Aside from being more than a bit gross, worms also have harmful implications for your horse. Left untreated, they can lead to ulcers, stomach upset, colic, respiratory conditions, and even death.

Worms 101

Several types of worms occur in horses, ranging in commonality and detectability.

• Tapeworms and small strongyles are the most common. Tapeworms typically cause problems like impaction. While small strongyles cause damage to the intestinal lining, causing gastric upset and difficulty absorbing nutrients.
• Ascarids are another type and are less common but are most detrimental to foals. Once ingested, they can make their way from the intestines to the liver or lungs and cause respiration issues, such as a cough or runny nose.
• Other less aggressive worms include bot flies, pinworms, and habronema worms. These three are less harmful overall but can cause problems like stomach ulcers if left untreated.
• The least common but most damaging are the large strongyles. These worms are ingested during grazing and can enter the gastrointestinal system, move to the blood vessels of the cecum and colon, and compromise gut function and vitality.

Testing

• Managing worms requires following prevention-based practices and a surveillance-based deworming program. Typically, a vet will recommend testing for parasites annually. Horses with a history of high parasite load may require more frequent testing.
• Tapeworms, encysted small strongyles, pinworms, and bots are some examples of worms that may not be detected with fecal egg count reduction tests (FECRT). For those, horse owners can use other home tests and tricks for detection.
• Horses with pinworms often itch their hind end on any surface available. Your vet can use adhesive tape to lift a sample from your horse and examine it under a microscope.

Treatment

To reduce resistance from over-deworming, it is important to take extra steps to identify and test for worms rather than universally administer the same medication every year.

Unless specific parasites are suspected or confirmed as present, it’s only necessary to preventatively deworm for tapeworms and small strongyles every year. If no other parasites are detected, treat for tapeworms once per year. Use a dewormer containing praziquantel, such as Quest Plus. Moxidectin is typically the drug of choice for small strongyles. It should be administered at the end of grazing season before the start of winter.

{READ: Taking the Horse Path]