How to Use Faecal Worm Egg Counts to Manage Parasites This Spring

As horses spend more time grazing and parasite activity increases in warmer weather, knowing how to use faecal worm egg counts to manage parasites is key.

One of the best ways to do this is through a faecal worm egg count. As a simple test, it helps you understand your horse’s parasite burden so you can make better decisions about treatment.

Used correctly, a faecal worm egg count can reduce unnecessary worming, protect pasture quality, and support the overall wellbeing of your horse. Spring is an important time to start to carry out this type of testing, as they’ll likely be spending more time outside grazing in the field with the better weather.

In this blog, we’ll explain what a faecal worm egg count is, how it’s done, what it can and can’t detect, and why it’s such a useful tool – especially during the spring months.

At Cura, we’re a vet-owned and vet-run online pharmacy offering a wide range of prescription and non-prescription products, alongside pet toys and accessories. We love your pets as if they were our own, so you can be confident the advice you’re receiving always has your horse’s best interests at heart.

What Is A Faecal Worm Egg Count?

A faecal worm egg count (FWEC) looks for worm eggs in your horse faeces. A small sample is examined under a microscope to see whether parasite eggs are present and, if so, the amount can be calculated.

Worm egg counts are usually carried out at regular periods throughout the grazing season which runs from April to October as this is when horses are most at risk due to increased exposure.

The results help show whether a horse is carrying a level of worms that actually requires treatment. FWECs can also be used to check how effective a wormer has been after treatment, making them a useful tool in managing parasites in the long run.

By using faecal worm egg counts alongside wormers, horses only receive treatment when it’s needed which helps avoid unnecessary medication and helps reduce the risk of worms developing resistance to commonly used wormers.

Why Is A Faecal Worm Egg Count Important?

Horse worm egg counts are important as worms are becoming increasingly resistant to wormers.

One of the main reasons for this is an over-reliance on blanket worming, where all horses on a yard were treated at the same time regardless of whether they actually needed it. Over time, this has reduced the effectiveness of worming treatment due to worm resistance.

In contrast, horse worm egg counts allow owners to check whether parasites are present before reaching for a wormer so that treatment is only given when it’s genuinely needed. This helps slow the development of resistance while still protecting long-term horse health.

Aside from that, avoiding unnecessary treatments can save money as you’re not buying wormers for horses that don’t need it. From a practical perspective, checking for worms before administering drugs also helps protect shared grazing. By identifying and treating higher shedders, it reduces contamination and lowers the risk to other horses in the field.

For the best results, always seek advice from your vet to ensure testing frequency and treatments are appropriate.

What A Faecal Worm Egg Count Can Detect (and What It Can’t)

A faecal worm egg count (FWEC) is a helpful measurement for identifying the presence of parasite eggs in your horse’s droppings, but it’s important to understand what it can’t and can’t detect.

FWECs are able to detect eggs from:

• Small redworm (cyathostomes)
• Large redworm (strongyles)
• Large roundworm (ascarids)

However, a low egg count doesn’t mean your horse is free of worms. Many parasites (especially in their immature or larval stages) do not produce eggs, so they won’t show up in a standard FWEC.

For example:

• Encysted small redworm larvae: These live in the gut wall and can be present in high numbers without shedding eggs.
• Pinworm, bots, and tapeworm: These species either don’t shed eggs in faeces in detectable amounts or require specific tests.
• Immature worms: Newly developed worms that haven’t started laying eggs yet.

FWECs should be seen as part of a wider parasite management program, rather than a test to be used in isolation. Seasonal testing for encysted redworm and tapeworm is also recommended, alongside FWECs, to ensure all parasite risks are managed.

How to Carry Out A Faecal Worm Egg Count

Knowing how to carry out a faecal worm egg count is the first step to managing the spread and treatment of worms.

Below is a simple step-by-step guide to help any horse owner carry out the test correctly.

Collect a fresh sample

Gather the horse droppings while they are fresh (preferably still warm) using a disposable glove, then place it into an air-tight container. It’s important the dung is fresh as older samples may give inaccurate results.

Take a representative portion

As worm eggs are not evenly distributed within droppings, take small amounts from different “dung balls” within the same pile. The total sample should weigh about 4 grams, which is around the size of a golf ball. This helps optimise the value of the test as the lab needs a sufficient amount of droppings.

Collect separately for each horse

Make sure you test each horse individually even if you’re testing multiple horses at the same time. Each horse’s faeces needs to be collected individually to ensure accurate results.

Remove air from the sample

Make sure the container or bag is securely sealed (which is why an air-tight container is best). Try to remove as much air as possible to preserve the sample until it reaches the lab.

Label your sample

So it can be correctly identified and tested at the lab, include your horse’s name, your surname, your postcode, and the date the sample was collected.

Send it away for testing

Your sample can either be sent directly to a specialist equine laboratory or submitted via your vets. Many owners prefer to go through their usual veterinary practice, who may analyse the sample in-house or forward it to a specialist lab. Using your vet can be helpful if you’d like support interpreting the results or advice on treatment.

Horse Faecal Worm Egg Count FAQs

When should I carry out a horse faecal worm egg count?

You should conduct faecal worm egg counts at regular intervals (every 8-12 weeks) during the grazing period which runs from April to October.

What are the different types of eggs?

Large and small redworm eggs look similar, so they are usually grouped together as strongyles. Small redworm are the most common worms affecting horses in the UK, so most strongyle eggs found will be from this type.

Tapeworm eggs might be found present in worm egg counts, but standard tests are not the best way of detecting tapeworm, so a worm egg count should not be used as a definitive diagnostic tool. In foals and young horses, roundworms (ascarids) are often found and they can be a big concern. Can we link to tapeworm tests etc at this part of the blog post?

How long does it take to get results?

Results are usually available within a few days, depending on where you sent the sample. Your vet or laboratory will provide guidance on whether treatment is required based on the results of the test.

How to Use Horse Faecal Worm Egg Counts to Manage Parasites This Spring

Knowing how to use horse faecal worm egg counts to preserve the effectiveness of worming is key. There’s no point worming a whole group of horses without first understanding who really needs it (and will get the most benefit).

Routine, blanket testing is a thing of the past as owners now understand the advantages of testing for the presence of worms first. Not only does this reduce resistance to the treatment but also saves you money.

Instead of buying wormers for every horse, you can focus on your efforts on those that really need it. The best thing to do if you’re unsure is to contact your vet. They can provide advice and support on the best route forward, including testing and treatment.

For additional support in keeping your horse healthy, you can explore a range of horse health products designed to protect them in areas such as worming and general care.