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What are pinworms?

The pinworm, or oxyuris, is a white-grey worm that colonises the rectum of an affected horse.

The male worms are small, but the females can reach 4in in length and have a long tail tapering to a point, hence the name pinworm.

The larvae feed on the mucous lining in the intestine and once they have matured, the adult females move to the anal area, where they lay eggs covered with a sticky fluid.

Signs that your horse has pinworms:

• A white-grey worm protrudes from your horse’s back passage and re-enters shortly afterwards

• Your horse may rub its tail and bite and scratch its hindquarters

• Sores may develop around the rear end and can spread to other areas of the body and resemble sweet itch

• Your horse may suffer from loss of appetite and general depression

How to confirm the presence of pinworms

There are two straightforward tests that confirm the presence of pinworms:

• Examination of a sample of specially prepared droppings under a high-power microscope

• Applying sticky tape to the skin around the back passage and then viewing the tape under a microscope to identify presence of eggs.

Both of these procedures must be carried out in a veterinary laboratory.

For the full article on tackling pinworms, see the current issue of Horse & Hound (18 March, ’10)

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