Sexually Transmitted Diseases Among Pastoralists in Kaokoland, Namibia: Epidemiology, Ecology and Behavior.

Abstract

The pastoralist communities in Kaokoland, Namibia, have long been presumed to have high prevalence of sexually transmitted diseases (STDs) and associated morbidities. Though their geographic remoteness makes access to healthcare difficult, rapid ecological and sociological changes may decrease their remoteness while simultaneously bringing dramatic shifts in disease risk. This dissertation research uses an interdisciplinary approach—combining fieldwork, laboratory methods and theoretical mathematical models—to estimate and characterize endemic herpes and gonorrhea in rural Kaokoland. To our knowledge this is the first set of cross-sectional studies to report on STD burden in a population as remote and undertreated as the Kaokoland pastoralists. Both diseases were found to be highly prevalent and some unique patterns emerged. Positive herpes status was significantly associated with female gender, increasing age (by category, not year) for both men and women, and, with increased wealth among men. We speculate that sex-based differences in risk are exacerbated, in part, by local hygiene practices and a preference for “dry” sex. There was also considerable variation in prevalence by region, which may be due to geographic barriers that limit access to partners. Meanwhile, 64% of participants were positive for gonorrhea. Sixteen percent of participants had high-level infections (> ID50 dose) that were temporally and spatially clustered; 48% had low-level infections (< ID50 dose) that were distributed homogeneously. The vast majority of infections were asymptomatic, which is problematic because all disease is managed syndromically. We further explored the role of low-level GC infections in a compartmental mathematical model. This model suggests that asymptomatic infections—both high and low level—have a longer duration than previously thought and that low level infections might reveal an important role for strain-specific immunity in populations where gonorrhea is highly endemic.