Increased frequency of detection of anti-Toxoplasma gondii antibodies in domestic cats after outbreak of human toxoplasmosis.

Toxoplasmosis affects various organisms, including humans. In 2018, the largest outbreak of human toxoplasmosis described so far was reported in southern Brazil, with 809 human cases reported, and water as the potentially primary source of infection. Therefore, in this study, we aimed to evaluate the seroprevalence of Toxoplasma gondii in naturally infected domestic cats before and after the human toxoplasmosis outbreak, as well as the potential for environmental contamination by the number of cats infected after the outbreak. We evaluated 381 serum samples from domestic cats in southern Brazil, using an indirect immunofluorescence assay, with samples considered positive at a titer of 1:20. We found that 73% (204/279) and 27% (75/279) of the samples analyzed before the outbreak were negative and positive, respectively. After the outbreak, 62% (69/112) were negative of the samples were and 38% (43/112) were positive. Notably, the proportion of positive samples before the outbreak before (27%) was significantly lower than that after the outbreak (38%; P = 0.020). Therefore, the increased seroprevalence of T. gondii in cats was probably correlated with the ingestion of contaminated water. Therefore, it is important to monitor animals, mainly definitive hosts, after toxoplasmosis outbreaks, considering that these animals can contaminate the environment and, consequently, humans.