Concern about cases of pinworm (Oxyuris equi) has been on the increase over the last few years. The life cycle is different to the majority of other worms found in the horse’s gastrointestinal system in a number of ways:
- Pinworm eggs are ingested by the horse, hatching to live in the intestine. There is no intermediate host and no migration through any other organ in the body.
- The life cycle is also relatively long; worms can take up to five months to mature. Immature stages of the worm are less sensitive to wormers so may survive post treatment.
- Eggs are laid on the skin surrounding the horse’s bottom and not passed in the faeces like other worms. A sticky residue which contains the eggs can sometimes be seen around the anus of infected horses.
Effects in horses
Fortunately pinworm does not cause a problem to the horse’s digestive system or internal damage like other worms. However infection can cause irritation, sometimes so severe that horses will rub themselves raw around their tail head; this can lead to skin infections and further problems.
If a pinworm problem is suspected then a worm count is unlikely to show the worm eggs because they are not laid in the droppings. Instead use the more reliable sellotape test.
The sellotape test
To test for pinworm take a sellotape impression from under the horse’s tail. Test kits are available from Westgate Labs.
Collect the sample in the morning, ideally before 9am. Pinworm are most active at night so this will give the best chance of detecting any activity that is present.
Take a 4” length of clear sticky tape and press this firmly onto the skin around the anus (not the hair).
Fold the tape in half, sticky side to sticky side.
Pop the folded piece of tape into the sample bag ensuring this is clearly labelled.
Post to Westgate Labs in the prepaid envelope with your completed paperwork selecting how you want to recieve your results.
The sample will be put under the microscope in the laboratory to look for the presence of pinworm eggs.
If pinworm is confirmed then one of the more old fashioned wormers like pyrantel (Strongid P) or fenbendazole (Panacur 5 day guard) is a good choice of treatment. Couple this with good stable hygiene to prevent reinfection. For persistent cases you may need to contact your vet who could prescribe treatment off licence.