In the wild, horses used to roam freely over thousands of acres, with continuous access to clean and fresh pasture. Worms and horses evolved together in this environment, developing a relatively healthy balance to maintain both populations. As domesticated horses are kept on more restricted grazing, they have limited opportunity to move onto cleaner pasture and this exposes them to worm re-infection at a much greater level, upsetting the horse/worm balance. Our job as horse owners is to re-establish this balance by controlling the amount of worms our horses are exposed to, helping to keep our horses healthy and able to perform to the best of their ability.
Breaking the lifecycle of parasites reduces the amount of worm challenge our horses face. An essential part of breaking the cycle is reducing the number of worms on the pasture by picking up droppings therefore keeping the re-infection challenge to a minimum. In turn, managing the pasture can also reduce our reliance on wormers, reducing the drive for wormer resistance.
The most important equine parasites are small redworms (also called small strongyles or cyathostomins) including their encysted stages, large redworms (also called large strongyles), large roundworms (also called ascarids), tapeworm and bots.
The symptoms of a worm infection can be very varied depending on the type of parasite involved. They can include signs of gastrointestinal disease such as weight loss, poor appetite, colic and diarrhoea. Alternatively, foals may also show signs of respiratory disease such as a cough and a snotty nose.
It is important to have a comprehensive worm control plan that has been tailored to your horse by your vet or Suitably Qualified Person (SQP). Control requires: pasture management; testing using faecal worm egg counts (FWECs) and antibody tests; planning for your individual circumstances and dosing correctly using the correct wormer for the type of worm at the right time of year.
1. AAEP Parasite Control Guidelines (2016)
2. Kaplan and Nielsen (2010) An evidence-based approach to equine parasite control: It ain’t the 60s anymore. Equine vet. Educ. (2010) 22 (6) 306-316