Q.  In the interest of checking fecal samples for types of worms actually present in individual horses, and since I have the equipment, I'd like to do fecal checks here at home. Can you direct me to a chart or a book containing information and illustrations of eggs of various parasites? My veterinarian is an integral part of my horses' health, and he agrees that I could perform this task myself.


A. It is entirely feasible for a horse owner to perform equine fecal examinations, if they have access to a microscope, follow standardized techniques, and have a pictorial key for identification of parasite eggs.

A suitable microscope doesn't have to be expensive. Routine fecal exams are usually conducted at 100X total magnification, the product of the magnifications of the ocular lens (the one you look through) and the objective lens (the one nearest the slide) so that total=ocular X objective. Most ocular lenses are 10X magnification (displayed on the outside of the lens housing), so the total magnification would be 100X if one used a 10X objective lens.

Techniques are fairly simple, and they are described in detail in various reference sources. A complete, reasonably priced resource is Veterinary Clinical Parasitology by Sloss, Kemp, and Zajac (Iowa State University Press). This book can be purchased from the publisher or through retailers on the web. Those concerned about anthelmintic resistance also might consider purchasing a simple kit for conducting quantitative fecal egg counts. The Paracount kit is available from Chalex Corporation, 5004 228th Ave. S.E., Issaquah, WA, 98029; 425/391-1169; fax 425/391-6669; chalexcorp@att.net.

Any fecal examination technique will require disposable containers (e.g., paper cups), stirring sticks, microscope slides, and flotation solutions such as sodium nitrate, zinc sulfate, or concentrated sucrose (sugar). Your veterinarian can help you locate the required items.

The most common equine parasites are strongyles, and their eggs comprise 98% of the usual fecal spectrum in adult horses. In addition, it's desirable to be able to identify ascarid eggs (Parascaris equorum), which are found in horses less than two years of age, and tapeworm eggs (Anoplocephala spp.), which might occur in horses of weaning age and older. If your veterinarian is willing, the best preparation would be to watch a technician perform a few equine fecal examinations and show you some strongyle eggs through a scope.

Finally, I would encourage a horse owner who performs "in-house" fecal exams to work closely with his/her veterinarian to interpret the findings. Your veterinarian can answer such critical questions as: "Is deworming necessary?" "When should it be done?" and "What drug should be used?"

About the Author

Craig R. Reinemeyer, DVM, PhD

Craig R. Reinemeyer, DVM, PhD, is president of East Tennessee Clinical Research, Inc., an independent business in Knoxville, Tenn., that conducts clinical pharmaceutical research for animal health companies.

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