Background & objectives: Visceral leishmaniasis is a zoonotic disease and is considered as the most important disease in dogs. The disease has been reported in North West and South of the country, in Iran. In addition to stray dogs, some apparently healthy dogs can be contaminated without showing any sign or symptoms in this area. In the present study, canine visceral leishmaniasis was investigated in dogs lacking clinical signs in Meshkinshahr city in Ardabil, Iran.

Methods: This study was a cross-sectional survey conducted during 2011-2014. A total of 110 serum samples collected from dogs either having or lacking clinical signs and tested by direct agglutination test (DAT) assay. Then 10 dogs (41.6%) showing clinical signs and 15 dogs (17.4%) without any symptoms were autopsied and their spleens were sampled. The samples were used for smear preparation and culturing.

Results: Based on the results, among 24 dogs with clinical signs 20 cases (83.3%) and of 86 dogs without signs, 16 cases (18.6%) found to be positive. On the other hand, smear and culture results were found to be positive in 100% and 60% of dogs with and without clinical signs, respectively. The interesting and impressive results of this study was that the dogs with symptoms but negative DAT and asymptomatic dogs with negative DAT were positive in parasitological tests.

Conclusion: This proves that asymptomatic dogs like symptomatic dogs can be effective in L. infantum infection and is able to maintain the transmission of the disease in endemic areas. On the other hand, a number of symptomatic dogs with negative anti-leishmania antibodies were positive in parasitological tests. Thus, this study also shows that although DAT is effective in determining asymptomatic dogs and canine visceral leishmaniosis control programs but it does not seem to be satisfying in endemic areas such as Meshkin-shahr. Thus in endemic areas, it is recommended that the low antibody titer should be considered.