Molecular and biologic characterization of Trypanosoma cruzi from the United States of America
Roellig, Dawn Marie
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Trypanosoma cruzi, the causative agent of Chagas disease, is a flagellated protozoan parasite endemic to the Americas. There are an estimated 7.6 million people infected within Latin America, with 200,000 new cases occurring annually. In the United States, only six autochthonous human cases have been reported, but screening of US blood donors since January 2007 by the Chagas’ Disease Biovigilance Network has confirmed over 1,000 seropositive donations, some of which are believed to be autochthonously acquired infections. In addition to autochthonous human cases, naturally acquired infections have been reported in domestic dogs, captive exotic animals, and a wide range of wildlife species. Although T. cruzi is common in the sylvatic cycle (transmission between wildlife and vectors) and the peridomestic cycle (between animals that move between the wild and around homes), circulation within the domestic cycle (between hosts within or around homes) is less often documented in the US. In the sylvatic cycle, a number of wild mammals have been identified as reservoirs and the prevalence of T. cruzi in US wildlife based on serology, culture isolation, and/or PCR can be equally as high as in South America. Considerable work on T. cruzi has been conducted in Central and South America, but due to limited numbers of human cases in the US, little work has been conducted to characterize US isolates. Previous studies have determined prevalence in some host species through the use of serology, hemoculture, and/or PCR, identified transmission routes for a few reservoirs using non-native isolates, and molecularly characterized a limited number of isolates. With new human cases, increasing numbers of veterinary cases, and influx of potentially infected immigrants, understanding the ecology in the US is imperative. The goal of this dissertation was to elucidate characteristics of T. cruzi isolates from the US using molecular and in vivo techniques to better understand T. cruzi epizootiology in the region.