This is Thelazia californiensis in the western U.S. (in Europe and Asia it is T. callipaeda). Clinical signs include epiphora, conjunctivitis, ocular pruritus, keratitis w/ corneal opacity and ulceration, and blindness (occasionally).
T. californiensis is zoonotic and carried by muscid and fruit flies. The flies act as intermediate hosts and deposit infective larvae on the eye while feeding on ocular secretions.
Click here to see a video of T. californiensis in a dog’s eye.
Tx: Manually remove worms with forceps after sedation and local anesthetic. Additional Tx options include ivermectin subQ, spot-on moxidectin, or oral milbemycin oxime. Ocular moxidectin or levamisole solution are an option but may cause irritation.
Spirocera lupi cause parasitic nodules in the aorta, esophagus, and stomach of dogs worldwide.
Theileria spp. are tick-borne blood parasites affecting horses and cattle.
Onchocerca cervicalis causes ophthalmic lesions and ventral midline dermatitis in equids.
Dirofilaria immitis is the causative agent of heartworm in dogs and cats.
Image courtesy of the CDC.
