Old rule: Deworm the entire herd regularly, rotating through different classes of dewormers.
New rule: Evaluate horses individually, deworm only as necessary utilizing one effective product.
Equine parasitologists are advising veterinarians and horse owners to rethink their traditional methods of parasite control. The outdated practice of treating every horse the same and with products from different classes of dewormers has been found to be ineffective according to Hoyt Cheramie, DVM, MS, a manager of Merial’s Large Animal Veterinary Services.
Let’s look at some facts that will help you understand why conventional thinking has changed and how it impacts deworming.
FACT. Rotating dewormers is not only unnecessary; it actually may be contributing to the problem of resistance.
Horse owners have long believed that by rotating dewormers, they’ve been fighting drug resistance. “Using several products blindly, some of which may no longer be effective on the parasites infecting horses on your farm, simply doesn’t make sense,” says Dr. Cheramie. “Not only is the program not the best it can potentially be, but experts agree that alternating drug classes does not delay the development of drug resistance. Using products which may no longer be effective is neither medically sound nor cost effective.”
FACT. As it turns out, leaving a residual worm population on a farm is not only harmless – it’s necessary.
True – as long as it’s the right population. That population is called “refugia.” As illogical as it may sound, you should actually welcome some parasites on the farm as long as they are susceptible to the dewormers you’re using. By leaving that refuge population of non-resistant (susceptible) worms to interbreed with resistant parasites, you help reduce the development of resistance. Using selective deworming practices will keep a balance between managing this population and keeping your horses healthy.
FACT. Only about 20 percent of the horses in a herd shed about 80 percent of the farm’s worm eggs.
Most worm contamination on a farm comes from a small subset of high shedders. Dr. Cheramie suggests utilizing Fecal Egg Counts to identify that subset and then developing a comprehensive deworming strategy. By developing treatment plans based on shedding levels, optimum worm control can be achieved, and the risk of developing worm populations that are dewormer resistant is reduced.
FACT. No dewormer classes are immune to the eventual development of resistance.
“Although resistant populations and species of worms have developed at different rates of speed depending on the parasite, drug and frequency of use,” says Dr. Cheramie, “the fact is every class of dewormer currently available is at risk for resistant worm populations to arise. That is why it is so important for horse owners to work with their veterinarians and take action to ensure their deworming programs are both effective and responsible.”
About ZIMECTERIN® Gold (ivermectin/praziquantel)
ZIMECTERIN Gold combines ivermectin, a leading ingredient that controls a wide variety of parasites, with praziquantel, an ingredient that specifically controls tapeworms. Together, they provide excellent equine parasite control. ZIMECTERIN Gold is approved to control more species and stages of equine parasites than any other brand, including benzimidazole-resistant small strongyles.It controls 47 species and stages of equine parasites in all.
Plus, ZIMECTERIN Gold was the first dewormer approved by the FDA to effectively control tapeworms* with a single dose. Tapeworms have been recognized as a significant threat to the health of horses.
About Merial
Merial is a world-leading, innovation-driven animal health company, providing a comprehensive range of products to enhance the health, well-being and performance of a wide range of animals. Merial employs approximately 5,600 people and operates in more than 150 countries worldwide. Its 2010 sales were more than $2.6 billion. Merial is a Sanofi company.
For more information, please see www.merial.com.
Important Safety Information
Warning: Not for use in humans. Keep this and all drugs out of reach of children. In horses, there have been rare reports of swelling and irritation of the mouth, lips, and tongue following administration of ZIMECTERIN Gold. These reactions have been transitory in nature. Do not use in other animal species as severe adverse reactions, including fatalities in dogs, may result.
