Anti-Toxoplasma gondii and Leishmania spp. antibodies in household and shelter dogs in the municipality of Arapiraca, Alagoas, Northeastern Brazil

Domestic dogs are considered effective sentinels for zoonotic diseases due to their abundance, ecological ubiquity, and frequent exposure to pathogens through scavenging and carnivorous behaviors. This study aimed to determine the seroprevalence of antibodies against Toxoplasma gondii and Leishmania spp. and to investigate potential infection risk factors in household and shelter dogs in Arapiraca, a semi-arid municipality in Northeastern Brazil. A total of 292 serum samples were analyzed, comprising 142 from shelter dogs and 150 from household dogs. The Indirect Immunofluorescence Assay (IFA) was used for serological testing, with cut-off titers of ≥1:16 for T. gondii and ≥ 1:40 for Leishmania spp. Antibodies against T. gondii were detected in 5.8 % (17/292) of the dogs, with a higher frequency in shelter dogs 8.4 % (12/142) compared to household dogs at 3.3 % (5/150). For Leishmania spp., 9.2 % (27/292) of the animals tested seropositive: 11.2 % (16/142) in shelter dogs and 7.3 % in household dogs (11/150). None of the seropositive animals presented clinical signs of disease. Statistical analysis did not reveal significant associations between seropositivity and the evaluated variables. These findings highlight the role of dogs as silent reservoirs and sentinels for zoonotic pathogens, reinforcing the need for active surveillance strategies, particularly in socioeconomically vulnerable and ecologically sensitive areas. The results also suggest that canine serological monitoring may serve as a useful indicator of environmental risk for human exposure to toxoplasmosis and leishmaniasis.