‘Worms don’t go on holiday’: owners urged not to delay testing as heat and drought may increase parasite risk
“Worms don’t go on holiday” is the message to equestrians this summer, and higher temperatures may mean more horses need treating than normal.
Parasite specialist Westgate Labs is urging people to stick to eight- to 12-week testing intervals as the high temperatures are replicating conditions in 2025, when “significantly more” horses needed treatment than usual.
“As 2026 has already brought record-breaking spring temperatures and repeated summer heatwaves, the laboratory is encouraging owners to keep to the recommended testing intervals, even for horses that have historically returned low worm egg counts,” a spokesperson for Westgate Labs said.
The company has analysed more than 50,000 egg count results from last autumn and winter and found that 27% of horses exceeded the treatment threshold, compared to 21% in 2024-2025 and 18% the previous year.
“After allowing for the normal seasonal rise in egg shedding through autumn and winter, the increase remained statistically significant,” the spokesperson said.
“The small redworm has a fast lifecycle of around four to six weeks. Experts have summarised that the warm weather accelerates the larval development phase of the parasites, allowing horses to become more readily infected as they graze. This, combined with burnt-off paddocks and low grass growth means reduced opportunity to rest and rotate grazing. With less forage available, horses have been cropping the grass closer to the soil and dung piles, further increasing infection potential.”
Misconceptions
Westgate Labs director Kristy Hodgson said a common misconception is that a horse “looks fine” so testing can be delayed.
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“Last year’s data showed that isn’t always the case,” she said.
“Regular testing allows us to spot changes before they become a problem. If owners stretch the interval between tests, there’s a greater chance that horses shedding higher numbers of parasite eggs will contaminate the pasture for longer, increasing infection pressure for the whole group.
“Testing every eight to 12 weeks means you’re responding to what’s happening now, rather than what happened three or four months ago. This intervention could easily prevent a bigger problem down the line.”
Research suggests that warmer temperatures and milder winters are likely to favour parasite development. England has had its warmest spring on record this year, and there have been heatwaves and droughts across the country.
To encourage testing, Westgate Labs is offering a daily prize draw from 17 to 28 August. One customer, drawn at random, will get their next tests for free, to the value of the tests submitted. The draw will take place on social media, each day, Monday to Friday.
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Eleanor is an experienced journalist who spent over eight years working for local and national newspapers before joining H&H as news editor in March 2016. Passionate about equine welfare and exposing the truth, Eleanor has reported on all aspects of the industry, from Brexit to anti-bullying campaigns, and from dressage rules to mules. Her sport of choice is showjumping, in which she competes her own horses, and she also enjoys reporting at local jumping shows through to international championships.