Why Deworming is Important
by Boehringer Ingelheim / May 17, 2024
What is Deworming?
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 while at pasture.1 In some cases, horses can become infected by internal parasites via contaminated water, although this is generally only specific to roundworm eggs.
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 is Deworming 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,” said 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 parasitic 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.2
You do not need to completely rid all internal parasites from 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 a nonclinical 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 determine eggs per gram of feces.3 Many factors can influence an 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 parasites
- Overall health and medical history
“Knowing your horse’s level of shedding onto the pasture helps you determine an appropriate deworming protocol,” explained Dr. Grubbs.
For the most comprehensive care, consider using an 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 days 10–14) helps determine how well your dewormer is working.3
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.4
ZIMECTERIN (ivermectin paste) 1.87% and ZIMECTERIN GOLD oral paste were shown to be effective against small strongyles resistant to benzimidazole products. When it comes time to administer a dewormer, both products are a great choice to ensure control over small strongyles and other parasites.5
Both dewormers provide effective treatment and control against the following important internal parasites in horses6:
- Small and large strongyles
- Ascarids
- Bots
- Pinworms
- Threadworms
- Lungworms
ZIMECTERIN GOLD paste 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.
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.
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.
REFERENCES
1American Veterinarian Medical Association. Internal parasites in horses. Available at https://ebusiness.avma.org/files/productdownloads/internalparasitehorse_en.pdf. Accessed February 7, 2023.
2 Smarsh D and Kirkland B. Prevalent parasites: Common types of equine internal parasites. Penn State Extension, College of Agricultural Sciences. Available at https://extension.psu.edu/prevalent-parasites-common-types-of-equine-internal-parasites. Accessed February 3, 2023.
3 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.
4 Boehringer Ingelheim, Equine Products. Available at https://bi-animalhealth.com/equine/dewormers/zimecterin-gold. Accessed February 3.
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):330–334
6 Zimecterin® Product Label
7 Zimecterin Gold® Product Label
ZIMECTERIN® is a registered trademark of Boehringer Ingelheim Animal Health France, used under license. ©2025 Boehringer Ingelheim Animal Health USA Inc., Duluth, GA. All rights reserved. US-EQU-0140-2024
