Using FEC as a monitoring tool

Faecal egg counts are a good tool for monitoring the need for anthelmintic treatment in horses spring till autumn. 

Individual horses handle small redworm (strongyle) infections differently, some have a high egg count (high shedders), whilst others with the same number of adult worms inside will maintain a low egg count (low shedder). This is due to the individual horse’s immune system.

Conducting frequent egg counts can identify high shedders, combine this knowledge with the risk factors described below and you can design anthelmintic (wormer) treatment programs which ensure your horses stay healthy and pasture parasite contamination doesn’t get too high.

Questions faecal egg counts can answer:

	Are worms the problem? Evidence-based treatment establish whether small redworms (strongyles) or ascarid roundworms are the cause of poor condition and diarrhoea confirm the presence of adult worms to inform treatment choice Testing could save the time and costs of worming horses if worms are not the problem
	When to treat? Regular egg counts ~8-12 weeks apart Frequent monitoring can provide an indication of which paddocks are more wormy Highlights the optimal time for treatment Can be useful to improve health and welfare Correct timing = greatest benefit from wormer treatments
	Which horses to treat? Treating only those horses which need treatment reduces excess chemical usage and costs. This will also reduce selection pressure for wormer resistance (anthelmintic resistance)
	Did the treatment work? Only viable test to check if wormer treatments are working Avoid wasting money on treatments which are ineffective Wormer resistance is common – understand what works in your yard to treat effectively
	What egg counts CAN’T tell you… Egg counts cannot tell you about encysted larvae as only adult female worms produce eggs (see types of worms for more information) Encysted larvae are common in autumn/winter. Horse owners should conduct a risk assessment and if high, treat with a larvicidal treatment – see your vet or advisor for advice.   A single faecal egg count only provides a snapshot of what is happening…frequent testing is required to maximize benefit (test every 8-12 weeks) Egg counts can differentiate between strongyle eggs and ascarids but they can’t tell you which type of strongyle eggs are present (small redworms or large strongyles) – this would require larval culture as the eggs look very similar Egg count results do not always reflect the number of adult worms in the horse Different types of worms producing different numbers of eggs Some horses can maintain good condition and have low egg count despite harboring worms (resilience/low shedders) Egg counts are not a reliable test for tapeworm in horses. Other available tests e.g. saliva testing are more appropriate for tapeworm.

Click here for further information on targeted roundworm control in horses.