Guide to Horse Health: Deworming’s Three Rights

Yellow eggs on the horse’s flanks and legs, diminishing appetite followed by weight loss, tail rubbing, dull hair coat, coughing, all these clinical signs mentioned might lead horse owners to pick up a dewormer the next time they go to their veterinarian or the nearest feed store.

But before getting a tube of dewormer, make sure that you check with your veterinarian and know the three “rights” when it comes to deworming. Today, it is very important to work with the veterinarian and take a more significant and active role in the horse’s parasite control process.

Considering what dewormer to use needs to be the priority. Horse farms are unique. It means that the horses and the parasite burdens are also unique and can benefit from solutions that go beyond chemical control strategies that target parasites. The primary goal when doing a strategic deworming program is not to eliminate all the pests of horses on the farm.

To know why animal deworming is important, click here to find out more.

It is to help reduce the parasite burden in every horse so that they will be healthy. The only way to accomplish this goal using deworming products is to ask the help of your veterinarian and take a more science-based approach to help identify the horses that needed the treatment and give them the right dewormer at the right time.

Right horse

People need to keep in mind that there is no universal, one-size-fits-all program for deworming horses. The horses in the pasture do not have the same parasites as the 10-year-old racing horse in the stall. Each animal’s age, environment, and exposure need to be taken into consideration when determining their parasite risk, as well as their deworming protocol.

Because more or less 20% of these animals shed 80% of the eggs on a farm. FEC or fecal egg counts should be conducted by a registered veterinarian to help identify which animals are actually shedding parasite eggs. The next thing to do is to rank them according to the level of their shedding, as designated in the American Association of Equine Practitioners Parasite Control Guidelines.

A lot of experts agree that animals need to be treated differently based on the shedding history of the animals. In might be the same horse that requires more treatment, but the method can help eliminate the use of dewormers that don’t need to be treated. By going with this approach, there is a big chance to decrease in fecal egg shedding, as well as pasture contamination, at the same time minimizing the exposure to parasites and anthelmintics, thus reducing the creation of resistance.

Right animal dewormer

Every anti-parasite medicine available on the market has a level of resistance, and the strength differs depending on geographic location, as well as the type of parasite. The only way people know for sure if there is a resistance to that dewormer on the farm is to have the veterinarian perform fecal egg count tests before deworming the animals and doing a FERCT or fecal egg count reduction test on the same animals after two weeks.

If the anthelmintic is still working, the fecal egg count reduction test will show 99% effectiveness. If the problem is the resistance, the fecal egg count reduction test may be showing less than 80% to 90% effectiveness. Resistance to medicine can differ from farm to farm to a select number of animals at every location that needs to be tested. The veterinarian can help you determine what products to use and when to use it. For more information about this topic, visit websites like

Right time

Hypothetically, deworming needs to be conducted at the right time and on the right animals based on their parasite load. Horses that have LES or Low Egg Shedders bases on its Facal Egg Count may need to get treatment two to three times a year. A high shedder might require five to six treatments per year.

Seasons for parasites differ depending on their geographic location. Summer months (June to September) are the parasite season in the northern part of the United States. In the southern part of the country, the primary transmission takes place during the spring (March to June) and fall (September to November).

Transmission of the parasite is not as high during very hot or/and cold months of the year; that is why these are no right time to use dewormers to the animals. For low egg shedder horses, deworming during the peak season of parasite transmission based on the geographic location may be sufficient.

It means that you need to do two treatments per year, one that targets migrating large amounts of strongyles, and the other treatment will target every stage of encysted small strongyles. The guidelines apply to moderate egg shedders. The veterinarian can also recommend a third treatment for the horses.

Animals that are considered as high egg shedders need to get every recommendation mentioned above, as well as include a non-larvicidal treatment during the larval transmission – usually during summertime – and a second treatment during larval transmission off-season – usually during winter – in your area.

Parasites that may threaten equine health

Listed below are some parasites that can threaten equine health:

Ascarids or roundworms – These parasites are the primary threat to young equine – usually found in foals, yearlings, and weanlings. Clinical signs include weight loss, respiratory disease, diarrhea, bowel rupture, and impaction colic.

Small strongyles or cyathostomes – These parasites are considered as today’s equine biggest problem. They encyst and burrow in the lining of the large intestines and can stay there for many years. Clinical signs include poor performance, recurring colic, dull hair coat, weight loss, diarrhea, and, ultimately, death.

Pinworms – This parasite causes tail rubbing since female pinworms lay their eggs in the perianal region. Immunity to this parasite occurs as the animal ages.