Various roundworms affect horses and can cause weight loss, poor performance as well as contributing to colic and general debilitation. Regular worming is strongly recommended throughout the grazing season.

The extent of infestation with roundworms is readily estimated by faecal worm egg count. Resistance to roundworm treatments is a growing concern, and for this reason a rotation of products and therapeutic groups is recommended on either a seasonal or individual treatment basis. The Avermectin group of products include ‘Equest’, ‘Equvalan’/ ‘Equvalan Duo’, or ‘Vectin’ , the Benzimidazole products include ‘Panacur’. ‘Strongid–P’,‘Embotape’and ‘Pyratape’ have an effect against roundworms.

It is also very important to treat all in contact horses and to remove droppings regularly from the pasture.

Encysted Redworm Larvae

The life cycle of round worms begins with an ingested egg from the pasture which develops through larval stages to adult worms within the bowels in about 3 weeks,dependant on the species of worm. The development of larvae involves stages within the bowel wall which can become arrested in the form of cysts. These encysted larvae can lie dormant for long periods of time and result insignificant damage to the bowel lining. During this period of dormancy the larvae are not sensitive to many of the usual roundworm anthelmintic products. Only‘Equest’ and ‘Panacur Guard’ are recognized to be effective treatments.


Tapeworms are rarely obve tapeworm ‘Anoplocepha perfoliata’ has long been known as a cause of colic. Traditionally treated in tious and are often not detected on faecal examination but can now be tested for on blood samples. Thhe Autumn,recent recommendations suggest a second treatment in the Spring. Available treatments include‘Equitape’, ‘Equvalan Duo’ and‘Strongid–P’.


Lice can be a problem, especially in stabled horses during the winter time. The Avermectin products such as‘Equest’,‘Equvalan’, or‘Vectin’ not only control round worms, but also ectoparasites including lice and mites.

Written by Arnold