Thelazia

A parasitic nematode affecting the eyes of various animals and humans

Thelazia

Thelazia callipaeda female

Thelazia is a genus of parasitic nematodes in the family Thelaziidae. These parasites are commonly known as "eye worms" due to their predilection for the conjunctival sac and tear ducts of various mammals, including humans, dogs, and cats. The most well-known species within this genus is Thelazia callipaeda, which is often referred to as the "oriental eye worm."

Life Cycle

The life cycle of Thelazia species involves an intermediate host, typically a fly from the family Muscidae or Fannidae. The adult worms reside in the conjunctival sac of the definitive host, where they release larvae. These larvae are ingested by the fly during feeding and develop into infective larvae within the fly. When the fly feeds again, the infective larvae are deposited onto the eye of a new host, where they mature into adult worms.

Pathogenesis

Infection with Thelazia species can lead to a condition known as thelaziasis, characterized by conjunctivitis, excessive tearing, and in severe cases, keratitis and corneal ulceration. The presence of the worms can cause mechanical irritation and inflammation of the eye tissues.

Diagnosis

Diagnosis of thelaziasis is typically made by direct observation of the worms in the conjunctival sac or tear ducts. The worms are small, white, and thread-like, making them visible to the naked eye or with the aid of a magnifying glass.

Treatment

Treatment of thelaziasis involves the mechanical removal of the worms from the eye, which can be done with fine forceps under local anesthesia. In addition, anthelmintic medications such as ivermectin may be used to kill the worms.

Prevention

Preventive measures include controlling the population of the intermediate host flies and protecting animals from exposure to these flies. This can be achieved through the use of insect repellents and maintaining good hygiene and sanitation practices.

Related pages

• Nematode
• Parasitic disease
• Conjunctivitis
• Ivermectin