The Horse

APR 2019

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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28 April 2019 The Horse | follow-up sample comes back with a high count, it's safe to assume that horse was not treated for some reason, rather than the problem being dewormer resistance." If all or most of the horses still have worms after treatment, it warrants further investigation but doesn't necessarily mean they have resistant worms. Treat the horses with anthelmintics again, using the same active ingredients as the first time, and redo the FEC two weeks later. "Resistance doesn't show up in one test and then disappear in the next," Nielsen says. "If the second treatment is effective, the problem the first time was not caused by anthelmintic resistance. If the second treatment is still not effective, it is highly possible that you have a problem with resistance on your property." Parasitologist Caroline Jacobson, BVMS, PhD, senior lecturer of biochemis- try and nutrition in Murdoch University's School of Veterinary and Life Sciences, in Western Australia, also emphasizes the importance of using FECs to check treat- ment efficacy. "By the time we see treatment failure in adult worms evident as poor egg count reduction, resistance to that treatment in the worm population is already ad- vanced," she says. The earliest sign of emerging resistance in strongyles to the macrocyclic lactones (dewormers that target parasite nervous systems) is reduction in the time it takes for FECs to rise after treatment—the egg reappearance period. Macrocyclic lactones, such as ivermectin and moxidec- tin, revolutionized equine parasite control when they were released in the 1980s and '90s, respectively, and continue to be important worm control drugs. Maintain- ing their efficacy is a key component of a parasite management program. "If FECs start to rise sooner than expected, this is a warning sign that resistance is emerging, and steps should be put in place to (keep resistance from) worsening to a point where treatments become ineffective," says Jacobson. "This is already happening all over the world," Nielsen adds. "We commonly see egg reappearance periods around four weeks now, where it used to be nine to 13 weeks for ivermectin and 16 to 22 weeks for moxidectin." Maintaining Refugia The old recommendation to deworm all horses every six weeks hastened the RISK & REALITY ISTOCK.COM Cross-grazing your horses with ruminants such as cows is an effective nonchemical means of worm control. Colors Available Pink, Blue and Orange Sizes Available Mini, Pony/Donkey Yearling, Small Medium and Large Sizes MADE IN Patented Design US6508205B1 Exclusively Distributed By: QUALITY • SERVICE • INNOVATION STOP THE STOMP! STOP THE STOMP! Use loose-fitting, chemical free during fly season to prevent painful fly bites and reduce stressful stomping. • Prevents Botflies from laying eggs causing hoof damage • Decreases healing time of abrasions and wounds by allowing air flow • Easy to attach, comfortable to wear and will not sag due to their unique sewn-in plastic stays

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