Title: Host-parasite relationships of trematode-vectored bacteria (Neorickettsia spp.) with larval trematodes from African freshwater snails
Authors: Cassandra A. Valdez1, Valerie Sanchez1, Sarah K. Buddenborg1, and Eric S. Loker1
Affiliations: 1Center for Evolutionary and Theoretical Immunology, University of New Mexico
Abstract: Neorickettsia, a bacterial genus closely related to Wolbachia, is transmitted as far as is known exclusively in the life cycle stages of digenetic trematodes. These bacteria are hyperparasites (parasites of parasites). The overall prevalence of Neorickettsia in larval trematodes is poorly known as is the degree of host specificity and geographic range shown by these bacteria. Thus far they have not been reported from trematodes from Africa, including from the many species that infect humans and domestic animals there. We hypothesize that we will identify Neorickettsia spp. from African trematode cercariae and suggest that different trematode lineages will be shown to harbor distinct lineages of Neorickettsia. To answer these questions, we have procured, courtesy of Dr. Michael Kent of Oregon State University, specimens of the trematode Nanophyetus salmincola, a species known to be positive for Neorickettsia helminthoeca. We have extracted DNA from larval stages of N. salmincola, and using primers designed to be Neorickettsia specific by Dr. Cristina Takacs-Vesbach, have amplified DNA by PCR from the sample, and are in the process of confirming the amplified product as being from Neorickettsia. This will establish a positive control by which to gauge our future results. We have also obtained cercariae from many different African snails, and are poised to survey them for Neorickettsia infection. We are particularly curious to learn if cercariae of the human blood fluke, Schistosoma mansoni, are infected. If so, then it is possible that these bacteria are carried into the human host upon infection with schistosomes.