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Professional and Research Interests:
I work in the field of evolutionary epidemiology, which is an emerging interdisciplinary field that applies methods in evolutionary biology and ecology to understand pathogen evolution, transmission, disease dynamics, and control.
My research focuses on the following topics:
- Transmission dynamics of parasitic organisms
- Speciation, hybridization, and genome introgression
- Determining the ecological and physiological limits of host specificity and its underlying genetic architecture. (i.e. what are good hosts for parasites, and why are they good hosts?)
- Systematics and phylogenetics of parasites
- Mating systems of parasites
Evolutionary Epidemiology of Schistosomiasis in Kenya
Schistosomiasis is one of the world’s great neglected diseases that exemplifies an insidious, chronic, and debilitating infection with a life cycle that resists control. Schistosome parasites are trematode worms that are vectored through snail hosts, species of the genus Biomphalaria. These parasites asexually reproduce in the snail host, emerge in the water, and penetrate the skin of hosts they contact. Our research focuses on Schistosoma mansoni in relation to its human and vector host in east Africa, where the burden of infections are among the highest.
This work is funded through the National Institutes of Health and is an ongoing collaboration with Dr. Eric Loker (University of New Mexico) and Dr. Gerald Mkoji (Kenya Medical Research Institute). We have four major aims:
1. Determination of micro- to macrogeographic genetic structuring in schistosomes (i.e. from pedigree relationships among kin within hosts to landscape-scale genetic subdivision). This work will elucidate transmission cycles of S. mansoni and aid the understanding of the development and spread of drug resistance.
2. Monitoring the evolution of drug resistance in Kenya. Currently, there is only one major drug, Praziquantel, that is available for control of schistosomiasis in Africa. We are monitoring populations for the evolution and spread of drug resistance.
3. Understanding patterns of hybridization and gene introgression between species of Schistosoma. The goal is to understand how interactions between S. mansoni and a rodent schistosome, S. rodhaini influence human disease.
4. Determining intra- and interspecific interactions between parasite individuals that share snail hosts. In its natural environment, an individual snail is often exposed to more than one pathogen. We are exploring how infections with multiple individuals or multiple species influence the progression of infection. We are particularly interested in competition and cooperation between pathogens and how kin selection may influence these interactions.
Alternate Transmission Patterns of Hantaviruses
Despite intensive research and control efforts, a significant number of zoonotic pathogens have emerged in the last decade, crossed species boundaries and become a health hazard to humans. Hantaviruses are a prime example. They are negative sense RNA viruses, of the family Bunyaviridae, that typically infect murid rodents. Several hantaviruses (e.g. Andean virus in Chile) have highly significant public health impacts: when transmitted to humans: there is no cure, fatality rates are high, and infection can cause a considerable disease burden.
One of the difficulties of controlling human hantavirus infections is understanding how virus is transmitted among rodents and from rodents to humans. Transmission is a formidable challenge for pathogens because they need to transfer between hosts, a discontinuous resource in space and time. To bridge this gap, pathogens have evolved multiple strategies to increase their success including the use of vectors for transit between hosts. The primary goal of this project is to investigate alternative transmission pathways of hantaviruses between hosts by determining the role of arthropod ectoparasites as competent vectors for transmission.
Steinauer, M.L. & B.D. Horne. 2002. The enteric helminths of Graptemys flavimaculata Cagle, 1954 a threatened chelonian species from the Pascagoula River in Mississippi, U.S.A. Comparative Parasitology 69(2): 219-222.