Horse Guides – Ask the Expert

Drug Group Rotation?

It is widely accepted that to reduce the build up in worm resistance to a particular drug group, a rotation should be adopted on an annual basis between the three major drug groups. Many horse owners don’t find this easy to follow as the drug groups aren’t always evident in the name of the wormer you may be using.

For reference, the three major groups are:

Macrocylic Lactones                        These include Ivermectin and Moxidectin

Tetrahydropirimidines                     Such as Pyrantel Embonate

Benzimidazoles                               Including Fenbendazole, Mebendazole & Oxibendazole.

How? I often hear, are you supposed to know what to use and when!

Most of the manufacturers of horse wormers recommend an annual programme to follow. We have provided copies of these programmes on our ‘worming calendar’ page on www.wormerclub.co.uk. We have also attempted to offer some optional annual programmes that utilise a range of manufacturer products, and work out cheaper over the course of a year. If you are in any doubt, please contact us on enquiries@wormerclub.co.uk and we will be delighted to help.

Is it true my horse can get re-infected within days of worming?

A common mis-understanding about wormers is that they stay in a horses system for a period of say 6–12 weeks and therefore provide protection against a worm infection for this period. However in most cases (not all), the wormer has an ‘instant and one off effect’ in killing the worms, larvae and eggs in a horses system on the day it is used. Within days after worming a horse can become re-infected with worms from eggs and larvae picked up when grazing. There is however a period of time before these larvae or eggs develop to a stage where they can be a burden on your horse, at which point your horse will need worming again. This period is therefore considered the effective period of the wormer.

When and why do I double dose?

Some products such as Exodus or Strongid P are suitable as all round general wormers in  a single dose, but when used as a double dose, they can treat for tapeworm also.

As tapeworm is typically treated twice a year, this can mean you are using single doses of a wormer, say every 6 – 10 weeks depending on the product you are using, then at two points in the year (normally March/April & Oct/Nov) you will double dose with the same product to treat for Tapeworm and general worms.

As always, should you have questions or are unsure of what to use and when, then please consult a vet or suitably qualified person. Always dose wormers accurately to the weight of your horse and rotate drug groups as discussed earlier to help avoid the build up of resistance to these horse wormers in the UK.

Further information including a worming calendar with different programmes you can rotate your drug groups with is available on www.wormerclub.co.uk. If you have questions or are unsure please contact us on 0333 600 6101.