Strain Typing of Trypanosoma cruzi in the Southern United States
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Date
2019-04-19
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Abstract
Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, is endemic in Latin America and has also been documented in the United States. The disease has a wide range of symptoms, ranging from acute, cold-like symptoms, to chronic afflictions of the heart and gastrointestinal systems. While treatment options are available for humans, a low percentage of infected individuals can access and afford these treatments and no antiparasitic treatments are approved for dogs. T. cruzi has a large amount of genetic diversity. Seven strain types, TcI-TcVI and Tcbat, have been identified, with geographic distribution varying with the region. In South America north of the Amazon, TcI dominates, while TcV and TcVI dominate south of the Amazon. TcI and TcIV are the main strains of Central America and have also been previously identified in the Texas, yet there is little research attention on the strains in other regions of the southern United States. The goal of this project is to characterize the T. cruzi parasite genetic strain distribution across the southern US. The DNA from the gut tissue of the triatomine vector (‘kissing bug’), collected through Texas A&M University’s Citizen Science Program, was analyzed using PCR assay to identify the presence of T. cruzi. Then, a PCR assay with probes for the strain types was used to identify the strain type of positive samples. A geographic map of the southern United States was created to illustrate the distribution of the strain types found in the sample. It was found that 54% of the sample (n=2129) was positive for T. cruzi. Of the sample size 1174 kissing bugs were tested for the strain type. Of this tested set, 41% were TcI, 36% were TcIV, 10% were co-infected with TcI and TcIV, and 13% were untypable. Co-infected bugs were only found in Texas, while TcI was localized to Texas and the southwest and TcIV was located in the southeast. There is evidence of a link between the various strains and their propensity to cause chronic symptoms, so it is critical to not just know where T. cruzi is cycling and infecting people and animals in the United States, but also to have a clear understanding of which strains are present where. The results of this study will help bridge the gap in knowledge on T. cruzi strain types and will help public health officials, doctors, and veterinarians better assess the risk of humans and animals in the southern United States.
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Chagas disease, Trypanosoma cruzi, strain typing, discrete typing units, United States, vector, Triatomine