Atlas of livestock parasites
digitized collection of microscopical preparations

Atlas of Parasites Contents Information sources Glossary Administration

Parascaris equorum



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Large Roundworms (Parascaris equorum) is a very important parasite of horses

especially for young foals. The infective larva remains within the egg and can survive for

years in the environment. The prepatent period which is from the time on infection until

an adult worm is present for Parascaris is reported to be between a1 and 12 weeks.

Adult roundworms are very prolific worms that can lay thousands of eggs, which pass back into

the environment.

The transmission of this parasite is the results of foals ingesting the eggs from previously

infected animals that have contaminated the

environment where the foals are kept. The larvae

hatch from the eggs soon after ingestion and

migrate from the intestine through the liver to the

lungs and then are coughed up and swallowed

back into the small intestine where they grow to

an adult parasite. Coughing and the development

of pneumonia are common. Also, blockage of the

small intestine by these very large adult parasites

can be a problem in the young foal.


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