Fate and Dissemination of Pathogens in Aquatic Wildlife and Their Ecosystems
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The world is experiencing an increase in emergent infectious diseases as a result of expanding world markets, urbanization and intensified animal husbandry. It is not just humans that are affected, but also domestic and wild animals. Many diseases affecting humans are of animal origin and because of population increases and globalization of society we will continue to see increased interactions between humans, domestic animals, and wildlife. The wildlife component of this triad has received inadequate focus in the past to effectively protect not only human health, but also biodiversity of wildlife, agriculture and trade. The objective of this thesis work is to assess the presence of microbial pathogens such as the bacterium Salmonella enterica and the fungus Batrachochytrium dendrobatidis (Bd) in aquatic environments and elucidate the effects of specific environmental conditions on the fate of these pathogens in the non-host environment and the resulting impact of these conditions to persistence and prevalence of infections. The first studies provided evidence that there are many species of aquatic animals that can serve as potential reservoirs for the long term persistence of Salmonella. Additional studies confirmed the notion that the terrestrial environment can act as a significant source of contamination of the aquatic environment by Salmonella. Finally, studies performed demonstrated that naturally occurring biofilms can provide a mechanism for long term persistence and contamination of the aquatic ecosystem by Salmonella. An inexpensive and sensitive nested PCR protocol was developed for studies involving Bd. Using this technique, in addition to a qPCR method, the presence of Bd in populations including endangered and endemic amphibians in Central Texas was demonstrated and later affirmed. In addition to its presence, spatial and temporal differences in prevalence and intensity of infection were detected. Studies suggest that seasonal temperatures, water quality and permanency of water can contribute to increased infections by the pathogen. Understanding interactions of pathogens such as these with their host and non-host environments could provide a greater understanding of the organism and be the foundation for preemptive actions and responses that could potentially help limit future impacts to the health of both humans and wildlife populations.