The small strongyles and ascarids are becoming increasingly resistant to the chemicals in our worming products. To prolong the life of these products, frequent interval or calendar-based deworming should be avoided, but how do you know when a wormer is necessary? Faecal egg counts can be a great investment for your worm control program and can help you understand what’s happening at the ground level!
What is a faecal egg count and what does it tell me?
A faecal egg count (FEC) is a laboratory test that estimates the number of strongyle or ascarid eggs per gram (EPG) of manure. It is an extremely useful tool for managing pasture contamination and informing de-worming decisions.
What threshold should I use for treatment and why?
The FEC threshold that justifies a treatment can be flexible depending on the circumstances, but a general rule of thumb for healthy adult horses is that a ‘high’ count (>500 EPG) would warrant a treatment. This is to limit the amount of pasture contamination, not because a high count indicates a risk of disease.
How do I use FEC results to inform my worming decisions?
Adult horses tend to have consistent strongyle egg-shedding patterns, and a few well-timed FEC’s during periods of high parasite transmission (Spring and Autumn) can help you tailor a worming plan for each individual. Naturally high-shedding horses may need 3-4 treatments annually, while low/moderate shedders (<500 EPG) may only require 1 or 2.
What is a FECRT and when should I use it?
FECRT stands for ‘Faecal Egg Count Reduction Test’, which is a test of how effective a wormer is against particular worms on your property. It checks for resistance issues by comparing pre- and post-deworming FECs. When there is no resistance, a wormer should decrease FEC by at least 99%. Testing for resistance every couple of years ensures you are only using effective products.
Can I diagnose tapeworm infections with a FEC?
Tapeworm eggs aren’t always visible in routine FECs and can lead to a ‘false negative’ result. A modified test can be conducted to improve the detection of tapeworm eggs in manure, but you would need to ask your service provider if this is possible.
How can I diagnose encysted cyathostomin infections?
In Australia, we have no tools or tests that can confirm the presence of encysted cyathostomins, but fortunately, cases of larval cyathostominosis are not common in well-managed horses. Provided you are using effective wormers (confirmed by FECRT) and implementing non-chemical strategies where practical, the risk of clinical disease should remain low.
Using FEC results to guide your decision making can lead to a range of benefits including a reduced reliance on chemical deworming, slowing the development of resistance, and in many cases, a reduction in the long-term cost of wormers! But one of the more interesting outcomes is that you will become more knowledgeable about your horse and the life cycles of important parasites.
Author: Dr. Anne Beasley Ph. D.
On behalf of Virbac Australia
