Molecular characterization of human Dirofilaria isolates from Kerala.

Background & objectives: Human dirofilariosis is a well-recognized zoonosis caused by several species of the genus Dirofilaria. The disease is prevalent among canines and human beings in Kerala. The objective of the present study was to confirm the human Dirofilaria isolates by molecular characterization.

Methods: The worms or segments obtained from human sources were subjected to diagnostic polymerase chain reaction (PCR) targeting the cytochrome oxidase subunit 1 (COI) and 5S ribosomal RNA (rRNA) genes of Dirofilaria repens. The amplicons were sequenced and analyzed.

Results: The filariid nematodes recovered from ocular as well as subcutaneous tissue of human origin were identified as D. repens based on PCR targeting COI as well as 5S rRNA genes. The phylogenetic analysis of the COI gene nucleotide sequence obtained in the present study showed that D. repens shared the closest evolutionary relationship with D. honkongensis.

Interpretation & conclusions: Molecular identification of D. repens isolated from human source assumes significance from the point of zoonotic threat of this mosquito-borne nematode. Phylogenetic analysis revealed a close evolutionary relationship with Asian isolate of D. honkongensis. Timely detection and treatment of infection in dogs, together with mosquito control, should be an integral part of the control strategy of this disease.