Subconjunctival Granuloma Caused by Dirofilaria repens in an Indoor Dog From Thailand: A Case Report and Mitochondrial Genome Analysis

Objective To describe a subconjunctival granuloma caused by Dirofilaria repens in a dog from Rayong province, eastern Thailand, along with the successful treatment outcomes. The causative nematode was identified through morphological examination and molecular techniques. Animal Studied A 5‐year‐old female mixed‐breed dog was presented with a subconjunctival mass at the temporal part of the left bulbar conjunctiva. The dog lived indoors with its owner. Methods A complete ophthalmic examination was performed. The mass was surgically removed and submitted for histopathological examination. During the surgery, a long, slender, white‐creamy nematode emerged from the mass, which was sent for parasitology examination and molecular identification. The left eyelids were closed using temporary tarsorrhaphy. Selamectin spot‐on and doxycycline were prescribed. Results Two weeks after surgery, the temporary tarsorrhaphy was removed. The excision site had healed completely without recurrence. The histopathological examination revealed eosinophilic granulomatous inflammation. A parasitic nematode was identified in the genus Dirofilaria spp. The full‐length mitochondrial genome analysis showed 99.8% coverage of Dirofilaria repens sequences. Conclusion D. repens infection caused a subconjunctival granuloma in the current case. The treatments, combined with surgical excision and selamectin spot‐on, resulted in a good response. The conjunctival wound had healed completely within 2 weeks, without complications or recurrences. To the authors' knowledge, this was the first report of canine subconjunctival dirofilariasis caused by D. repens in Thailand. The vector‐borne transmission of D. repens , a zoonotic nematode, via mosquito bites in humans, should be a concern in Thailand, particularly in the eastern region.