Molecular and serological survey of Trypanosoma vivax in Crioulo Lageano Cattle from southern Brazil

Bovine trypanosomiasis, caused by infection with the protozoan Trypanosoma vivax, is harmful to livestock worldwide. Knowing its epidemiology is relevant to evaluate the susceptibility, resistance, and tolerance of animals. The objective of this study was to determine the prevalence of T. vivax in Crioula Lageana cattle and relate them to clinical, hematological, and biochemical findings to elucidate the breed's health and disease tolerance characteristics. Venous blood samples from 310 bovines considered healthy during the clinical examination were used to perform polymerase chain reaction (PCR) analysis, Immunofluorescence Antibody Test (IFAT) assays, hemogram tests, and serum biochemistry. The collected data were subjected to statistical analyses to compare seropositive and negative groups. IFAT indicated that the seroprevalence for T. vivax was 8% (24/310); however, all tested animals were negative in the conventional PCR (0%, 0/310). Higher amounts of platelets and less cholesterol were detected in seropositive animals but were within the reference values. Ruminal hypomotility and mild tachycardia were observed in all sampled animals. Considering the non-specific clinical signs and the absence of hematological alterations in infected animals, the seropositivity found indicates previous exposure to the protozoan, and the absence of clinically affected animals may result from characteristics inherent to this breed.