What is rotational deworming? This is the method of deworming your equine with alternating anthelmintics (dewormers) on a set schedule, usually every 6-8 weeks. Most people rotate the products, thinking that this will better protect their horse from intestinal parasites. Unfortunately, veterinarians have been noticing an increase in drug-resistant intestinal parasites and rotational deworming/overuse of one type of dewormer is thought to be a leading cause. Encysted small strongyles are the most concerning parasite for adult horses today. They have shown resistance to two of the three classes of anthelmintics we have available to us today, with only ivermectin or moxidectin being considered effective against them.

So, what can we do instead to protect our adult equine partners and not contribute to rising parasite resistance? Fecal Egg Counts! Fecal egg counts are now considered the gold standard in any equine deworming program. A small sample of your horses’ feces is sent off to the lab where they look at it under a microscope to count the number of eggs per gram of stool. This number determines where your horse is classed, low shedder < 200 EPG, medium shedder 200-500 EPG and high shedder > 500 EPG. Depending on the classification of your horse a proper deworming protocol will be recommended to you. All horses still need to be dewormed, but most on a much less frequent basis.

This information applies to adult horses over one year of age. Foals are much more susceptible to intestinal parasites due to their immature immune system. They are also susceptible to different types of parasites that don’t usually affect adult horses, such as strongyloides (threadworms) and ascarids (roundworms). Foals should be dewormed on a set schedule up until one year of age with a fecal egg count done around 6 months of age and then again at one year.

Here is a link to our deworming schedule that you can use once we have completed a fecal egg count on your horse. Please call us to schedule an appointment today!


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