Equine Dewormers Appropriate for Autumn and Early Winter

In this third part of our fall equine deworming series, we look at what parasites to worry about and what products work best.
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autumn pasture horse

Autumn and early winter are strategic times to deworm your horses.

In this series on fall deworming, we looked at several topics that you should review in your horse's health program. In this segment, we talk about dewormers that are appropriate for use in autumn and early winter.

Pests to Worry About

Horses that have been out on pasture during warm months are at risk of contracting tapeworms, which are acquired through accidental consumption of mites, an intermediate host that live in grass. Following a good freeze, the mites no longer pose as much as a risk, so in late autumn after a cold snap is a good time of year to deworm with praziquantel against tapeworms.

Similarly, following a good freeze, botflies won’t be in abundance. Therefore, use of an avermectin class of dewormer (ivermectin or moxidectin) will kill bot fly larvae that have been ingested during the warm months.

Another parasite concern that is known for significant gastrointestinal issues is small strongyles (cyanthostomes), which encyst within the lining of the large intestine and remain dormant over the winter. Emergence of cyanthostomes in the spring might be accompanied by intestinal upset or colic. Late fall or early winter is a good time to use a dewormer that targets encysted strongyles as well as those that have not yet encysted. There are two anthelmintic options that work reasonably well:

  • Moxidectin
  • Double dose of fenbendazole given for five consecutive days.

It is also a good idea to repeat one of these two products in the spring if there is concern of an unusual parasite load in an individual horse.

Previous Articles in This Series

We highly recommend that you read the other two articles in this series to get the best overall perspective of deworming your horses in the autumn and early winter.

The Bottom Line

Deworming is often considered casually by horse owners, but with no new deworming class of chemicals available in future, it is important to follow veterinarian recommendations of how often to deworm and with what product. Take into consideration climatic variations in different parts of the country, and be sure test at least once or twice a year to check how much of an egg burden each individual horse sheds. This enables you to maximize success using a strategic and targeted deworming protocol.

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