Ecoepidemiology of Trypanosoma cruzi in Texas
Date
2016-10-14
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Abstract
This dissertation focused on elucidating factors affecting Trypanosoma cruzi transmission in the southern US, using triatomine, canine, and wildlife samples.
Collection of triatomine vectors from 2012-2015 included standard entomological sampling, as well as submissions through a citizen science program. The insects were identified to species, dissected, and tested for T. cruzi infection. T. gerstaeckeri and T. sanguisuga were the most abundant species in the collection. Kissing bugs were captured primarily April-October, and peak activity varied by species. A T. cruzi infection prevalence of 58.9% was found in 1,226 triatomines of 6 species, and infection prevalence varied by species. Amplification and sequencing of the TcSC5D gene revealed Triatoma gerstaeckeri was approximately equally infected with TcI and TcIV, and 10 individuals showed mixed TcI/TcIV infections. In contrast, Triatoma sanguisuga was more frequently found infected with TcIV than TcI. Relative abundance of parasite DTUs varied spatially, with both TcI and TcIV co-circulating nearly equally in vectors in central Texas, while TcIV predominated in northern Texas.
A study of T. cruzi infection in dogs in south central Texas using paired IFA and Chagas Stat-Pak serological testing showed a seroprevalence of 57.6%. The odds of being seropositive were greater for dogs older than 6 years of age than dogs less than 2 years of age. PCR analyses of blood revealed 26.7% of dogs, including both seronegative and seropositive dogs, harbored parasite DNA in their blood. Sequencing of the TcSC5D gene from blood and tissue samples showed TcI and TcIV were present, including a co-occurrence of both DTUs in an individual dog.
Cardiac tissue and blood were collected from wildlife—including raccoons (Procyon lotor), coyotes (Canis latrans), gray foxes (Urocyon cinereoargenteus), and bobcats (Lynx rufus)—from central Texas. PCR analyses found 2 bobcats (14.3%), 12 coyotes (14.3%), 8 foxes (13.8%), and 49 raccoons (70.0%) were positive for T. cruzi in at least one sample (right ventricle, apex, and/or blood clot). Strain typing revealed raccoons infected with DTU TcIV, and a single raccoon with TcI/TcIV
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Trypanosoma cruzi, Triatoma, Chagas disease, disease ecology