeshow test: χ2 = 5. 83, df = 7; P = 0. 56).
There are a few limitations that need to be considered while interpreting the present findings. Firstly, the findings were based on one time point collection within a certain period without being able to identify the relationship of current infection with previous and future infections. Secondly, the study population was quite small and represented only 8. 3% of the total Negrito population. Therefore, it may not reflect the community of OA as a whole. Thirdly, the sampling was based on convenient, snowball method and this may provide some biased outcomes, as the sampling is not random. Nevertheless, the sampling approach was the most appropriate and feasible considering the challenges and strict procedures to recruit the OA participants, especially in the IJV communities. In addition, the prevalence of S. stercoralis could be underestimated because all the methods used have a low sensitivity for this particular parasite. Despite a slight reduction of intestinal parasitism in the RPS, the ex situ development plan has not profoundly contributed to a positive impact on the status of helminth infestation among the OA. In fact, the burden of T. trichiura was more intense due to further poverty, adoption of similar poor hygienic behaviors and lack of proper sanitation. Nevertheless, the concept of RPS for demarginalization and consequently reduction of STH endemicity, can still be further improved taking into consideration holistic development of proper sanitation and socio-economic improvement, biannual mass deworming programs, and more importantly coupled with health educations strategies to change mindsets in both RPS and IJV communities. For long-term intervention and better uptake, these strategies must inclusive, with the participation and empowerment of the OA of the respective community, respecting their traditional customs and accompanied by recruitment of more OA people in the health-care taskforce. Importantly, the increased involvement of OA people in policy-making and political affairs which are related to the changes of ecological, social and economic drivers among them may indirectly improve their health and consequently reduce the burden of helminth infections. Otherwise, the malady among them will remain unchanged and unsolved, increasing the cost of economic burden in controlling these infections.
Pattern of diseases in a community are associated with changes of culture, socio-economic and environmental conditions. In Malaysia, while transition towards modernity by socio-economic development has shown significant reduction in intestinal parasitism in the general population, no significant difference was observed among the Orang Asli (indigenous) communities. Nevertheless, since the 1970s, the Malaysian government has initiated the Resettlement Plan Scheme (RPS) to improve health, socio-economic status and education opportunities of the OA. Known as hunter gatherers, the Negritos represent a good model to study the effects of living conditions transition on intestinal parasitism. Like other tribes, they are also undergoing the transition from foraging and gathering practices towards demarginalization primarily by resettlement. Thus, the present study aims to evaluate STH infections in two categories of Negritos; (i) Inland Jungle Villages (IJV) communities, living in the interior forested areas and (ii) the Negritos who have been gathered and relocated to designated settlements closer to towns (RPS). A study to compare the current pattern of STH profiles in terms of prevalence and intensity of infection together with their associated risk factors among these two categories of communities was conducted. Since STHs are still plaguing the OA communities, the information gathering in the present study will be crucial for customizing a cost-effective deworming program involving selection of drug dosages, frequency of administration, type of modalities and most importantly community inclusion and empowerment programs through health education.
invertebrates
medicine and health sciences
ecology and environmental sciences
water resources
helminths
tropical diseases
hookworms
parasitic diseases
animals
physiological processes
ascaris
ascaris lumbricoides
neglected tropical diseases
medical risk factors
natural resources
epidemiology
defecation
helminth infections
eukaryota
physiology
nematoda
biology and life sciences
soil-transmitted helminthiases
organisms
Prevalence, intensity and associated risk factors of soil transmitted helminth infections: A comparison between Negritos (indigenous) in inland jungle and those in resettlement at town peripheries