Summer temperatures Spark
05 December 2025
Higher Autumn Worm Egg Count results
Postal worm egg count specialists, Westgate Labs, are reporting a notable rise in worm egg count results through this autumn’s test results in UK horses. The increase is thought to be linked to the unusually warm, dry summer weather, with experts recommending regular testing and poo picking as the first line of defence to protect horses from this increased risk of parasite infection.
Many owners carrying out their routine autumn tests were surprised to see higher counts than expected, with horses that had previously shown low or clear results now presenting with medium or even high readings despite no change in management. It’s thought that the relatively high temperatures in summer combined with intermittent rain may have provided ideal conditions for larvae to develop and survive on pasture, leading to infection and, subsequently, higher levels of egg shedding.
The Stats
The monthly summary of equine worm egg count results for 2025 shows a higher proportion of horses shedding more strongyle eggs compared with previous years. In September, 13.34% and 19.42% of worm egg count results were above 200 eggs per gram (epg.) in 2023 and 2024 respectively, rising to 24.12% in 2025. A similar pattern was seen in October, with 13.44% of tests above 200 epg. in 2023, 19.18% in 2024, and 25.04% in 2025. Egg shedding stayed high November 2025 with 25.29% above the threshold, compared to 20.46% in 2023 and 20.56% in 2024.
The threshold of 200 epg. is important, as it marks the level at which treatment is indicated for most healthy adult horses within a targeted parasite control programme. * Statistical testing indicates that the increase is not yet significant, but the upward trend is notable and will continue to be monitored as more data becomes available later in the year.
INFLUENCING FACTORS
Professor Jacqui Matthews, Recognised Specialist in Parasitology and Director of Veterinary Science at Austin Davis Biologics, commented:
“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. 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’ business director, Kristy Hodgson, echoed this advice:
“Alongside worm egg counts every 8–12 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.”
Mitigating the Impact
Regular worm egg counts every season remain the cornerstone of good parasite control. Testing all horses every 12 weeks, alongside twice-yearly tapeworm testing, ensures targeted treatment and helps avoid unnecessary worming that contributes to drug resistance. Horse owners are recommended to risk assess their horses for parasite infection, using either the CANTER or What’s Your Worm Risk profiling tools and speak to their prescribers to decide on their approach to encysted stages of small redworm this autumn/winter.
These statistics were first presented in a live webinar streamed to Facebook on Horse First Autumn worm control October 16th 2025. Watch again here: https://www.westgatelabs.co.uk/videos/
By popular request a follow up webinar, focussing on redworm infection will take place 7pm Wednesday 14th January, titled ‘All Redworms Large and Small’. Click 'going' on the Facebook event page here:
Footnotes
These findings are based on thousands of equine worm egg count samples analysed each year at Westgate Labs. This dataset provides one of the most representative snapshots of parasite infection levels across the national horse population. All testing is performed in house in a purpose-built laboratory using a Concentrated Modified McMaster method, ensuring high accuracy and consistency.
*Industry guidance commonly uses 200 epg. as a threshold above which anti-redworm treatment for adult horses is often indicated under targeted parasite control programmes.