First report on the enzootic maintenance of Dirofilaria sp. hongkongensis in the canine hosts and mosquito vector Armigeres subalbatus (Coquillet) in Puducherry.

Abstract

Background: Dirofilariasis is a re-emerging zoonosis caused by the nematode Dirofilaria spp., parasitizing canines, felines and humans and transmitted by mosquito vectors of the Culicidae family. Currently, reports of human dirofilariasis are increasing in India and thus we explored the occurrence of Dirofilaria infection among dogs and mosquitoes in Puducherry, India.

Methods: Two millilitres of blood collected from 293 dogs from Puducherry was subjected to microscopy and Dirofilaria screening polymerase chain reaction (PCR) targeting the ITS2 gene. Mosquitoes trapped from areas with filaria-positive dogs were also subjected to PCR and representative samples were dissected for microscopy. The partially amplified ITS1, COX1 and 12s recombinant RNA genes from positive samples were sequenced for phylogeny.

Results: Only 4 among the 293 dogs tested positive for Dirofilaria by microscopy and PCR and the parasite was identified as Dirofilaria sp. hongkongensis. None of the mosquito pools (n=39) tested positive by PCR. However, the presence of microfilaria and larvae was evident in Armigeres subalbatus (n=2) mosquitoes.

Conclusions: The abundance of the vectors, susceptible dog population and ecosystem in Puducherry confers a congenial niche for the parasite and poses a risk for human transmission. Implementation of one health-based control measure would help to curtail the infection.