Quick guide to seasonal worming for horses

To help keep your horse free from illness, you need an effective worm control plan. Parasite life cycles are linked to the seasons, so your worm control plan should consider the time of year. We offer year-round FECPAK testing at selected Wynnstay Stores to help ensure that your horses are kept parasite-free, use our store locator to find a store offering FECPAK testing near you.

You also need to consider the problem of resistance. There is a growing threat of worms becoming resistant to the chemical ingredients in wormers. This means you should always look at the bigger picture. It’s no longer acceptable to simply dose all horses routinely throughout the year. It is key to dose correctly, as little as possible but as much as necessary. This can be achieved by assessing every horse individually, always practising good pasture management and using faecal worm egg counts (FWECs).

Read more on changes to worming for horses in the 21st Century here

Spring is when encysted small redworms (ESRW) mature and emerge from the large intestine, damaging the gut wall and potentially causing health problems such as, weight loss, diarrhoea colic and sometimes death. If you have treated effectively for ESRW throughout the winter, your horse shouldn’t have any problems. However, if there are any unexplained health problems, it is important to contact your vet for advice immediately.

Spring is also the perfect time to start faecal worm egg counts (FWECs) to identify any horses that may need treatment. FWECs are never 100% accurate. This is because not all parasites eggs are easily detectable, and some parasites stages don’t lay eggs. Another problem is that the number of eggs laid by parasites will vary from horse to horse, even if they have the same level of equine worm burden. FWECs can indicate horses with particularly high equine worm burdens and can also identify the horses passing (shedding) the most eggs and contaminating the pasture, which is important to know.

• Tapeworms- Treat at the beginning and end of the grazing season, roughly six months apart. This is usually recommended to keep this parasite under control. Alternatively, you may test for antibodies to tapeworm, but expert advice is needed to correctly interpret the result.
• Encysted small redworm- Treating any horse that has not previously been given a wormer effective against ESRW in the preceding late autumn/winter period is advised.
• Redworms- Treatment is usually recommended if FWECs >200epg.

Ideal environmental conditions for the development of eggs and equine worm larvae on the pasture in the spring, lead to high pasture contamination and increase the potential for your horse to acquire new parasite burdens. You can easily reduce pasture contamination by poo-picking at least twice a week.

Ideally, you should also conduct a FWEC every two to three months to identify horses that need dosing for redworms, which are the main summer parasite.

• Redworms- treatment is usually recommended if FWECs >200epg.
• Roundworms- Foals should receive at least two doses effective against roundworms in the first six months of life. Speak to your vet or SQP for specific advice regarding timing and the most appropriate wormer for your foal.
• Encysted small redworm- Dose all horses (>six months of age) in November/December regardless of the FWEC, using a specifically indicated wormer
• Tapeworms- Dose now if your previous dose was in the spring.
• Bots- The bot fly lay eggs in late autumn and bot fly larvae develop in the horse’s stomach so they should be treated now.
• Encysted small redworm- Dose now if not previously treated in the late autumn.

Autumn is where most parasites enter a less active phase and the pasture contamination is reduced. Ideally, you should continue with FWECs until the end of the grazing season (around when the grass stops growing) and if your horse has a strongyle count of >200epg, they should be treated.

Many young foals may need their second roundworm dose in autumn, depending on their age.

In late autumn, if your horse has picked up any new small redworm larvae from the pasture, these may encyst within your horses gut wall and must be treated. In addition, late autumn/early winter is the time to treat tapeworm and bots.

This is a quiet time of year for equine worms. Roundworms can lie dormant in the soil for long periods of time, even in freezing weather. Small redworms will ‘hibernate’ in their encysted state in your horse’s gut wall and won’t lay any eggs so faecal egg worm counts will not detect them. A build up of these 'hibernating' encysted small redworms can lead to dangerous complications such as colic, diarrhoea and even death if left untreated in your horses gut wall.

• Encysted small redworm - Dose now if not previously treated in the late autumn.

In addition to these seasonal threats, ensure at least one of the doses given throughout the year is effective against large redworm. Pinworm, liver fluke and lungworm may be a concern for some horses. It is best to check with your vet if you horse may be at risk of these.

Owners may be asked to show horse passports before medicines are supplied. Our AMTRA SQPs have a legal requirement to ascertain the status of any animal before prescribing or supplying medicines.

If the AMTRA SQP prescribing and supplying medicines has not recently seen the horse’s passport and been able to confirm personally that it has been signed out of the food chain, they have to act accordingly.

For more information, visit the government website by clicking here.