Are egg counts for horses worth it?

Sunday, 9th June 2013

We are asked often at Hyperdrug: Are egg counts for horses worth it?

As with all simple questions the answer is often more complicated! While egg counts for horses can be a useful tool to monitor how effective some aspects of worm control are, and can help to safeguard equine health they do not detect all worms. Examples of these worms are tapeworm in horses, pin worms and the small encysted redworm because eggs from these do not appear in the horses dung. These worms are important to treat as when encysted redworms emerge they can cause massive internal bleeding which may lead to death. Pinworms can cause intense irritation and tapeworms are a common cause of colic.

So is there any point in worm egg testing?

An effective way to use testing is for checking how well the horse worming programme is working; this is called a faecal egg reduction test. The dung is tested before worming and then again afterwards. Effective worming should reduce the number of worms found by 95% but what happens if the worms are not reduced by 95%? A common reaction may be that the worms are resistant to the horse wormers, but not necessarily.

Why worming can be ineffective.

Is the horse wormer effective against the worm being treated? For example double dosing with Pyrantel wormers are often used for tapeworm but this only treats one of the three varieties of tapeworm and only kills the adult stages of roundworm so that the eggs and larvae will develop into fresh adult worms in a very short time.

Was the correct dose given and was all of it swallowed? Many horses are under-dosed often because different syringes treat weight ranges from 575 kg to 700kg or the weight of the horse may have been estimated incorrectly. Using a weigh tape is invaluable or the weight can be calculated from the following formula.

Weight in Kg is



Under-dosing leads to resistance as those worms left untreated are the “toughies”

which survive to breed more.

Are pinworms resistant to horse wormers?

Again not necessarily !

The problem is often that not enough wormer reaches the rectum where they live. If symptoms of Pinworm are seen (often the irritation causes the horse to rub its posterior against a fence or tree) then the area under the tail should be washed every few days to soothe the area and remove any eggs. Fences, stables etc can be disinfected to reduce chance of re-infection.

To treat a infestation you are advised to use a pyrantel wormer every two

weeks repeated 4-5 times.

How can Hyperdrug- Home of the Equine Pharmacy Help?

1). Impartial expert advice on worming available by phone 01833 641112, email or our website

2). Our laboratory provides a testing service and a quick hygienic sampling device.

3). There is a 50% discount on the recommended “follow up” test.

4). We can supply weigh-tapes, disinfectants and horse wormers