Faecal testing in horses: what does the EPG value mean?

What exactly does an EPG value measure?

EPG stands for Eggs Per Gram: the number of worm eggs counted per gram of horse dung under a microscope. Laboratories use the McMaster technique for this, in which a fixed amount of dung is dissolved in a liquid and the eggs float to the surface in a counting chamber. A standard faecal test covers strongyle worms (small and large redworms). A separate test is needed for tapeworm (ELISA blood test or saliva test) and botfly larvae. The EPG therefore does not give a complete worm picture, but it is the most practical everyday measure of the worm burden in your horse.

What are normal and elevated values?

Most vets use the following threshold values for strongyles:

• 0–200 EPG: low worm burden, no treatment needed
• 200–500 EPG: moderate worm burden, discuss with your vet
• 500+ EPG: high worm burden, worming advised
• Foals and young horses (< 3 years): lower threshold, treat from 200 EPG onwards
• After a treatment: retest after 14 days to check for resistance (FECRT)

How do you collect a good dung sample?

A reliable result starts with a good sample. Follow these steps:

• Collect fresh dung, preferably from the inner layer of a freshly dropped dung ball
• Use a clean container or the sample tube provided by your laboratory
• Collect at least 3 grams — approximately one tablespoon
• Keep the sample cool (refrigerator, max. 4°C) and send it within 24 hours
• Note down the horse, the date, and any medications it has recently received

How often should you carry out a faecal test?

The frequency depends on the result. Horses with consistently low EPG values (so-called 'low shedders') can generally be tested twice a year: in spring and in autumn. Horses that regularly exceed 500 EPG ('high shedders') deserve more frequent attention — three to four times a year. Also take the season into account: the worm burden is highest in spring and early summer when larvae are active on the grass. A retest after a worming treatment — the Fecal Egg Count Reduction Test (FECRT) — is a smart way to detect resistance in time. Record all results in your horse's EquiSight horse profile, so that you can see your horse's pattern over multiple years.

Resistance: why targeted worming matters

Resistance to worming products is a growing problem, particularly against benzimidazoles (e.g. fenbendazole). If you worm blindly every three months, you are actually selecting for the worms that survive — and those multiply rapidly. Targeted worming means: only treating when the EPG actually exceeds the threshold value. This preserves the population of susceptible worms and extends the useful life of available products. Ivermectin and moxidectin currently still work well against strongyles, but resistance to these is also increasing. Keep track of your FECRT results and discuss any anomalies directly with your vet.

Recording faecal test results in EquiSight

All EPG results, the products used, and the dates of retests are valuable health data. In your horse's EquiSight horse profile you store this information per horse, so that at a next consultation or with a new stable manager you can immediately show the complete worming history. EquiCoach also helps you, based on your recorded results, to be reminded when a retest is due, and provides explanations for unusual values. That way you don't have to keep track of everything yourself.