Merck Manual

Please confirm that you are a health care professional

honeypot link

Eyeworm Disease (Thelaziasis) in Dogs

By

David G. Baker

, DVM, MS, PhD, DACLAM, Division of Laboratory Animal Medicine, School of Veterinary Medicine, Louisiana State University

Last full review/revision Jun 2018 | Content last modified Oct 2020
Topic Resources

Eyeworms (Thelazia californiensis and T. callipaeda) are parasites found in dogs, cats, and other animals, including humans, in the western United States, Europe, and Asia. They are whitish, 0.5 to 0.75 inches (7 to 19 millimeters) long, and move in a rapid snake-like motion across the eye. Up to 100 eyeworms may be seen in the conjunctival sac, tear ducts, and on the conjunctiva under the nictitating membrane (third eyelid) and eyelids. Filth flies (including the common house fly) and, possibly, fruit flies serve as intermediate hosts and deposit the infective eyeworm larvae on the eye while feeding on secretions from the eyes.

Signs include excessive watering of the eyes, inflammation of the conjunctiva, itchiness of the eyes, opaque corneas with slow-healing sores, and rarely, blindness. After a local anesthetic is applied, diagnosis and treatment are accomplished by observing and carefully removing the parasites with forceps. Some veterinarians have reported the successful elimination of Thelazia infections from dogs with medications injected under the skin, taken by mouth, or applied to the skin as a spot-on. Certain eye solutions or ointments also may be effective. Your veterinarian will evaluate your pet’s situation and take the most appropriate treatment approach.

To diagnose, examine, and remove eyeworms, a veterinarian might numb the affected areas.

To diagnose, examine, and remove eyeworms, a veterinarian might numb the affected areas.
Others also read
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Test your knowledge
Fluid Therapy in Animals
Abnormalities of circulation can be due to a number of causes and may result in circulatory shock, an emergency situation. All types of circulatory shock respond to administration of fluid therapy to some extent, but some types require additional medications. Which type of circulatory shock is most readily handled with fluid therapy alone?
Become a Pro at using our website 

Also of Interest

Become a Pro at using our website 
TOP