The Best Horse DEWORMER Schedule

Equine Deworming 

There are so many things horse owners have to keep track of. One of the most critical routines to maintain is a regular horse dewormer schedule. 

Deworming horses every two months has become common practice and has resulted in resistance to worming treatments. 

Veterinarians urge horse owners to perform fecal egg counts each spring to determine the number of eggs in a horse’s manure. This is so owners can tailor the horse deworming schedule to avoid overmedicating.

chestnut horse in the dust

Adult Horse Dewormer Schedule

Veterinarians recommend performing a fecal egg count before deworming in spring and fall. This is to determine which deworming schedule suits your horse. Our guide has three categories for general horse worming schedules: low shedders, moderate shedders, and high shedders. 

These categories stem from the number of eggs found in the manure. Low shedders present <200 eggs per gram (0.04 ounces) of manure. Moderate shedders present 200-500 eggs per gram of manure. High shedders present >500 eggs per gram of feces. 

Placing your horse in a category helps you to avoid overmedicating by administering too many worming treatments. For example, low shedders need less frequent worming (two deworming treatments over the year). On the other hand, high shedders need more frequent worming (four deworming treatments over the year).

Low Shedders <200 eggs

  1. Perform fecal egg count before deworming in spring and fall.
  2. Spring (March) – Moxidectin (Quest) and Ivermectin (Equell, Zimecterin, Ivercare, or Rotectin).
  3. Fall (October) – Moxidectin with Praziquantel (Quest Plus) and Ivermectin with Praziquantel (Zimecterin Gold, Equimax).

Moderate shedders 200-500 eggs

  1. Perform fecal egg count before deworming in spring and fall.
  2. Spring (March) – Moxidectin (Quest) and Ivermectin (Equell, Zimecterin, Ivercare, or Rotectin) or double-dose five-day course of Fenbendazole (PowerPack or Panacur).
  3. Summer (July) – Fenbendazole (Panacur, Safe-Guard) and Pyrantel Pamoate (Tapecare Plus or Strongid paste).
  4. Winter (November) – Moxidectin with Praziquantel (Quest Plus) and Ivermectin with Praziquantel (Zimecterin Gold or Equimax).

High shedders >500 eggs

  1. Perform fecal egg count before deworming in spring and fall.
  2. Spring (March) – Moxidectin (Quest) and Ivermectin (Equell, Zimecterin, Ivercare, or Rotectin) or double-dose 5-day course of Fenbendazole (PowerPack or Panacur).
  3. Summer (June) – Fenbendazole (Panacur, SafeGuard), Pyrantel Pamoate (Strongid paste, Tapecare Plus), or Oxibendazole (Anthelcide). 
  4. Fall (September) – Ivermectin with Praziquantel (Zimecterin Gold, Equimax) or Moxidectin with Praziquantel (Quest Plus). 
  5. Winter (December) – Fenbendazole (Panacur, SafeGuard), Pyrantel Pamoate (Tapecare Plus, Strongid Paste), or Oxibendazole (Anthelcide). 
Horse run in desert

Dewormer Information for Pregnant Mares

The deworming schedule for pregnant mares is not complex or too different at all. Follow the regular fecal egg count cycle and worming schedule for your horse. But, when the mare receives vaccines in the four to six weeks before foaling, deworm with Ivermectin, Moxidectin, and Praziquantel (Quest Plus) or praziquantel (Zimecterin Gold, Equimax).

Foal Dewormer Schedule

  • Two months old – Ivermectin (Zimecterin, Equell, Rotectin, Ivercare).
  • Four months old – Oxibendazole (Anthelcide EQ) and treat at five months with pyrantel pamoate (Strongid).
  • Six months old – Moxidectin with Praziquantel (Quest Plus).
  • Eight months old – Pyrantel Pamoate (Strongid) and treat at nine months of age with Fenbendazole (Panacur, SafeGuard).
  • Ten months old – Ivermectin (Zimecterin, Equell, Rotectin, Ivercare).
  • Twelve months old – Fenbendazole (Panacur, SafeGuard).

Horse Deworming Protocol Guidelines

We are breaking down the most important tips around horse deworming and guidelines to give your horse, pregnant mare, or foal the best and most accurate deworming schedule.

Non-Chemical Parasite Management

  1. If possible, cross graze pasture with ruminants. 
  2. Rotate pastures. 
  3. Harrow pastures in hot and dry weather (ensure you keep the horses out for two months). 
  4. Do not overstock pastures. 
  5. Remove manure frequently. 

Measure success of deworming schedule via fecal analysis

  • A fecal flotation will be the best way to estimate the number of parasite eggs within your horse. 
  • It is crucial to ensure that enough time passes since the last deworming treatment to allow eggs to reappear in the feces. The egg reappearance period will differ depending on the product used, and it is best to consult your veterinarian on this matter. 
  • The fecal egg count reduction test will show a decrease of 90% in the worm egg count when measured fourteen days after. 

Deworming schedules 

  1. Even if many horses live in the same environment, each case is individual and may need different deworming schedules. 
  2. Deworm foals every two months (beginning at two months of age) for the first year of their life. 
  3. A personalized worming schedule can save money on deworming products as it allows you to use fewer deworming items. 

Tapeworms

  • Eliminate Tapeworms from your horse at least once a year.
  • The dewormer suited to eliminating tapeworms is a product that contains Praziquantel. 

Strongyles

  1. Encysted strongyles (small strongyles) will be resistant to many dewormers while in their larval stage.
  2. When in their encysted stage, they will be resistant to all dewormers except Moxidectin or the five-day course of Fenbendazole.
  3. Treat for the encysted form during early spring or winter and keep the yearlings separated as they tend to shed small strongyles the most. 

Pasture Rotation

  • It is essential to rotate your pastures and paddocks to ensure they are not used year after year. This is because of ascarid eggs which can live for years in the environment. 
  • By rotating the pastures that you use, you can ensure that the horses are not exposed to high levels of ascarid eggs while grazing. 

Facts on Horse Worms

Pinworms

Pinworms are worms that can cause discomfort to your horse around the anal region. This is because the female pinworm deposits her eggs around the anus and secretes a substance that feels highly itchy to your horse. 

Some common signs of horses infected with pinworms include tail rubbing and injury to the rump or tail. You may lessen the symptoms by washing the affected area to relieve the itching. However, remember to discard any products used as you can spread the worms to another horse. 

Pinworms transmit eggs through contaminated water, bedding, feed, stalls, and grooming materials. Determining the presence of pinworms in a manure sample is difficult. Pressing scotch tape to the skin around the anus provides a more accurate diagnosis. 

Ascarids

The ascarid is also known as a large roundworm, and the adult stages of this worm exist in the small intestine. The female passes large quantities of eggs into the manure. Within two weeks, the eggs will become infective to horses that pick them up while grazing. 

The infective larvae will travel through the blood vessels and into the lungs and liver. Finally, the horse coughs up the immature worms and swallows them again. This allows them to migrate to the small intestine and mature to complete their life cycle. 

Large Strongyles (blood worm)

The adult strongyle lives in the large intestine and attaches to the walls of the intestine. The females will then pass large quantities of eggs into the horses’ manure. The eggs that pass will hatch and allow the larvae to climb the grass until a grazing horse swallows them. 

The larvae travel to the large arteries that supply blood to the intestines. This damages the artery walls that result in blood clots and causes the wall to break away which can, in turn, cause colic. 

Small strongyles (also known as Cyathostomins) are ubiquitous parasites and will infect almost all grazing horses. They are a mild pathogen unless found in large quantities in a horse. 

Tapeworms

A horse will ingest the intermediate host of a tapeworm which is a mite found on plants while grazing. Once ingested by the horse, the tapeworm causes colic, malnourishment, and digestive issues. They can be challenging to diagnose as they often go undetected in standard fecal flotation methods. Tapeworms affect around 40% of horses in the United States.

Bots

Bots are the immature maggot stages of the common bot fly. Females will lay eggs that become attached to the hairs on areas that horses will lick to clean themselves (front legs, underside, etc.). Once the horse licks the larvae’s area of infestation, they will attach themselves by burrowing into the tissue around the lips and tongue. 

Once ingested, they will attach to the lining of the stomach and cause damage to the horse’s gastrointestinal system. 

Brown pedigree horse

Key Highlights

It’s time to get rid of the outdated worming schedule of deworming horses every two months. Instead, it’s time for horse owners to adopt a proactive approach to their horse deworming schedules by creating individual deworming programs for each horse. 

This is so important in the fight against drug resistance to medications that have come about from overmedicating. Plus, it will also save you money by using fewer deworming products. 

So as long as you perform the fecal egg flotations, follow the guidelines for your horse’s category, and factor in the exceptions for mares and foals, you and your horse will reap the rewards.