Foal Deworming

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A mother horse feeds her foal.

Though deworming the mare can offer protection from threadworms passed through mare’s milk, foals should receive a minimum of four deworming treatments during the first year of life. Photo by Liz Waguespack

Spring has officially arrived, and we’ve entered another foaling season, welcoming this year’s crop of foals and with it concern for the parasite load in our young horses. Foals are typically more susceptible to parasites, and while we are all deworming our horses based on fecal egg counts, this approach is not recommended for foals.

Foals who have been born to mares who have been dewormed with ivermectin or benzididazole one to three days prior to foaling will typically be protected from threadworms (Strongyloides westeri) passed through the mare’s milk. However, foals should receive a minimum of four deworming treatments within the first year.

At 2 to 3 months old, a benzimidazole based drug (e.g., like PANACUR at 4.6 mg per pound) is recommended to treat roundworms (ascarids). Ascarids are most damaging to the immature immune systems of young horses and can cause a variety of symptoms including stunted growth, gastrointestinal upset, colic, respiratory dysfunction, etc.

At weaning (4 to 6 months old), fecal egg counts should be utilized to determine the foal’s parasitic load. Ivermectin or pyrantel (Strongid) is recommended for foals with more strongyles, and fenbendazole (PANACUR) for foals with more ascarids. If strongyles and ascarids are present at an equal level, use pyrantel or fenbendazole since ascarids display a high resistance to ivermectin.

The third deworming should occur around 9 months old and should target strongyles and tapeworms and utilize ivermectin plus praziquantel (Equimax or Zimectrin Gold). As many as 60% of horses living in the Southeast were found to be infected with tapeworms. The highest infection rates occurred in October which will typically fall around the time when a foal is 9 to 10 months old or the third deworming.

The fourth deworming should occur around 12 months old and will target strongyles with ivermectin or pyrantel. During the next year from 12 to 24 months old, assume your foal is a high shedder and treat for strongyles with ivermectin at least three times. You should also treat the foal once around October or November with moxidectin (Quest) or moxidectin plus praziquantel (Quest Plus) for bots and tapeworms. Keep in mind that moxidectin cannot be used until your horse weighs more than 500 pounds, so it is important to get an accurate weight and dose appropriately.

Additional management techniques include turning foals in the pasture with the lowest suspected parasite burden. Use creep feeders or similar products to keep the foal’s feed off the ground to reduce parasite ingestion during feeding. Rotating pastures, cleaning up manure, cross grazing with ruminants and avoiding overstocked pastures will also help reduce the potential parasite concerns for your foal.

Age Treatment
2-3 months Fenbendazole (Panacur) - Ascarids
4-6 months Ivermectin or Pyrantel (Strongid) - Strongyles OR
Fenbendazole (Panacur) - Ascarids
8-10 months Ivermectin + Praziquantel (Equimax or Zimectrin Gold) - Strongyles and Tapeworms
12 months Ivermectin or Pyrantel (Strongid) - Strongyles
15 months Ivermectin
18 months Ivermectin
21 months Moxidectin (Quest) or Moxidectin + Praziquantel (Quest Plus)
24 months Ivermectin


AAEP Parasite Control Guidelines accessed 4/9/2024.

Tapeworms in horses accessed 4/9/2024.

5/16/2024 3:09:12 PM
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