Unlocking the identity of a case of feline subcutaneous dirofilariasis in Hong Kong
Year: 2026
Type: article
Abstract: Background Dirofilaria asiatica Colella et al., 2025 is a recently recognised zoonotic filaria of dogs in Asia, but uncertainty remains regarding its taxonomy as a single species or species-complex and the role of noncanid reservoir hosts. Methods A single male filarial nematode was surgically removed from a subcutaneous nodule of a domestic cat in Hong Kong presenting with a microfilaremia of 36,907 microfilariae/ml. The adult worm and circulating microfilariae were examined morphologically and morphometrically. Phylogenetic inference was performed using the whole mitochondrial genome sequence obtained from microfilariae and partial sequences of the mitochondrial cytochrome c oxidase subunit 1 ( cox1 ) gene and 12S mitochondrial ribosomal RNA (12S rRNA) of the adult worm. Results Qualitative adult male morphology was congruent with original descriptions of Dirofilaria minor Sandground, 1932, from leopard cats ( Felis bengalensis ) in Vietnam, Dirofilaria repens Railliet and Henry, 1911, from dogs in Italy, and D. asiatica from dogs in Sri Lanka. Quantitative morphometric indices of the adult worm, particularly male spicule length and ratio and the number of pre-anal papillae aligned with D. minor . Morphometric measurements of methylene blue-stained microfilariae overlapped with those reported for D. repens and D. asiatica . Phylogenetic analysis of the whole mitochondrial genome derived from microfilariae, as well as analysis of 12S rRNA and cox1 gene fragments of the adult worm, placed Dirofilaria sp. from this study within a well-supported clade comprising D. asiatica from dogs in Sri Lanka and Dirofilaria sp. “hongkongensis” from a human infection in India. Conclusions The adult nematode and microfilariae in this study were genetically identified as D. asiatica . Despite exhibiting morphometric variation, the adult worm was morphologically indistinguishable from the original descriptions of D. minor . Based on these observations, the species long referred to as Dirofilaria sp. “hongkongensis” and recently described as D. asiatica may be D. minor . Further detailed morphological and genetic studies using additional specimens from Vietnam (the type locality of D. minor ) are needed to confirm this hypothesis.
Source: Parasites & Vectors
Institutions: City University of Hong Kong, Murdoch University
Language: English
Subfield: Infectious Diseases
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $3,090
Funder: City University of Hong Kong
OpenAlex ID: W7212070619
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