Let’s talk worming foals & youngstock
March 17, 2026
Lead Reproductive Veterinary Surgeon Gemma Kirk BVetMed MRCVS has produced this useful Q&A for breeders wishing to follow best practice when it comes to worming.
Gemma graduated from the Royal Veterinary College in 2008 and has been involved in equine practice ever since. As a new graduate she worked for a branch of Minster Equine Clinic in Yorkshire. She then undertook an internship at Arundel
Equine Hospital in West Sussex where she looked after inpatients, carried out anaesthesia and was involved in lameness investigations and diagnostic imaging. Upon completion of her internship, she stayed at Arundel initially as a hospital/lameness assistant and latterly as part of the ambulatory and stud team.
Gemma spent four years dividing her time between Northern and Southern Hemisphere stud seasons as a resident vet at Vinery Stud, Australia. Vinery is a large Thoroughbred farm that is home to around 300 horses with 150-200 mares being bred each season and 150-200 foals arriving every year. Time spent here served as a valuable experience in all areas of equine reproduction and foal care.
Gemma has been with us at Towcester Equine Vets since March 2016 and is our lead breeding vet; however, having been practising for the last seventeen years, she is also a very valuable asset in all areas of the practice.
Stud worming advice Q&A
Q. Do we need to worm foals and young stock?
A. Yes. These are amongst the most at risk and important group of horses to consider when worming.
Q. Why are young stock most at risk?
A. Because foals are born with no innate immunity and have had no time to develop their own immunity against parasites.
Q. What worms are foals most susceptible to?
A. The types of worms that horses are most susceptible can depend on their age and the time of year. Ascarids/ large round worms are the most dangerous/ problematic type of worms for foals. Strongyloides Western (threadworm) can also be an issue causing gastrointestinal disease/ diarrhoea in younger foals.
Q. Why are Ascarids so dangerous in foals?
A. Insufficient knowledge, inappropriate/ insufficient worming protocols, development of concerning levels of resistance to wormers and poor paddock management all increase risk of ascarid infection.
Q. What signs may a foal with an ascarid burden display?
A. Normal signs of parasite burdens such as poor growth rates, poor coat and or loose faeces/ diarrhoea.
Due the extraordinary life cycle of Ascarids, with the larval stages migrating for the intestine to the liver, into the circulation and then into the lungs before being swallowed and re-entering the gut to mature further, they can cause respiratory signs as well as gastrointestinal signs. Respiratory signs displayed include a nasal discharge, cough and elevated breathing rate. Very high burdens can cause colic and in the most severe of cases can be so numerous that they completely occlude the small intestine. That can be fatal without surgical intervention.
Q. What can be done to reduce the risk to foals and young stock?
A. Good pasture management. Adopt appropriate worming protocols for the premises, seek veterinary advice when needing guidance.
Manage paddocks to reduce the worm burden, including poo picking, saving the ‘cleanest’ paddocks for foals, avoiding turning foals out in paddocks that foals/ young horses have inhabited previously (as young horses are more likely to shed/ burden the pasture) and consider resting paddocks or grazing with ruminants to reduce the worm burden on the pasture. Consider rotating wormers if resistance is suspected, the yards has high stocking densities or horses have been on the land for many years.
In summary…what is an ideal worming protocol? Protocols vary dependant on the premises, stocking density and management. Seak veterinary advice for a tailored worming protocol specific to a premises.
Best practice guidelines are listed below:
-Manage pastures as advised above to reduce exposure to high worm burdens and resistant worms.
– Ideally worm individual foals based on faecal egg counts (FEC’s), the threshold is lower in foals and generally foals with an worm egg count of around 150 eggs per gram (EPG) or higher require worming.
– If performing individual WECs is not possible a protocol of treating foals from 8 weeks of age and repeating treatment ~ every 8 weeks is advised.
– Consider rotating the product used on each occasion to account for resistance. Ideally start with a single dose of fenbendazole (Panacur) then pyrantel then ivermectin.
– Take care using products that cause paralysis of worms (pyrantel) if high ascarid burdens are suspected.
– Treat for tapeworm in the autumn (double dose pyrantel, praziquantel or a combined praziquantel product).
– Treat for cyathastomes (with Equest/ Equest Pramox) in winter and when greater than 6.5 months of age.
– Consider faecal egg count reduction tests (FECRTs), so taking a WEC pre and post worming, if resistance if suspected.
– Always seek veterinary assistance if concerned.
Special considerations for different products when treating foals:
– Fenbendazole (panacur) and ivermectin products can be used safely in foals, even from a young age.
– Pyrantel can be used safely from 4 weeks.
– Moxidectin/ Equest can be used safely from 4 months.
– Combined products, Equest Pramox can be used safely from 6.5 months.
If you wish to discuss worming your youngstock or any of our Breeding Services at Towcester Equine Vets please reach out to Gemma at your nearest clinic.
Onley (CV23 8AJ) 01788 523000
Towcester (NN12 6LQ) 01327 811007
