Infection with Trypanosoma cruzi is a major risk in Latin America, and dogs are believed to be good models for evaluating Chagas disease. Here, we evaluated the clinical and immunopathological alterations developed by mongrel dogs experimentally infected with different infective doses (2,000, 20,000, and 200,000 metacyclic trypomastigotes of Sylvio X10/4 strain kg−1 via intraperitoneal). Clinical and electrocardiographic parameters, as well as antibody production and pathologic lesions were evaluated. All three doses of this strain of T. cruzi induced a similar pattern of infection characterized by cardiac arrhythmias and severe and diffuse myocarditis. Specific anti-T. cruzi IgG indicated seroconversion by day 14 after infection, and IgG levels increased during the period of evaluation. Mortality was observed only in dogs infected with the medium or high parasite doses, but not in the group infected with a low dose of 2,000 parasites kg−1. Infection with a low dose of parasites provides an excellent nonlethal model to evaluate the immunopathology of the acute disease in dogs infected with the Sylvio X10/4 strain of T. cruzi.
American trypanosomiasis is a growing health issue in the Americas. México is an endemic country, where some locations such as in the State of México are considered highly prevalent. In the valley of Toluca city, the capital of the State of Mexico, there exists an apparent high prevalence in dogs. The absence of triatomine vectors suggests that dogs may not be infected. Therefore, we conducted a directed survey to domiciliated and nondomiciliated dogs to reassess dogs' T. cruzi seroprevalence status. HAI and ELISA serologic tests were applied to 124 and 167 serums of domiciliated and nondomiciliated dogs in the target city. Risk factors were estimated, but the results did not show any evidence to assess them. No domiciliated dogs tested positive to both tests, whereas only one non-domiciliated dog resulted positive. This animal may have acquired the infection in an endemic area and then migrated to Toluca. Research results indicate that T. cruzi infection is not actively transmitted among dogs, and it is pointed out that dogs are the main sentinel animal population to evaluate a possible expansion of the territory affected by Chagas' disease.
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