While faecal worm egg counts (FWECs) can help you keep control of worms during the grazing season some pesky parasites need special attention during the autumn and winter, particularly encysted small redworm. Responsible and sustainable worm control is crucial to help keep your horse healthy and performing at his best.
During the autumn, the larval stages of the small redworm can stop developing inside the horse’s gut and enter a type of hibernating state known as encysted small redworm (ESRW). Large numbers of encysted small redworm larvae can be present and because larval stages do not produce eggs they cannot be tested for using faecal worm egg counts. 1
Large burdens of encysted small redworm can cause a condition known as larval cyathostominosis when they emerge from their hibernating state. The resulting diarrhoea, colic, and severe weight loss can be fatal, especially in young horses.
All horses of more than six months of age should be dosed with a wormer that will treat for encysted small redworm in autumn/winter time regardless of their FWEC.
Moxidectin (the active ingredient found in Equest & Equest Pramox) is the only active ingredient licensed to treat encysted small redworm in a single dose. A five-day course of fenbendazole is also licensed to treat encysted small redworm but there is widespread evidence of small redworm resistance to fenbendazole, including the five-day dose so a resistance test is recommended before using it. Treating with a wormer that does not specifically target the encysted stages (ivermectin, pyrantel or single dose fenbendazole) during late autumn and winter can actually increase the risk of a horse with a high ESRW burden developing larval cyathostominosis.
For the best advice always speak to your vet or one of our AMTRA qualified SQPS on 01425 474455