Prevalence of Trypanosoma Cruzi in Free-Ranging Mammalian Populations in South Texas
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Chagas disease, also known as American trypanosomiasis, is caused by the etiological flagellate protozoan Trypanosoma cruzi (T. cruzi). It is a significant health concern in South and Central America where millions of people are infected or at risk of infection, and an emerging health concern in the United States. Kissing bugs (Triatoma sp.) are vectors for Chagas disease and feed upon a variety of taxa including humans and sylvatic free-ranging mammals. It is likely that free-ranging mammals are important in the maintenance and transmission of Chagas in the environment, but solid empirical support is lacking. In an effort to address this information gap, I conducted a field study to determine T. cruzi prevalence in free-ranging mammals in Bexar and Val Verde Counties, Texas. My research objectives were to (1) determine disease prevalence of T. cruzi parasites in free-ranging mammals and species population densities in various vegetation communities, (2) determine if the use of immunoassay lateral rapid flow diagnostic devices is feasible in field environments to detect Chagas antibodies in meso-mammals, and (3) determine the behavior of Peromyscus pectoralis and communal tolerance to collective triatomine insects in the burrow, and (4) to measure vector defecation intervals for pathogen potential. The study analyzed 483 whole blood and tissue samples from free-ranging meso-mammal species using immunochomatographic assay strips and polymerase chain reaction (PCR) methodologies to screen for T. cruzi. I documented overall infection presence in 60% of animal species. T. cruzi prevalence was determined through whole-blood and tissue analysis to ensure identification of the protozoan parasite that could be occurring in either the acute or chronic infection stage. I further evaluated cave dwelling Peromyscus pectoralis for behavioral response to hematophagous triatomine insects, and found the communal species to possibly be codependent. Meso-mammals tolerated insect blood feeding activity and routinely bite or consume insect vectors as an antagonistic response or nutritional requirement. Triatomine insect defecation intervals occurred 11 – 24 minutes after a blood meal and away from the host mammal. Delayed triatomine insect defecation indicates pathogen occurs from direct insect ingestion or meso-mammal grooming activities rather than at the site of the bite. My results indicate that cave and burrow dwelling free-ranging meso-mammals serve as primary pathogen hosts, and facilitate Chagas disease prevalence. Findings support the emerging disease as a major zoonotic and public health concern for south Texas Counties.
Kramm, Mathew M (2015). Prevalence of Trypanosoma Cruzi in Free-Ranging Mammalian Populations in South Texas. Doctoral dissertation, Texas A & M University. Available electronically from