Q. What’s the best way to go about making the decision to deworm if my horse is boarded at a large facility? For instance, historically my horse has tested as a low to no shedder, and he only goes out with two other horses. Should we have the recommended three fecal test this year and then decide? Are there other considerations to keep in mind?

Let’s say all three horses test as low to no shedders, and the recommendation is not to deworm. Any suggestions for effecting change at a farm that follows tradition (i.e., generally they deworm all the horses without fecal egg counts)?

—Louise, via e-mail

A. Thank you for your question, which is very relevant as lots of people are in a very similar situation.

The best approach is always to coordinate efforts at the facility so all horses are included in an overall parasite control program. This does not mean all horses are necessarily treated with the same products at the same time, but it’s important to avoid the patchwork-type programs where one person doesn’t know what the next one is doing when and why. Parasite control is about controlling the parasite population present in a given equine operation.

The parasite population is shared between all the horses present on a farm, but that doesn’t mean all horses have identical deworming needs. A constant low-shedding adult horse in good health doesn’t need more than one or two treatments within a year—often to be considered in the spring and fall.

In addition to strongyle parasites, it’s important to also consider tapeworms, which are likely to be present on a majority of farms. Horses in the high-shedding category (typically above 500 strongyle eggs per gram) could require one or two additional treatments to ensure that contamination of paddocks and pastures is reduced. Then, you can collect follow-up samples to check the efficacy of each treatment to ensure that everything worked as intended. The latter is of extreme importance, because many horse owners are wasting their money on products that don’t work anyway (due to parasites’ anthelmintic resistance).

Spending a little money on fecal egg counts is a good investment in your horse’s health and well-being rather than conducting blindfolded chemical warfare.

As mentioned above, a surveillance-based parasite control principle should really be applied to the entire boarding facility. This is a management decision, of course, but I know of many examples where parasite control is part of monthly  boarding fee and is coordinated by one veterinary practice. That’s the way forward.