Ophthalmomyiasis caused by the sheep bot fly Oestrus ovis in northern Iraq

Abstract

Myiasis is the feeding of fly larvae on vertebrates. The sheep bot fly larva of Oestrus ovis is a mammalian parasite of the skin, nose, ears, and eyes. When the larvae infest and feed on the structures of the eye, the condition is termed ophthalmomyiasis. Most often this infestation is limited to the external structures of the eye and is referred to as ophthalmomyiasis externa. The features of this condition are severe local inflammation, positive foreign body sensation, erythema, and lacrimation. Vision may or may not be reduced, depending on involvement of the cornea. A 20-year-old white male soldier sought treatment for an inflamed eye and an irritated cornea OS. His eyelids were swollen with marked periorbital edema and conjunctival erythema OS. On slitlamp examination, small whitish organisms were viewed on the conjunctiva OS. The organisms were removed, preserved, and sent to Nova Southeastern University where they were identified as O. ovis first-stage larvae. The patient was treated with antibiotic ointment, and the inflammation resolved within 1 week. O. ovis has a worldwide distribution, and although sheep are the preferred host, humans may also serve as an intermediate host in the organism's life cycle. This case represents one of several reports of ophthalmomyiasis in the Middle East caused by O. ovis. U.S. troops stationed in Iraq and surrounding areas are vulnerable to eye infestation by fly larvae, and health care providers need to include this condition in their differential diagnosis of anterior segment inflammatory disorders.