The soil association recommend that rotational and multi-species grazing should be used to control worms in order to prevent the routine use of wormers and other veterinary treatments. Where five or more horses are kept on the organic holding a pasture management plan addressing the control of internal worms and a health plan will be required.
Where five or more horses are kept the use of avermectin-based products for the control of worms is restricted. No restrictions apply where less than five animals are kept but in all cases animals must be housed or dung removed from the pasture for 48 hours after treatment with avermectin products.
Here are the wormers from the avermectin family (they use ivermectin as the active ingredient) currently supplied by wormers-direct.co.uk:
Equimax (also contains praziquantel)
Eqvalan Duo (also contains praziquantel)
Noromectin Horse paste
Herbal worming products are now available. These use a combination of plants to repel parasites. No scientific data is available on how effective these preparations are in combating worm burdens. It is therefore best to gain expert advice before relying on herbal products: