Atlas of livestock parasites
digitized collection of microscopical preparations

Atlas of Parasites Contents Information sources Glossary Administration

Thelazia spp. (cattle)

Category:


Species:
Endoparasite


Description:
Untitled document

Thelazia spp.
Eyeworm

General Description:
White roundworms, 7 to 18 mm in length.

Life Cycle:
Indirect - female worms in the eye deposit larvae, which are picked up from the tears by muscid flies. Third stage larvae infect cattle via the fly mouth parts.

Location:
Tissues surrounding the eye; eyelids, anterior chamber.

Geographical Distribution:
Widespread.

Significance:
Infection may bother animals; thelaziasis may resemble pinkeye.

Effect on Host:
Tissues of inner eyelids are irritated, causing tearing. The cornea or outer part of the eye may become scarred if the infection is prolonged. This scarring may whiten the eye, causing blindness. With infection, eyes become more sensitive to light.

Diagnostic Information:
Worms can be seen around the eye and in eyelids. Thelaziasis should be considered when animals do not respond to pinkeye treatment.

Control:

Reduce fly populations; remove adult worms. Ivermectin has been shown to be effective against these parasites.


Pictures:

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