Soil-transmitted helminth (STH) (A. lumbricoides, T. trichiura and hookworm) infections are a significant public health concern in Honduras. These infections are treatable using inexpensive anthelmintic medications, however long-term control and eradication will require large investments in public and private sanitation infrastructure. Importantly, both types of interventions are targeted towards high-risk populations and regions rather than individuals. The goal of this thesis is to contribute to improving the efficiency of soil-transmitted helminth control efforts in Honduras. In our first study, we use multiple regression analyses to identify determinants of STH infections and generate estimates of A. lumbricoides, T. trichiura and hookworm infection prevalence, as well as recommended deworming frequencies, for each of Honduras’ 298 municipalities. Our estimates suggest that prevalence of all three infections has declined over time, however 75% of municipalities still require annual or semi-annual deworming. In our second study, we quantify how the type of region used for measuring prevalence and allocating resources can impact the success and efficiency of public health programs. More specifically, we compare administrative regions to alternative zoning schemes at the same geographic scale. Our findings suggest that regions designed to be homogeneous with respect to prevalence can be more efficient than existing municipalities (at the same scale) for distributing resources. This research has implications on future control efforts. / Thesis / Master of Science (MSc)

The sex hormone testosterone supports male reproduction. However, testosterone is hypothesized to suppress immune activity, resulting in a tradeoff between energetic investment in reproductive effort and immune function. The Immunocompetence Handicap Hypothesis (ICHH) therefore argues that testosterone-linked masculine traits honestly signal health status to prospective mates, as only uninfected males should be able to maintain high testosterone levels. Still, this proposed tradeoff remains poorly tested among human men, especially among natural fertility populations experiencing high infectious disease burdens. This dissertation therefore tested the ICHH among indigenous Shuar men of Amazonian Ecuador. Specifically, this project examined testosterone variation patterns and assessed how male investment in reproductive effort is associated with reproductive success and immune function. The first study tested testosterone level variation among Shuar men in relation to body composition, age, and style of life factors. This study demonstrated that age and BMI interactions shape testosterone levels in complex ways, such that the relationship between body composition and testosterone profile varies throughout the life course. The second study investigated whether individual reproductive success was significantly influenced by masculine trait development and parasite load. These results failed to support the hypotheses that masculine traits increased reproductive success or honestly signaled lack of parasitic disease. Instead, a significant positive association was observed between a composite score of masculine traits and Ascaris lumbricoides infection load; suggesting that male investment in reproductive effort may increase parasitic infection risk. The final study assessed whether testosterone levels were negatively associated with four measures of immune function (parasite load, C-Reactive Protein [CRP], Immunoglobulin-G [IgG], and Immunoglobulin-E [IgE]). Testosterone levels were inversely associated with CRP levels and a positive relationship between testosterone levels and Trichuris trichiura infection load was documented, suggesting increased investment in reproductive effort may suppress some aspects of immune function and increase parasite burden. Overall, these studies fail to support the ICHH, but do indicate a context-dependent tradeoff between energetic investment in male reproductive effort and some aspects of immune function; thereby demonstrating complex interactions between physical characteristics, physiological processes, and immune activity in human men. This dissertation includes unpublished, co-authored material.