The Big Wriggler

Tapeworms are the biggest worms to affect horses in this country. The most common type of tapeworm can grow up to 20cm long, but there is a much rarer type that can grow up to 80cm!

Tapeworms are flattened, white, segmented worms that rely on the harvest mite to help them complete their life cycle. To infect horses, the harvest mite ingests tapeworm eggs from dug and the horse then ingests the harvest mites when eating forage. The larvae then develop into adult tapeworms in the horse’s digestive system.

The most common species of tapeworm, Anoplocephala perfoliata, are usually found at the junction of the small and large intestine, where they attach themselves to the gut wall using suckers. The much rarer tapeworm, Anoplocephala magna, can grow up to 80 cm and live in the small intestine.

Unfortunately, they can. They can result in several health-related problems which include loss of condition, diarrhoea and colic. An infected horse has been shown to be 26 times more likely to develop colic associated with an obstruction of part of the small intestine (ileal impaction colic) than a non-infected horse, and eight times more likely to experience a type of cramping of the intestine resulting in spasmodic colic.

Tapeworms don’t reliably show up in faecal worm egg counts (FWECs). This is because the tapeworm eggs are contained within the body segments of the tapeworm, which intermittently break off to be passed out in droppings. Sometimes, it is possible to pick up some tapeworm eggs on a faecal worm egg count, but because of the intermittent shedding and containment in body segments, absence of eggs seen does not rule out tapeworm infection. This means that even if your horse has a negative FWEC, it still could have a tapeworm problem.

The accepted method to control tapeworms is to break the cycle by using a wormer specifically licensed for tapeworms. This should be used every six months, usually in the spring and autumn. Speak to your vet for more information.

Alternatively, a different tapeworm test can be done using a saliva swab or a blood sample. A horse with high level of tapeworm infection will produce many antibodies, which can be detected in blood or saliva. Using the saliva method, a swab sample of the horse’s saliva is taken by its owner with a specifically developed swab, whereas the blood sample is taken by a vet. After the samples have been taken, they are then sent off to the laboratory and analysed. This is where it will be determined if you should use wormer or not. As tapeworm antibodies can persist for several months after successful treatment, the results must be interpreted with care and the test cannot be used immediately after a worming medication to check that it has worked.

For more information on how to keep your horse safe from worms, ask for advice from your vet.