Horse Worming Programme

Does My Horse Need Worming?

The short answer is yes!

A thought-through horse worming programme, specific to your circumstances, is essential – especially in spring and late autumn each and every year. 

How To Develop A Horse Worming Programme

The first step in establishing your horse worming programme is to understand the faecal egg count (FEC).

This will show the extent of the horse’s worm burden and therefore provide an essential baseline against which you can establish the necessary frequency and type of wormer.

You will need a sensible deworming schedule, combined with proper pasture management, to reduce your horse’s worm population to less than 200 eggs per gramme (epg) all year round.

As a general rule:

  • As a general rule:
  • A low result less than 200 epg but above zero will signify that deworming is necessary, but not urgent
  • Over 250 epg but less than 750 epg indicates deworming is needed as soon as possible.
  • Over 750 epg means that grazing is infected with worm larvae. 

Faecal Egg Count Limitations

Whilst the general rule that a Faecal Egg Counts (FEC) 200 eggs per gram needs little action – there is a flaw.

The flaw being FECs do not show encysted redworm larvae, which emerge to occupy the void when the mature redworms are cleared by wormers. 

Your horse can have a low result less than 200epg, but within three or four weeks be riddled with new mature redworms. FECs alone will not control the redworm population. 

How Do I Check Faecal Egg Count?

Faecal worm counts can prove a most useful aid in worm control. 

Regular worm counts taken 14 days after worming show the efficacy of the wormer used. Worm counts done before worming can show the level of worm infestation on your pasture. 

If your worming schedule and control measures are working, the results should be low to medium less than 250 epg, high counts over 500 epg are cause for concern

Faecal egg count kits are quite cheap and widely available – one of the more popular kits is from Westgate labs that provide a postal analysis service – and all the items needed for sample collection

horse worming programme fec kit

When Should I Start?

Traditionally, a horse worming programme would follow the cycles of the moon. 

Worming started 2 days before a full moon (the moon waxing) and finishing 2 days after a full moon (the moon waning), 5 days in total. 

This practice is still followed in many parts of rural Europe. We have had consistently good results using the moon cycles every 3rd to 4th month. 

Light attracts adult red worms, as does gravitational pull (we don’t know why), and therefore red worms become active over the full moon phase. 

This could possibly be explained by some programming in their genes? What rural peasants have always known, science has yet to discover!

Whatever time of year or season you decide to de-worm your horse, the starting point is a Faecal Egg Count (FEC) test. The results will show the level of worm burden before using a wormer. 

Horse Worming Programme Timetable

The two most important deworming dates are Spring & late November, even though your horse’s FEC results are consistently low, don’t miss out on these crucial dates.

Regular de-worming is necessary to keep the worm population of your pasture under control. A regular schedule starts with the first flush of Spring grass within 3 weeks of horses being put out to grass. Followed by regular applications every 8 weeks throughout the summer and autumn months. 

This regime can be relaxed over the winter months (November to late February) if the horse is stabled in a clean environment. 

The re-infestation rate from pasture is virtually nil once the temperatures drop below 10 degrees celsius, early December through to early March. 

If your horse is left out all year round then the last deworming will be in late November for encysted redworm, then left to overwinter until early Spring when temperatures start to rise. 

Contrary to belief, frost and low temperatures do not kill worm larvae. They hibernate until Spring then moult into infective larvae.

SpringIdeally, your deworming schedule should start in spring. The lengthening daylight hours, coupled with warmth and moisture, activates worm activity. 

Eggs that have overwintered on grazing, start to hatch once the temperatures reach double figures, over 10 degrees centigrade. 

The old rule was three weeks after horses go out to grass start deworming. 

No matter what your horse’s FEC result, it is essential to deworm in spring followed by a FEC test. This will remove young, new season, larvae picked up from grazing and encysted larvae emerging from the gut wall. Think of this as an internal parasite spring clean.

A FEC taken 14 days after the last dose of wormer is essential to establish the worm burden. 

If results are not as expected – a higher result than the FEC test taken before worming, confirms the presence of encysted larvae emerging into the gut. Encysted redworm larvae often fill the void when the small intestine is cleared of larvae and adult worms. Much like squatters, they note a vacant home and waste no time in occupying. 

Immediately re-dose to clear the unwanted (squatters) encysted larvae maturing into adult worms, followed by a FEC.
JuneIn June, dose again to check the redworm population building up, followed by a FEC.

A low egg count less than 200 epg means deworming can be put on hold over the hot summer months of July and August. 
SeptemberThe September rains, misty mornings with warmth and moisture again encourage worm activity, eggs hatch and larvae survive on grazing.
Autumn & WinterA FEC should follow the Autumn dosing. Results over 750 epg again point to emerging encysted larvae maturing into egg-laying adults. Redworm larvae can encyst, hibernate for 2 or 3 years then emerge when conditions suit (spring & autumn). 

The squatters move in once the wormer clears the resident mature worms. 

Dose again, to clear the newly arrived squatter redworms. The emergence of large numbers of encysted redworm larvae shows the neglect of a proper approach to deworming in previous years.

Mid to Late November, before temperatures dip under 10 degrees centigrade, do your last worming followed by a FEC test. This will clear any redworm larvae that would otherwise start encysting, to hibernate through winter.

How do I reduce a high worm burden?

High worm burden points to poor pasture hygiene.

Poo picking, composting and seasonal deworming are therefore essential to control your horse’s worm burden. 

Click here to find out more about natural products for your horse worming programme

Scroll to Top