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Developing effective deworming programs (Sponsored by Intervet/Schering-Plough Animal Health)


The best way to prolong the efficacy of deworming programs is to use vaccinations and sound nutrition in conjunction with the right anthelmintics.

It's a well-established fact that some common dewormers are becoming less effective. Farms across the country that traditionally use only one class of dewormer for an extended period are experiencing significant resistance issues, resulting in documented cases of parasite resistance for every chemical class of anthelmintic.


According to Wendy Vaala, VMD, DACVIM, ineffective deworming programs, combined with a decades-long wait for new drugs, are increasing the prevalence of drug-resistant parasites in the horse population. The new motto large animal veterinarians and horse owners need is a simple one, says Dr. Vaala: The right dewormer, at the right time, for the right horse. "Random use of drugs throughout the year just isn't effective any longer," she says.

Developing balanced programs

Dr. Vaala, an equine technical services specialist at Intervet Schering-Plough Animal Health (ISPAH), says that there hasn't been a new class of deworming drugs on the market in 25 years."I think the whole industry faces tiiis concern," she says. "We need to keep as many drugs as possible working for as long as possible until a new molecule to combat parasites is discovered. And when a new class of anthelmintics does arrive, we need to use it wisely."

The best way to prolong the efficacy of deworming programs is to use vaccinations and sound nutrition in conjunction with the right anthelmintics. With that in mind, ISPAH is campaigning to get horse owners back in touch with their veterinarians.

"We want to drive equine clients to the veterinarian first and foremost," Dr. Vaala says. "We're also focused on helping practitioners train their technical teams. There's no reason an equine veterinary technician can't do a sensitive fecal examination and help translate the importance of those findings for the client. This approach saves practitioners time, can increase revenue for the practice, and makes technicians a valuable source of information for the clients."

Getting horse owners expert advice

Part of the problem, she says, is the misuse of dewormers. They're being used at the wrong time, on too many horses, or too frequently. "Looking down the road, we may be creating more drug-resistance throughout the horse population. If we overuse or misuse current drugs, we could end up with entire farms at risk," she says.

Dr. Vaala says that horse owners too often make the decision about the type of dewormer and its frequency of use. And ISPAH wants to send horse owners the message that they need to reconnect with their veterinarian instead.

Ideally, she says, the veterinarian or technician should perform a fecal examination on a regular basis—maybe as often as three to five times a year—to determine the proper therapeutic regimen. This strategy will help ensure that the horse's deworming program remains effective and it creates a profit center throughout the year for the practice. Regularly monitoring parasite control strategies also helps you develop clients that use dewormers more efficiently and economically.

ISPAH will release two brochures on the deworming program this year—one for veterinarians and their teams and one for horse owners. ISPAH is including a worksheet for the veterinarian to record a complete deworming history for each horse and—through timely and more sensitive fecal examinations— determine the egg shedding potential of individual animals. With this information, you can evaluate the efficacy of each class of dewormers.

"Once you know which horses are the high and low egg shedders and which dewormers are still effective, you can map out a reasonable treatment plan for the year that includes a strategic use of dewormers, regular fecal egg count monitoring, and sound pasture management," Dr. Vaala says.

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