Winning against worms: how one yard hits the targeting bullseye

Home to over 80 equines at any one time, the Redwings Ada Cole Centre in Essex has used targeted worming for more than a decade. In the past, it would have taken dozens of wormers to routinely treat every horse on site, now the number of individuals requiring a wormer is often in single figures. Manager Hollie Palmer outlines how the centre runs its successful worm control programme.

At Redwings, we are very aware that some of the biggest threats to our horses are not the most visible, and parasitic worms are definitely something we take very seriously. As many Redwings residents have arrived with a high worm burden and/or no known health history, their parasite risk profile is already increased. Having a number of residents below the age of five is an additional factor. It’s therefore essential that we manage the site to minimise any further risk, while also reducing use of wormers as much as possible to help slow the spread of resistance which is such a worry for the whole UK horse population.

Testing

All our equines have a worm egg count (WEC) four times a year and are only treated with an anthelmintic drug (wormer) if the count is above a certain level, usually over 200 eggs per gram (epg).

The count will identify eggs from redworms (cyathostomines/strongyles) and roundworm (Parascaris). More than 90% of parasitic worms in UK horses over one year of age are known to be small redworm, while roundworm is a particular risk in foals, weanlings and yearlings.

As the table below shows, testing has cut our use of wormers by more than 70% compared to routinely worming all equines. It has also improved our worm control programme through building individual worming histories for every equine we care for.

We will sometimes use an additional faecal worm egg count reduction test (FWECRT) to recheck that treatment with a wormer has been effective in horses who presented with a moderate or high count. This will also help to flag any concerns around resistant worms present in our horses.

A WEC isn’t a reliable test for tapeworm detection, so we either treat horses routinely for this parasite or test horses’ saliva using a commercially available test.

We also have to be mindful of the danger presented by the encysted stage of the small redworm lifecycle. As encysted redworm larvae aren’t producing eggs, they won’t be detected by a WEC so we currently worm all equines annually towards the end of the year with a product to target any encysted larvae. However, now we have achieved such consistently good WEC results we are moving to a more risk-based approach to reduce our use of wormers still further. Some of our residents who consistently show zero or low WEC results can be exempt from this treatment in future, further reducing our anthelminitic use.

in line with current best practice recommendations. Some of our residents who consistently show zero or low WEC results may be good candidates for the recently developed blood test that will help reduce worming even further.

Using WECs also mean that, when we do worm, we use the most appropriate worming product in the few individuals who need it. This is often different products for different horses, so we’re not only using far fewer wormers but the small number we do administer are much more likely to be effective. In addition, we always weigh our equines to ensure we worm at the accurate dose as underdosing is known to contribute to worms developing resistance.

Of course, testing itself doesn’t reduce the number of worms a horse is carrying, but it gives us the information we need to check our worm control practices are having the desired effect. I would say there are three factors that make all the difference to keeping worms under control across our site:

Routine quarantine

Every equine that arrives at Redwings or is returned from a loan home is quarantined as a precaution. During this time, they are not only tested for strangles but also undergo at least one WEC so we gauge their worm population and can treat individuals if needed.

Many of our rescued horses arrive with high worm burdens, even worm damage or disease, so preventing these parasites from spreading in large numbers onto our pasture and into other residents is essential.

Managed grazing

We operate 24/7 turnout for our horses, so we need healthy pasture to support that. Pasture is never overstocked, and our annual grazing cycle allows for paddocks to be rested for several months at a time. Both these factors contribute to effective worm control along with other benefits.

Poo picking

More than anything else, keeping our paddocks clear of muck is the simplest way to break the worm lifecycle, as well as keeping our grazing in good condition and making the site presentable. We poo pick every day, year-round, rain or shine. It’s not the most glamorous job in the world, but I’ve done worse!

We take pride in our horses and our paddocks and knowing that poo picking is not just about good housekeeping but essential to horse health and tackling worm resistance is a good motivator on even the most unpleasant days.

Multiple benefits

The test results show that by focusing on environmental management, we’re good at keeping a lid on parasitic worms in what would be classed as a relatively high-risk horse population. Not only that, but we can catch worm problems early and treat them in the most effective way at an individual level.

Studies have shown that some horses naturally carry more worms than others, with roughly 20% of UK horses holding around 80% of worms. Our test results confirm this pattern, with some individuals having higher WEC results more regularly than others. Even these horses don’t require worming every time, and testing is important to ensure we don’t contribute to resistance in these horses by worming more than is absolutely necessary, as they are individuals who are most likely to need them in the future.

Although collecting faecal samples from every equine on site does take time, it’s no more time-consuming than having to worm everyone. We also have far fewer behavioural issues around worming now too. There are so many benefits to using a test-based approach to worming, it isn’t only about tackling resistance and making sure we have effective wormers for the future, vital as that is, it also gives us so much more control over what is happening in our horses today without routinely putting drugs into their bodies and their pasture that they simply don’t need.