The Facts of Fecal Egg Count Exams

September 21, 2016
By Deb M. Eldredge, DVM

Horse owners are constantly looking for economical ways to provide high-quality care for their horses. The fecal egg count exam (FEC) is a great, inexpensive way to learn about the overall health of your horse and the effectiveness of your deworming program.

The reality is that all horses, even those kept in immaculate stalls, will have some parasites. Horses eat dropped grain and hay off the ground, where manure gets mixed in, and they graze in paddocks and fields, exposing them to parasites pretty much 24-7. Although it is unrealistic for your horse to be completely parasite free, you do need to control his parasite load.

Identifying the Parasites

If you would like your veterinarian to conduct a fecal egg count exam on your horse, you’ll need to collect one manure ball for a complete fecal analysis – fresh is best. Your veterinarian (or vet technician) will then do two different evaluations, the first of which is a qualitative analysis.

In this evaluation, part of the manure is broken up, mixed with a special flotation solution and centrifuged. The material from this mixture is examined under a microscope to identify parasite eggs that cannot be seen with the naked eye. Different parasites have eggs of different sizes and shapes, which helps your veterinarian identify which species are present.

Determining Parasite Load

After your vet identifies the kinds of parasites your horse has in the first evaluation, he or she determines how heavy your horse’s parasite load is. Some horses may have a low parasite load and never have a large population in their gut. Other horses, even if they’re kept in the same fields and paddocks, will have more serious and heavy parasite loads that can cause health concerns.

This evaluation involves mixing the manure with a solution and then counting the eggs under a special grid on a microscope slide. The count tells you how severe the infestation is. Once you have all the data about which parasites are present and how large the populations are, you can determine the appropriate deworming schedule with your veterinarian.

Horses with a good immune system and a light parasite load may need maintenance deworming, but horses with a heavy load may require deworming at more frequent intervals. Your veterinarian can help you decide on a schedule and which deworming actives are the best choices for your horse.

Other Parasites to Look For

There are a couple of parasites for which a fecal egg count evaluation won’t be helpful. Tapeworms in horses don’t appear as wiggly segments like they do in dogs and cats. In order to detect if tapeworms are present in your horse, a blood test is needed; however, your veterinarian will be able to tell you if tapeworms are a concern in your area.

Bot flies can lay eggs on your horse’s mane, shoulders, muzzle or legs. They are small, whitish, nit-like eggs that you can see when grooming your horse, and generally show up in the late summer. Bot larvae can cause gastrointestinal disturbances if your horse ingests them, which can occur if he rubs or chews on his coat where the eggs are attached. The warm, moist breath causes the larvae to hatch and crawl into your horse’s mouth. You can minimize bot infestations by removing the eggs from his hair, but most veterinarians suggest a deworming in the late fall regardless. 

Deworming Methods

In the past, horses were dewormed by “tubing.” Your veterinarian would pass a tube into your horse’s stomach via his nose and pour deworming medication down the tube. This was effective, but also expensive and dangerous for both horses and veterinarians. Luckily, there are now alternative dewormer options that horse owners can easily administer.

The most popular dewormers are the paste variety. They come in a plastic syringe with a dial that you adjust according to your horse’s weight. You put the syringe in the corner of his mouth, aim toward the back and squeeze. The paste dispenses at the back of the horse’s mouth and swallows it. No horse “likes” being dewormed, so many pastes are flavored to make them more attractive to your horse. Alternatively, some dewormers can be added to your horse’s feed as a top-dress. They are flavored, but you may need to add some molasses to hide the smell if your horse becomes suspicious. 

Overall, a fecal egg count exam is a good tool to have at your disposal as another method to evaluate your horse’s health. It is important to know which parasites your horse has because different parasites have different dewormer sensitivities, and it doesn’t make sense to spend money on a dewormer that won’t kill the right parasites!