Biogeography and genetic variation of triatomine chagas disease vectors and trypanosoma cruzi isolates from texas



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Trypanosoma cruzi is endemic in the U.S., infecting humans, dogs, and wildlife. This study identified a new geographic distribution for triatomine species within Texas based on 2,449 records obtained from published data and new field studies. Triatomine vectors of T. cruzi were reported from 97 counties covering all ecological zones. Triatoma gerstaeckeri was the most commonly collected species followed by T. sanguisuga. New field collections resulted in 233 specimens from 37 counties and a 52% T. cruzi infection rate. A second trypanosome, Blastocrithida triatomae was found in two specimens from different locations. A habitat suitability model for T. gerstaeckeri was developed using GIS and remote sensing applications. Forest and rangeland were the predominant land cover classes found within T. gerstaeckeri habitat, where as water and agriculture proved to have little influence on habitat suitability. Genetic variation of seven triatomine species from Texas was evaluated using cytochrome b DNA sequences from 61 new specimens. This is the first study of the taxonomic status of T. gerstaeckeri, T. indictiva, and T. neotomae using molecular markers. Intraspecific variation for T. sanguisuga and T. gerstaeckeri suggests significant gene flow across their ranges within Texas. Genetic variation of T. cruzi isolates from Texas was evaluated using SSU rRNA gene sequences. Included were 63 new sequences from five triatomine species, canine, baboon, and human isolates. Sequences partitioned into two groups in agreement with previous studies on U.S. isolates. Genetic variation of T. cruzi did not occur according to host, geographic location, or collection site. The extent of Chagas disease in domestic canines of Texas is described by geographic distribution, signalment, and clinical presentation and histopathology. Based on data from 553 cases, the geographic distribution in Texas is widespread (46 counties) and closely matches the distribution of the Triatomine vectors. Chagas disease was diagnosed in 33 breeds, primarily sporting/working dogs. This study represents the most comprehensive characterization of components of the Chagas disease transmission cycle in the U.S. to date. These findings should raise awareness among physicians, veterinarians, and public health practitioners regarding T. cruzi, its vectors, canine infection, and human risk for Chagas disease in Texas.