The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.
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34 TheHorse.com THE HORSE August 2015 organism, it's possible to inadvertently contribute to resistance among the tril- lions of bacterial species you'd consider out of the line of fire. Appropriate timing of the targeted, cor- rect treatment also influences outcome and resistance development. "The drugs themselves don't make the parasites resistant," says Peregrine, adding that inappropriate deworming methods are more to blame. "If you are treating all animals every time, that's probably the worst type of selection pres- sure you can apply," meaning that you're killing off any remaining susceptible parasites in horses that don't need to be and, thus, enabling survival and perpetu- ation of parasites with natural resistance to these drugs. He cautions that any development of new antiparasitic drugs will not be enough to eliminate the drug-resistant parasite problem; instead, owners and veterinarians need to continue focusing on treating only the most heavily af- fected animals to preserve the remaining effectiveness of the weapons we have. Another problem Peregrine sees in antiparasitic strategies is underdosing. "There is a lot of evidence that underdos- ing strongly selects for parasites with resistant genes," he says. Operational Intelligence Weese cautions against basing drug use decisions on fear or hype. For instance, he says, "It's easy to have a knee-jerk response of 'Don't use antibiotics,' while there are some situations where anti- biotics are used (advisedly) to prevent disease, and the flip side—having to treat existing disease, and often with more important drugs—isn't always good. In other words, while it's tempting to try to minimize resistance by only bringing out the antimicrobial arsenal in the face of an invasion, in certain cases it might be better to use a drug less important in human medicine to prevent disease in animals, thus saving the "big guns" (and delaying resistance against them) for human use. And even though veterinarians have decades—even centuries!—of experi- ence in battling these bugs, Weese says there's plenty left to learn: "We still don't understand a lot about optimal dosing and treating different sites (e.g., the lung vs. the skin). We overestimate how much we know." For now, diagnostic measures such as fecal egg count reduction testing for parasites, which allows monitoring their response to anthelmintic drugs; viral di- agnostic testing (respiratory swabs); and bacterial or fungal culture and sensitivity testing can help veterinarians select the proper "anti" drug to kill the pathogen at hand and effectively treat your horse. h ABOUT THE AUTHOR Christy Corp-Minamiji, DVM, is a former equine practitioner who now works as a freelance writer in Northern California. She has three children and writes fiction and creative nonfiction and blogs in her spare time. The Battle Against the BUGS Our antibiotics aren't smart enough to just go where they're told." DR. SCOTT WEESE Tickets Available Now: www.toba.org • (859) 276-2291 Photo by: Lee Thomas 30 th Annual National Awards Dinner Friday, September 11, 2015 • 6:30 p.m. Hill 'n' Dale Farms • Lexington, Kentucky Cocktail attire. Limited reserved seating. Please J oin Us