Soil-transmitted helminth reinfection after drug treatment: a systematic review and meta-analysis

Assessment of health education products aimed at controlling and preventing helminthiases in China

BACKGROUND

Helminthiases have placed a huge burden of disease on the population in China. However, widespread control activities have led to significant achievements. As health education has been widely disseminated and plays an important role in the control and elimination of these diseases, we collected health education products aimed at controlling and preventing helminthiases in China. We analyzed their characteristics and assessed their quality.

METHODS

Firstly, health education products aimed at controlling and preventing helminthiases were collected from a diverse range of organizations. Secondly, the expert brainstorming and Delphi methods were applied to establish an evaluation system, which was then used to assess the collected products systematically. Those deemed excellent were awarded. Characteristics - including type, source, targeted disease(s), targeted population, and languages - of the collected products and the awarded products were presented here.

RESULTS

In total, 96 health education products on helminthiases were collected from 53 organizations. Most products belonged to either the graphic design (47) or daily-use (24) category. Seventy were collected from Centers for Disease Control and Prevention and 20 from institutes or control stations of parasitic diseases, primarily at the provincial and county levels. Regarding disease targets of the products, 67 focused on a single helminthiasis, 25 on multiple helminthiases, and the remaining four on non-specific diseases. Of the 67 single helminthiasis-focused products, most targeted schistosomiasis (37), followed by echinococcosis (16). The majority of products (79) targeted the general population, while 11 targeted students specifically. Regarding languages, 86 products were only in Chinese, while the other ten were in both Chinese and the minority languages of China. Out of these ten products, one targeted schistosomiasis and the other nine targeted echinococcosis. Thirty-four products were awarded. The characteristics of the awarded products were similar to those of the collected products.

CONCLUSIONS

A diverse range of health education products have been designed and applied for the prevention and control of helminthiases in China. Many products have good features such as specifying the targeted diseases and populations. However, there are significant gaps in terms of both the quantity and quality of products pertaining to some of the diseases. Experiences from the awarded products could be drawn upon to design more products aimed at a range of different helminthiases.

Risk factors for infection with soil-transmitted helminths during an integrated community level water, sanitation, and hygiene and deworming intervention in Timor-Leste

Water, sanitation and hygiene interventions have been advocated as important complements to deworming programs to improve soil-transmitted helminth control. Evidence for the impact of water, sanitation and hygiene on soil-transmitted helminth infections is mixed, and based mainly on cross-sectional studies. In this study, we assessed associations between individual- and household-level water, sanitation and hygiene variables and soil-transmitted helminth infections, using data collected during the 2 year follow-up study period of the WASH for WORMS randomised controlled trial in Timor-Leste. Data were collected across four surveys, conducted at 6 monthly intervals in 23 communities. We analysed water, sanitation and hygiene and sociodemographic variables as risk factors for infection with Necator americanus, Ascaris spp., and undifferentiated soil-transmitted helminth infection, using generalised linear mixed models to account for clustering at community, household and participant levels. Water, sanitation and hygiene risk factors were examined both concurrently and with a 6 month lag period that coincided with the most recent deworming. The analysis included 2333 participants. Factors associated with N. americanus infection included age group, male sex (adjusted odds ratio (aOR) 3.1, 95% confidence interval (CI) 2.4-4.2), working as a farmer (aOR 1.7, 95% CI 1.2-2.4), and completing secondary school or higher (aOR 0.29, 95% CI 0.16-0.53). Risk factors for Ascaris spp. infection included age group, living in a dwelling with more than six people (aOR 1.6, 95% CI 1.1-2.3), having a tube well or borehole as the household water source (aOR 3.7, 95% CI 1.3-10.8), and using a latrine shared between households 6 months previously (aOR 2.3, 95% CI 1.2-4.3). Handwashing before eating was protective against infection with any soil-transmitted helminth (aOR 0.79, 95% CI 0.65-0.95). In the context of regular deworming, few water, sanitation and hygiene-related factors were associated with soil-transmitted helminth infections. Future research examining the role of water, sanitation and hygiene in soil-transmitted helminth transmission is required, particularly in low transmission settings after cessation of deworming. Identifying improved indicators for measuring water, sanitation and hygiene behaviours is also a key priority.

Results of a national school-based deworming programme on soil-transmitted helminths infections and schistosomiasis in Kenya: 2012-2017

Background

Soil-transmitted helminth (STH) and schistosome infections are among the most prevalent neglected tropical diseases (NTDs) in the world. School-aged children are particularly vulnerable to these chronic infections that can impair growth, nutritional status and cognitive ability. Mass drug administration (MDA) delivered either once or twice annually is a safe and effective approach recommended by the World Health Organization (WHO) to reduce worm burden. In 2012, Kenya began a national school-based deworming programme (NSBDP) aimed at reducing infection and associated morbidity. The change in prevalence and intensity of these infections was monitored over five years (2012–2017). Here, we present the changes in STH and schistosome infections between baseline and endline assessments, as well as explore the yearly patterns of infection reductions.

Methods

We used series of pre- and post-MDA intervention, repeat cross-sectional surveys in a representative, stratified, two-stage sample of schools in 16 counties of Kenya. The programme consisted of two tiers of monitoring; a national baseline, midterm and endline surveys consisting of 200 schools, and pre- and post-MDA surveys conducted yearly consisting of 60 schools. Stool and urine samples were collected from randomly selected school children and examined for STH and schistosome infections using Kato-Katz and urine filtration techniques respectively.

Results

Overall, 32.3%, 16.4% and 13.5% of the children were infected with any STH species during baseline, midterm and endline assessment, respectively, with a relative reduction of 58.2% over the five-year period. The overall prevalence of S. mansoni was 2.1%, 1.5% and 1.7% and of S. haematobium was 14.8%, 6.8% and 2.4%, respectively, for baseline, midterm and endline surveys. We observed inter-region and inter-county heterogeneity variation in the infection levels.

Conclusions

The analysis provided robust assessment of the programme and outlined the current prevalence, mean intensity and re-infection pattern of these infections. Our findings will allow the Government of Kenya to make informed decisions on the strategy to control and eliminate these NTDs. Our results suggest that complimentary interventions may have to be introduced to sustain the chemotherapeutic gains of MDA and accelerate attainment of elimination of these NTDs as a public health problem in Kenya.

Electronic supplementary material

The online version of this article (10.1186/s13071-019-3322-1) contains supplementary material, which is available to authorized users.

The Effectiveness of Triple Dose Albendazole in Treating Soil Transmitted Helminths Infection

Soil transmitted helminths (STH) infection is a major health problem in tropical countries such as Indonesia. Albendazole is an effective and widely used anthelmintic agent to treat STH; however, it is not effective towards T. trichiura and its effectiveness varies between populations. Hence, we conducted a study to determine the effectiveness of triple dose albendazole in children of Perobatang village, Southwest Sumba, Indonesia. A pre-post study was carried out in Perobatang village on July 2016. Children aged 1-15 years old were enrolled in the study and asked to collect stool samples which were then examined using Kato-Katz method. The children infected with STH were given albendazole 400 mg for three consecutive days. From 246 subjects examined, 192 (78%) were positive for any STH consisting of T. trichiura (64%), A. lumbricoides (60%), and hookworms (10%). After treatment, the prevalence of STH decreased significantly (McNemar test, p<0.001) to 27%, T. trichiura 25%, A. lumbricoides 2%, and hookworm 0%. Cure rate for T. trichiura, A. lumbricoides, and hookworms was 61%, 97%, and 100%, respectively. Significant decrease of eggs per gram of feces was found in all STH (Wilcoxon test, p value <0.001 for A. lumbricoides and T. trichiura, p value = 0.027 for hookworms); egg reduction rate for T. trichiura was 91%, A. lumbricoides was 100%, and hookworms was 100%. In conclusion, triple dose albendazole is effective in controlling STH in children of Perobatang village, Southwest Sumba, Indonesia.

Hymenolepiasis in a Pregnant Woman: A Case Report of Hymenolepis nana Infection

Hymenolepiasis is an infection caused by Hymenolepis nana (H. nana) and H. diminuta (H. diminuta). Hymenolepiasis is prevalent throughout the world with human infections with H. nana being frequently reported in the literature as compared to H. diminuta. Hymenolepiasis is more frequent among children, and most human infections remain asymptomatic and self-limited. Symptoms including abdominal pain, diarrhea, and vomiting are frequently noted in the cases of heavy infections. We report a case of hymenolepiasis caused by H. nana in a pregnant woman.

Intervention strategies to reduce the burden of soil-transmitted helminths in India

Soil-transmitted helminth (STH) infections continue to be a major global cause of morbidity, with a large proportion of the burden of STH infections occurring in India. In addition to direct health impacts of these infections, including anaemia and nutritional deficiencies in children, these infections also significantly impact economic development, as a result of delays in early childhood cognitive development and future income earning potential. The current World Health Organization strategy for STH is focused on morbidity control through the application of mass drug administration to all pre-school-aged and school-aged children. In India, the control of STH-related morbidity requires mobilization of significant human and financial resources, placing additional burdens on limited public resources. Infected adults and untreated children in the community act as a reservoir of infection by which treated children get rapidly reinfected. As a result, deworming programmes will need to be sustained indefinitely in the absence of other strategies to reduce reinfection, including water, hygiene and sanitation interventions (WASH). However, WASH interventions require sustained effort by the government or other agencies to build infrastructure and to promote healthy behavioural modifications, and their effectiveness is often limited by deeply entrenched cultural norms and behaviours. Novel strategies must be explored to provide a lasting solution to the problem of STH infections in India other than the indefinite provision of deworming for morbidity control.

Effect of Deworming on Indices of Health, Cognition, and Education Among Schoolchildren in Rural China: A Cluster-Randomized Controlled Trial

AbstractSoil-transmitted helminths (STHs) infect over one billion people worldwide. There is concern that chronic infection with STHs among school-aged children may detrimentally affect their development, including their health, cognition, and education. However, two recent Cochrane reviews examining the impact of deworming drugs for STH on nutrition, hemoglobin, and school performance found that randomized controlled trials (RCTs) in the literature provide an insufficient evidence base to draw reliable conclusions. This study uses a cluster-RCT to add to existing evidence by assessing the impact of a deworming intervention on nutrition, cognition, and school performance among schoolchildren in rural China. The intervention, implemented by local health practitioners in a setting with a baseline infection prevalence of 41.9% (95% confidence interval [CI] = 39.8%, 43.9%) and infection intensity of 599.5 eggs per gram of feces among positive-tested schoolchildren (95% CI = 473.2, 725.8), consisted of distributing a 400-mg dose of albendazole accompanied with educational training about STH infection, treatment, and prevention. The intervention was conducted twice over the course of the study-at baseline in May 2013 and later in November 2013. We found that the deworming intervention reduced both infection prevalence and infection intensity, but these declines in infection were not accompanied by an impact on outcomes of nutrition, cognition, or school performance. Our interpretation is that the impact of deworming was attenuated by the light infection intensity in our sample population. Evidence from future RCTs is needed to assess the effect of deworming on key outcomes in areas with moderate and severe worm infections.

IgG Induced by Vaccination With Ascaris suum Extracts Is Protective Against Infection

Human ascariasis has a global and cosmopolitan distribution, and has been characterized as the most prevalent neglected tropical disease worldwide. The development of a preventive vaccine is highly desirable to complement current measures required for this parasitic infection control and to reduce chronic childhood morbidities. In the present study, we describe the mechanism of protection elicited by a preventive vaccine against ascariasis. Vaccine efficacy was evaluated after immunization with three different Ascaris suum antigen extracts formulated with monophosphoryl lipid A (MPLA) as an adjuvant: crude extract of adult worm (ExAD); crude extract of adult worm cuticle (CUT); and crude extract of infective larvae (L3) (ExL3). Immunogenicity elicited by immunization was assessed by measuring antibody responses, cytokine production, and influx of tissue inflammatory cells. Vaccine efficacy was evaluated by measuring the reductions in the numbers of larvae in the lungs of immunized BALB/c mice that were challenged with A. suum eggs. Moreover, lung physiology and functionality were tested by spirometry to determine clinical efficacy. Finally, the role of host antibody mediated protection was determined by passive transfer of serum from immunized mice. Significant reductions in the total number of migrating larvae were observed in mice immunized with ExL3 61% (p < 0.001), CUT 59% (p < 0.001), and ExAD 51% (p < 0.01) antigens in comparison with non-immunized mice. For the Ascaris antigen-specific IgG antibody levels, a significant and progressive increase was observed with each round of immunization, in association with a marked increase of IgG1 and IgG3 subclasses. Moreover, a significant increase in concentration of IL-5 and IL-10 (pre-challenge) in the blood and IL-10 in the lung tissue (post-challenge) was induced by CUT immunization. Finally, ExL3 and CUT-immunized mice showed a marked improvement in lung pathology and tissue fibrosis as well as reduced pulmonary dysfunction induced by Ascaris challenge, when compared to non-immunized mice. Moreover, the passive transfer of specific IgG antibodies from ExL3, CUT, and ExAD elicited a protective response in naïve mice, with significant reductions in parasite burdens in lungs of 65, 64, and 64%, respectively. Taken together, these studies indicated that IgG antibodies contribute to protective immunity.

The public health benefit and burden of mass drug administration programs in Vietnamese schoolchildren: Impact of mebendazole

BACKGROUND

Mass anthelmintic drug administration is recommended in developing countries to address infection by soil-transmitted helminthiases (STH). We quantified the public health benefit of treatment with mebendazole in eight million Vietnamese children aged 5-14 years from 2006 to 2011. This was compared to the environmental impact of the pharmaceutical supply chain of mebendazole, as the resource use and emissions associated with pharmaceutical production can be associated with a public health burden, e.g. through emissions of fine particulate matter.

METHODOLOGY

Through Markov modelling the disability due to STH was quantified for hookworm, Ascaris lumbricoides and Trichuris trichiura. For each worm type, four levels of intensity of infection were included: none, light, medium and heavy. The treatment effect on patients was quantified in Disability-Adjusted Life Years (DALYs). The public health burden induced by the pharmaceutical supply chain of mebendazole was quantified in DALYs through Life Cycle Assessment.

PRINCIPAL FINDINGS

Compared to 'no treatment', the modelled results of five-year treatment averted 116,587 DALYs (68% reduction) for the three worms combined and largely driven by A. lumbricoides. The main change in DALYs occurred in the first year of treatment, after which the results stabilized. The public health burden associated with the pharmaceutical supply chain was 6 DALYs.

CONCLUSIONS

The public health benefit of the Mass Drug Administration (MDA) averted substantially more DALYs than those induced by the pharmaceutical supply chain. These results were verified in a sensitivity analysis. The starting prevalence for each worm was the most sensitive model parameter. This methodology is useful for policymakers interested in a holistic approach towards the public health performance of MDA programs, enveloping both the treatment benefit received by the patient and the public health burden associated with the resource consumption and environmental emissions of the pharmaceutical production and supply chain.

First Responders: Innate Immunity to Helminths

Helminth infections represent a significant public health concern resulting in devastating morbidity and economic consequences across the globe. Helminths migrate through mucosal sites causing tissue damage and the induction of type 2 immune responses. Antihelminth protection relies on the mobilization and activation of multiple immune cells, including type 2 innate lymphocytes (ILC2s), basophils, mast cells, macrophages, and hematopoietic stem/progenitor cells. Further, epithelial cells and neurons have been recognized as important regulators of type 2 immunity. Collectively, these pathways stimulate host-protective responses necessary for worm expulsion and the healing of affected tissues. In this review we focus on the innate immune pathways that regulate immunity to helminth parasites and describe how better understanding of these pathways may lead to the development of new therapeutic strategies.

Intestinal parasite infections and associated risk factors among schoolchildren in Dolakha and Ramechhap districts, Nepal: a cross-sectional study

Background

Infections with soil-transmitted helminths and pathogenic intestinal protozoa pose a considerable public health burden, particularly in low- and middle-income countries, including Nepal. We assessed the extent of intestinal parasite infections among schoolchildren in two districts of Nepal and determined underlying risk factors.

Methods

A cross-sectional survey was conducted between March and May 2015 in the districts of Dolakha and Ramechhap, Nepal. A total of 708 children, aged 8–16 years from 16 purposively selected schools, were enrolled. Each child provided a single stool sample that was subjected to a suite of copro-microscopic diagnoses for intestinal protozoa and helminths. Drinking water samples from different sources at schools (n = 29), community places (n = 43) and households (n = 562) were analysed for contamination with thermotolerant coliforms (TTC). A questionnaire was administered to determine individual- and household-level risk factors of intestinal parasite infections. Self-reported symptoms were assessed and a clinical examination was undertaken by a physician. Haemoglobin was measured and used as a proxy for anaemia. Mixed logistic regression models were applied to investigate associations.

Results

The overall prevalence of intestinal parasite infections was 39.7%. Trichuris trichiura (30.9%), Giardia intestinalis (30.5%) and hookworm (30.2%) were the predominant intestinal parasite infections. Children from households lacking soap for handwashing were at higher odds of intestinal parasite infections than children who had soap [adjusted odds ratio (aOR) 1.81; 95% confidence interval (CI): 1.13–2.89; P = 0.01]. Children from households without freely roaming domestic animals showed lower odds of G. intestinalis compared to children from households with freely roaming animals (aOR 0.52; 95% CI: 0.33–0.83; P = 0.01). One out of three (31.0%) children suffered from fever and 22.4% had watery diarrhoea within a two-week recall period. Anaemia was diagnosed in 23.6% of the children. Water contamination with TTC showed no clear association with intestinal parasite infection.

Conclusions

Intestinal parasites are common among schoolchildren in the two surveyed districts of Nepal. An important risk factor was lack of soap for handwashing. Our findings call for efforts to control intestinal parasite infection and emphasis should be placed on improvements in water, sanitation and hygiene interventions.

Trial registration

ISRCTN17968589 (date assigned: 17 July 2015).

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3105-0) contains supplementary material, which is available to authorized users.

Helminthiasis Epidemiology and Control: Scoring Successes and Meeting the Remaining Challenges

Parasitic helminth infections remain a significant challenge to global health. These are highly prevalent diseases, affecting over 1 billion persons worldwide. Their prevalence is closely linked to the presence of severe poverty and its associated sub-standard housing and sanitation. The last decade has seen a remarkable increase in our understanding of the true disease burden of helminth infections, and there has been increasing momentum on the part of national and non-governmental developmental organizations for prevention and control of these diseases. The expansion in mass treatment programmes for their control has yielded some significant successes. However, challenges remain in terms of ecological heterogeneity in transmission, incomplete drug uptake, and the likelihood of emerging drug resistance. The development of new, more-sensitive diagnostics is now broadening our knowledge of infection prevalence and of the risk of reinfection and has enhanced our knowledge of the prevalence of concurrent helminth infections. Adoption of these new diagnostic techniques for large-scale screening and surveillance will require adaptation of current mass treatment guidelines for control as programmes move from initial morbidity control objectives toward coordinated interventions aimed at local elimination.

Worms: Pernicious parasites or allies against allergies?

Type 2 immune responses are most commonly associated with allergy and helminth parasite infections. Since the discovery of Th1 and Th2 immune responses more than 30 years ago, models of both allergic disease and helminth infections have been useful in characterizing the development, effector mechanisms and pathological consequences of type 2 immune responses. The observation that some helminth infections negatively correlate with allergic and inflammatory disease led to a large field of research into parasite immunomodulation. However, it is worth noting that helminth parasites are not always benign infections, and that helminth immunomodulation can have stimulatory as well as suppressive effects on allergic responses. In this review, we will discuss how parasitic infections change host responses, the consequences for bystander immunity and how this interaction influences clinical symptoms of allergy.

Impact of community-based integrated mass drug administration on schistosomiasis and soil-transmitted helminth prevalence in Togo

Background

Togo has conducted annual, integrated, community-based mass drug administration (MDA) for soil-transmitted helminths (STH) and schistosomiasis since 2010. Treatment frequency and target populations are determined by disease prevalence, as measured by baseline surveys in 2007 and 2009, and WHO guidelines. Reported programmatic treatment coverage has averaged over 94%. Togo conducted a cross-sectional survey in 2015 to assess the impact of four to five years of MDA on these diseases.

Methodology/Principal findings

In every sub-district in the country outside the capital, the same schools were visited as at baseline and a sample of fifteen children age 6 to 9 years old was drawn. Each child submitted urine and a stool sample. Urine samples were tested by dipstick for the presence of blood as a proxy measure of Schistosoma haematobium infection. Stool samples were analyzed by the Kato-Katz method for STH and Schistosoma mansoni. At baseline, 17,100 children were enrolled at 1,129 schools in 562 sub-districts; in 2015, 16,890 children were enrolled at the same schools. The overall prevalence of both STH and schistosomiasis declined significantly, from 31.5% to 11.6% for STH and from 23.5% to 5.0% for schistosomiasis (p<0.001 in both instances). Egg counts from both years were available only for hookworm and S. mansoni; intensity of infection decreased significantly for both infections from 2009 to 2015 (p<0.001 for both infections). In areas with high baseline prevalence, rebound of hookworm infection was noted in children who had not received albendazole in the past 6 months.

Conclusions/Significance

After four to five years of MDA in Togo, the prevalence and intensity of STH and schistosomiasis infection were significantly reduced compared to baseline. Data on STH indicate that stopping MDA in areas with high baseline prevalence may result in significant rebound of infection. Togo’s findings may help refine treatment recommendations for these diseases.

Mass drug administration (MDA) is a key component of programs aimed at controlling soil-transmitted helminths (STH) and schistosomiasis, diseases that disproportionately impact individuals in developing countries and adversely affect physical and cognitive development. The World Health Organization recommends evaluating the impact of mass drug administration on the prevalence of these infections after five years of MDA. We present here a study of the impact of four to five years of MDA on the prevalence and intensity of STH and schistosomiasis infections in school children in Togo. The prevalence and intensity of these infections in 2015 were significantly reduced compared to a baseline survey conducted in 2009. Local baseline prevalence in 2009 was the strongest predictor of infection in 2015. These infections are more prevalent in boys than in girls, and in older versus younger children. We found that in areas with high baseline prevalence of hookworm the risk of rebound of infection is high among children who do not receive bi-annual treatment. This information is important for programs weighing the decision to stop MDA in areas where prevalence has been reduced through treatment. This and other findings from this study may help refine treatment recommendations for these diseases.

Are schoolchildren less infected if they have good knowledge about parasitic worms? A case study from rural Côte d'Ivoire

BACKGROUND

Parasitic worms (helminths) are common infections in low- and middle-income countries. For most helminth species, school-aged children are at highest risk of infection and morbidity, such as impaired cognitive and physical development. Preventive chemotherapy is the current mainstay for helminthiases control. Sanitation improvement and hygiene-related education are important complementary strategies, which act by altering children's behaviour. However, little is known about the effect of improved knowledge on the risk of helminth infection. The aim of this study was to assess the potential influence of knowledge that children acquired at home or in school, without any specific health education intervention, on helminth infections.

METHODS

In May 2014, we conducted a cross-sectional survey in western Côte d'Ivoire. A total of 2498 children, aged 9-12 years, were subjected to three consecutive stool examinations using duplicate Kato-Katz thick smears to determine infections with soil-transmitted helminths and Schistosoma mansoni. Additionally, children were interviewed to assess their knowledge about helminth infections. Four knowledge scores were constructed by factor analysis; one, reflecting general knowledge about helminths and three manifesting helminth species-specific knowledge. The effect of general and specific knowledge on children's helminth infection status was determined using meta-analysis.

RESULTS

Children who scored high in the hookworm-specific knowledge were less likely to be infected with hookworm but no association was found for the other helminth species. Moreover, greater general knowledge was not associated with lower odds of being infected with any helminth species. Most of the children interviewed believed that the effect of preventive chemotherapy is permanent, and hence, re-treatment is not necessary.

CONCLUSIONS

Specific knowledge about different types of helminths might not suffice to induce behavioural change which in turn reduces infection and reinfection with helminths. Health education interventions should strive to strengthen the perception of risk and to clarify the true benefit of preventive chemotherapy.

A Role for Epitope Networking in Immunomodulation by Helminths

Helminth infections, by nematodes, trematodes, or cestodes, can lead to the modulation of host immune responses. This allows long-duration parasite infections and also impacts responses to co-infections. Surface, secreted, excreted, and shed proteins are thought to play a major role in modulation. A commonly reported feature of such immune modulation is the role of T regulatory (Treg) cells and IL-10. Efforts to identify helminth proteins, which cause immunomodulation, have identified candidates but not provided clarity as to a uniform mechanism driving modulation. In this study, we applied a bioinformatics systems approach, allowing us to analyze predicted T-cell epitopes of 17 helminth species and the responses to their surface proteins. In addition to major histocompatibility complex (MHC) binding, we analyzed amino acid motifs that would be recognized by T-cell receptors [T-cell-exposed motifs (TCEMs)]. All the helminth species examined have, within their surface proteins, peptides, which combine very common TCEMs with predicted high affinity binding to many human MHC alleles. This combination of features would result in large cognate T cell and a high probability of eliciting Treg responses. The TCEMs, which determine recognition by responding T-cell clones, are shared to a high degree between helminth species and with Plasmodium falciparum and Mycobacterium tuberculosis, both common co-infecting organisms. The implication of our observations is not only that Treg cells play a significant role in helminth-induced immune modulation but also that the epitope specificities of Treg responses are shared across species and genera of helminth. Hence, the immune response to a given helminth cannot be considered in isolation but rather forms part of an epitope ecosystem, or microenvironment, in which potentially immunosuppressive peptides in the helminth network via their common T-cell receptor recognition signals with T-cell epitopes in self proteins, microbiome, other helminths, and taxonomically unrelated pathogens. Such a systems approach provides a high-level view of the antigen-immune system signaling dynamics that may bias a host's immune response to helminth infections toward immune modulation. It may indicate how helminths have evolved to select for peptides that favor long-term parasite host coexistence.

A Critical Role for Thermosensation in Host Seeking by Skin-Penetrating Nematodes

Skin-penetrating parasitic nematodes infect approximately one billion people worldwide and are a major source of neglected tropical disease [1-6]. Their life cycle includes an infective third-larval (iL3) stage that searches for hosts to infect in a poorly understood process that involves both thermal and olfactory cues. Here, we investigate the temperature-driven behaviors of skin-penetrating iL3s, including the human-parasitic threadworm Strongyloides stercoralis and the human-parasitic hookworm Ancylostoma ceylanicum. We show that human-parasitic iL3s respond robustly to thermal gradients. Like the free-living nematode Caenorhabditis elegans, human-parasitic iL3s show both positive and negative thermotaxis, and the switch between them is regulated by recent cultivation temperature [7]. When engaging in positive thermotaxis, iL3s migrate toward temperatures approximating mammalian body temperature. Exposing iL3s to a new cultivation temperature alters the thermal switch point between positive and negative thermotaxis within hours, similar to the timescale of thermal plasticity in C. elegans [7]. Thermal plasticity in iL3s may enable them to optimize host finding on a diurnal temperature cycle. We show that temperature-driven responses can be dominant in multisensory contexts such that, when thermal drive is strong, iL3s preferentially engage in temperature-driven behaviors despite the presence of an attractive host odorant. Finally, targeted mutagenesis of the S. stercoralis tax-4 homolog abolishes heat seeking, providing the first evidence that parasitic host-seeking behaviors are generated through an adaptation of sensory cascades that drive environmental navigation in C. elegans [7-10]. Together, our results provide insight into the behavioral strategies and molecular mechanisms that allow skin-penetrating nematodes to target humans.

Helminth-Bacterial Interactions: Cause and Consequence

Intestinal helminths, along with mutualistic microbes, have cohabited the intestine of mammals throughout evolution. Interactions between helminths, bacteria, and their mammalian hosts may shape not only host-helminth and host-microbiome interactions, but also the relationship between helminths and the microbiome. This 'ménage à trois' situation may not be completely balanced in that it may favor either the host or the parasite, possibly at the cost of the other partner. Similarly, helminths may favor the establishment of a particular microbiome with either positive or negative consequences for the overall health and well-being of the host. Recent studies indicate that infection with intestinal helminths can and does impact the intestinal microbiome, with important consequences for each partner in this tripartite relationship.

An Integrated Approach to Control Soil-Transmitted Helminthiasis, Schistosomiasis, Intestinal Protozoa Infection, and Diarrhea: Protocol for a Cluster Randomized Trial

Background

The global strategy to control helminthiases (schistosomiasis and soil-transmitted helminthiasis) emphasizes preventive chemotherapy. However, in the absence of access to clean water, improved sanitation, and adequate hygiene, reinfection after treatment can occur rapidly. Integrated approaches might be necessary to sustain the benefits of preventive chemotherapy and make progress toward interruption of helminthiases transmission.

Objective

The aim of this study was to assess and quantify the effect of an integrated control package that consists of preventive chemotherapy, community-led total sanitation, and health education on soil-transmitted helminthiasis, schistosomiasis, intestinal protozoa infection, and diarrhea in rural Côte d’Ivoire.

Methods

In a first step, a community health education program was developed that includes an animated cartoon to promote improved hygiene and health targeting school-aged children, coupled with a health education theater for the entire community. In a second step, a cluster randomized trial was implemented in 56 communities of south-central Côte d’Ivoire with 4 intervention arms: (1) preventive chemotherapy; (2) preventive chemotherapy plus community-led total sanitation; (3) preventive chemotherapy plus health education; and (4) all 3 interventions combined. Before implementation of the aforementioned interventions, a baseline parasitologic, anthropometric, and hygiene-related knowledge, attitudes, practices, and beliefs survey was conducted. These surveys were repeated 18 and 39 months after the baseline cross-sectional survey to determine the effect of different interventions on helminth and intestinal protozoa infection, nutritional indicators, and knowledge, attitudes, practices, and beliefs. Monitoring of diarrhea was done over a 24-month period at 2-week intervals, starting right after the baseline survey.

Results

Key results from this cluster randomized trial will shed light on the effect of integrated approaches consisting of preventive chemotherapy, community-led total sanitation, and health education against infections with soil-transmitted helminths, schistosomes, an intestinal protozoa and prevention of diarrhea in a rural part of Côte d’Ivoire.

Conclusions

The research provided new insights into the acceptability, strengths, and limitations of an integrated community-based control package targeting helminthiases, intestinal protozoa infections, and diarrhea in rural communities of Côte d’Ivoire. In the longer term, the study will allow determining the effect of the integrated control approach on infection patterns with parasitic worms and intestinal protozoa, diarrheal incidence, anthropometric measures, and hygiene-related knowledge, attitudes, practices, and beliefs.

Trial Registration

International Standard Randomized Controlled Trial Number (ISRCTN): 53102033; http://www.isrctn.com/ISRCTN53102033 (Archived by WebCite at http://www.webcitation.org/6wpnXEiHo)

Registered Report Identifier

RR1-10.2196/9166

Changes in parasite traits, rather than intensity, affect the dynamics of infection under external perturbation

Understanding the mechanisms that generate complex host-parasite interactions, and how they contribute to variation between and within hosts, is important for predicting risk of infection and transmission, and for developing more effective interventions based on parasite properties. We used the T. retortaeformis (TR)-rabbit system and developed a state-space mathematical framework to capture the variation in intensity of infection and egg shedding in hosts infected weekly, then treated with an anthelminthic and subsequently re-challenged following the same infection regime. Experimental infections indicate that parasite intensity accumulates more slowly in the post-anthelminthic phase but reaches similar maximum numbers. By contrast, parasite EPG (eggs per gram of feces) shed from rabbits in the post-treatment phase is lower and less variable through time. Inference based on EPG alone suggests a decline in parasite intensity over time. Using a state-space model and incorporating all sources of cross-sectional and longitudinal data, we show that while parasite intensity remains relatively constant in both experimental phases, shedding of eggs into the environment is increasingly limited through changes in parasite growth. We suggest that host immunity directly modulates both the accumulation and the growth of the parasite, and indirectly affects transmission by limiting parasite length and thus fecundity. This study provides a better understanding of how within-host trophic interactions influence different components of a helminth population. It also suggests that heterogeneity in parasite traits should be addressed more carefully when examining and managing helminth infections in the absence of some critical data on parasite dynamics.

Current prevalence of intestinal parasitic infections and their impact on hematological and nutritional status among Karen hill tribe children in Omkoi District, Chiang Mai Province, Thailand

Intestinal parasitic infection represents a substantial problem for children living in rural or limited resources areas and significantly relates to anemia and nutritional status. This study aimed to determine the current prevalence of intestinal parasitic infections among school-age children of Karen hill tribe population in Omkoi District, Chiang Mai Province, Thailand and assess the impact of intestinal parasitic infection on hematological and nutritional status in those children. A total of 375 Karen hill tribe children, 6-14 years of age, in Omkoi District were randomly selected to participate in this study. Stool samples were collected and examined for intestinal parasitic infection through formalin-ether concentration method. Blood samples were collected for hematological and iron analysis. The overall prevalence of intestinal parasitic infection was 47.7% (179/375), with single infections (29.3%) and polyparatism (18.4%). The most common pathogenic parasite was Trichuris trichiura (16.0%), followed by Ascaris lumbricoides (13%) and Giardia lamblia (3.5%). In addition, non-pathogenic amoeba, Entamoeba coli was observed with a high prevalence rate (31.2%). Anemia and eosinophilia prevalence were 6.40% (24/375) and 74.7% (280/375), respectively. Eosinophilia was significantly more prevalent in children with intestinal parasitic infection compared to uninfected children. Among 249 children, 13.7% were iron deficiency, 9.6% were thalassemia and hemoglobinophathy and 8% were G-6-PD deficiency. A high prevalence infection rate was significantly associated with eosinophilia, but independently related to anemia and iron deficiency. Intestinal parasitic infections are endemic in school-age children of Karen hill tribe population in Omkoi District. These data highlight the need for an integrated approach to control transmission of intestinal parasites and improve the health and sanitation status of Karen hill tribe children in Thailand.

The associations between water and sanitation and hookworm infection using cross-sectional data from Togo's national deworming program

Background

Sustainable control of soil-transmitted helminths requires a combination of chemotherapy treatment and environmental interventions, including access to safe drinking water, sufficient water for hygiene, use of clean sanitation facilities, and handwashing (WASH). We quantified associations between home-, school-, and community-level WASH characteristics and hookworm infection—both prevalence and eggs per gram of stool (intensity)—among Togolese school children in the context of community-based chemotherapy treatments administered in the country from 2010 through 2014.

Methodology/Principal findings

We analyzed data from two surveys conducted by the Togo Ministry of Health: a school-based survey of students aged 6–9 years across Togo conducted in 2009 and a follow-up survey in 2015, after four to five years of preventive chemotherapy. Data were available for 16,473 students attending 1,129 schools in 2009 and for 16,890 students from 1,126 schools in 2015. Between surveys, children in study schools received 0 to 8 rounds of deworming chemotherapy treatments. Few WASH conditions (only unimproved drinking water) were found to be significantly associated with the presence or absence of hookworms in an individual; however, quantitative eggs per gram of feces was associated with availability of unimproved drinking water, availability of improved drinking water either on or off school grounds, having a handwashing station with water available, and access to a sex-separate non-private or private latrine. The association between school WASH conditions and hookworm infection or burden often depended on the 2009 prevalence of infection, as more WASH characteristics were found to be significant predictors of infection among schools with high underlying endemicity of hookworm.

Conclusions/Significance

Our findings emphasize the complex and often inconsistent or unpredictable relationship between WASH and hookworm. Specifically, we found that while preventive chemotherapy appeared to dramatically reduce hookworm infection, WASH was associated with infection intensity.

Preventive chemotherapy plays a critical role in breaking transmission of soil-transmitted helminths but it is likely that sustainable control of soil-transmitted helminths will require environmental improvements such as access to water for hygiene and hygienic sanitation, access to and use of a clean toilet facility, and handwashing with soap at key times (WASH). Here, we report on school-, home- and community-level WASH and the relationship of these characteristics with the prevalence and intensity of hookworm infection, one of the most prevalent soil-transmitted helminths, observed in the context of preventive chemotherapy among Togolese school children. In this large, country-wide assessment, few WASH conditions were found to be significant predictors of the presence or absence of hookworms in an individual, however, intensity of infection was associated with several WASH characteristics. Our analysis emphasizes the complex and often unpredictable role of WASH characteristics on hookworm, particularly relevant for Togolese and other international policy makers aiming to understand the interaction between WASH, preventive chemotherapy and hookworm. Further research taking into account not only WASH conditions but also use of WASH resources and practices would further strengthen our understanding of the interaction between WASH and deworming treatment as effective hookworm control strategies.

Differential human gut microbiome assemblages during soil-transmitted helminth infections in Indonesia and Liberia

BACKGROUND

The human intestine and its microbiota is the most common infection site for soil-transmitted helminths (STHs), which affect the well-being of ~ 1.5 billion people worldwide. The complex cross-kingdom interactions are not well understood.

RESULTS

A cross-sectional analysis identified conserved microbial signatures positively or negatively associated with STH infections across Liberia and Indonesia, and longitudinal samples analysis from a double-blind randomized trial showed that the gut microbiota responds to deworming but does not transition closer to the uninfected state. The microbiomes of individuals able to self-clear the infection had more alike microbiome assemblages compared to individuals who remained infected. One bacterial taxon (Lachnospiracae) was negatively associated with infection in both countries, and 12 bacterial taxa were significantly associated with STH infection in both countries, including Olsenella (associated with reduced gut inflammation), which also significantly reduced in abundance following clearance of infection. Microbial community gene abundances were also affected by deworming. Functional categories identified as associated with STH infection included arachidonic acid metabolism; arachidonic acid is the precursor for pro-inflammatory leukotrienes that threaten helminth survival, and our findings suggest that some modulation of arachidonic acid activity in the STH-infected gut may occur through the increase of arachidonic acid metabolizing bacteria.

CONCLUSIONS

For the first time, we identify specific members of the gut microbiome that discriminate between moderately/heavily STH-infected and non-infected states across very diverse geographical regions using two different statistical methods. We also identify microbiome-encoded biological functions associated with the STH infections, which are associated potentially with STH survival strategies, and changes in the host environment. These results provide a novel insight of the cross-kingdom interactions in the human gut ecosystem by unlocking the microbiome assemblages at taxonomic, genetic, and functional levels so that advances towards key mechanistic studies can be made.

Effect of an integrated intervention package of preventive chemotherapy, community-led total sanitation and health education on the prevalence of helminth and intestinal protozoa infections in Côte d'Ivoire

Background

Preventive chemotherapy with donated anthelminthic drugs is the cornerstone for the control of helminthiases. However, reinfection can occur rapidly in the absence of clean water and sanitation coupled with unhygienic behaviour. The purpose of this study was to assess the effect of an integrated package of interventions, consisting of preventive chemotherapy, community-led total sanitation (CLTS) and health education, on the prevalence of helminth and intestinal protozoa infections and on participants’ knowledge, attitude, practice and beliefs (KAPB) towards these diseases including water, sanitation and hygiene (WASH).

Methods

A cross-sectional survey was carried out in nine communities of south-central Côte d’Ivoire to assess people’s infection with helminths and intestinal protozoa and KAPB. Subsequently, interventions were targeted to five communities, while the remaining communities served as control. The intervention encouraged latrine construction and an evaluation was done 6–7 months later to determine open defecation status of the respective communities. Anthelminthic treatment was provided to all community members. A follow-up cross-sectional survey was conducted approximately one year later, using the same procedures.

Results

Overall, 810 people had complete baseline and follow-up data and were given anthelminthic treatment. The baseline prevalence of hookworm, Schistosoma haematobium, Trichuris trichiura, Schistosoma mansoni and Ascaris lumbricoides was 31.1%, 7.0%, 2.0%, 1.0% and 0.3%, respectively. Four of the five intervention communities were classified open-defecation free. For hookworm infection, we observed higher negative changes in terms of proportion of decrease (-0.10; 95% confidence interval (CI): - 0.16, -0.04) and higher egg reduction rate (64.9 vs 15.2%) when comparing intervention with control communities. For intestinal protozoa, prevalence reduction was higher in intervention compared to control communities (8.2 vs 2.6%) and WASH indicators and intervention outcomes associated with lower odds for infection at follow-up. The intervention significantly impacted on reported latrine use (before: 15.5%, after: 94.6%), open defecation in the community surroundings (before: 75.0%, after: 16.7%) and awareness for environmental contamination through open defecation (before: 20.4%, after: 52.2%).

Conclusions

An integrated package of interventions consisting of preventive chemotherapy, health education and CLTS reduces the prevalence of helminth and intestinal protozoa infection. Additional studies in other social-ecological settings are warranted to confirm our findings.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-2642-x) contains supplementary material, which is available to authorized users.

Epidemiology of intestinal parasite infections in three departments of south-central Côte d'Ivoire before the implementation of a cluster-randomised trial

Hundreds of millions of people are infected with helminths and intestinal protozoa, particularly children in low- and middle-income countries. Preventive chemotherapy is the main strategy to control helminthiases. However, rapid re-infection occurs in settings where there is a lack of clean water, sanitation and hygiene. In August and September 2014, we conducted a cross-sectional epidemiological survey in 56 communities of three departments of south-central Côte d'Ivoire. Study participants were invited to provide stool and urine samples. Stool samples were examined for helminth and intestinal protozoa infections using the Kato-Katz technique and a formalin-ether concentration method. Urine samples were subjected to a filtration method for the diagnosis of Schistosoma haematobium. Information on sociodemographic characteristics, knowledge, attitude, practices and beliefs with regard to hygiene, sanitation and intestinal parasitic diseases were collected using a questionnaire administered to household heads. Multivariable logistic regression models were employed to analyse associations between parasite infections and risk factors. Overall, 4,305 participants had complete parasitological and questionnaire data. Hookworm was the predominant helminth species (21.2%), while Ascaris lumbricoides, Trichuris trichiura, Schistosoma mansoni and S. haematobium showed prevalences below 10%. Infections with pathogenic intestinal protozoa (e.g. Entamoeba histolytica/E. dispar and Giardia intestinalis) were similarly prevalent in the three departments. Hookworm infection was associated with open defecation and participants' age and sex. Entamoeba coli infection was negatively associated with the use of tap water at home (odds ratio (OR) = 0.66; p = 0.032). Disposal of garbage in close proximity to people's home was positively associated with G. intestinalis (OR = 1.30; p = 0.015). Taken together, helminth and intestinal protozoa infections affected a considerable proportion of rural dwellers in south-central Côte d'Ivoire at the onset of a cluster-randomised intervention trial. Our results will serve as baseline to monitor the effect of a package of interventions, including preventive chemotherapy, sanitation and health education on re-infection with helminths and intestinal protozoa.

TRIAL REGISTRATION

ISRCTN53102033 (date assigned: 26 March 2014).

The Immune and Non-Immune Pathways That Drive Chronic Gastrointestinal Helminth Burdens in the Wild

Parasitic helminths are extremely resilient in their ability to maintain chronic infection burdens despite (or maybe because of) their hosts’ immune response. Explaining how parasites maintain these lifelong infections, identifying the protective immune mechanisms that regulate helminth infection burdens, and designing prophylactics and therapeutics that combat helminth infection, while preserving host health requires a far better understanding of how the immune system functions in natural habitats than we have at present. It is, therefore, necessary to complement mechanistic laboratory-based studies with studies on wild populations and their natural parasite communities. Unfortunately, the relative paucity of immunological tools for non-model species has held these types of studies back. Thankfully, recent progress in high-throughput ‘omics platforms provide powerful and increasingly practical means for immunologists to move beyond traditional lab-based model organisms. Yet, assigning both metabolic and immune function to genes, transcripts, and proteins in novel species and assessing how they interact with other physiological and environmental factors requires identifying quantitative relationships between their expression and infection. Here, we used supervised machine learning to identify gene networks robustly associated with burdens of the gastrointestinal nematode Heligmosomoides polygyrus in its natural host, the wild wood mice Apodemus sylvaticus. Across 34 mice spanning two wild populations and across two different seasons, we found 17,639 transcripts that clustered in 131 weighted gene networks. These clusters robustly predicted H. polygyrus burden and included well-known effector and regulatory immune genes, but also revealed a number of genes associated with the maintenance of tissue homeostasis and hematopoiesis that have so far received little attention. We then tested the effect of experimentally reducing helminth burdens through drug treatment on those putatively protective immune factors. Despite the near elimination of H. polygyrus worms, the treatment had surprisingly little effect on gene expression. Taken together, these results suggest that hosts balance tissue homeostasis and protective immunity, resulting in relatively stable immune and, consequently, parasitological profiles. In the future, applying our approach to larger numbers of samples from additional populations will help further increase our ability to detect the immune pathways that determine chronic gastrointestinal helminth burdens in the wild.

The COUNTDOWN Study Protocol for Expansion of Mass Drug Administration Strategies against Schistosomiasis and Soil-Transmitted Helminthiasis in Ghana

(1) Background: Current international policy for schistosomiasis and soil-transmitted helminthiasis (STH) control emphasises mass administration of deworming drugs in school-based programmes. However, this approach is insufficient to control the transmission of these diseases, and their burden in non-school cohorts is recognised, albeit under-researched. This research will investigate the feasibility and acceptability of expanding access to praziquantel (PZQ) against schistosomiasis, and albendazole (ALB) against STH, to communities in selected transmission settings in Ghana. (2) Methods: A three-site longitudinal study will be implemented to investigate the effectiveness of expanding treatment strategies for PZQ and ALB to community members. In the context of community mass drug administration (to preschool children, school non-attending children, and adults, including pregnant women), the intervention will be assessed in a random sample of community members, at baseline with follow-up at 6, 12, and 18 months. In each community, 658 participants will be enrolled, and 314 followed up at each time point. The primary outcome measure is the prevalence of infection of Schistosoma haematobium and/or S. mansoni at study endpoint, as assessed by longitudinal surveys. Secondary outcomes are to quantify the infection of schistosomiasis and STH infections in non-treated cohorts, reductions in prevalence of STH, and intensity of schistosomiasis and STH, and treatment coverage. Nested within this study will be qualitative, cost-benefit, and cost-effectiveness evaluations that will explore accessibility, feasibility, and economic impact of expanded treatment from different complementary perspectives. (3) Discussion: Using a multidisciplinary approach, this study will generate evidence for improved availability, acceptability, affordability, and accessibility to deworming drugs against schistosomiasis and STH to individuals and communities in Ghana. This is likely to have considerable research, programmatic, and political value to contribute evidence for national programme policy development within Ghana, and, more broadly, World Health Organization policy development.

Soil-transmitted helminth infections

More than a quarter of the world's population is at risk of infection with the soil-transmitted helminths Ascaris lumbricoides, hookworm (Ancylostoma duodenale and Necator americanus), Trichuris trichiura, and Strongyloides stercoralis. Infected children and adults present with a range of medical and surgical conditions, and clinicians should consider the possibility of infection in individuals living in, or returning from, endemic regions. Although safe and effective drugs are donated free to endemic countries, only half of at-risk children received treatment in 2016. This Seminar describes the epidemiology, lifecycles, pathophysiology, clinical diagnosis, management, and public health control of soil-transmitted helminths. Previous work has questioned the effect of population-level deworming; however, it remains beyond doubt that treatment reduces the severe consequences of soil-transmitted helminthiasis. We highlight the need for refined diagnostic tools and effective control options to scale up public health interventions and improve clinical detection and management of these infections.

Strongyloides stercoralis and hookworm co-infection: spatial distribution and determinants in Preah Vihear Province, Cambodia

BACKGROUND

Strongyloides stercoralis and hookworm are two soil-transmitted helminths (STH) that are highly prevalent in Cambodia. Strongyloides stercoralis causes long-lasting infections and significant morbidity but is largely neglected, while hookworm causes the highest public health burden among STH. The two parasites have the same infection route, i.e. skin penetration. The extent of co-distribution, which could result in potential high co-morbidities, is unknown in highly endemic settings like Cambodia. The aim of this study was to predict the spatial distribution of S. stercoralis-hookworm co-infection risk and to investigate determinants of co-infection in Preah Vihear Province, North Cambodia.

METHODS

A cross-sectional survey was conducted in 2010 in 60 villages of Preah Vihear Province. Diagnosis was performed on two stool samples, using combined Baermann technique and Koga agar culture plate for S. stercoralis and Kato-Katz technique for hookworm. Bayesian multinomial geostatistical models were used to assess demographic, socioeconomic, and behavioural determinants of S. stercoralis-hookworm co-infection and to predict co-infection risk at non-surveyed locations.

RESULTS

Of the 2576 participants included in the study, 48.6% and 49.0% were infected with S. stercoralis and hookworm, respectively; 43.8% of the cases were co-infections. Females, preschool aged children, adults aged 19-49 years, and participants who reported regularly defecating in toilets, systematically boiling drinking water and having been treated with anthelmintic drugs had lower odds of co-infection. While S. stercoralis infection risk did not appear to be spatially structured, hookworm mono-infection and co-infection exhibited spatial correlation at about 20 km. Co-infection risk was positively associated with longer walking distances to a health centre and exhibited a small clustering tendency. The association was only partly explained by climatic variables, suggesting a role for underlying factors, such as living conditions and remoteness.

CONCLUSIONS

Both parasites were ubiquitous in the province, with co-infections accounting for almost half of all cases. The high prevalence of S. stercoralis calls for control measures. Despite several years of school-based de-worming programmes, hookworm infection levels remain high. Mebendazole efficacy, as well as coverage of and compliance to STH control programmes should be investigated.

Geographical distribution of soil transmitted helminths and the effects of community type in South Asia and South East Asia - A systematic review

BACKGROUND

Soil-transmitted helminth (STH) infections are among the most prevalent neglected tropical diseases (NTD) worldwide. Since the publication of the WHO road map to combat NTD in 2012, there has been a renewed commitment to control STH. In this study, we analysed the geographical distribution and effect of community type on prevalence of hookworm, Trichuris and Ascaris in south Asia and south east Asia.

METHODOLOGY

We conducted a systematic review of open-access literature published in PubMed Central and the Global Atlas of Helminth Infection. A total of 4182 articles were available and after applying selection criteria, 174 studies from the region were retained for analysis.

PRINCIPAL FINDINGS

Ascaris was the commonest STH identified with an overall prevalence of 18% (95% CI, 14-23%) followed by Trichuris (14%, 9-19%) and hookworm (12%, 9-15%). Hookworm prevalence was highest in Laos, Vietnam and Cambodia. We found a geographical overlap in countries with high prevalence rates for Trichuris and Ascaris (Malaysia, Philippines, Myanmar, Vietnam and Bangladesh). When the effect of community type was examined, prevalence rates of hookworm was comparable in rural (19%, 14-24%) and tribal communities (14%, 10-19%). Tribal communities, however, showed higher prevalence of Trichuris (38%, 18-63%) and Ascaris (32%, 23-43%) than rural communities (13%, 9-20% and 14%, 9-20% respectively). Considerable between and within country heterogeneity in the distribution of STH (I2 >90%) was also noted. When available data from school aged children (SAC) were analysed, prevalence of Ascaris (25% 16-31%) and Trichuris (22%, 14-34%) were higher than among the general population while that of hookworm (10%, 7-16%) was comparable.

CONCLUSIONS/SIGNIFICANCE

Our analysis showed significant variation in prevalence rates between and within countries in the region. Highlighting the importance of community type in prevalence and species mix, we showed that tribal and rural communities had higher hookworm infections than urban communities and for ascariasis and trichuriasis, tribal populations had higher levels of infection than rural populations. We also found a higher prevalence of ascariasis and trichuriasis in SAC compared to the general population but comparable levels of hookworm infections. These key findings need to be taken into account in planning future MDA and other interventions.

Assessing the feasibility of interrupting the transmission of soil-transmitted helminths through mass drug administration: The DeWorm3 cluster randomized trial protocol

Current control strategies for soil-transmitted helminths (STH) emphasize morbidity control through mass drug administration (MDA) targeting preschool- and school-age children, women of childbearing age and adults in certain high-risk occupations such as agricultural laborers or miners. This strategy is effective at reducing morbidity in those treated but, without massive economic development, it is unlikely it will interrupt transmission. MDA will therefore need to continue indefinitely to maintain benefit. Mathematical models suggest that transmission interruption may be achievable through MDA alone, provided that all age groups are targeted with high coverage. The DeWorm3 Project will test the feasibility of interrupting STH transmission using biannual MDA targeting all age groups. Study sites (population ≥80,000) have been identified in Benin, Malawi and India. Each site will be divided into 40 clusters, to be randomized 1:1 to three years of twice-annual community-wide MDA or standard-of-care MDA, typically annual school-based deworming. Community-wide MDA will be delivered door-to-door, while standard-of-care MDA will be delivered according to national guidelines. The primary outcome is transmission interruption of the STH species present at each site, defined as weighted cluster-level prevalence ≤2% by quantitative polymerase chain reaction (qPCR), 24 months after the final round of MDA. Secondary outcomes include the endline prevalence of STH, overall and by species, and the endline prevalence of STH among children under five as an indicator of incident infections. Secondary analyses will identify cluster-level factors associated with transmission interruption. Prevalence will be assessed using qPCR of stool samples collected from a random sample of cluster residents at baseline, six months after the final round of MDA and 24 months post-MDA. A smaller number of individuals in each cluster will be followed with annual sampling to monitor trends in prevalence and reinfection throughout the trial.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03014167.

X-ray micro-computed tomography (μCT): an emerging opportunity in parasite imaging

X-ray micro-computed tomography (μCT) is a technique which can obtain three-dimensional images of a sample, including its internal structure, without the need for destructive sectioning. Here, we review the capability of the technique and examine its potential to provide novel insights into the lifestyles of parasites embedded within host tissue. The current capabilities and limitations of the technology in producing contrast in soft tissues are discussed, as well as the potential solutions for parasitologists looking to apply this technique. We present example images of the mouse whipworm Trichuris muris and discuss the application of μCT to provide unique insights into parasite behaviour and pathology, which are inaccessible to other imaging modalities.

The Effect of Deworming Using Triple-Dose Albendazole on Nutritional Status of Children in Perobatang Village, Southwest Sumba, Indonesia

High prevalence of STH leads to malnutrition, anemia, cognitive impairment, and growth disorders. Triple-dose albendazole 400 mg is a broad-spectrum anthelminthic; however, its effectiveness varies in every region. This study aims to determine the benefits of deworming using triple-dose albendazole on children's nutritional status in Perobatang Village, Southwest Sumba, Indonesia. This pre-post study was conducted in July 2016 and January 2017. Children aged 1–15 years were asked to collect stool for diagnosis of STH infection (Kato-Katz method), were measured for anthropometry status to obtain the nutritional status, and took albendazole 400 mg for three consecutive days. Data was analyzed with SPSS version 20. Prevalence of STH prior to the treatment was 95.4%: T. trichiura 85.2%, A. lumbricoides 71.6%, and hookworm 18.2%. After treatment, prevalence of STH decreased significantly (McNemar test, p < 0.001) to 53.4%, (T. trichiura 39.8%, A. lumbricoides 22.7%, and hookworm 1.1%). Before treatment, 33% participants were in normal nutritional status, 47.7% underweight, and 19.3% severely underweight. After treatment, children in normal nutritional status increased to 75%, underweight children decreased to 25%, and there were no severely underweight children. In conclusion, deworming with triple-dose albendazole 400 mg is effective in improving the nutritional status of children in Perobatang Village.

Status of soil-transmitted helminth infections in schoolchildren in Laguna Province, the Philippines: Determined by parasitological and molecular diagnostic techniques

BACKGROUND

Soil-transmitted helminths (STH) are the most common parasitic infections in impoverished communities, particularly among children. Current STH control is through school-based mass drug administration (MDA), which in the Philippines is done twice annually. As expected, MDA has decreased the intensity and prevalence of STH over time. As a result, the common Kato Katz (KK) thick smear method of detecting STH is less effective because it lacks sensitivity in low intensity infections, making it difficult to measure the impact of deworming programs.

METHODOLOGY/PRINCIPAL FINDINGS

A cross-sectional study was carried out over a four-week period from October 27, 2014 until November 20, 2014 in Laguna province, the Philippines. Stool samples were collected from 263 schoolchildren, to determine the prevalence of STH and compare diagnostic accuracy of multiplex quantitative polymerase chain reaction (qPCR) with the KK. A large discrepancy in the prevalence between the two techniques was noted for the detection of at least one type of STH infection (33.8% by KK vs. 78.3% by qPCR), Ascaris lumbricoides (20.5% by KK vs. 60.8% by qPCR) and Trichuris trichiura (23.6% by KK vs. 38.8% by qPCR). Considering the combined results of both methods, the prevalence of at least one type of helminth infection, A. lumbricoides, and T. trichiura were 83.3%, 67.7%, and 53.6%, respectively. Sensitivity of the qPCR for detecting at least one type of STH infection, A. lumbricoides, and T. trichiura were 94.1%, 89.9%, and 72.3% respectively; whereas KK sensitivity was 40.6%, 30.3%, and 44.0%, respectively. The qPCR method also detected infections with Ancylostoma spp. (4.6%), Necator americanus (2.3%), and Strongyloides stercoralis (0.8%) that were missed by KK.

CONCLUSION/SIGNIFICANCE

qPCR may provide new and important diagnostic information to improve assessment of the effectiveness and impact of integrated control strategies particularly in areas where large-scale STH control has led to low prevalence and/or intensity of infection.

High prevalence of soil-transmitted helminth infections among primary school children, Uttar Pradesh, India, 2015

Background

Soil-transmitted helminth (STH) infections often affect the poorest and most deprived communities. In order to generate reliable data for planning a school based deworming program, we conducted a survey among primary school children studying in government schools in the Indian state of Uttar Pradesh. The objectives of our survey were to estimate the prevalence and intensity of STH infections.

Methods

We conducted a cross-sectional survey among children studying in 130 primary schools from 9 agro-climatic zones, during May – August 2015. Information about socio-demographic details, defecation and hand-hygiene practices, and stool samples were collected from the school children. Stool samples were examined using the Kato-Katz method.

Results

Stool samples from 6421 school children were examined. The overall weighted prevalence of any STH in the State was 75.6% (95% CI: 71.2–79.5). The prevalence was more than 50% in six of the nine agro-climatic zones. A. lumbricoides was the most prevalent STH (prevalence: 69.6%), followed by hookworm (prevalence: 22.6%) and T. trichura (4.6%). The majority of the STH infections were of low intensity. The practice of open defecation and not washing hands with soap after defecation and residence in kutcha house were significant risk factors of STH infection.

Conclusions

STH prevalence among primary school children in Uttar Pradesh was high. Given the WHO guidelines on deworming frequency according to STH prevalence, Govt of Uttar Pradesh needs to implement a school-based deworming program with bi-annual frequency. The findings of our survey would also help monitor the performance of school based deworming programme.

Electronic supplementary material

The online version of this article (10.1186/s40249-017-0354-7) contains supplementary material, which is available to authorized users.

Effective drug combination for Caenorhabditis elegans nematodes discovered by output-driven feedback system control technique

Infections from parasitic nematodes (or roundworms) contribute to a significant disease burden and productivity losses for humans and livestock. The limited number of anthelmintics (or antinematode drugs) available today to treat these infections are rapidly losing their efficacy as multidrug resistance in parasites becomes a global health challenge. We propose an engineering approach to discover an anthelmintic drug combination that is more potent at killing wild-type Caenorhabditis elegans worms than four individual drugs. In the experiment, freely swimming single worms are enclosed in microfluidic drug environments to assess the centroid velocity and track curvature of worm movements. After analyzing the behavioral data in every iteration, the feedback system control (FSC) scheme is used to predict new drug combinations to test. Through a differential evolutionary search, the winning drug combination is reached that produces minimal centroid velocity and high track curvature, while requiring each drug in less than their EC₅₀ concentrations. The FSC approach is model-less and does not need any information on the drug pharmacology, signaling pathways, or animal biology. Toward combating multidrug resistance, the method presented here is applicable to the discovery of new potent combinations of available anthelmintics on C. elegans, parasitic nematodes, and other small model organisms.

Controlling Taenia solium and soil transmitted helminths in a northern Lao PDR village: Impact of a triple dose albendazole regime

Taenia solium taeniasis-cysticercosis and soil-transmitted helminths (STHs) are parasitic Neglected Tropical Diseases endemic throughout Southeast Asia. Within Lao PDR, a remote northern hill tribe village had previously been identified as a hyper endemic focus for T. solium. To reduce this observed prevalence, a One Health intervention covering both pigs and humans was implemented, which included two Mass drug administrations (MDA1 and MDA2) for village residents using a triple dose albendazole 400mg treatment regime. In addition to the effect on T. solium levels, the dual impact of this anthelmintic regime on STHs within the community was also monitored. Faecal samples were collected pre and post MDA1 and MDA2 and analysed for the presence of Taenia species and the STHs Ascaris lumbricoides, Trichuris trichiura and hookworm species. The McMaster technique was used to measure the changes in both prevalence and intensity of infection. Molecular characterisation of Taenia and hookworm species was conducted to detect zoonotic species. The level of taeniasis within the sampled population decreased by 79.4% after MDA1, remained steady during the five month inter-treatment interval and decreased again by 100% after MDA2. The prevalence of STHs decreased by 65.5% and 62.8% after MDA1 and MDA2 respectively; however an increase to 62.1% of pre MDA1 levels was detected during the inter-treatment interval. Individually, hookworm prevalence decreased by 83.4% (MDA1) and 84.5% (MDA2), A. lumbricoides by 95.6% and 93.5% and T. trichiura by 69.2% and 61%. The intensity of infection within the sampled population also decreased, with egg reduction rates of 94.4% and 97.8% for hookworm, 99.4% and 99.3% for A. lumbricoides and 77.2% and 88.5% for T. trichiura. Molecular characterisation identified a T. solium tapeworm carrier from 21.6% (13/60) of households in the village. T. saginata was identified in 5% (3/60) of households. The zoonotic hookworm A. ceylanicum was detected in the resident dog population. These results suggest that the triple dose albendazole 400mg treatment regime achieved a significant reduction in the level of taeniasis whilst simultaneously reducing the STH burden within the village. The increased STH prevalence detected between MDAs reflects the need for behavioural changes and a sustained chemotherapy programme, which may also need to include the resident dog population.

Prospects for elimination of soil-transmitted helminths

PURPOSE OF REVIEW

Soil-transmitted helminths (STH) are endemic in 120 countries and are associated with substantial morbidity and loss of economic productivity. Although current WHO guidelines focus on morbidity control through mass drug administration (MDA), there is global interest in whether a strategy targeting disease elimination might be feasible in some settings. This review summarizes the prospects for switching from control to an elimination strategy.

RECENT FINDINGS

STH control efforts have reduced the intensity of infections in targeted populations with associated reductions in morbidity. However, adults are not frequently targeted and remain important reservoirs for reinfection of treated children. Recent modeling suggests that transmission interruption may be possible through expanded community-wide delivery of MDA, the feasibility of which has been demonstrated by other programs. However, these models suggest that high levels of coverage and compliance must be achieved. Potential challenges include the risk of prematurely dismantling STH programs and the potential increased risk of antihelminthic resistance.

SUMMARY

Elimination of STH may offer an opportunity to eliminate substantial STH-related morbidity while reducing resource needs of neglected tropical disease programs. Evidence from large community trials is needed to determine the feasibility of interrupting the transmission of STH in some geographic settings.

"Koko et les lunettes magiques": An educational entertainment tool to prevent parasitic worms and diarrheal diseases in Côte d'Ivoire

Background

Integrated control programs, emphasizing preventive chemotherapy along with health education, can reduce the incidence of soil-transmitted helminthiasis and schistosomiasis. The aim of this study was to develop an educational animated cartoon to improve school children’s awareness regarding soil-transmitted helminthiasis, diarrheal diseases, and related hygiene practices in Côte d’Ivoire. The key messages included in the cartoon were identified through prior formative research to specifically address local knowledge gaps.

Methodology

In a first step, preliminary research was conducted to assess the knowledge, attitudes, practices, and beliefs of school-aged children regarding parasitic worm infections and hygiene, to identify key health messages to be included in an animated cartoon. Second, an animated cartoon was produced, which included the drafting of the script and story board, and the production of the cartoon’s initial version. Finally, the animated cartoon was pilot tested in eight selected schools and further fine-tuned.

Principal findings

According to the questionnaire results, children believed that the consumption of sweet food, eating without washing their hands, sitting on the floor, and eating spoiled food were the main causes of parasitic worm infections. Abdominal pain, diarrhea, lack of appetite, failure to grow, and general fatigue were mentioned as symptoms of parasitic worm infections. Most of the children knew that they should go to the hospital for treatment if they experienced symptoms of parasitic worm diseases. The animated cartoon titled “Koko et les lunettes magiques” was produced by Afrika Toon, in collaboration with a scientific team composed of epidemiologists, civil engineers, and social scientists, and the local school children and teachers. Pilot testing of the animated cartoon revealed that, in the short term, children grasped and kept key messages. Most of the children who were shown the cartoon reported to like it. Acceptance of the animated cartoon was high among children and teachers alike. The messaging was tailored to improve knowledge and practices for prevention of helminthiases and diarrheal diseases through prior identification of knowledge gaps. Integration of such education tools into the school curriculum, along with deworming campaigns, might improve sustainability of control and elimination efforts against helminthiases and diarrheal diseases.

Soil-transmitted helminthiases, schistosomiasis, and diarrhea remain important public health issues in sub-Saharan Africa. Health educational animated cartoons can help raise awareness and improve hygiene practices, and thus contribute to the control and elimination of these diseases. For the development of an educational animated cartoon, we first evaluated the knowledge, attitudes, practices, and beliefs of school-aged children in Côte d’Ivoire regarding soil-transmitted helminthiases, diarrhea, and schistosomiasis in order to identify setting-specific health messages for our animated cartoon. We found that children believed that the consumption of sweet food, eating without washing their hands, sitting on the floor, and eating spoiled food were the main causes of parasitic worm infections. As a next step, the alpha version of the animated cartoon was produced and given the title: “Koko et les lunettes magiques”. The animated cartoon was pre-tested in eight schools and further developed. Our study found that children could retain most of the information provided by the animated cartoon. It is suggested that such a tool, integrated into the school curriculum, together with deworming campaigns in Côte d’Ivoire, might improve the sustainability of control and elimination efforts against soil-transmitted helminthiases, diarrhea, and schistosomiasis.

Prevention of intestinal parasites in a tri-border area of Latin America: Children perceptions and an integral health education strategy

To investigate knowledge of school-aged children and their perception on intestinal parasites, and to assess knowledge reconstruction on prevention practices after specific training in the subject. We performed an activity package that included the analysis of children's drawings of intestinal parasites, and information and communication technologies (ITCs) to transfer knowledge about these pathogens and prevention measures. Retrieval learning activities were performed to fixation of general and specific prevention and control measures.Overall, we found that there is a knowledge gap in many aspects of parasite biology and ecology, and therefore on the risk of infection and acquisition mechanisms. After ITCs, the children improved their knowledge over non-trained children.The approaches used to transfer knowledge and for learning, fixation were valuable tools for incorporating changes in misconceptions and in the deep-rooted habits that favour entero-parasitic diseases. This has important implications for the specific design of future education materials and campaigns. Understanding of perceptions helps to provide justifications and knowledge to achieve changes in unhealthy habits, and it constitutes the basis for the transformation of many risky practices.

Trichuris trichiura infection and its relation to environmental factors in Mbeya region, Tanzania: A cross-sectional, population-based study

Background

The intestinal nematode Trichuris trichiura is among the most common causes of human infectious disease worldwide. As for other soil-transmitted nematodes, its reproductive success and thus prevalence and intensity of infection in a given area strongly depend on environmental conditions. Characterization of the influence of environmental factors can therefore aid to identify infection hot spots for targeted mass treatment.

Methodology

We analyzed data from a cross-sectional survey including 6234 participants from nine distinct study sites in Mbeya region, Tanzania. A geographic information system was used to combine remotely sensed and individual data, which were analyzed using uni- and multivariable Poisson regression. Household clustering was accounted for and when necessary, fractional polynomials were used to capture non-linear relationships between T. trichiura infection prevalence and environmental variables.

Principal findings

T. trichiura infection was restricted to the Kyela site, close to Lake Nyasa with only very few cases in the other eight sites. The prevalence of T. trichiura infection in Kyela was 26.6% (95% confidence interval (CI) 23.9 to 29.6%). Multivariable models revealed a positive association of infection with denser vegetation (prevalence ratio (PR) per 0.1 EVI units = 2.12, CI 1.28 to 3.50) and inverse associations with rainfall (PR per 100 mm = 0.54, CI 0.44 to 0.67) and elevation (PR per meter = 0.89, CI 0.86 to 0.93) while adjusting for age and previous worm treatment. Slope of the terrain was modelled non-linearly and also showed a positive association with T. trichiura infection (p-value p<0.001).

Conclusion/Significance

Higher prevalences of T. trichiura infection were only found in Kyela, a study site characterized by denser vegetation, high rainfall, low elevation and flat terrain. But even within this site, we found significant influences of vegetation density, rainfall, elevation and slope on T. trichiura infection. The inverse association of rainfall with infection in Kyela is likely due to the fact, that rainfall in this site is beyond the optimum conditions for egg development. Our findings demonstrate that use of remotely sensed environmental data can aid to predict high-risk areas for targeted helminth control.

'Fit for school' - a school-based water, sanitation and hygiene programme to improve child health: Results from a longitudinal study in Cambodia, Indonesia and Lao PDR

BACKGROUND

The Fit for School (FIT) programme integrates school health and Water, Sanitation and Hygiene interventions, which are implemented by the Ministries of Education in four Southeast Asian countries. This paper describes the findings of a Health Outcome Study, which aimed to assess the two-year effect of the FIT programme on the parasitological, weight, and oral health status of children attending schools implementing the programme in Cambodia, Indonesia and Lao PDR.

METHODS

The study was a non-randomized clustered controlled trial with a follow-up period of two years. The intervention group consisted of children attending public elementary schools implementing the FIT programme, including daily group handwashing with soap and toothbrushing with fluoride toothpaste, biannual school-based deworming; as well as construction of group handwashing facilities. Control schools implemented the regular government health education curriculum and biannual deworming. Per school, a random selection of six to seven-year-old grade-one students was drawn. Data on parasitological infections, anthropometric measurements, dental caries, odontogenic infections and sociodemographic characteristics were collected at baseline and at follow-up (24 months later). Data were analysed using the χ²-test, Mann Whitney U-test and multilevel logistic and linear regression.

RESULTS

A total of 1847 children (mean age = 6.7 years, range 6.0-8.0 years) participated in the baseline survey. Of these, 1499 children were available for follow-up examination - 478, 486 and 535 children in Cambodia, Indonesia and Lao PDR, respectively. In all three countries, children in intervention schools had a lower increment in the number of decayed, missing and filled permanent teeth between baseline and follow-up, in comparison to children in controls schools. The preventive fraction was 24% at average. The prevalence of soil-transmitted helminth infection (which was unexpectedly low at baseline), the prevalence of thinness and the prevalence of odontogenic infections did not significantly differ between baseline and follow-up, nor between intervention and control schools.

CONCLUSIONS

The study found that the FIT programme significantly contributed to the prevention of dental caries in children. This study describes the challenges, learnings and, moreover, the importance of conducting real-life implementation research to evaluate health programmes to transform school settings into healthy learning environments for children. The study is retrospectively registered with the German Clinical Trials Register, University of Freiburg (Trial registration number: DRKS00004485, date of registration: 26th of February, 2013).

Soil-transmitted helminths and plasmodium falciparum malaria among individuals living in different agroecosystems in two rural communities in the mount Cameroon area: a cross-sectional study

Background

Soil-transmitted helminths (STHs) and Plasmodium falciparum infections remain public health problems in Cameroon. A cross-sectional study was carried out in the Mount Cameroon area to determine the prevalence and intensity of STHs and P. falciparum infections in individuals living in different agroecosystems; to assess the influence of these infections on haematological parameters; and to identify the risk factors associated with STH infections.

Methods

STH and malaria parasites were detected using the Kato-Katz method and Giemsa staining of blood films, respectively. Complete blood count values were obtained using an automatic haematology analyser. Soil samples were analysed using the sucrose floatation sedimentation method. Categorical and continuous variables were compared as required and logistic regression models were used to assess the risk factors for STH infections and anaemia.

Results

Of the 450 participants examined, STHs, P. falciparum and mixed co-infections were detected in 14.0, 33.3 and 5.6% of participants, respectively. Significantly higher prevalences of Ascaris (18.8%) and Trichuris (7.9%) infections were observed in participants from tea plantation areas compared to those from banana and palm plantation areas, with similar trends in egg density. P. falciparum prevalence and parasite density were comparable between the different agroecosystems. The overall prevalence of anaemia was 64.2%. The prevalence of haematological manifestations such as moderate (48.0%) and severe (8.0%) anaemia, leucopenia (26.9%) and microcytosis (30.8%) was significantly higher among Plasmodium-STH co-infected participants. Soil samples from plantations showed the highest prevalences of STH eggs compared to soil samples from areas around pit toilets and public water taps. Living in a tea plantation area (OR = 3.07), age (AOR = 1.49) and lack of access to potable water (OR = 2.25) were identified as risk factors for STH infections, while the age groups 15–25 years (OR = 2.928) and 26–35 years (OR = 2.832), and being female (OR = 2.671) were significant risk factors for anaemia.

Conclusions

STHs, malaria and anaemia are still of public health concern in plantation communities. Co-infections negatively influence haematological parameters. The tea farming agroecosystem, age and lack of access to potable water were identified as significant risk factors for STH infections.

Trial registration

Not applicable.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-017-0266-6) contains supplementary material, which is available to authorized users.

Study design and baseline results of an open-label cluster randomized community-intervention trial to assess the effectiveness of a modified mass deworming program in reducing hookworm infection in a tribal population in southern India

Introduction

Hookworm infection is a leading cause of iron deficiency anemia and malnutrition in resource-poor settings. Periodic mass deworming with anthelminthic drugs remains the cornerstone of hookworm control efforts worldwide. Reinfection following treatment occurs, reflecting the human host's inability to acquire immunity following exposure to an untreated reservoir of infection. This cluster randomized trial will evaluate the effectiveness of a modified, population-based, mass deworming strategy in reducing hookworm infection in an endemic southern Indian population.

Methods

Forty five tribal villages were randomized into three groups: one received annual treatment; the second received two rounds of treatment at 1-month intervals; and the third received four rounds of treatment – two rounds 1 month apart at the beginning, followed by another two after 6 months. Stool samples collected through cross-sectional parasitological surveys pre- and post-intervention, and at 3-monthly intervals for a period of 1 year were tested for presence of hookworm ova. Long-term effectiveness of treatment will be assessed through another survey conducted 2 years after the last treatment cycle.

Results

From a population of 11,857 individuals, 8681 (73.2%) were found to be eligible and consented to participate, out-migration being the primary reason for non-participation. Baseline stool samples were obtained from 2082 participants, with 18.5% having hookworm infection, although majority were low intensity infections (<2000 eggs per gram of feces).

Discussion

This study will help identify the optimal mass deworming strategy that can achieve the greatest impact in the shortest period of time, particularly in settings where long-term program sustainability is a challenge.

Prevalence and distribution of soil-transmitted helminth infections in India

Background

Understanding the prevalence of soil-transmitted helminth infections is necessary to plan control strategies and focus on highly endemic regions for preventive chemotherapy and improved sanitation facilities. India is known to be endemic for soil-transmitted helminth infections.

Methods

To understand the prevalence, spatial distribution and identify high-risk zones, a systematic search of published literature was carried out based on PRISMA guidelines from the year 2000 to 2015.

Results

A careful screening of the identified literature yielded 39 studies that reported the prevalence of soil-transmitted helminth infections from 19 different states of India. Ascaris lumbricoides was the most prevalent parasite. Higher than 50% prevalence was reported from six states. Nearly 90% studies reported the prevalence of more than one parasite species in the same sample population.

Conclusion

This is the first study to comprehensively review the literature associated with soil-transmitted helminth infections from India giving a clear idea of its prevalence, distribution and high endemic areas.

Assessment of the burden of soil-transmitted helminthiasis after five years of mass drug administration for Onchocerciasis and Lymphatic filariasis in Kebbi State, Nigeria

There is a hypothesis that Mass drug administration (MDA) of ivermectin and albendazole for the treatment of onchocerciasis and lymphatic filariasis could have an impact on the burden of soil-transmitted helminthiasis (STH) in MDA communities. We, therefore, assessed the burden of STH (Ascaris lumbricoides, Trichuris trichiura, and hookworm) infections in nine communities from 3 LGAs (two MDA local government areas (LGAs) and one control LGA) in Kebbi State, Nigeria after 5-years (2010–2015) of MDA for onchocerciasis and/or lymphatic filariasis. We also administered questionnaire to obtain demographic information and history of MDA in the past five years. The three LGAs are Bagudo (Ivermectin MDA); Zuru (Ivermectin/Albendazole MDA) and Dandi (No MDA). The study was a cross sectional survey. The total number of people that complied with provision of stool samples and questionnaire were 1357 persons; stool samples collected were examined for STH infections in the three LGAs. Zuru LGA had the highest prevalence of STH (41.89, 95% CI: 37.08–46.81) followed by Dandi LGA (24.66, 95% CI: 20.69–28.97) and Bagudo LGA (3.36, 95% CI: 1.97–5.32). Prevalence of STH infection was not significantly different among age group and sex. Geometric mean intensity per gram of infection for both A. lumbricoides and Hookworm were highest in Zuru LGA with (1.16 GMI, 95% CI: 0.97–1.36) and (1.49 GMI, 95% CI: 1.29–1.70) respectively. Treatment coverage was less than 65% from 2010 to 2013 in the intervention LGAs. The study shows that STH is still a public health problem in Zuru LGA (IVM + ALB) and requires MDA of albendazole for STH control to continue, while Dandi LGA (No MDA history) requires MDA with albendazole to scale up treatment for STH control.

Impact of single annual treatment and four-monthly treatment for hookworm and Ascaris lumbricoides, and factors associated with residual infection among Kenyan school children

Background

School-based deworming is widely implemented in various countries to reduce the burden of soil-transmitted helminths (STHs), however, the frequency of drug administration varies in different settings. In this study, we compared the impact of a single annual treatment and 4-monthly treatment over a follow-up among Kenyan school children, and investigated the factors associated with residual infection.

Methods

We performed a secondary analysis of data from a randomized trial investigating whether deworming for STHs alters risk of acquiring malaria. Children received either a single treatment or 4-monthly albendazole treatments were followed longitudinally from February 2014 to October 2014. The relative impact of treatment and factors associated with residual infections were investigated using mixed-effects regression models. Predisposition to infection was assessed based on Spearman’s rank and Kendall’s Tau correlation coefficients.

Results

In the 4-monthly treatment group, the proportion of children infected with hookworm decreased from 59.9 to 5.7%, while Ascaris lumbricoides infections dropped from 55.7 to 6.2%. In the single treatment group, hookworm infections decreased over the same time period from 58.7 to 18.3% (12.6% absolute difference in reduction, 95% CI: 8.9–16.3%), and A. lumbricoides from 56.7 to 23.3% (17.1% absolute difference in reduction, 95% CI: 13.1–21.1%). There was strong evidence for predisposition to both STH types. Residual hookworm infection among children on 4-monthly treatment were associated with male sex and baseline nutritional status, whereas A. lumbricoides infection was associated with individual and school-level infection at baseline, latrine cleanliness at schools.

Conclusions

This study found that 4-monthly treatment w more effective than single annual treatment. Repeated treatments led to dramatic reductions in the intensities of STHs, but did not completely clear infections among school children in Kenya, a presumed reflection of reinfection in a setting where there is ongoing transmission.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-017-0244-z) contains supplementary material, which is available to authorized users.