Molecular Characterization of Visceral Leishmaniasis in Asymptomatic Dogs in North Khorasan, Northeastern Iran

Leishmania infantum parasites are the main causative agents of visceral leishmaniasis that threaten a wide range of humans and canines in Iran.

Our aim was to survey Leishmania parasite species and simultaneous comparison of canine organs in endemic areas for the diagnosis of visceral leishmaniasis using the ITS-rDNA gene, sequencing, and phylogenetic analysis.

In this study, sampling was done with vacuum tubes containing EDTA from blood and sterile swabs from the snout and conjunctiva of asymptomatic sheepdogs (n = 37) using a non-invasive method in north Khorasan, northeastern Iran, from 28 July to 4 August 2018. The DNA of collected samples was extracted, amplified, and sequenced by targeting the ITS-rDNA gene. To demonstrate the taxonomic status of Leishmania spp., sequences were subjected to phylogenetic analysis based on the maximum likelihood method.

We obtained 37 samples from asymptomatic dogs of which, 10 dogs were definitely diagnosed with L. infantum and one dog infected with L. tropica. The blood (n = 8) and right conjunctiva (n = 6) samples were the most infected samples. The highest number of infections in dogs was in the age group of 5 - 10 years indicating that this group is more sensitive to visceral leishmaniasis in this region.

The current findings indicate that non-invasive sampling and molecular methods are reliable and suitable in the detection of visceral leishmaniasis. This is the first report of the visceral involvement of a shepherd dog with L. tropica in northeastern Iran. The remarkable occurrence of visceral leishmaniasis (29.7%) in asymptomatic sheepdogs reflects a health alert to conduct the surveillance and monitoring of susceptible individuals/reservoirs in the region.