What is deworming?  

While it’s not the most glamourous part of horse ownership, deworming is an essential part of managing your horse’s overall health. Horses can become infected with internal parasites such as roundworms, small strongyles, tapeworms, bots and others on pasture by eating grass that has been contaminated by parasite eggs.¹ In some cases, horses can become infected by internal parasites by contaminated water although this is generally only specific to roundworm eggs.

In some instances, roundworm eggs can hatch in a horse's intestinal tract and migrate through the liver and lungs.

To combat these pesky parasites, you can prioritize pasture management to ensure your horse is safely grazing. Horses should also be given anthelmintics, a drug used to control parasitic infections in animals to ensure a happy and healthy horse.

Why deworming is important

Although horses can tolerate small numbers of parasites, uncontrolled parasitic infections can result in clinical issues, especially in foals, yearlings, older, pregnant and immunocompromised horses.

“Untreated parasitic infections may lead to a variety of health complications in horses,” says Steve Grubbs, DVM, PhD, DACVIM, Technical Services Veterinarian for Boehringer Ingelheim. “Weight loss, diarrhea, and colic can all be possible outcomes for horses with extreme parasite loads.”

Externally, poor growth, coarse and dull coats, potbellies and/or excessive tail scratching can all be signs that your horse may be dealing with internal parasites.³

You do not need to completely rid all internal parasites in your horse as it is expected that all horses will have some level of parasitic burden. The goal of deworming is to keep parasitic loads at an acceptable level.

When it's time to deworm

When it comes time to deworm your horse, consult with your veterinarian who can evaluate the current condition of your horse and offer advice regarding fecal testing.

A Fecal Egg Count (FEC) is a tool used to assess a horse’s shedder category and what type of parasite eggs are potentially inside your horse’s digestive tract.⁴ Many factors can influence a FEC test and should be kept in mind when developing a deworming schedule, including:

• Age
• Location
• Season
• Travel to location(s) that may expose your horse to contaminated environments
• Pasture mate(s) that may be shedding high number of eggs
• Overall health and medical history

“Fecal testing should be performed at least once per year, once in the spring and possibly again in the fall,” says Dr. Grubbs. “Knowing your horse’s level of shedding and egg types helps you determine an appropriate deworming protocol.”

For the most comprehensive care, consider using a FEC test before any deworming treatment and another FEC test 10-14 days after your deworming treatment. The before-treatment test identifies your horse’s parasite load. The after-treatment test (percent egg reduction on day 10-14) helps determine how well your dewormer is working. ⁴

It’s also important to note that the overuse and/or misuse of dewormers can result in anthelmintic resistance.

Keeping your horse protected

Keeping your horses safe from internal parasites can be a challenging task, but using a trusted, safe horse dewormer can help. Zimecterin^® Gold (ivermectin 1.55% / praziquantel 7.75%) Paste can control more species and stages of parasites than any other product.⁷ Zimecterin GOLD has not been tested in foals younger than two months of age.

ZIMECTERIN^® (ivermectin paste) 1.87% and ZIMECTERIN GOLD have been shown to be effective against small strongyles resistant to benzimidazole products – making both products a great choice when it comes time to ensure broad-spectrum parasite control.⁵

ZIMECTERIN and ZIMECTERIN GOLD provide effective treatment and control against the following important internal parasites in horses ⁶:

• Small and large strongyles
• Ascarids
• Bots
• Pinworms
• Threadworms
• Lungworms

ZIMECTERIN GOLD also provides effective treatment and control against tapeworms. ⁷

Both can be easily administered by a horse owner. However, it is best to consult with your veterinarian before treating your horse to determine which dewormer medication is right for your horse.

To learn more about ZIMECTERIN and ZIMECTERIN GOLD, visit bi-animalhealth.com/equine/dewormers/zimecterin or talk to your veterinarian.

ZIMECTERIN IMPORTANT SAFETY INFORMATION: Not for use in humans. Keep this and all drugs out of the reach of children. Do not use in other animal species as severe adverse reactions, including fatalities in dogs, may result. Ivermectin and excreted ivermectin residues may adversely affect aquatic organisms. Do not contaminate ground or surface water. Dispose of the syringe in an approved landfill or by incineration.

ZIMECTERIN GOLD IMPORTANT SAFETY INFORMATION: ZIMECTERIN GOLD has not been tested in foals younger than two months of age, mares at or near the time of breeding, pregnant or lactating mares, and breeding stallions. There have been rare reports of swelling and irritation of the mouth, lips, and tongue following administration of ZIMECTERIN GOLD. This product should not be used in other animal species as severe adverse reactions, including fatalities in dogs, may result. Not for use in humans.

References

¹ American Veterinarian Medical Association, Internal Parasites in Horses. Available at https://ebusiness.avma.org/files/productdownloads/internalparasitehorse_en.pdf Accessed February 7,2023.

² Carson D. and Ricketts S. Deworming in Horses. Available at https://vcahospitals.com/know-your-pet/deworming-in-horses#:~:text=Small%20numbers%20of%20worms%20can,population%20of%20worms%20under%20control Accessed February 7, 2023.

³ Smarsh D. and Kirkland B. Prevalent Parasites: Common Types of Equine Internal Parasites. Available at https://extension.psu.edu/prevalent-parasites-common-types-of-equine-internal-parasites#:~:text=Internal%20parasites%20can%20cause%20gastrointestinal,with%20large%2C%20overwhelming%20parasite%20loads Accessed February 3, 2023.

⁴ Zero Egg Count, What is a Fecal Egg Count Test? Available at https://zeroeggcount.com/blogs/news/what-is-a-fecal-egg-count-test#:~:text=A%20horse%20with%20a%20fecal,parasite%20burden%20or%20worm%20load Accessed February 3, 2023.

⁵ McFarlane D, Hale GM, Johnson EM, Maxwell LK. Fecal egg counts after anthelmintic administration to aged horses and horses with pituitary pars intermedia dysfunction. J AM Vet Assoc. 2010; 236(3):331

⁶ Zimecterin^® Product Label

⁷ Zimecterin Gold^® Product Label 

ZIMECTERIN^® is a registered trademark of Boehringer Ingelheim Animal Health France, used under license. ©2024 Boehringer Ingelheim Animal Health USA Inc., Duluth, GA. All rights reserved. US-EQU-0053-2024