What is a fecal egg count test?

A fecal egg count test is a quantitative assessment and identification of how many parasite eggs a horse is shedding at the time of the test.  In order words, a fecal egg count test tells you what type and how many parasites are potentially inside your horse’s digestive tract.  Several factors can influence a fecal egg count test result including a horse’s age or immune status, time of year, the age of the parasite population, and the residual effects of any recent deworming treatments.

Fecal egg count tests are performed on a sample of your horse’s manure (the fresher, the better). For additional information on the collection, packaging, and shipping of equine fecal samples, check out Zero Egg Count’s Sample Shipping and Collection Instructions.

After a sample is collected, it is measured and mixed with a solution to prepare the manure sample for examination under a microscope.  The examination consists of counting the number of parasite eggs visible in the prepared sample.  The number of parasite eggs visible is reported on an eggs per gram basis (e.g., Small Strongyles at 200 EPG).  Eggs per gram is a standard measure for fecal egg counts so you can compare your current findings to previous testing results.  The higher the EPG count, the higher the number of parasites in your horse’s digestive system.  The parasite EPG calculation is often referred to as a horse’s parasite load or worm burden. 

A parasite load or worm burden can be used to classify a horse into a shedding or contaminator category. The American Association of Equine Practitioners Subcommittee’s Parasite Control Guidelines classifies horses into three different levels of egg shedding categories – Low, Medium and High.  A horse with a fecal egg count result between 0 and 200 EPG is classified as a low shedder.  A medium or moderate shedder has an EPG between 201 to 500, and a high shedder has an EPG of above 500.  Fecal egg counts are an estimate of your horse’s parasite burden or worm load.  Fecal egg tests do not reflect any parasite larva remaining in the host (i.e., encysted larvae).

Knowing your horse’s shedder classification helps you determine an appropriate deworming treatment protocol.  A low shedding horse will typically need less deworming treatments than a medium or high shedder. 

Conduct two sets of fecal egg count tests annually.  One set of tests in the Spring and another set of tests in the Fall.  Each set consists of a fecal egg count test before any deworming treatment and another fecal egg count test 14 days after your deworming treatment.  The before-treatment test identifies your horse’s worm burden and shedder category.  The after-treatment test helps determine the efficacy of the anthelmintic (how well your dewormer is working).

Regular fecal egg testing avoids subjecting your horse to excessive chemical treatments and delivers valuable information to you and your Veterinarian which may adversely impact your horse’s health.


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