Create The Best Horse Deworming Protocol For Your Horse


Internal parasites were once targeted with random doses of horse wormers on a predetermined deworming schedule.  Now, the American Association of Equine Practitioners (AAEP) guidelines call for managing internal parasites with egg counts and strategic deworming.  Worming your horse safeguards your horse’s health, helps with coat bloom and shine, and assists in colic prevention.

Types of Internal parasites

Ascarids are both large strongyles and small strongyles.  The adult forms live in the large intestine, usually.  Other types of strongyles, like the bloodworm, migrate through the horse’s intestines and sometimes liver, into vessels.  

Tapeworms in horses live in the junction between the small and large intestines.  They can create a traffic jam, resulting in colic.  Unlike dogs and cats that get tapeworms from fleas, horses eat a microscopic mite that is infected with larvae.  

Pinworms are a bit different, they live in the far ends of your horse’s digestive system.  The adults come out of your horse’s anus to lay eggs under his tail.  This is quite itchy! 

Roundworms typically only live in horses under the age of two, in the large intestine.  

Lungworms are found in the lungs of donkeys and horses.  In horses, the parasite rarely develops into a reproducing adult, but they can still cause problems. 

Threadworms are rare in horses, and live in a major ligament, near the withers.  Their larvae, called microfilaria, travel up the neck and around the shoulders, and for some horses create massive itching and hair loss. 

Testing for worms and parasite control protocols 

The life cycle of intestinal parasites is usually started when a horse eats pasture or hay that has worm eggs.  Once inside your horse, they develop into larvae, and then adults.  The adults reproduce and their eggs are passed by your horse’s manure.  Horse dewormers interrupt this life cycle to control the number of worms.  You can get horse treat recipes here.

Fecal egg counts measure the number of ascarid eggs in your horse’s manure.  A numerical value of eggs per gram (EPG) is measured.  Horses with under approximately 250 EPG are considered low shedders, meaning they do have internal ascarid parasites and will likely not need deworming.  For horse with about 250 EPG and more, deworming with a targeted paste dewormer is needed.

The egg count test should be repeated after two weeks to measure the reduction in the amount of eggs.  A different brand or combination of dewormer may be needed. Your veterinarian should always be involved in developing a horse health plan, including parasite control.  Some medications may not be suitable for foals or young horses, and your vet can guide you. 

Types of deworming medications

Ivermectin  and ivermectin paste are the gold standard for parasite control, attacking over 40 types of internal parasites including strongyles, pinworms, bots, threadworms, and lungworms.  Farnam’s Ivercare is ivermectin paste for horses.  If you are looking for apple flavors to treat your horse, Durvet’s Ivermectin paste has you covered. 

Pyrantel and pyrantel pamoate target including strongyles, pinworms, and roundworms. 

Moxidectin targets strongyles, encysted gnathostomes, pinworms, bots, and a few other worms in horses.  Zoetis, formerly Pfizer,  Quest Plus gel is moxidectin, with added praziquantel to rid your horse of tapeworms.

Praziquantel specifically targets tapeworms in horses. Bimeda Equimax, containing ivermectin plus praziquantel, is the best of both worlds in one paste wormer.  Zimecterin gold combines ivermectin and praziquantel and is another option.

Strongid and Strongid c 2x removes large and small strongyles, roundworms, and pinworms.  

Benzimidazole is a class of drugs that includes oxibendazole and fenbendazole.  While they target ascarids, small strongyles are resistant to these dewormers.  Merck SafeGuard and Panacur are both fenbendazole. Panacur powerpac is also available for an extended dose for heavy parasite loads and is not a single dose, like the other brands.  In the same class of medications, Zoetis makes Anthelcide Eq with oxibendazole.

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