Thelaziosis

Abstract

Thelaziosis (or eye worm infection) is a disease caused by spirurid nematodes of the genus Thelazia, which are transmitted by several species of secretophagous, nonbiting flies (e.g., Musca autumnalis, Musca larvipara, and Phortica variegata) which feed on ocular secretions, tears, and conjunctiva of many animal species, including humans. When present under the lids and the nictitating membrane, in nasolachrymal ducts, conjunctival sacs, and excretory ducts of lachrymal glands, these worms may cause mild to severe eye disease in affected animals. Hosts of Thelazia spp. comprise a wide range of wild and domestic animals and some may also infest humans. Several studies have been carried out in the United States, Europe, and Asia, but there is still little information regarding the biology and ecology of many species of Thelazia. Due to their zoonotic relevance, Thelazia callipaeda has been more studied. This chapter reviews aspects related to the etiology, epidemiology, clinical signs, diagnosis, treatment, and control of thelaziosis. Some aspects of the biology and ecology of Thelazia nematodes are also discussed.