I have a 10-year-old riding horse, Toby. Recently the owner of the stable where I board him told me that I should rotate wormers. What does this mean? Will Toby get colic if I don't do this
Nobody knows why some horses get colic (intestinal pain) and others do not, but it is well known that their risk for developing colic increases when there are a large number of parasites in the intestines. Colic can be a very severe problem, at times resulting in a horse's death, so it is important to minimize the number of parasites a horse carries. Veterinarians are most worried about the bloodworm, strongylus vulgaris, which causes severe damage to the blood supply leading to the intestine. There are many other horse parasites which also can cause problems. In the past, horse owners were encouraged to rotate wormers to reduce the chance that the parasites would become resistant to any one medication. But recently parasitologists are coming to believe that rotating wormers is not so important. It is important to consult your veterinarian when starting a parasite control program. Such factors as your horse's age, the amount of parasite eggs in the environment, and other parasite control measures will determine exactly how often your horse should be wormed and the product to use. When there is reason to believe your horse is exposed to high numbers of parasites all the time, it should receive continuous wormer daily. This is the most expensive, but also the most effective way to prevent parasite infestation in your horse. On the other extreme, if a horse is kept alone with little exposure to parasites, two or three treatments a year may be sufficient. Your veterinarian can choose the products which will work best for your horse. This makes more sense than alternating wormers merely for the sake of change. No matter what control program you use, it is important to check to see how well it is working. This is done by testing the horse's manure for parasite eggs several weeks or months after starting the worming program. If the wormers are working as they should be, there will be no parasite eggs in the manure. If parasites are still present, you need to make adjustments in the worming schedule until your horse is parasite-free.