Exotic Worm In An English Eye

Intraocular dirofilarial infestation is rare. We present a case of subconjunctival dirofilariasis that mimicked orbital cellulitis. After surgical excision the parasite was confirmed on microscopy as Dirofilaria spp and on PCR as Dirofilaria repens. New hot spots of infection are appearing in previously non-endemic countries. Our case occurred in an unusual geographic location, in London, England- not endemic to this parasite, which may be attributed to global climatic changes toward warmer temperatures. Documented human cases are rare and typically "imported" from regions where the disease is endemic. This condition presents a diagnostic challenge for clinicians unfamiliar with "exotic" parasites and can be initially misdiagnosed.

This case presented to the eye casualty at King’s College Hospital, London.

A 76-year-old white British gentleman presented to the eye casualty in January 2025 with a swollen left upper lid for four days. He denied any trauma/ fever/ insect bites/ recent flu. His best corrected visual acuity in the right eye was 6/6, left eye was 6/9. There was an erythematous swelling of the left upper lid with conjunctival hyperaemia and mild chemosis. Cornea was clear and rest of the ocular examination was unremarkable. He identified 13/17 plates in the right eye and 10/17 plates on Ishihara test. In view of these features, a diagnosis of left sided preseptal vs orbital cellulitis was made. A course of oral antibiotics was commenced and CT head and orbit was requested which reported evidence of subcutaneous left periorbital and facial swelling/oedema.

He presented after 8 weeks with similar symptoms and a conjunctival swelling was noted superotemporally in the left eye. A worm moving inside the swelling was noted. He was prescribed oral and topical antibiotics, topical steroids and listed for urgent left conjunctival exploration and removal of the worm under local anaesthesia. There was a superotemporal encapsulated parasite with surrounding inflammation intraoperatively. The parasite was removed in toto and sent to London school of Tropical Medicine. His eye settled well postoperatively on a combination of antibiotic/steroid drops and vision improved to 6/7.5. The excised parasite confirmed on microscopy as Dirofilaria spp and on PCR as Dirofilaria repens.