When should a foal be dewormed? How do you deworm a foal? The good news for foals is that they arrive into the world with no parasites from their mother while in utero. But once they are born, that changes. There are two types of parasites that we must protect foals against: Intestinal endoparasites which are parasites that live inside the digestive tract of the horse, and ectoparasites such as ticks. This article will discuss horse intestinal endoparasites.

Foal Intestinal Parasites

While foals are born without parasites, within the first few days of life a foal will have intestinal parasites in their body, via the milk they drink from the mare and from eggs/larvae they ingest in the environment. At this point, foals have no immunity to these parasites. Their immune system is immature. As they get older, they will gain immunity to certain parasites such as intestinal threadworms and roundworms. Once a foal gets immunity to these parasites, that means adult parasites will not live in them, so therefore no eggs will be produced in them, but foals will still be subject to larval stages.

Signs of Worms in Foals?

Worms damage the gut lining of the foal by attaching to it and creating inflammation. This leads to blood loss as the worms physically punch all the way through the gut lining as they do larval migration. This can also lead to small bacterial abscess issues, damage to blood vessels in the body, and alter gut motility. It causes the horses gut to go slower which creates gas colic, spasmodic colic and possibly fecal water syndrome as the worms burst out of encysted stages or impactions from just large numbers of worms blocking food passage.

How Often Should Foals Be Dewormed?

Foals (birth to yearling) are dewormed four to five times a year on a schedule determined by the farm and farm veterinarian. Equine fecal tests can be done for information, but the set number of dewormings will still be four to five times a year.

Owners of young and adult horses are often unaware of the low sensitivity of fecal tests – the low ability to find all parasites. A problem that is common in thinking a negative fecal test means “my horse is clean, has no parasites”. Fecal tests are able to find only a very few egg types – you can have a negative fecal and be packed in worms that can damage the health of your foal/yearling/adult horse.

An equine fecal test will pick up: strongyloides eggs, roundworm eggs, strongyle eggs – usually nothing else but these three. Due to their known presence, it’s recommended to have a set foal deworming schedule put in place.

What are the Most Common Worms in Foals?

For a foals first five months of life in a foal, it’s intestinal threadworms (Strongyloides) and roundworms (Ascarids) that present the worst problems. These two parasites can lead to sickness and death – medical and surgical treatment can be unrewarding. Simple deworming can save expensive treatment attempts and save lives.

Once your horse hits six months old, strongyles and tapeworms are now on site in your horse and these become the greatest threats for the rest of their lives. From six months to one year old, your foal will be dewormed two to three more times to address other parasites and to push back roundworms until immunity occurs at 12 to 18 months. *Work with your veterinarian to set up a program to address parasites from 6 to 12 months.

Dewormers for Foals

Ivermectin paste, such as Eqvalan Paste Generic, will kill threadworms in foals. Ivermectin is approved in all ages of foals and kills the adults and the larvae. Many owners treat foals with ivermectin at day 10 to 20 of life to try to reduce diarrhea and then in two months use Oxibendazole to cover threadworms and roundworms until immunity.

How Early Can You Deworm a Foal

Certain dewormers have age restrictions. When choosing a foal dewormer, always look at the label and don’t use certain dewormers until the foal reaches a certain age.

Here are some guidelines to follow when it comes to dewormer age restrictions:

Ivermectin/praziquantel combo:

• • a) Equimax– 4 weeks or older
  • b) Zimecterin Gold – 2 months old or older

Moxidectin (by itself or in combination with praziquantel as in Quest Plus) foals need to be 6 months or older to start to use.

Note: The other deworming classes have no age restrictions on their label. Those include Fenbendazole (Safe-Gard), Ivermectin by itself, Pyrantel and Oxibendazole.

Foal Heat Diarrhea

Foal heat diarrhea is often seen in foals at about day 10 of life. Many think this diarrhea is threadworm related since the fecal parasite egg counts about this time will show adult threadworms in the foal’s intestine creating eggs. However, other items may also contribute to this diarrhea. Treating foal diarrhea can be difficult. Providing a probiotic such as Probios Equine One Gel, or a colostrum supplement such as Breeder’s Edge Nurture Mate for Foals, can help support a foals immune system and normal digestive function during this time. Thankfully foals will get immunity to threadworms by six months of age so no more eggs will be seen after this.

Can Parasites Cause Colic in Horses?

Small strongyles are thought to be one of the biggest causes of colic in horses. By age three to six months, a foals immunity to strongyloides will kick in so no more eggs. And usually by one year old, roundworm immunity will kick in, so no more roundworm eggs. So by the time the horse reaches six months of age, only roundworm and strongyle eggs are seen in fecal tests and by one year old, only strongyle eggs are seen on fecal tests.

It’s important to keep in mind that fecal tests give you information, but it’s only a small amount of information. That’s why deworming needs to be done on a set schedule throughout the life of the horse. At times, owners will mistakenly skip dewormings, thinking a negative fecal means “all clear”. However, then colic caused by parasites comes along. When you look closely at the things missed in a fecal, it’s easy to see why skipping months and years of deworming is a mistake.

Fecal tests are not the basis for deworming in foals. If you have further questions on equine deworming, putting together a foal deworming schedule or need help finding the best dewormer for foals, give us a call at 800.786.4751.

Downloadable Horse Dewormer Chart