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Parasite Control:  Its Not Just Deworming Anymore

For the last 10 to 15 years managing your horses parasites was easy.  You gave your horse a paste wormer every 2 months, rotated which wormer you used to prevent resistance and voila!  Problem solved.  Then came the daily dewormers such as, Strongid C, and we were able to do even better for our horses.  As a result, horses were healthier, lived longer, and parasite induced colics became a thing of the past.  Something as unglamorous as deworming has helped increase the average horse’s life span by 5 years!  After vaccination, that’s more benefit than all the modern surgeries and medical treatments combined.  The daily dewormers are so successful that Pfizer, the company that makes Strongid C, offers a program that covers $5000 of the cost of colic surgery if you use their product.  But times change and so do the worms.  Research is showing that parasites are becoming resistant to dewormers and that our rotational deworming program is part of the problem.  By using our dewormers based on a schedule rather than by targeting the parasites that the horse actually has, we can be wasting time and money by trying to kill parasites that your horse doesn’t have.  This also makes the parasites harder to kill the next time.  In addition, you can also be deworming too frequently which also creates resistance. 

So how do we know which wormers to use and when to deworm?  The answer is through  fecal tests.  So does your manure need to be studying up for the test?  No of course not. There are new fecal tests that tell us how many and what type of parasite eggs are in each gram of manure.  By knowing this we can figure our how often and what type of dewormers to use on your horse.  The good news is that because of Colorado’s dry climate we’re finding less parasite problems than other parts of the country.  This means that if we target our deworming we can deworm less frequently.  For example, horses that do not go out to pasture can often times be dewormed only twice a year, in the late fall (after a frost to kill the bot flies) and early spring (the wettest time of the year).  Horses on pasture have more exposure to parasite eggs so they need to be dewormed more frequently.  A fecal test will give us the information we need to develop a deworming program that is  healthiest for your horse.  All that is required is to bring 1 fresh road apple to our office in a ziplock.  The fecal sample must be kept cool to keep the test accurate. 

So why should we care?  Paste wormers are cheap and much easier to figure out than    fecal tests.  The answer is because at the same time parasites have become resistant, no new dewormers have been developed to fight them.  In fact, no new dewormers have come on the market in the last 10 years!  Because of this it is much harder to fix resistance, then to prevent it.  In addition, colic is still the number one cause of death in horses. A resurgence of parasites as a cause of colic would make colic a much bigger, more deadly.


Dr. John Marion

Castlewood Canyon Equine - Quality Horse veterinarian Services for Franktown CO, Elizabeth, Parker and the surrounding areas.

1115 Castlewood Canyon Road
Franktown, CO 80116
(303) 660-1492

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