You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Horses often contract worms when grazing, particularly if they graze land with other animals such as farm stock, wild deer and so on. As a result regular worming is usually recommended, rather than waiting until the horse or pony shows clinical signs associated with a heavy worm burden.

Most authors recommend that horses and ponies are wormed every 6-8 weeks during the grazing season - which in the UK extends from about April to September. It is best to use a broad spectrum anthelmintic - that is one that is effective against a large number of different types of worm. 

Because worms in the environment can develop resistance if they have long term exposure to drugs, it is advisable to use a different type of wormer each grazing season. In the UK licensed products for use in horses include :

• Febantel (Bayverm - Bayer)
• Fenbendazole (Panacur- Intervet ; Multiwurma - Day Son & Hewitt Ltd ; Zerofen - Chanelle Animal Health)
• Ivermectin (Eqvalan - Merial Animal Health ; Furexel-Janssen Animal Health)
• Mebendazole (Telmin - Janssen Animal Health)
• Moxidectin (Equest - Fort Dodge Animal Health)
• Oxibendazole (Lincoln Horse & Pony Wormer - Battle, Hayward & Bower Ltd)
• Pyrantel embonate (Strongid - Pfizer; Pyratape P - Intervet)

In addition to this general recommendation understanding of the life cycle of different worms allows specific treatment to be given as set times of the year to kill them. In the UK a seasonal worm planner would look something like this :

• JAN
• FEB  - Treat small encysted red worms
• MAR - Treat Tapeworms
• APR - Grazing season - routine treatment every 6-8 weeks
• MAY - Grazing season - routine treatment every 6-8 weeks
• JUN - Grazing season - routine treatment every 6-8 weeks
• JLY - Grazing season - routine treatment every 6-8 weeks
• AUG - Grazing season - routine treatment every 6-8 weeks
• SEP - Grazing season - routine treatment every 6-8 weeks. Treat for Tapeworms.
• OCT - Treat against migrating large red worms and small encysted red worms
• NOV - Treat against migrating large red worms and encysted small red worms
• DEC - Treat against migrating large red worms, encysted small red worms and Bots

Some recommended therapies are :

• Small encysted red worms - Fenbendazole, febantel, mebendazole, moxidectin (about 80% effective), oxibendazole
• Large migrating red worms - Fenbendazole , febantel, mebendazole, moxidectin, oxibendazole
• Tapeworms - Pyrantel
• Bots - Ivermectin
• Routine treatment - Fenbendazole, febantel, ivermectin, mebendazole or pyrantel

The occurrence of parasites varies from one geographical region to another so it is important to discuss the planned worming schedule with your veterinarian.

When handling wormers it is important to avoid contact with the skin, so wear protective gloves and wash hands after handling.

Updated October 2013