Tapeworms belong to the group of parasites called flatworms or cestodes. There are three species of tapeworms that effect horses in the UK, the most common of which is Anoplocephala perfoliata.
Horses become infected with tapeworm when grazing or eating hay and bedding that is infected with immature tapeworms, called oribatid mites.
After about two months inside the horse, these immature tapeworms migrate to the intestine where they develop into the adult form.
Eggs develop within tapeworm body segments, which are then passed out in the faeces and are eaten by oribatid mites.
The tapeworm segments disintegrate and release eggs on the pasture, which are eaten by the mites.
When inside the mites, the immature stages develop in two to four months, and infected mites are then eaten by horses and the tapeworm cycle continues.
Effects of tapeworm infestation
Adult worms attach themselves at the junction of the small and large intestine. In large numbers tapeworms can cause local irritation and thickening at the site of attachment, and have been associated with other gut disorders.
Diagnosis and treatment
Diagnosing tapeworm infection in live horses is difficult. Detection of their eggs in horses’ faeces is not reliable by standard techniques.
Not finding tapeworm eggs in faeces does not mean these parasites are not present in the horse.
The eggs are angular and vary in appearance, and specimens can sometimes be found in faeces after a horse has been treated with a drug active against these parasites.
The Equine Division of Liverpool University’s Veterinary Faculty has set up a service, Diagnosteq This gives veterinary surgeons access to a new test they have developed for the detection of tapeworms. Your vet should be able to provide you with more information on this service.
Treatment is recommended in the autumn once the tapeworm’s intermediate host, the forage mite, has died. In areas of heavy tapeworm infestation treatment is also recommended in the spring.
Routine worming with a product containing either pyrantel or praziquantel will help control tapeworms.
For queries about worming or setting up a worming programme, contact the Merial Customer Support Centre (tel: 0845 601 4236).
Click here to readabout worming and pasture management