Westgate Labs is urging horse owners not to delay routine worm egg count testing this summer as sustained high temperatures replicate the conditions that saw significantly more horses requiring treatment in 2025.
With 2026 having 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.
Analysis of Westgate Labs’ autumn and winter worm egg count results showed that around 27% of horses exceeded the treatment threshold during 2025/26, compared with 21% during 2024/25 and 18% during 2023/24.
After allowing for the normal seasonal rise in egg shedding through autumn and winter, the increase remained statistically significant. The findings are based on more than 50,000 worm egg count tests submitted between September and February, making this one of the largest datasets of its kind in the UK.
The small redworm has a fast lifecycle of around 4-6 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.
Kristy Hodgson, director at Westgate Labs, said: “One of the biggest misconceptions we hear is ‘my horse looks fine, so I can leave it another month’. Last year’s data showed that isn’t always the case.
“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 twelve 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.”
While no single season can be attributed to climate change, research suggests that warmer temperatures and milder winters are likely to favour parasite development and extend periods of pasture challenge.
The Met Office has already confirmed that England experienced its warmest spring on record in 2026, followed by widespread heatwaves and emerging drought conditions throughout the UK.
Horse owners are encouraged to review when they last tested. If it has been eight weeks or more, now is the time to collect fresh samples and find out what is happening on your pasture before heading into the autumn.
To encourage uptake of testing, Westgate Labs is offering a daily prize draw from August 17-28. One lucky 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 from the post bag.
