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

Abstract

Background: Leishmania infantum parasites are the main causative agents of visceral leishmaniasis that threaten a wide range of humans and canines in Iran. Objectives: 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. Methods: 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. Results: 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. Conclusions: 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.