Cases of pinworm (Oxyuris equi) have been on the increase over the last few years.
Although pinworm is not a serious threat to horse health and won't cause internal damage like other worms they can be a pesky problem to get rid of. Pinworm 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.
Horses can itch for a number or reasons, including sweetitch and fly irritation as well as pinworm. If a pinworm problem is suspected then a worm count is unlikely to show the worm eggs as the worms live in the hind gut and lay eggs outside the body under the tail. Instead use the more reliable sellotape test available from Westgate to help pinpoint the problem.
Pinworms look like bean sprouts with a thin pointy end. Because of where they live in the hind gut they are often seen in droppings.
The Pinworm test
Our pinworm test kit consists of a sticky sellotape strip that you will use to take an impression from the skin under your horse's tail - this is where the female worms come out and lay their eggs. Once you have pressed this firmly on the skin around the horse's anus, fold the sellotape back on itself, sticky side to sticky side, place in the bag and post back to our laboratory in the prepaid envelope. We will examine this under the microscope to determine whether there are any pinworm eggs present.
If pinworm is confirmed, either with a sellotape test or by seeing them in the horse's droppings, treat with one of the more old fashioned wormers like pyrantel (Strongid P) or fenbendazole (Panacur 5 day guard) which are more effective at treating pinworm than ivermectin or moxidectin becuase of the way these are metabolised in the horse's gut.
Using neem oil on the horse's skin is also sometimes beneficial to prevent the eggs sticking once they're laid. Couple this with good stable hygiene and scrub down areas where the horse may rub his tail to help reinfection.
If the pinworm problem is really persistent then a vet can prescribe a paste on invermectin off lience in order to treat the problem.
The life cycle of a pinworm is different to the majority of other worms found in the horse’s gastrointestinal system, in a number of ways:
- The life cycle is direct; this means there is no intermediate host and no migration through any other organ in the body other than the gut.
- The life cycle is long; worms can take up to 5 months to mature (in most other worms this takes only 3 weeks)
- The adult worms live in the rectum, in contrast to other worms which spend their time in the intestines. Immature stages of the worm are less sensitive to wormers so may survive post worming. Most infestations take about 12 months to clear up.
- Eggs are laid on the skin surrounding the horse’s bottom and not passed in the faeces like other worms, so will not show in a worm egg count.