The costs and cost-effectiveness of mass treatment for intestinal nematode worm infections using different treatment thresholds

Prevalence of anemia and its social determinants among the male residents of an urban area in Tamil Nadu, India

Introduction

India has a high burden of anemia among the South Asian countries. Anemia has been extensively studied in the female and child population, with less attention given to males. The present study aims to assess the prevalence of anemia among males residing in an urban area and associated social determinants.

Methods

A community-based cross-sectional study was conducted among 300 males (during September and October 2021) in an urban area of Coimbatore, Tamil Nadu. A portable hemoglobin photometer was used to detect the prevalence of anemia. A structured questionnaire was used to collect details on social determinants of anemia such as dietary practice, education, income, and sanitary practices.

Results

The mean age of study participants was 34 ± 5.23 years. The prevalence of overall anemia among men was 20.3% (95% confidence interval [CI]: 15.9-25.3%), with moderate and severe anemia being 5.7% (95% CI: 3.3-8.9%) and 1% (95% CI: 0.2-2.9%), respectively. Belonging to a lower socioeconomic class (odds ratio [OR] = 6.50, P < 0.05) and consuming more than two cups of tea (OR = 7.28, P < 0.05) were significantly associated with anemia.

Conclusion

Our study depicts a high burden of anemia among males. Health education on the role of dietary factors contributing to anemia needs to be emphasized with special focus on the frequency of tea intake. Primary care physicians can include screening for anemia in their routine practice for men belonging to lower socioeconomic groups. Consideration should be made to include male populations also under the National Anemia Control program.

A district-level geospatial analysis of anaemia prevalence among rural men in India, 2019-21

BACKGROUND

Despite its considerable impact on health and productivity, anemia among men has received limited attention. In a country as diverse as India, characterized by extensive geographic variations, there is a pressing need to investigate the nuanced spatial patterns of anemia prevalence among men. The identification of specific hotspots holds critical implications for policymaking, especially in rural areas, where a substantial portion of India's population resides.

METHODS

The study conducted an analysis on a sample of 61,481 rural men from 707 districts of India, utilizing data from the National Family Health Survey-5 (2019-21). Various analytical techniques, including Moran's I, univariate LISA (Local Indicators of Spatial Association), bivariate LISA, and spatial regression models such as SLM (Spatial Lag Model), and SEM (Spatial Error Model) were employed to examine the geographic patterns and spatial correlates of anaemia prevalence in the study population.

RESULTS

In rural India, three out of every ten men were found to be anemic. The univariate Moran's I value for anaemia was 0.66, indicating a substantial degree of spatial autocorrelation in anaemia prevalence across the districts in India. Cluster and outlier analysis identified five prominent 'hotspots' of anaemia prevalence across 97 districts, primarily concentrated in the eastern region (encompassing West Bengal, Jharkhand, and Odisha), the Dandakaranya region, the Madhya Pradesh-Maharashtra border, lower Assam, and select districts in Jammu and Kashmir. The results of SLM revealed significant positive association between anaemia prevalence at the district-level and several key factors including a higher proportion of Scheduled Tribes, men in the 49-54 years age group, men with limited or no formal education, individuals of the Muslim faith, economically disadvantaged men, and those who reported alcohol consumption.

CONCLUSIONS

Substantial spatial heterogeneity in anaemia prevalence among men in rural India suggests the need for region-specific targeted interventions to reduce the burden of anaemia among men in rural India and enhance the overall health of this population.

Developing a Lay First Responder Program in Chad: A 12-Month Follow-Up Evaluation of a Rural Prehospital Emergency Care Program

INTRODUCTION

The World Health Organization (WHO; Geneva, Switzerland) recommends lay first responder (LFR) programs as a first step toward establishing formal Emergency Medical Services (EMS) in low- and middle-income countries (LMICs) to address injury. There is a scarcity of research investigating LFR program development in predominantly rural settings of LMICs.

STUDY OBJECTIVE

A pilot LFR program was launched and assessed over 12 months to investigate the feasibility of leveraging pre-existing transportation providers to scale up prehospital emergency care in rural, low-resource settings of LMICs.

METHODS

An LFR program was established in rural Chad to evaluate curriculum efficacy, using a validated 15-question pre-/post-test to measure participant knowledge improvement. Pre-/post-test score distributions were compared using a Wilcoxon Signed-Rank test. For test evaluation, each pre-test question was mapped to its corresponding post-test analog and compared using McNemar's Chi-Squared Test to examine knowledge acquisition on a by-question basis. Longitudinal prehospital care was evaluated with incident reports, while program cost was tracked using a one-way sensitivity analysis. Qualitative follow-up surveys and semi-interviews were conducted at 12 months, with initial participants and randomly sampled motorcycle taxi drivers, and used a constructivist grounded theory approach to understand the factors motivating continued voluntary participation to inform future program continuity. The consolidated criteria for reporting qualitative research (COREQ) checklist was used to guide design, analysis, and reporting the qualitative results.

RESULTS

A total of 108 motorcycle taxi participants demonstrated significant knowledge improvement (P <.001) across three of four curricular categories: scene safety, airway and breathing, and bleeding control. Lay first responders treated 71 patients over six months, encountering five deaths, and provided patient transport in 82% of encounters. Lay first responders reported an average confidence score of 8.53/10 (n = 38). In qualitative follow-up surveys and semi-structured interviews, the ability to care for the injured, new knowledge/skills, and the resultant gain in social status and customer acquisition motivated continued involvement as LFRs. Ninety-six percent of untrained, randomly sampled motorcycle taxi drivers reported they would be willing to pay to participate in future training courses.

CONCLUSION

Lay first responder programs appear feasible and cost-effective in rural LMIC settings. Participants demonstrate significant knowledge acquisition, and after 12 months of providing emergency care, report sustained voluntary participation due to social and financial benefits, suggesting sustainability and scalability of LFR programs in low-resource settings.

Economic performance and cost-effectiveness of using a DEC-salt social enterprise for eliminating the major neglected tropical disease, lymphatic filariasis

Background

Salt fortified with the drug, diethylcarbamazine (DEC), and introduced into a competitive market has the potential to overcome the obstacles associated with tablet-based Lymphatic Filariasis (LF) elimination programs. Questions remain, however, regarding the economic viability, production capacity, and effectiveness of this strategy as a sustainable means to bring about LF elimination in resource poor settings.

Methodology and principal findings

We evaluated the performance and effectiveness of a novel social enterprise-based approach developed and tested in Léogâne, Haiti, as a strategy to sustainably and cost-efficiently distribute DEC-medicated salt into a competitive market at quantities sufficient to bring about the elimination of LF. We undertook a cost-revenue analysis to evaluate the production capability and financial feasibility of the developed DEC salt social enterprise, and a modeling study centered on applying a dynamic mathematical model localized to reflect local LF transmission dynamics to evaluate the cost-effectiveness of using this intervention versus standard annual Mass Drug Administration (MDA) for eliminating LF in Léogâne. We show that the salt enterprise because of its mixed product business strategy may have already reached the production capacity for delivering sufficient quantities of edible DEC-medicated salt to bring about LF transmission in the Léogâne study setting. Due to increasing revenues obtained from the sale of DEC salt over time, expansion of its delivery in the population, and greater cumulative impact on the survival of worms leading to shorter timelines to extinction, this strategy could also represent a significantly more cost-effective option than annual DEC tablet-based MDA for accomplishing LF elimination.

Significance

A social enterprise approach can offer an innovative market-based strategy by which edible salt fortified with DEC could be distributed to communities both on a financially sustainable basis and at sufficient quantity to eliminate LF. Deployment of similarly fashioned intervention strategies would improve current efforts to successfully accomplish the goal of LF elimination, particularly in difficult-to-control settings.

With less than three years remaining for meeting the initial 2020 target set by WHO for accomplishing the global elimination of Lymphatic Filariasis (LF), concerns are emerging regarding the feasibility of meeting this goal using the current tablet-based Mass Drug Administration strategy. Salt fortified with the antifilarial drug, diethylcarbamazine (DEC), could offer an intervention that avoids many of the barriers connected with tablet-based elimination programs. We analyzed the economic performance and cost-effectiveness of a novel DEC-salt social enterprise developed and tested in Léogâne arrondissement, Haiti, as a particularly significant strategy for accomplishing sustainable LF elimination in such complex settings. We show that because of increasing revenue from the sale of the DEC salt over time, expansion of its delivery in the population, and the adverse effect of continuous consumption of the drug on worms, the delivery of DEC through a salt enterprise can represent a significantly more cost-effective option than annual DEC tablet-based MDA for accomplishing LF elimination in settings, like Léogâne. We indicate that development of policy and research into how to deploy similarly-fashioned interventions, or work with the salt industry to increase population use of medicated salt, would improve present efforts to successfully accomplish the elimination of LF.

Health, financial, and education gains of investing in preventive chemotherapy for schistosomiasis, soil-transmitted helminthiases, and lymphatic filariasis in Madagascar: A modeling study

BACKGROUND

Neglected tropical diseases (NTDs) account for a large disease burden in sub-Saharan Africa. While the general cost-effectiveness of NTD interventions to improve health outcomes has been assessed, few studies have also accounted for the financial and education gains of investing in NTD control.

METHODS

We built on extended cost-effectiveness analysis (ECEA) methods to assess the health gains (e.g. infections, disability-adjusted life years or DALYs averted), household financial gains (out-of-pocket expenditures averted), and education gains (cases of school absenteeism averted) for five NTD interventions that the government of Madagascar aims to roll out nationally. The five NTDs considered were schistosomiasis, lymphatic filariasis, and three soil-transmitted helminthiases (Ascaris lumbricoides, Trichuris trichiura, and hookworm infections).

RESULTS

The estimated incremental cost-effectiveness for the roll-out of preventive chemotherapy for all NTDs jointly was USD125 per DALY averted (95% uncertainty range: 65-231), and its benefit-cost ratio could vary between 5 and 31. Our analysis estimated that, per dollar spent, schistosomiasis preventive chemotherapy, in particular, could avert a large number of infections (176,000 infections averted per $100,000 spent), DALYs (2,000 averted per $100,000 spent), and cases of school absenteeism (27,000 school years gained per $100,000 spent).

CONCLUSION

This analysis incorporates financial and education gains into the economic evaluation of health interventions, and therefore provides information about the efficiency of attainment of three Sustainable Development Goals (SDGs). Our findings reveal how the national scale-up of NTD control in Madagascar can help address health (SDG3), economic (SDG1), and education (SDG4) goals. This study further highlights the potentially large societal benefits of investing in NTD control in low-resource settings.

Prevalence and distribution of soil-transmitted helminth infections in Nigerian children: a systematic review and meta-analysis

Background

Soil transmitted helminth (STH) infections still remain a notable health problem in resource-limited countries due to difficulties in the implementation of control measures. In Nigeria for instance, despite several community-based and provincial reports, national data on prevalence, burdens and risk zones (RZs) for STH infections are lacking.

Methods

The present study employed the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) to determine the prevalence, distribution and RZs for STH infections among Nigerian children through a meta-analysis of data published between 1980 and 2015. Pooled prevalence estimate (PPE) was determined by the random-effects model while heterogeneity was evaluated using the Cochran’s Q-test.

Results

A total of 18 901 of the 34 518 Nigerian children aged 0–17 years examined across 19 Nigerian states during the period under review were infected with one or more species of STHs. The overall PPE for STH infections was 54.8% (95% CI: 54.2–55.3). PPEs for sub-groups ranged between 13.2% (95% CI: 11.5–15.1) and 80.9% (95% CI: 80.0–81.7). Highest PPEs for STH infections were observed among children within community settings (59.0%, 95% CI: 57.7–60.4) and school-aged children (54.9%, 95% CI: 54.3–55.5). Ascaris lumbricoides was the most prevalent species (44.6%, 95% CI: 44.0–45.2). Over 36% (15/41) of the studies were published from south-western Nigeria. South-western region was the only high risk zone (HRZ) for STH infections while the rest of the regions were low risk zones (LRZs).

Conclusions

STH infections involving Ascaris lumbricoides, Strongyloides stercoralis, Trichuris trichiura and hookworms are highly prevalent across Nigeria. Strategic use of anthelmintics, health education and adequate sanitation, taking into account this epidemiologic information will help in the control of these infections in Nigeria.

Electronic supplementary material

The online version of this article (10.1186/s40249-018-0451-2) contains supplementary material, which is available to authorized users.

Host immunity, nutrition and coinfection alter longitudinal infection patterns of schistosomes in a free ranging African buffalo population

Schistosomes are trematode parasites of global importance, causing infections in millions of people, livestock, and wildlife. Most studies on schistosomiasis, involve human subjects; as such, there is a paucity of longitudinal studies investigating parasite dynamics in the absence of intervention. As a consequence, despite decades of research on schistosomiasis, our understanding of its ecology in natural host populations is centered around how environmental exposure and acquired immunity influence acquisition of parasites, while very little is known about the influence of host physiology, coinfection and clearance in the absence of drug treatment. We used a 4-year study in free-ranging African buffalo to investigate natural schistosome dynamics. We asked (i) what are the spatial and temporal patterns of schistosome infections; (ii) how do parasite burdens vary over time within individual hosts; and (iii) what host factors (immunological, physiological, co-infection) and environmental factors (season, location) explain patterns of schistosome acquisition and loss in buffalo? Schistosome infections were common among buffalo. Microgeographic structure explained some variation in parasite burdens among hosts, indicating transmission hotspots. Overall, parasite burdens ratcheted up over time; however, gains in schistosome abundance in the dry season were partially offset by losses in the wet season, with some hosts demonstrating complete clearance of infection. Variation among buffalo in schistosome loss was associated with immunologic and nutritional factors, as well as co-infection by the gastrointestinal helminth Cooperia fuelleborni. Our results demonstrate that schistosome infections are surprisingly dynamic in a free-living mammalian host population, and point to a role for host factors in driving variation in parasite clearance, but not parasite acquisition which is driven by seasonal changes and spatial habitat utilization. Our study illustrates the power of longitudinal studies for discovering mechanisms underlying parasite dynamics in individual animals and populations.

Soil-Transmitted Helminths: Mathematical Models of Transmission, the Impact of Mass Drug Administration and Transmission Elimination Criteria

Infections caused by soil-transmitted helminthias (STHs) affect over a billion people worldwide, causing anaemia and having a large social and economic impact through poor educational outcomes. They are identified in the World Health Organization (WHO) 2020 goals for neglected tropical diseases as a target for renewed effort to ameliorate their global public health burden through mass drug administration (MDA) and water and hygiene improvement. In this chapter, we review the underlying biology and epidemiology of the three causative intestinal nematode species that are mostly considered under the STH umbrella term. We review efforts to model the transmission cycle of these helminths in populations and the effects of preventative chemotherapy on their control and elimination. Recent modelling shows that the different epidemiological characteristics of the parasitic nematode species that make up the STH group can lead to quite distinct responses to any given form of MDA. When connected with models of treatment cost-effectiveness, these models are potentially a powerful tool for informing public policy. A number of shortcomings are identified; lack of critical types of data and poor understanding of diagnostic sensitivities hamper efforts to test and hence improve models.

Cost and cost-effectiveness of soil-transmitted helminth treatment programmes: systematic review and research needs

BACKGROUND

In this time of rapidly expanding mass drug administration (MDA) coverage and the new commitments for soil-transmitted helminth (STH) control, it is essential that resources are allocated in an efficient manner to have the greatest impact. However, many questions remain regarding how best to deliver STH treatment programmes; these include which age-groups should be targeted and how often. To perform further analyses to investigate what the most cost-effective control strategies are in different settings, accurate cost data for targeting different age groups at different treatment frequencies (in a range of settings) are essential.

METHODS

Using the electronic databases PubMed, MEDLINE, and ISI Web of Knowledge, we perform a systematic review of costing studies and cost-effectiveness evaluations for potential STH treatment strategies. We use this review to highlight research gaps and outline the key future research needs.

RESULTS

We identified 29 studies reporting costs of STH treatment and 17 studies that investigated its cost-effectiveness. The majority of these pertained to programmes only targeting school-aged children (SAC), with relatively few studies investigating alternative preventive chemotherapy (PCT) treatment strategies. The methods of cost data collection, analysis and reporting were highly variable among the different studies. Only four of the costing studies were found to have high applicability for use in forthcoming economic evaluations. There are also very few studies quantifying the costs of increasing the treatment frequency.

CONCLUSIONS

The absence of cost data and inconsistencies in the collection and analysis methods constitutes a major research gap for STH control. Detailed and accurate costs of targeting different age groups or increasing treatment frequency will be essential to formulate cost-effective public health policy. Defining the most cost-effective control strategies in different settings is of high significance during this period of expanding MDA coverage and new resource commitments for STH control.

Factors associated with the performance and cost-effectiveness of using lymphatic filariasis transmission assessment surveys for monitoring soil-transmitted helminths: a case study in Kenya

Transmission assessment surveys (TAS) for lymphatic filariasis have been proposed as a platform to assess the impact of mass drug administration (MDA) on soil-transmitted helminths (STHs). This study used computer simulation and field data from pre- and post-MDA settings across Kenya to evaluate the performance and cost-effectiveness of the TAS design for STH assessment compared with alternative survey designs. Variations in the TAS design and different sample sizes and diagnostic methods were also evaluated. The district-level TAS design correctly classified more districts compared with standard STH designs in pre-MDA settings. Aggregating districts into larger evaluation units in a TAS design decreased performance, whereas age group sampled and sample size had minimal impact. The low diagnostic sensitivity of Kato-Katz and mini-FLOTAC methods was found to increase misclassification. We recommend using a district-level TAS among children 8-10 years of age to assess STH but suggest that key consideration is given to evaluation unit size.

Antiparasitic efficacy of a novel plant-based functional food using an Ascaris suum model in pigs

Ascaris lumbricoides is the most prevalent soil-transmitted helminth (STH) infection of human beings worldwide. Chemotherapy with synthetic anthelmintics such as albendazole, mebendazole, and pyrantel pamoate is the current method of treatment; however, the emergence of anthelmintic resistance could substantially decrease the efficacy of such treatments and the sustainability of STH control programs. Additionally, benzimidazoles are not recommended for pregnant women or children under age one. A blinded, controlled study was conducted to evaluate the efficacy of two microencapsulated, plant-based essential oil blends, TTN1013 (α-pinene, linalyl acetate, p-cymene, and thymol octanoate) and TTN1014 (α-pinene, linalyl acetate, p-cymene, and thymol acetate) as functional foods against Ascaris suum infection in pigs, an important pathogen that closely resembles human infections with A. lumbricoides. Four groups of 16 female, 21-24 day old, Yorkshire-cross pigs were treated daily with 0.5 or 1.0mg/kg TTN1013, 1.0mg/kg TTN1014, or 1.0mg/kg equivalent of empty capsules, delivered inside a cream-filled sandwich cookie for 14 weeks. Three days after the initiation of daily treatments, pigs were inoculated daily with A. suum eggs for four weeks. Pigs were weighed weekly and fecal egg counts (FEC) were conducted weekly starting five weeks after initial inoculation with A. suum eggs. Fourteen weeks after first infection with eggs, pigs were necropsied and worms were recovered, counted and separated according to sex. TTN1013 administered daily at a dose of 1.0mg/kg yielded a statistically significant reduction in total worm counts (76.8%), female worm counts (75.5%), FEC (68.6%), and worm volume (62.9%) when compared to control group. Reduction of total and female worm numbers and FEC were not significant for TTN1014 or at the 0.5mg/kg dose of TTN1013. All treatments were well-tolerated by all pigs and did not cause any adverse reactions. All pigs remained clinically normal and showed no signs of reduced intestinal health for the duration of treatment. Based on these results, TTN1013 shows promise as a daily supplement to reduce infection burdens of soil transmitted helminths in both pigs and human beings.

Routine deworming of children at deployed military healthcare facilities

The World Health Organization advocates mass antihelminthic treatment of school-age children in areas of high prevalence of soil-transmitted helminths. Soil-transmitted helminths prevalence in Afghanistan is 20-50%, but a high proportion of children do not attend school, so may be missed by deworming programs. The primary function of military medical assets in a theater of war is to provide life, limb and eyesight saving treatment. Additional humanitarian aid in the form of nonemergency treatment has also been provided in Afghanistan for thousands of civilian children. Children represent 3-15% of the patients treated at deployed military medical facilities. We report on recent experience of deployed surgical teams in southern Afghanistan who have noticed high levels of soil-transmitted helminths in war-injured patients. Military medical assets may provide an opportunity to integrate a policy of deworming of children into existing programs of humanitarian support. This would not be a substitute for mass deworming programs, but a supplementation.

Frequency and intensity of exposure mediate resistance to experimental infection with the hookworm, Ancylostoma ceylanicum

Hookworms are bloodfeeding intestinal nematodes that are a major cause of anemia in resource-limited countries. Despite repeated exposure beginning in early childhood, humans retain lifelong susceptibility to infection without evidence of sterilizing immunity. In contrast, experimental infection of laboratory animals is typically characterized by varying degrees of resistance following primary infection, although the mechanisms underlying this phenomenon remain unknown. In this study, hamsters subjected to a single drug-terminated infection with 100 third stage hookworm larvae were confirmed to be resistant to pathological effects following a subsequent challenge. In a second experiment, hamsters infected twice-weekly with 10 third stage larvae (low inoculum) exhibited clinical and parasitological evidence of continued susceptibility, while those given 100 L3 (high inoculum) developed apparent resistance within 3 days following the initial exposure. The kinetics of parasite-specific IgA, IgM, and IgG antibody production varied by group, which suggests that the humoral immune response to hookworm infection is stimulated by the nature (frequency and intensity) of larval exposure. These results suggest that intermittent low-inoculum larval exposure, which is characterized by prolonged susceptibility to infection, may serve as a more representative model of human hookworm disease for studies of pathogenesis, as well as drug and vaccine development.

The role of nutrition in integrated programs to control neglected tropical diseases

There are strong and direct relationships between undernutrition and the disease caused by infectious organisms, including the diverse pathogens labeled as neglected tropical diseases (NTDs). Undernutrition increases the risk of infection, the severity of disease and the risk that children will die, while the physical damage, loss of appetite, and host responses during chronic infection can contribute substantially to undernutrition. These relationships are often synergistic. This opinion article examines the role of nutrition in controlling NTDs and makes the point that mass drug treatment--the major strategy currently proposed to control several diseases--is crucial to controlling disease and transmission, but is only the start of the process of physical recovery. Without adequate energy and nutrients to repair damaged tissues or recover lost growth and development, the benefits of treatment may not be evident quickly; the effects of control programs may be not appreciated by beneficiaries; while vulnerability to reinfection and disease may not be reduced. There is substantial potential for nutritional interventions to be added to large-scale programs to deliver drug treatments and thereby contribute, within a broad strategy of public health interventions and behavior change activities, to controlling and preventing NTDs in populations, and to restoring their health.

Turning neglected tropical diseases into forgotten maladies

Because they afflict mostly poor people in poor countries, killing relatively few compared to the many who suffer from severe chronic disabilities, a large cluster of infections deserve the label of neglected tropical diseases (NTDs). That is changing as these diseases' enormous health, educational, and economic toll is better understood, including how they interact with HIV/AIDS, malaria, and other illnesses. Several NTDs could be controlled or even eliminated within a decade, using integrated, highly cost-effective mass drug administration programs together with nondrug interventions. Research is needed to provide additional means of control for these conditions and make elimination feasible for still others.

Effects of annual mass treatment with ivermectin for onchocerciasis on the prevalence of intestinal helminths

We evaluated the effect of annual ivermectin (IV) distribution for onchocerciasis on the prevalence of soil transmitted helminth (STH) infections in school-aged (SAC) and preschool-aged (PAC) children by comparing children in villages that had received treatment for 13 years to those from socioeconomically similar villages in untreated areas. We enrolled 1,031 SAC and 211 PAC for Kato Katz examinations. Treated areas had a lower prevalence of Ascaris (SAC: 3% versus 12%, P < 0.0001; PAC: 3% versus 10%, P < 0.051) and Trichuris (SAC: 6% versus 10%, P = 0.012; PAC: 1% versus 8%, P = 0.019), but not hookworm (SAC: 38% versus 42%, P = 0.20; PAC: 21% versus 27%, P = 0.30). The prevalence of Ascaris or Trichuris in treated areas was below the WHO threshold for mass antihelminthic treatment (MDA), but not for hookworm. We conclude that benzimidazole MDA in IV treatment areas is indicated to effectively control hookworm.

Optimal survey designs for targeting chemotherapy against soil-transmitted helminths: effect of spatial heterogeneity and cost-efficiency of sampling

Implementation of helminth control programs requires information on the distribution and prevalence of infection to target mass treatment to areas of greatest need. In the absence of data, the question of how many schools/communities should be surveyed depends on the spatial heterogeneity of infection and the cost efficiency of surveys. We used geostatistical techniques to quantify the spatial heterogeneity of soil-transmitted helminths in multiple settings in eastern Africa, and using the example of Kenya, conducted conditional simulation to explore the implications of alternative sampling strategies in identifying districts requiring mass treatment. Cost analysis is included in the simulations using data from actual field surveys and control programs. The analysis suggests that sampling four or five schools in each district provides a cost-efficient strategy in identifying districts requiring mass treatment, and that efficiency of sampling was relatively insensitive to the number of children sampled per school.

Immunity against helminths: interactions with the host and the intercurrent infections

Helminth parasites are of considerable medical and economic importance. Studies of the immune response against helminths are of great interest in understanding interactions between the host immune system and parasites. Effector immune mechanisms against tissue-dwelling helminths and helminths localized in the lumen of organs, and their regulation, are reviewed. Helminth infections are characterized by an association of Th2-like and Treg responses. Worms are able to persist in the host and are mainly responsible for chronic infection despite a strong immune response developed by the parasitized host. Two types of protection against the parasite, namely, premune and partial immunities, have been described. Immune responses against helminths can also participate in pathogenesis. Th2/Treg-like immunomodulation allows the survival of both host and parasite by controlling immunopathologic disorders and parasite persistence. Consequences of the modified Th2-like responses on co-infection, vaccination, and inflammatory diseases are discussed.