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Research Note: Onchocerca lupi

Ophthalmology

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April 2017

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This case report from Greece described an unusual presentation of an Onchocerca lupi adult worm in the anterior chamber of a dog’s eye. 

Ocular onchocercosis is an important disease with increasing prevalence and zoonotic potential in Europe and North America. Black flies and gnats are intermediate hosts, but the life cycle is not well understood. Typical presentation in dogs involves adult worms located in subconjunctival granulomas and/or cysts, which can cause clinical signs such as ocular discomfort, photophobia, periocular swelling, nictitating membrane elevation, conjunctival hyperemia and chemosis, corneal edema, corneal ulceration, and uveitis. 

A 4-year-old male mixed-breed dog was presented with severe blepharospasm and lacrimation in the right eye. Ophthalmologic examination revealed mucopurulent discharge, periorbital swelling, conjunctival hyperemia, chemosis, decreased intraocular pressure, corneal edema, miosis, iridal hyperemia, and the presence of a filarial-like parasite in the anterior chamber. CBC revealed eosinophilia. Test results for Dirofilaria immitis, Ehrlichia canis, and Leishmania infantum were negative, and thoracic radiography did not reveal evidence of heartworm disease. 

Pilocarpine was administered preoperatively to induce miosis and prevent posterior parasite migration. The worm was removed from the anterior chamber via an incision at the limbus followed by irrigation with balanced salt solution. The parasite was classified as O lupi based on morphologic examination. Punch biopsies of periocular and frontal skin were performed, and no microfilariae were identified. Postoperative therapies included oral prednisolone and doxycycline, topical ophthalmic tobramycin and dexamethasone, and injectable melarsomine and ivermectin. 

This case likely represented aberrant parasite migration from the periocular tissues, although direct larval inoculation by the vector insect cannot be ruled out. 

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