First Commercial Test for Life-Threatening Large Redworm in Horses
23 June 2025
Launched in the UK by Westgate Labs
Larval culture now available to screen for Strongylus vulgaris infections in response to rising risk.
Westgate Labs, the UK’s leading equine parasite control specialists, have become the first laboratory in the country to offer larval culturing for large strongyles (Strongylus spp.) as a commercial test. This pioneering service, launched in June 2025, provides a practical solution to monitor for the re-emergence of large redworm, the most dangerous intestinal parasite affecting horses.
With increasing international horse movement and a shift towards more targeted worming, this potentially fatal parasite is reappearing on yards across Europe. The new test allows vets, prescribers, and horse owners to screen for large strongyles without over-relying on blanket treatment, helping to protect both horse health and the future efficacy of wormers.
Kristy Hodgson, Business Director at Westgate Labs, said:
“When we started seeing confirmed cases of large redworm in UK horses, alarm bells started ringing. We knew we needed to act quickly to provide a reliable way to identify these infections before they cause serious harm. Over the past year, we've supported selected yards and veterinary practices in piloting larval culture testing. We’re now proud to launch this as a national service.
We want to empower owners and prescribers with the tools to make informed decisions and not be forced back to over-worming as a precaution. This innovation sharpens our insight, allowing us to stay ahead of parasite threats while tackling resistance in the right way.”
Current testing practices rely heavily on worm egg counts, which are invaluable for assessing cyathostomin (small redworm) egg excretion, but they can’t distinguish between small and large strongyle eggs, which look identical under the microscope. This hasn’t been an issue while large strongyles remained such a rare possibility, but its potential resurgence changes that picture.
Large strongyle larvae spend a part of their life cycle in the horse’s blood vessels. Here, they can cause life-threatening damage, including colic, haemorrhage and intestinal infarction, often before any signs appear. That’s why detection of their presence within populations is so important.
Professor Jacqui Matthews, BVMS PhD FRSE FRCVS, RCVS Recognised Specialist in Parasitology and Director of Veterinary Science at Austin Davis Biologics, providers of the EquiSal tapeworm and small redworm blood testing services commented:
“The launch of a commercial larval culture test for large strongyles is a very timely and important step for equine health in the UK. While Strongylus vulgaris was once considered under control, recent published reports on its increasing prevalence from across Europe and growing concerns about the risk of clinical disease in the UK, highlight the urgent need for this service.
The move towards targeted worming is vital for preserving drug efficacy, but it must be backed by robust diagnostics to ensure we’re not leaving susceptible horses exposed to potentially life-threatening infections. Having access to an easy-to-use test that differentiates between small and large strongyles is a significant advancement and will support both effective treatment decisions and responsible parasite control.”
Westgate Labs now offers larval culture testing for individual or composite samples (up to four horses), with a turnaround time of two weeks.
Annual testing is especially recommended for:
- Studs and breeding operations with youngstock
- Competition and sales yards with frequent international movement
- Properties with high stocking density or recent horse introductions
- Horses on minimal or selective worming schedules
Taking the sample is very similar to performing a worm egg count test. An easy-to-use test kit to take the sample, including a postpaid return envelope in Westgate Labs’ trademark plastic free packaging, is included in the price, along with follow up help and support from their friendly, qualified team.
About the large strongyle larval culture test
The large strongyle larval culture test involves incubating faecal samples under controlled conditions to allow strongyle eggs present to hatch and develop into third-stage larvae. These larvae are then identified under a microscope, enabling accurate differentiation between the large strongyle species, Strongylus vulgaris, Strongylus edentatus, and Strongylus equinus and the more common small redworm species, which are not reported due to their ubiquity.
https://www.westgatelabs.co.uk/info-zone/parasites-affecting-horses/large-redworm/
About Westgate Labs
Westgate Laboratories is an award-winning veterinary parasitology lab, specialising in parasite control for horse. Pioneers of the postal worm egg count test, the lab has been leading the field in helping horse owners to manage the parasite control of their horses and other grazing animals since 1999. The laboratory offers a quick, easy to use, great value postal worm count and testing service, now including large strongyle larval culturing. All testing is backed by Westgate’s qualified, friendly advice to enable carers and keepers to target the wormers given to horses and slow resistance to working chemicals, keeping them as healthy as possible now and into the future.
About Austin Davis Biologics
Austin Davis Biologics is a leading UK-based biotechnology company specialising in innovative diagnostic testing for animal health. Best known in the equine sector for the EquiSal® Tapeworm Test and the Small Redworm Blood Test ELISAs, the company delivers scientifically validated, non-invasive tools that support evidence-based parasite control. With a strong foundation in research and a commitment to practical, accessible solutions, Austin Davis Biologics works closely with veterinary professionals and horse owners to improve parasite management and safeguard equine welfare.