Deworming Recommendations
What do we do now?
Learn to Live with Parasites: “The presence of parasites is not inherently bad; in fact the immune system of the horse evolved in the presence of parasites. So parasitism is a natural state: it’s only when they adversely affect the horse’s health that they become a problem.” -Craig R. Reinemyer, DVM, PhD.
Perform Fecal Egg Counts: Target your approach – know if your horse has parasites, how many and what type before administering a dewormer. “I’ll hear people say that deworming is cheaper than a fecal egg count, but if you’re deworming with a product that no longer works on your farm, it’s just wasted money.” -Ray Kaplan, DVM, PhD.
Focus on the Horses that Need It: It has been discovered that 20 percent of horses shed 80 percent of the parasite eggs (high shedders*). These are the horses that contaminate the pasture and their deworming program should be modified accordingly. “The only way to determine these ‘high shedders’ is through a fecal egg count test as they usually don’t look ‘wormy’ at all.” – Ray Kaplan, DVM, PhD.
Practice Good Timing: “A huge number of variables come into play, including the time of year, the age of the horse and the horse’s shedding classification.” -Craig R. Reinemyer, DVM, PhD.
Target the Worm: “Small strongyles, the leading parasite concern, can still be controlled with….moxidectin. Tapeworms require a treatment of praziquantel. In younger horses, ascarids may be a concern. Anthelmintic resistance has been demonstrated in ascarid as well, so fecal egg count reduction testing should be implemented to identify which products are effective in your herd.” -Craig R. Reinemyer, DVM, PhD.
Excerpts from: Equus, February 2011 by Christine Barakat.
* High-shedders refers to animals with high quantities of parasite eggs in their feces.
“As a working baseline, I think that every well-managed horse will be dewormed with a macrocyclic lactone, like ivermectin or moxidectin, twice a year, at about six-month intervals. This recommendation is essentially to maintain or achieve eradication of large strongyles.”
General Recommendations:
* Deworm horses shedding greater than 500 EPG before spring turnout and as needed during the grazing season based on post treatment FEC’s.
* Treat for tapeworms (with praziquantel) before going on pasture in the spring. If tapeworms are a big issue, another treatment can be done in the fall. Treat for bots after the second hard freeze in the fall.
* The concept of zero tolerance for small strongyles should be abandoned, as some degree of parasitism is necessary to stimulate an immune response.
* Individual horses vary greatly in their susceptibility to internal parasites; some limit infection almost entirely even without deworming drugs, while others carry very high parasite loads even with regular deworming. Thus, we can also reduce anthelmintic use by only deworming the horses that actually need it.
* Anthelmintics are not the only control measures for internal parasites. For example, removing feces from the environment every few days ensures that infective larvae are hauled off in the wheelbarrow.
