I know – it’s the less romantic aspect of horse ownership. Parasite control. Oh boy.
More and more veterinarians are recommending utilizing Fecal Egg Counts (# of parasite eggs in 1g of manure) and selective paste deworming instead of the traditional plan that called for the rotation of different classes of dewormers on a set schedule. The newer thought process is designed to help prevent parasite resistance to our existing deworming drugs.
We also have been schooled, in the past, that we can take a fecal sample from one herd member and assume similar parasite levels in all horses in that herd. That one sample would determine whether or not our deworming program is working. Now, evidence suggests that some horses have better natural immunity to parasitic infestation than others. Your herd actually consists of “low” and “high” shedders, the high shedders being the ones that shed parasite eggs in their feces to reinfest the rest of the herd. Approximately 20% of the horses account for 80% of the parasites. You can imagine how if you had taken your one sample randomly from either a high or low shedder, it did not provide you with an accurate picture of what your herd health is really like.
So the idea is to identify the high shedders and deworm them more often while reducing the frequency of deworming in the low shedders. Less use of the drug leads to a lower likelihood of parasites developing a resistance to it.
Janssen Veterinary Clinic has a nice overview article on parasite control: Correct Deworming Practices = $$$aving$ + Better Health.
Just to share my recent experience: I dewormed my (4) horses with ivermectin in March. FEC on two of them last week (October) yielded the results: Emma=0; Maia=6 (FEC<200 is a low shedder). I’ll submit samples for Jack & Leo next week.