Distribution and characterization of canine Chagas disease in Texas.

Although acute and chronic cases of canine Chagas disease have been reported from multiple areas in the southern region of the United States, little data are available on current disease occurrence patterns in endemic areas. Therefore, a study to assess frequency, geographic distribution, signalment, and clinical spectrum of Chagas disease in domestic dogs from Texas was conducted. Serology, histopathology, and clinical case records from multiple institutions for the time period 1993-2007 were analyzed. A total of 537 serologically and/or histopathologically confirmed cases were documented. Cases were reported from 48 of 254 counties within Texas, covering all major geographic regions. Forty-eight dog breeds were represented among the cases, primarily in the sporting and working groups. In histopathologically confirmed cases, acute death occurred in 42%, approximately half of which were <1 year of age. Nearly all cases with histopathology data reported myocarditis (97.9%) and observation of Trypanosoma cruzi organisms (81.7%). Predominant clinical observations included enlarged heart, lethargy, anorexia, ascites, cardiac conduction disturbances, and respiratory difficulties. An increasing rate of serologic test submissions was noted over the study period, with an overall positive test prevalence of 20.3%. The study results provide strong evidence that an active canine Chagas disease transmission cycle is present throughout all ecoregions of Texas, affecting a broad range of dog breeds and age groups.