Biology ETDs

Publication Date

Spring 5-9-2018


Human schistosomiasis is one of the great neglected tropical diseases (NTDs) of our time with more than 206 million individuals infected and more than 90% of those infected reside in Sub-Saharan Africa (WHO 2017). Chemotherapy based control programs play an essential role in contributing to the elimination of human schistosomiasis; however, there is an increasing consensus that chemotherapy needs to be supplemented by other means if interruption of transmission and elimination are to be achieved. Given this situation, the focus of this dissertation was to better understand transmission dynamics in a hyperendemic setting in western Kenya and to find alternative measures to supplement ongoing mass drug administration (MDA) using indigenous resources that disrupt the development of Schistosoma mansoni (the causative agent of intestinal schistosomiasis in Africa) within its obligatory aquatic snail intermediate host, Biomphalaria. The discipline of disease ecology emphasizes understanding the biotic context in which disease transmission occurs. S. mansoni and Biomphalaria exist within a complex ecological milieu in streams, ponds and lakes in Kenya. The research in this dissertation combined DNA barcodes, phylogenetics, host use patterns and morphology to determine the diversity of trematodes that use Kenyan Biomphalaria as an intermediate host. Along with S. mansoni, we found 21 additional digenetic trematodes that also use Biomphalaria species in Kenya as an intermediate host. The presence of other trematode species in Biomphalaria affects S. mansoni by causing competition for access to snail resources. Furthermore, we used experimental approaches to understand the competitive dynamics among these trematodes and to generate a dominance hierarchy among them. We found that several trematode species are dominant to S. mansoni and long-term agricultural practices have created a situation where an amphistome parasite of cattle relies on a facilitating effect by S. mansoni for its own successful development in the snail host. Coupled with these data are four years of observational survey data to predict how these trematodes influence S. mansoni’s prevalence in Biomphalaria and consequently the likelihood of influencing human infections.




Schistosomiasis, Biomphalaria, Schistosoma mansoni, Biodiversity, Disease Ecology, DNA Barcodes

Document Type


Degree Name


Level of Degree


Department Name

UNM Biology Department

First Committee Member (Chair)

Dr. Eric S. Loker

Second Committee Member

Dr. Jennifer A. Rudgers

Third Committee Member

Dr. Stephen A. Stricker

Fourth Committee Member

Dr. William E. Secor

Fifth Committee Member

Dr. Michelle L. Steinauer