Removal and identification of a subconjunvtival parasite

Background: Ophthalmic dirofilariasis is an uncommon zoonotic parasitic infection caused by species of Dirofilaria, a dog tapeworm
that is transmitted to human by mosquitoes. Man is a dead‑end host for the parasite. Ophthalmic involvement is rare and includes
periorbital, subconjunctival, subtenon, and intra‑ocular involvement. We report the removal of a subconjunctival worm and
identification by light microscopy (LM) and scanning electron microscopy (SEM). Purpose: A 62‑year‑old female presented with
complaints of redness, discharge, and foreign body sensation with difficulty in opening eyes in the left eye for the last 3 days. The patient
is a non‑vegetarian. On examination, her best corrected visual acuity in both eyes was 20/20. On slit lamp examination, there was a
long, thin, round, coiled white subconjunctival live worm in the left eye superiorly. The rest of anterior segment evaluation, intra‑ocular
pressure, and fundus was normal in both eyes. The parasite was removed under local anesthesia from subconjunctival space [Video].
External surface morphology under LM revealed fine transverse cuticular striations with tapered cephalic and caudal ends. Uterus was
long and coiled with indistinguishable masses inside. The finding was also confirmed by SEM. Synopsis: A subconjuctival parasite
was removed and identified as Dirofilaria repens by characteristic LM and SEM findings. Highlight: Dirofilaria species may lodge in
many tissues of human bodies including eye and adnexa. Dirofilaria is a natural parasite of carnivorous animals, mostly dogs, cats, and
foxes.[1] The most common mode of transmission to human is usually by bite of mosquitoes like Culex and Aedes, which are considered
as vectors, and it is often thought that parasitemia is because of accidental conduction.[1] Simple surgical removal of the worm is
curative. After removal, the worm should be visualized directly under LM. All the internal structures of the transparent worm could
be seen and compared with those under SEM.