Neospora caninum and Toxoplasma gondii in Urban Dogs from Espírito Santo, Brazil

Seroprevalence, Coinfection, and Associated Factors

Resumo

Background: Neospora caninum and Toxoplasma gondii are globally distributed intracellular protozoa of veterinary and public health importance. Dogs are the definitive hosts of N. caninum and act as epidemiological sentinels of environmental contamination by T. gondii. However, information regarding canine exposure to these protozoa in Espírito Santo State, Brazil, remains limited. Therefore, this study investigated the seroprevalence of anti-N. caninum and anti-T. gondii antibodies in dogs from an urban area of Espírito Santo State and evaluated factors associated with infection.

Materials, Method & Results: A total of 103 canine serum samples were analyzed by the Indirect Fluorescent Antibody Test (IFAT). Epidemiological information regarding sanitary management, feeding practices, housing conditions, and contact with other animal species was obtained through questionnaires applied to dog owners. Descriptive statistical analysis was performed to determine seroprevalence, followed by univariate and multivariate analyses to identify factors associated with seropositivity. Anti-Neospora caninum antibodies were detected in 24 (23.3%) dogs, whereas 33 (32.0%) were seropositive for Toxoplasma gondii. Coinfection was identified in 9 (8.7%) animals. For N. caninum, antibody titers ranged from 1:50 to 1:3200, with predominance of the 1:50 titer. For T. gondii, titers ranged from 1:16 to 1:2048, with the highest frequencies at 1:16 and 1:128. None of the evaluated variables was associated with N. caninum seropositivity (P > 0.05). For T. gondii, dogs living in houses showed a significantly higher seroprevalence than those living in apartments in the univariate analysis (P ≤ 0.05); however, no significant association remained after multivariate logistic regression.

Discussion: The seroprevalence observed in this study is consistent with previous reports demonstrating the circulation of Neospora caninum and Toxoplasma gondii in canine populations from different regions of Brazil. The wide variation reported among studies probably reflects differences in environmental conditions, management practices, diagnostic cut-off values, and characteristics of the evaluated canine populations. Previous studies conducted in Espírito Santo have also demonstrated exposure of dogs to both protozoa, confirming their circulation in different canine populations throughout the state. Dogs play an important epidemiological role because they are the definitive hosts of N. caninum and serve as sentinels of environmental contamination by T. gondii. The predominance of low anti-N. caninum antibody titers suggests previous exposure in most seropositive animals, whereas the heterogeneous distribution of anti-T. gondii titers may indicate differences in antigenic stimulation or host immune response. The occurrence of coinfection supports the simultaneous circulation of both protozoa in the same urban environment. Although household type was associated with T. gondii seropositivity in the univariate analysis, this association was not maintained in the multivariate model, suggesting that exposure is influenced by multiple environmental or behavioral factors. Overall, the high seroprevalence of anti-T. gondii and anti-N. caninum antibodies, together with the detection of coinfection, demonstrates the circulation of both protozoa in the studied urban environment. These findings reinforce the role of dogs as epidemiological sentinels and highlight the importance of continued surveillance and preventive measures within a One Health perspective.

Keywords: neosporosis, toxoplasmosis, sentinel animals, urban environment, One Health.