Thelazia californiensis

The·la·zi·a cal·i·for·ni·en·'sis

a nematode species occurring in the tear ducts, conjunctival sac, or under the nictitating membrane of dogs, coyotes, black bears, sheep, deer, jack rabbits, cats, and, occasionally, humans in the western and southwestern U.S.; heavy infections cause photophobia, lacrimation, eyelid edema, conjunctivitis, and even blindness.


a genus of spiruroid worms in the family Thelaziidae. They are all parasites of the lacrimal duct or conjunctival sac of mammals and birds. The larvae are deposited in the conjunctival sac by the intermediate host, Musca spp. flies. Causes thelaziasis.

Thelazia alfortensis
found in cattle.
Thelazia bubalis
found in water buffalo.
Thelazia californiensis
occurs in cat, dog, humans, sheep and deer.
Thelazia callipaeda
occurs in dog, rabbit and humans.
Thelazia erschowi
found in pig.
Thelazia gulosa
found in cattle.
Thelazia lacrymalis
found in horses.
Thelazia leesi
found in dromedary.
Thelazia rhodesii
found in cattle, but also sheep, goat, buffalo.
Thelazia skrjabini
found in cattle.
References in periodicals archive ?
Parasitic conjunctivitis is rare in North America, but in some cases bot fly larvae or, in the Western United States, the parasitic worm or nematode Thelazia californiensis can inhabit the conjunctival sac between eye and eyelid.