Case Report: Conjunctival Infestation with Thelazia gulosa: A Novel Agent of Human Thelaziasis in the United States

Abstract

We report a case of thelaziasis in a 26-year-old female, acquired in Oregon. A total of 14 worms were removed from the patient's left eye and were morphologically identified as being Thelazia gulosa. Until now, only two species of Thelazia have been implicated in causing human disease, Thelazia callipaeda in Asia and Europe and occasional reports of Thelazia californiensis from the United States of America. Here, we describe a third, previously unreported parasite of humans, T. gulosa (the cattle eyeworm) as an agent of human thelaziasis and the first reported case of human thelaziasis in North America in over two decades.

Figure 1.

Thelazia gulosa (A) in situ on the surface of the patient’s conjunctiva (circle); (B) adult female immediately after removal from the eye. Morphological identifying features of adult female worm submitted for analysis; (C) whole adult female (×40 magnification, cleared); (D) deep buccal cavity; (E) tail with nonprotruding anal opening and postanal papilla; (F) esophageal-intestinal junction; (G) nonprotruding vulval opening slightly anterior and to the left of the esophageal-intestinal junction; and (H) mid body with prominent cuticular striations, intestinal tube, and ovaries containing spirurid eggs (×200 magnification, cleared).