Horse owners, vets and SQPs are being urged to familiarise themselves with the risks posed by large redworm, following growing concern about the potential re-emergence of this historically dangerous equine parasite in the UK.
Westgate Labs has launched a free educational film on YouTube to help explain the threat posed by large strongyles (Strongylus spp.), how targeted worming strategies may influence parasite control, and why additional monitoring could now be advisable for some horses and yards.
The 10-minute film, created in partnership with Northumberland-based Equioptics and presented by Claire Shand, marketing director at Westgate Labs, takes viewers from the stable yard to the laboratory to explain why worm egg counts alone cannot identify large redworm infection and how larval culture testing can support targeted parasite control programmes.
Ms Shand said: “Large redworm was once considered one of the most dangerous parasites affecting horses, but decades of routine interval worming made it increasingly uncommon in the UK. As the industry quite rightly moves towards more targeted parasite control to help preserve wormer efficacy, there is growing discussion around the possibility of large strongyles re-emerging unnoticed.
“Current targeted control programmes rely heavily on worm egg counts, but these tests cannot differentiate between small and large strongyle eggs because they look identical under the microscope. While selective treatment is essential for slowing resistance in small redworm, we would seek to treat large strongyle infections as soon as they are detected.”
Ms Shand continued: “Parasite control can be highly technical and difficult to communicate clearly, so we wanted to create an accessible, practical resource that helps prescribers and horse owners better understand the risks and the reasoning behind additional monitoring. The film explains what large redworm is, why it matters, which horses may be at greater risk and how annual larval culture screening can be integrated into a risk-based parasite control programme.”
Large strongyles, particularly Strongylus vulgaris, have historically been associated with peritonitis type symptoms, intestinal damage, haemorrhage and sudden death due to larval migration through the horse’s blood vessels.
Westgate Labs was the first UK laboratory to commercially offer larval culture testing for large strongyles and have since developed a series of educational resources to support evidence-based parasite control.
In February 2026, the laboratory presented a scientific poster at the Horses Inside Out Conference exploring how large strongyle screening may be integrated into targeted parasite control programmes using a risk-based approach.
Annual screening is particularly recommended for:
- studs and breeding operations;
- competition and sales yards;
- horses travelling internationally;
- premises with frequent horse movement; and
- horses receiving minimal or highly selective worming treatments.
