A Novel Dirofilaria Species Causing Human and Canine Infections in Hong Kong

Dirofilariasis is globally the commonest manifestation of zoonotic filariasis. We report the detection of a novel canine species causing human and canine dirofilariasis in Hong Kong. Three human cases occurring over 10 months were identified, one pre-senting with cervical lymphadenopathy, one with an abdominal subcutaneous mass, and one with a subconjunctival nodule. Transected worms recovered from the resected abdominal subcutaneous mass were morphologically compatible withDirofi-laria. The cox1 gene sequences of the three human isolates were identical; however, they were only 96.2 % and 89.3 % identical to the cox1 gene ofDirofilaria repens andDirofilaria immitis, respectively. Sequencing of the 18S-ITS1-5.8S gene cluster was suc-cessful in the intact worm, and the nucleotide sequences were 94.0 % and 94.9 % identical to those ofD. repens andD. immitis, respectively. Screening of the blood samples from 200 dogs and 100 cats showed the presence of the novelDirofilaria species in 3 % (6/200) of the dogs ’ but none of the cats ’ blood samples. Nucleotide sequences of the cox1 gene and 18S-ITS1-5.8S gene clus-ters of the dogs ’ samples were identical to those in the human samples. The sera of canines infected by this novelDirofilaria spe