Foals are more susceptible to equine parasites compared to adult horses. So when is treating with Ivermectin for foals appropriate? There are three main types of parasites to watch out for, and a simple four-treatment plan will help to keep them at bay and help your foals grow into healthy horses.

Best practice for de-worming broodmares and foals.
Best practice for de-worming broodmares and foals.

Parasite Types Common in Foals

Three parasite types are common in foals: roundworm, tapeworm and strongyles.


The large roundworm or ascarid primarily affects horses less than two years of age. Ascarids are the most significant parasite in young horses because they are such large worms and can quickly develop into life threatening numbers. Ascarids have the potential to cause liver damage, which is repairable, and lung damage, which is permanent.


Tapeworm infestation is rare in foals that are less than seven months old.


Large strongyles (sometimes called bloodworms) are found in the large intestines either attached to the walls or in the intestinal contents. All horses can be affected by strongyles but young horses are most vulnerable. Signs of strongyle infection are loss of appetite, weight loss, fever, depression, weakness, anaemia, diarrhoea and death.

Worming in Mares & Foals

Exposure to parasites begins at an early age. Worms can find their way to the foal through their mother’s milk, or they can ingest the eggs of the parasites from manure. You should worm mares either 4-6 weeks before foaling, or within 24 hours after foaling.

For foals less than 12 months, deworming can be a good practice, though they must be used with care. Some agents may not be recommended in foals at a specific age. For instance, moxidectin is not recommended for use in foals less than six months old. Some treatments are safe, such as ivermectin, which you can use in foals from the age of 8 weeks. An ivermectin for foals dewormer is essential for controlling roundworms (also known as ascarids).

Creating a foal worming program

During their first year of life, young horses should receive a minimum of four deworming treatments.  The first deworming should be carried out at about 2-3 months of age. A benzimidazole drug is recommended to ensure efficacy against large roundworms. The second deworming treatment is recommend just before weaning (approximately six months of age). At weaning, fecal egg counts are recommended to determine whether worm burdens are primarily strongyles or large roundworms, to facilitate the right choice of drug class. Recently weaned foals should be turned out onto the “cleanest” pastures with the lowest parasite burdens. At about 9 and 12 months of age, third and fourth treatments should be considered respectively. Treatment should primarily be targeting strongyles. Tapeworm treatment should be included on one of these latter treatment occasions.

  1. First deworming: 2-3 months old. Use benzimidazole drug to ensure efficacy against roundworms.
  2. Second deworming: just before weaning (approx 6 months old). Fecal egg count will determine whether to treat for strongyles or large roundworms.
  3. Third deworming: nine months old. Use treatments targeting strongles. Either third or fourth deworming should also include treatment for tapeworm.
  4. Fourth deworming: Use treatments targeting strongles. Either third or fourth deworming should also include treatment for tapeworm.

Ivermectin Products Safe for foals:

Preventing Worms in Foals

You can protect foals from parasites and worms with good pasture management. Keeping the horse’s environment clean is a vital step in preventing and controlling parasite infestation. Complete eradication of parasites is close to impossible, which is why it is better to keep the parasites well controlled to avoid problems. This way, you are helping adult horses as well as their newborn and incoming foals avoid equine parasite infestation as much as possible.