Pinworms (Oxyuris equi) can affect horse of all ages. The most noticeable clinical sign of pinworms is anal itching. Horses will be restless, may not eat properly, and a yellow/gray discharge may be noticed coming from the anus. Pinworms can be diagnosed by examining fecal matter for eggs.
See Pinworms in Horses.
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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.