Current global helminth control guidelines focus on regular deworming of targeted populations for morbidity control. However, water, sanitation, and hygiene (WASH) interventions may also be important for reducing helminth transmission. We evaluated the impact of different potential helminth protective packages on infection prevalence, including repeated treatment with albendazole and praziquantel with and without WASH access. We conducted a cohort study nested within a randomized trial of empiric deworming of HIV-infected adults in Kenya. Helminth infections and infection intensity were diagnosed using semi-quantitative real-time PCR. We conducted a manual forward stepwise model building approach to identify if there are packages of interventions that may be protective against an STH infection of any species (combined outcome) and each helminth species individually. We conducted secondary analyses using the same approach only amongst individuals with no anthelmintis exposure. We used interaction terms to test for potential intervention synergy. Approximately 22% of the 701 stool samples provided were helminth-infected, most of which were of low to moderate intensity. The odds of infection with any STH species were lower for individuals who were treated with albendazole (aOR: 0. 11,95%CI: 0. 05,0. 20, p<0. 001), adjusting for age and sex. Although most WASH conditions demonstrated minimal additional benefit in reducing the probability of infection with any STH species, access to safe flooring did appear to offer some additional protection (aOR: 0. 34,95%CI: 0. 20,0. 56, p<0. 001). For schistosomiasis, only treatment with praziquantel was protective (aOR: 0. 30 95%CI: 0. 14,0. 60, p = 0. 001). Amongst individuals who were not treated with albendazole or praziquantel, the most protective intervention package to reduce probability of STH infections included safe flooring (aOR: 0. 34,95%CI: 0. 20,0. 59, p<0. 001) and latrine access (aOR: 0. 59,95%CI: 0. 35,0. 99, p = 0. 05). Across all species, there was no evidence of synergy or antagonism between anthelmintic chemotherapy with albendazole or praziquantel and WASH resources. Deworming is effective in reducing the probability of helminth infections amongst HIV-infected adults. With the exception of safe flooring, WASH offers minimal additional benefit. However, WASH does appear to significantly reduce infection prevalence in adults who are not treated with chemotherapy. ClinicalTrials. gov, NCT00507221.
The neglected tropical diseases (NTDs) are a group of parasitic and bacterial infections that are associated with substantial global disease and disability, particularly in low income communities. Among the NTDs, helminth infections including schistosomiasis and the soil transmitted helminthiasis (STH) are highly prevalent, infecting over two billion people [1]. Mass drug administration (MDA), or the presumptive treatment of all at risk individuals with preventive chemotherapy, is used to control helminth associated morbidity in endemic areas. In 2001 the World Health Organization (WHO) endorsed MDA as the recommended strategy for controlling STH and schistosomiasis, with a goal of reaching at least 75% of at risk populations and up to 100% of school-aged children [2,3]. The effectiveness of MDA as a control strategy is influenced by the treatment coverage of affected populations, the prevalence and intensity of different helminth species, drug susceptibility and socio-behavioral patterns that influence infection and re-infection rates [4]. In addition, while MDA reduces morbidity by decreasing parasite burden, treatment offers only temporary benefit, as individuals remain at risk of reinfection following treatment. Other strategies, including water, sanitation, and hygiene (WASH) interventions may be needed to reduce the risk of reinfection and ultimately to break transmission of schistosomiasis and STH [5–7]. The presence or absence of WASH, in addition to other social and economic factors, may influence the success of helminth control programs as the intensity of transmission (as estimated by the reproductive number, Ro) is influenced by the survival of free living helminth stages in the surrounding environment [8]. Recent modeling efforts highlight the potential importance of WASH in controlling helminth infections, particularly in high prevalence areas [9,10]. Data from a meta-analysis of water and hygiene protective measures suggest that drinking treated water, soap use, and wearing shoes were associated with approximately 45–60% lower odds of infection [11]. Access to and utilization of sanitation facilities is also associated with significant reductions in the prevalence of all three major STH infections; A. lumbricoides (OR: 0. 54,95% CI: 0. 43–0. 69), T. trichiura (OR: 0. 58,95% CI: 0. 45–0. 75), and hookworm species (OR: 0. 60,95% CI: 0. 48–0. 75) [12]. Despite these associations, data from randomized trials evaluating the impact of WASH interventions have demonstrated minimal or no benefit in reducing STH prevalence or intensity in children [13,14]. However, evaluations of the impact of school-based deworming programs indicate that treatment programs have a larger impact on reducing helminth prevalence in areas with improved sanitation facilities, as compared to areas with unimproved or no sanitation [15]. Integrating WASH and MDA strategies may be a promising approach to eliminating disease transmission, however data are limited [16,17]. One cluster-randomized trial in Kenya found a 44% reduction in the odds of A. lumbricoides infection (but not in other STH species) among children receiving both WASH and MDA, as compared to MDA alone [18]. However, another randomized participatory hygiene and sanitation behavior change intervention trial found no significant difference in helminth infection between the group receiving both WASH and deworming, as compared those receiving deworming alone [19]. Using data from a randomized controlled trial of deworming among HIV infected adults in Kenya, we evaluated associations between WASH access and utilization and helminth prevalence following repeated rounds of treatment with albendazole and praziquantel.
We conducted a retrospective cohort study nested within the Helminth Eradication to delay ART Trial (HEAT) [20]. HEAT was a randomized trial of single-dose albendazole (400 mg) provided every 3 months plus single dose praziquantel (25 mg/kg) provided annually for 2 years to HIV-infected adults. Participants were recruited from HIV clinics at three sites in Kenya (Kisii Provincial Hospital, Kisumu District Hospital, and Kilifi District Hospital) between February 6,2008, and June 28,2010. Individuals were eligible for inclusion if they were 18 years of age or older, were HIV seropositive, were not pregnant at the time of enrollment, and did not meet current criteria for ART initiation (on the basis of documented WHO disease stage and CD4+ cell count within the previous 3 months and a clinical assessment at enrollment). Participants were followed every 3 months for 24 months after enrollment. A single stool sample was obtained from participants after 24 months of follow up. All stool samples were initially examined with a combination of direct microscopy techniques, Kato-Katz and formol-ether concentration by trained laboratory technologists at each of the study sites. Stool aliquots of approximately 1 gram were placed in cryotubes and frozen at −80°C for subsequent DNA extraction and examination at the Leiden University Medical Center (the Netherlands). For this analysis, intensity of helminth infections was assessed by PCR only. Following a bead-beating step, DNA was isolated using DNeasy 96 Blood & Tissue Kit spin columns in accordance with the manufacturer’s instructions (Qiagen, Hilden, Germany) [21,22]. Phocin herpes virus-1 (PhHV-1) was added to the lysis buffer in each sample as an internal control and virus-specific primers and detecting probe were included in each reaction mixture. Two different multiplex real-time PCR detection panels were used for parasite specific DNA detection of STH and Schistosoma: (i) Ancylostoma spp (i. e. detecting both A. duodenale and A. ceylanicum), Necator americanus, Ascaris lumbricoides, and Strongyloides stercoralis, and (ii) Schistosoma spp (i. e. detecting both S. mansoni and S. haematobium DNA without differentiation) and Trichuris trichiura [21]. For the DNA isolation and setup of the PCR reactions a custom-made Hamilton robot platform was used, while amplification, detection and analysis were performed using the CFX real-time detection system (Bio-Rad Laboratories, USA). Negative and positive control samples for each parasite species were included in each PCR run. Fifty PCR amplification cycles were run per sample, with the output expressed as a cycle threshold (Ct). Ct reflects the amplification cycle in which the level of fluorescent signal exceeds background fluorescence and thus species-specific DNA loads in stool samples. For each parasite-specific target, DNA loads were arbitrarily categorized into the following intensity groups, according to previous publications: low (35≤Ct<50), moderate (30≤Ct<35) and high (Ct<30) [23]. In addition to deworming history, four WASH conditions were assessed; access to safe water via access to piped water, purchasing of purified water or treating water independently (filtration, chlorination, boiling, etc), access to a flush latrine or pit latrine in a house or on compound premises, consistent hand washing after using the latrine, and residence in a household in which the floors of the house are made of cement, iron, stone, or timber (i. e. not earthen). Latrines were not identified by improved or unimproved status. Access to these protective WASH conditions were ascertained during longitudinal HEAT surveys. If any of the responses regarding access to WASH resources varied over follow-up, we utilized a participant’s response from the end of the study (when stool samples were collected), or from the preceding three months if not available at study conclusion. Study teams were able to validate reported access to latrines and safe flooring during household visits. Hand washing and safe water access were self-reported by study participants. The primary outcome of interest was the detection of any STH species infection after 24 months follow-up. As numerous studies have found differential effects of both WASH and deworming by specific helminth species, secondary outcomes of interest included the detection of specific species of helminths [18]. Intensity of infection was examined but could not be assessed due to a lack of statistical power and precision. We conducted a manual forward stepwise model building approach to identify the potential package of interventions most protective against a helminth infection of any STH species (combined outcome). Individual sex and age were included as covariates in the forward stepwise model building process due to their hypothesized role as potential confounders in the relationship between WASH access and helminth infection. We did not further adjust for SES as the specific WASH resources of interest lie on the causal pathway between SES and helminth infections and access to these WASH resources is a modifiable characteristic that may influence susceptibility to helminth infections. Multiple imputation using the chained equations (MICE) method was used to address missing values for four of the exposure variables; water treatment status (22% missing), hand washing status (22% missing), safe latrine status (2% missing), and safe flooring status (2% missing). Among individuals not asked about water treatment and hand washing status during surveys, missingness was assumed to be random. Logistic regression was used to impute missing values with ten imputations. Derived estimates from each imputation were combined using Rubin’s methods [24]. We also performed a sensitivity analysis including only complete cases. Estimates from the complete case analysis did not differ qualitatively from those produced with multiple imputation. Therefore, only the effect estimates, 95% confidence intervals (CIs), and p-values derived through imputation are presented. We used logistic regression and a cutoff threshold of p≤0. 1 on the Wald Test as criteria for graduating a variable into the next stepwise model (i. e. branching), or as criteria for removing a variable from a model (i. e. pruning). We started with univariate models that included each independent variable and the outcome. We branched variables that met the cutoff threshold in univariate models into a single multivariate model. After pruning back any variables that did not meet the cutoff threshold, we introduced interaction terms for all independent variable combinations. The purpose of the interaction terms was to identify any potential synergy associated with access to more than one intervention (i. e. a larger protective effect than would be possible with access to one intervention alone). We pruned back any higher level interaction terms that did not meet the cutoff threshold. We then inspected the lower order interaction terms, and pruned back terms that did not meet the cutoff threshold. The branching and pruning stopped once all remaining terms met the cutoff threshold (i. e. equilibrium). Odds ratios (ORs) and their 95% CIs are reported, with significance determined at the alpha = 0. 05 level. We also utilized the manual forward stepwise model building method to identify the optimal package of protective resources relevant to each helminth species. This process was undertaken separately for A. lumbricoides, hookworm species (all identified infections were N. americanus), T. trichiura, S. stercoralis and Schistosoma spp. Finally, we evaluated the package of WASH resources most protective against helminth infections in HIV-infected adults without access to anthelmintic treatment (the HEAT placebo group) using the manual forward stepwise model building method described above. The University of Washington (UW) Human Subjects Review Committee and the Kenya Medical Research Institute (KEMRI) Ethical Review Committee approved the HEAT study protocol and the trial was registered (ClinicalTrials. gov, number NCT00507221). Study participants were adults who provided written consent in their preferred language (Kiswahili, Kisii, Luo, Giriama, or English) or, if unable to give written consent, provided oral consent in the presence of a witness and confirmed by thumbprint on HEAT study consent forms. Witnesses also signed the study consent forms.
Of the 740 individuals who participated in HEAT, stool samples were available from 701 individuals. These individuals were predominately young, 44% were 25–34 years old, female (78%) and socio-economically disadvantaged (42% earned less than 2000 Kenyan shillings per month (approximately $20 U. S. dollars). Individuals enrolled in the HEAT study were relatively immunocompetent; median CD4+ cell count was 517 cells/mm3 (interquartile range, IQR: 430–700 cells/mm3) and median viral load was 4. 2 log10 copies (IQR: 3. 5–4. 8 log10 copies) (Table 1). Exactly half (50% (n = 348) ) of the participants received albendazole and praziquantel in the 6 months preceding stool collection and half (n = 353) received placebo. Nearly 60% (n = 418) of the participants reported access to safe or treated drinking water and 56% (n = 393) reported consistent handwashing after using the latrine. Latrines were accessible in the homes or on the compounds of 66% (n = 480) of study participants and 46% (n = 325) lived in homes with safe, non-earthen flooring. Some of the participants (n = 59,8%) had access to deworming treatment and all of the protective WASH resources. Only 6 individuals (0. 9%) of the participants reported no protective WASH access of any kind. In total, 152 helminth infections were detected amongst 137 infected individuals using real-time PCR, including: 21 A. lumbricoides, 60 N. americanus, 43 Schistosoma spp. , 8 S. stercoralis, and 20 T. trichiura infections. There were 96 STH infections detected, none of which were Ancylostoma spp. (Table 2). When evaluating intensity of infection by qPCR, the majority of hookworm, A. lumbricoides, and T. trichiura infections were of moderate infection intensity while the majority of S. stercoralis and Schistosoma infections were of low intensity. S. stercoralis had the highest percentage of high intensity infections of any of the helminth species (25%), while T. trichiura had the lowest percentage of high intensity infections (5%) (Table 3). During the stepwise model building process pruning and branching steps were undertaken to derive the package of potential interventions most protective against any STH infection (combined outcome). Only two of the protective interventions remained in the final model: deworming treatment and safe flooring. The odds of infection with any STH species was lower for individuals who were treated relative to those who were not (aOR: 0. 11,95% CI: 0. 05,0. 20, p<0. 001). The odds of infections with any STH species was also lower for individuals with access to safe flooring relative to those without (aOR: 0. 34,95% CI: 0. 20,0. 56, p<0. 001) (Table 4). All interaction terms were pruned out of the model, indicating no statistical synergy (or antagonism) across interventions. The same process was undertaken to derive the most protective package of interventions for each helminth species individually. Treatment (aOR: 0. 03,95% CI: 0. 01,0. 11, p<0. 001), safe flooring (aOR: 0. 27,95% CI: 0. 14,0. 52, p<0. 001) and latrine access (aOR: 0. 51,95% CI: 0. 29,0. 92, p = 0. 03) were included in the potential N. americanus intervention package (Table 4). Only treatment was associated with reduced probability of infection with A. lumbricoides (aOR: 0. 32,95% CI: 0. 11,0. 88, p = 0. 03), T. trichiura (aOR: 0. 11,95% CI: 0. 02,0. 46, p = 0. 003) and Schistosoma sp. (aOR: 0. 30,95% CI 0. 14,0. 60, p = 0. 001). Interestingly, handwashing was associated with an elevated probability of Schistosoma sp. infection (aOR: 3. 14,95% CI: 0. 83,11. 85, p = 0. 09). No interventions were associated with reductions in S. stercoralis infection. In the absence of anthelminthic treatment, the most protective package for any STH infection included safe flooring (aOR: 0. 34,95% CI: 0. 20,0. 59, p<0. 001) and latrine access (aOR: 0. 59,95% CI: 0. 35,0. 99, p = 0. 05) (Table 5). For the specific outcome of N. americanus, safe flooring (aOR: 0. 25,95% CI: 0. 13,0. 50, p<0. 001) and latrine access (aOR: 0. 47,95% CI: 0. 26,0. 86, p = 0. 01) appeared most protective. For A. lumbricoides, the most protective package not including anthelmintics contained safe water only (OR: 0. 37,95% CI: 0. 12,1. 12, p = 0. 08). No intervention was effective at reducing the probability of T. trichiura infection in the absence of anthelminthics. Consistent handwashing was associated with an increased risk of Schistosoma sp. infection in the absence of anthelmintic therapy (OR: 3. 62,95% CI: 0. 78,16. 92, p = 0. 10). Finally, latrine access appeared to reduce the probability of infection with S. stercoralis in the absence of treatment (OR: 0. 13,95% CI: 0. 01,1. 15, p = 0. 07). Across all species, interaction terms were pruned out of the models, indicating no statistical synergy (or antagonism) across interventions. We assessed the pairwise correlation between the independent variables in order to understand if multicollinearity was affecting the variance in the models, and thus causing some independents variables to appear statistically insignificant and drop out of the stepwise model building process. Correlation appeared to be mild, ranging from -0. 05 (treatment and safe water) to 0. 17 (safe flooring and toilet access). We also performed a sensitivity analysis including only complete cases. Estimates from the complete case analysis did not differ qualitatively from those produced with multiple imputation. Therefore, only the effect estimates, 95% CIs, and p-values derived through imputation are presented.
Access to WASH is unequivocally essential, it is a human rights necessity and a hallmark of the Sustainable Development Goals. However evidence supporting the additive benefit of integrated deworming and WASH strategies has been mixed, in part due to the logistical and ethical challenges surrounding the design and implementation of large randomized WASH studies [43]. In this study, anthelmintic treatment was shown to be highly effective in reducing the probability of helminth infections. WASH resources, with the exception of safe flooring and latrine access, did not appear to provide substantial additive benefit to chemotherapy. However, among individuals not receiving chemotherapy, there was clear benefit of WASH in reducing the probability of helminth infections. Given the complexity of integrating multisectorial approaches to disease control [44], researchers and NTD programs should carefully consider if and how pursuing integrated chemotherapeutic and WASH strategies may influence capacity to deliver high quality interventions and achieve targeted outcomes.
More than 2 billion people are infected with soil transmitted helminthiasis (STH) and schistosomiasis globally. In addition to deworming with albendazole and praziquantel, water, sanitation, and hygiene (WASH) may be needed to reduce the risk of helminth reinfection and ultimately to break transmission. However evidence on the effectiveness of integrated deworming and WASH programs are mixed. Using data from a randomized controlled trial of deworming among HIV-infected adults in Kenya, we evaluated the associations between different potential packages of deworming and WASH interventions with helminth prevalence. We also aimed to understand if there was a benefit to accessing both WASH and deworming (i. e. synergy). Our findings indicate that deworming treatments were effective in reducing the probability of infection with most helminth species. Of the WASH conditions assessed, safe flooring and latrine access significantly reduced the probability of helminth infections among adults with access to treatment. However WASH may play a more prominent protective role among individuals without access to deworming treatments. These findings also suggest minimal synergistic benefit of coordinated anthelmintic chemotherapy and WASH in this population. These findings have important implications for adult populations who are currently not targeted by deworming campaigns.
schistosoma
invertebrates
medicine and health sciences
helminths
hookworms
parasitic diseases
animals
health care
necator americanus
ascaris
ascaris lumbricoides
sanitation
strongyloides stercoralis
public and occupational health
strongyloides
necator
helminth infections
environmental health
eukaryota
nematoda
biology and life sciences
organisms
Combined effectiveness of anthelmintic chemotherapy and WASH among HIV-infected adults