Thelazia

Thelazia is a genus of nematodes that are commonly referred to as "eyeworms". They are parasites that infect the eyes of various mammalian hosts, including humans. The adult worms live in the tear ducts, tear glands, and under the eyelids. The genus is named after the Greek word "thelazein", which means "to suckle", referring to the worm's feeding behavior.

Life Cycle

The life cycle of Thelazia involves a definitive host and an intermediate host. The definitive host, which can be a human or other mammal, is infected when the intermediate host, a species of fly, deposits the larvae onto the eye of the mammal while feeding on eye secretions. The larvae then mature into adult worms in the eye or surrounding tissues. Female worms release first-stage larvae, which are ingested by flies when they feed on the eye secretions of the infected mammal. The larvae develop into infective third-stage larvae within the fly and can then infect a new mammalian host.

Species

There are several species of Thelazia, including Thelazia callipaeda, Thelazia californiensis, and Thelazia gulosa. Each species has a slightly different life cycle and preferred host. For example, T. callipaeda is commonly found in dogs and cats in Europe and Asia, while T. californiensis is found in dogs, cats, and humans in the United States.

Symptoms and Treatment

Infection with Thelazia can cause a variety of symptoms, including irritation, inflammation, and watery eyes. In severe cases, it can lead to corneal ulcers and blindness. Treatment typically involves the physical removal of the worms from the eye, often under local anesthesia. In some cases, antiparasitic drugs may also be used.

Prevention

Prevention of Thelazia infection involves controlling the fly population and avoiding contact with flies. This can be achieved through the use of insect repellents and by keeping doors and windows closed.

See Also

• Nematode
• Parasitism
• Eye disease