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Parasite control is an important component of all equine health care programs. It is no longer enough to simply pull out a tube of dewormer and treat your horses every eight weeks. Today it is critically important to understand the basics of parasite resistance and develop a deworming program that will work for your farm. That program will need to be re-evaluated and modified as environmental conditions change from year to year, and farm management and number of horses fluctuate. It is imperative that all horse owners begin to combat resistant parasites that can spread from farm to farm, causing alarming consequences for the equine community.
With no new products on the horizon, it is important to protect our horses by keeping current products effective. Resistance is defined as the ability of parasitic worms in a population to survive a treatment that was once effective against the worms.
Today most horse owners continue to follow recommendations that are 30 to 40 years old and may be using products that are totally ineffective. The ground work for resistance was already in place in the late 1960's when new deworming products were introduced along with the recommendations that horse owners use them every 8 weeks. Prior to the introduction of these products, the large strongyle (Strongylus vulgaris) was the parasite of greatest concern. These large parasites migrated through arteries, interrupting blood supply to the gut, causing colic and sometimes death. However the use of the drugs of the 1960s and newer products of the 70's and 80's greatly reduced the prevalence of large strongyles on farms. Unfortunately, indiscriminate use of these products has lead to a drastic increase of another parasite, the small strongyle (cyathostomes). By the 1980s it was recognized that virtually 100% of the eggs being shed by horses were small strongyle eggs.
Thinking like a parasite will help you deal with them!
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