Thelaziasis

THELAZIASIS, a disease of the eyes of mammals and birds caused by nematodes of the genus Thelazia Bosc, 1819, family Thelaziidae, order Spirurata, which localize in the conjunctival sac of the eye. In cattle, thelaziasis sometimes causes severe enzootics and is usually manifested by conjunctivitis, and in more severe cases, by conjunctivokeratitis. In humans, according to world literature, thelaziasis has been registered 3 times (caused by the species T. callipaeda Railliet et Henry, 1910). In the USSR, thelaziasis has not been confirmed in humans, but one case of T. callipaeda infestation was recorded in a dog in the Far East (Dekhterev, 1929). The presence of the parasite in the conjunctival sac of the human eye causes severe irritation, pain, lacrimation, paralysis of the muscles of the lower eyelid, and ectropion. Therapy: the parasite can be easily removed with eye forceps. T. callipaeda is a thin, thread-like parasite (Fig. 1, 2). Fig. 1. The head end is equipped with a buccal capsule and papillae (6 lateral and 8 submedian). The male is 10–14 mm long; its tail end is tapered and strongly curved. The spicules are unequal: the larger one is 1.37–1.87 mm, the smaller one is 0.13–0.16 mm. There are 9 pairs of preanal papillae and 6 pairs of postanal papillae. The female is 12–18 mm long. The vulva is at the level of the posterior third of the esophagus. The anus is 0.077–0.115 mm from the tail end. They are viviparous. They require an intermediate host, which is apparently an insect. The definitive host is the dog.