Help With My Horse

The Essential Guide to Horse Worming

Worming for gastrointestinal parasites in horses is a crucial aspect of horse care. Neglecting this can lead to severe health issues, affecting the horse’s performance and well-being and possibly even death. This blog post aims to provide a comprehensive guide on horse worming, including recommended schedules, the importance of rotating wormer types, geographical considerations, and special cases like pregnant mares and young foals.

Recommended Equine Worming Schedules

Spring: Deworm with a product effective against small strongyles.
Early Summer: Use a product targeting tapeworms and bots.
Late Summer: Focus on large strongyles and ascarids.
Fall: Use a broad-spectrum dewormer that targets most parasites.
Fecal Egg Count (FEC)
It’s also recommended to perform a Fecal Egg Count (FEC) twice a year to tailor the worming schedule according to the specific needs of your horse.

Importance of Rotating Wormer Types

Rotating wormer types is essential to prevent resistance. Using the same wormer repeatedly can make parasites immune to its effects. It’s advisable to rotate between three main classes:
Macrocyclic Lactones: Ivermectin and Moxidectin
Benzimidazoles: Fenbendazole and Oxibendazole
Tetrahydropyrimidines: Pyrantel Pamoate and Pyrantel Tartrate

Geographical Considerations for Treating Equine Parasites in the USA

Northern States: Due to colder climates, certain parasites are less prevalent. Focus on tapeworms and bots.
Southern States: Warmer climates mean a higher prevalence of strongyles and ascarids.
Western States: Arid conditions may reduce the risk of certain parasites but increase the risk of others, like lung worms.

Dangers of Not Worming Horses

Weight Loss
Poor Coat Condition
Reduced Performance
Severe Infestations can lead to Death

Recent Wormer News

Recent studies have shown an alarming increase in resistance to common wormers. It’s crucial to consult your veterinarian for the most current advice.

How to Worm a Very Parasite-Infected Horse

For horses with severe infestations, consult a veterinarian for a tailored treatment plan, which may include:
Higher Dosages
More Frequent Treatments
Additional Supportive Care

Considerations for Pregnant Mares and Young Foals

Pregnant Mares: Consult your vet for a safe deworming schedule. Some wormers are not safe for pregnant mares.
Young Foals: Begin worming at 2–3 months of age. Use a mild wormer and consult your vet for a suitable schedule.

When to Start Worming a Young Horse

Start worming foals at the age of 2–3 months. Initial worming should be mild and targeted against ascarids.

University Studies on Horse Worming Research

University of Kentucky Study on Parasite Resistance
Focuses on the growing resistance among equine parasites to common wormers.

Cornell University Study on Deworming Pregnant Mares
Discusses the safety and efficacy of various dewormers for pregnant mares.

Great Resources for More Information about Equine Parasites

  1. Prevalent Parasites: Common Types of Equine Internal Parasites – Penn State Extension
    • Discusses common species of internal parasites that infect horses such as strongyles, ascarids, and tapeworms.
  2. Common Internal Parasites of the Horse – Oklahoma State University Extension
    • Talks about the internal parasites that commonly cause significant health problems in horses.
  3. Gastrointestinal Parasites of Horses – Merck Veterinary Manual
    • Explains how horses can get infected by swallowing flies containing infective larvae.
Disclaimer: Always consult your veterinarian for personalized medical advice.

University of Kentucky Study
Cornell University Study


Worming is an essential part of horse care that should never be neglected. By following recommended schedules, rotating wormers, and considering geographical and special conditions, you can keep your horse healthy and happy. I have many more Horse Care Blog articles that will help you give the highest care to your horses. I also have many articles about Horse Training Theory that will help you to understand how horses think and react to training.

All of the valuable information I have learned through 25+ years of horse training and showing, I share with you to help you to improve your equestrian knowledge. Thank You.


2 thoughts on “The Essential Guide to Horse Worming”

  1. Thank you for the article. I live in Colorado – arid. In addition to worming, I scrape the bot fly eggs off the hair with a flat razor but I’ve always wondered if fly spray kills the eggs.
    Thanks Tim! JS

Comments are closed.

Scroll to Top