Clinically infected dogs have been identified as the main reservoir hosts of visceral leishmaniasis (VL)
caused by Leishmania infantum. Recently asymptomatic infected dogs were regarded to be as important as
clinically ill dogs. This study was aimed to determine the seroprevalence of L. infantum infection among
asymptomatic dogs in the southwest and central parts of Iran and to investigate possible risk factors
associated with this infection. 548 serum samples were collected from dogs in three Iranian provinces and
subjected to direct agglutination test (DAT) in dilutions of 1:80 to 1:20480. Fifty three (9.67%) of the dogs
had detectable anti-L. infantum antibodies at dilutions of ≥1:80. Living status of the dogs (household or free roaming) was a potential risk factor for the infection; seroprevalence was significantly higher in free roaming dogs (P<0.001). Dogs of more than 2-year-old had a significantly higher infection rate in comparison with younger dogs (P<0.001). No significant statistical differences were seen between seroprevalences of the male and female dogs. The results of this study show relatively high sero-prevalence of L. infantum infection in evaluated regions and higher seroprevalence in old and free roaming dogs, which shows the importance of environmental contamination and access of the dogs to the other reservoir hosts.