The particularly warm and dry 2025 summer is thought to be linked to a “notable rise” in worm egg count results in UK horses – even among those horses who have historically had low or clear results.
Provisional Met Office statistics, shared on 1 September, confirm that summer 2025 was officially the warmest summer on record for the UK. Westgate Labs, which specialises in parasite control for horses and offers postal worm egg count testing, noticed the pattern through this autumn’s test results in UK horses – and believes the two are linked.
Experts are urging owners to test regularly and poo pick frequently as the “first line of defence” against worm infestations.
“What we’re likely seeing is the impact of a warm summer allowing the larval development phase to speed up, meaning horses can become more readily infected as they graze,” said Professor Jacqui Matthews, recognised specialist in parasitology and director of veterinary science at Austin Davis Biologics.
“There’s also been less forage available, so horses have been cropping the grass closer to the soil and dung piles and there’s been less opportunity to rest and rotate grazing, further increasing infection potential.
“What this means for horse owners is that they need to be regularly testing all horses as even those with historically good results may be more at risk of worm infection than in previous years and prioritising poo picking.”
Westgate Labs highlighted that many owners carrying out their routine autumn tests were surprised to see higher counts than expected – horses who had previously shown low or clear results are now presenting with medium or high readings, despite no change in management.
Westgate Labs’ director, Kristy Hodgson added: “Alongside worm egg counts every eight to 12 weeks, poo picking is our first line of defence in helping to combat parasite infection, physically breaking the life cycle by removing the eggs from the pasture.
“I chat to tens of horse owners every day and it’s consistently our customers who aren’t able to clear dung who have seen the biggest rise in the number of horses requiring treatment this autumn.
“The data reinforces the importance of pasture hygiene over harrowing, which in warm, damp conditions may spread larvae rather than destroy them.”
Westgate Labs recommends testing all horses every 12 weeks, plus twice-yearly tapeworm tests, to ensure targeted treatment and avoid unnecessary worming, which contributes to drug resistance.
Westgate Labs and Austin Davies Biologics are presenting a free webinar with a focus on redworm infection at 7pm on 14 January. Find out more at: fb.me/e/4rPYI7SHH
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