Horse Side Vet Guide ®

Equine Health Resource

Pinworm Infestation

Pinworms (Oxyuris equi) are an intestinal parasite that live in the horse’s lower intestines. They deposit their eggs around the anus, causing intense itchiness.

The classic sign of this parasite is frequent scratching of the area around the anus and tail head (against a fence, door or other structure). Tail hairs tend to be broken off at the base due to intense scratching.

This diagnosis actually requires the so-called “scotch tape test”, in which scotch tape is stuck to the anus and removed. The eggs adhere to the tape and can be examined and identified under a microscope.

Prognosis & Relevant Factors

Historically, treatment for pinworms has been effective in decreasing signs. There may be resistance in the pinworm population to our common dewormers, making treatment more difficult.


Prevention relies on all of the principles of a good parasite control program, manure management and targeted deworming.

Helpful Terms & Topics in HSVGWritten, Reviewed or Shared by Experts in Equine Health

Author: Doug Thal DVM Dipl. ABVP


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