High Seroprevalence Rates of Toxoplasma gondii and Neospora caninum in Dogs in the Pantanal Region of Mato Grosso, Brazil

Toxoplasma gondii and Neospora caninum are protozoan that infect animals worldwide. Dogs act as sentinels of these infections, indicating potential risks to human health, particularly in the case of T. gondii due to its zoonotic nature. Therefore, we aimed to determine the seroprevalence and associated factors for T. gondii and N. caninum infections in dogs living in the Pantanal biome, Brazil. This study evaluated the seroprevalence in 743 serum samples from dogs in Barão de Melgaço and Nossa Senhora do Livramento, municipalities endemic for canine visceral leishmaniasis located in the Pantanal biome of Mato Grosso, Brazil, by Indirect Immunofluorescence Assay. Overall, 66.4% (n = 493) were positive for T. gondii and 12.4% (n = 92) for N. caninum. Seropositivity was associated with dogs older than 3 years (T. gondii—p = 0.001; OR = 2.579; N. caninum—p = 0.004; OR = 7.621), living together with other dogs and/or cats (T. gondii—p = 0.04; N. caninum—p = 0.005), and absence of a public sewage system at home (T. gondii—p = 0.044; OR = 4.730; N. caninum—p = 0.035; OR = 1.376). For T. gondii, additional associations were found with street access (p = 0.015; OR = 3.966), contact with rodents (p = 0.025; OR = 1.539), and a diet including leftover food (p = 0.025; OR = 2.405). Infection by N. caninum was more frequent in rural dogs (p = 0.011; OR = 4.857) and in those coinfected with Leishmania infantum (p < 0.001; OR = 6.407). The investigated regions are endemic for T. gondii and N. caninum, with increased risk associated with environmental conditions and dog management practices. Furthermore, dogs infected with L. infantum showed a higher likelihood of coinfection with N. caninum.