Introduction Over the last decades, visceral leishmaniasis (VL) has spread to a number of metropolitan areas in Brazil. The aim was to determine the prevalence and the risk factors associated with Leishmania infantum infection among seronegative and molecular positive dogs in an area of active transmission in Southeast of Brazil.

Methods A cross-sectional study was conducted with 1443 dogs, random selected. Molecular methods were performed using polymerase chain reaction (PCR-RFLP) and serology was conducted using ELISA. Mixed logistic regression model was used to evaluate the risk factors associated with L infantum infection.

Principal findings Of the 1443 dogs examined, 230 (15.9%) were seropositive in ELISA assay, while PCR-RFLP revealed that 356 animals (24.7%) were positive and 1087 (75.3%) negative for L infantum DNA. To identify the risk factors associated with infection, only seronegative animals (n=1213) were evaluated, and of these 296 (24.4%) were PCR-positive and 917 (75.6%) PCR-negative for L infantum DNA. The risk factors associated with infection were family income < one minimum salary (OR.4.1; 95% CI 1.0 to 17.5), knowledge of the owner regarding the vector (OR.1.9; 95% CI 1.1 to 3.4), permanence of dog in the backyard (OR.2.3; 95% CI 1.2 to 4.4), and lack of examination for VL (OR.1.6; 95% CI.1.0 to 2.4).

Conclusions PCR is more accurate than serology in the early detection of infection among asymptomatic dogs, and its application on a large scale for the surveillance of VL could minimise false-negative results. Identification of the risk factors associated with canine visceral leishmaniasis is important for the definition of strategies of disease control.