Equine dewormers are more commonly referred to simply as 'wormers'. Each has one, or sometimes several, active ingredients. These are the chemicals which kill the worms. The choice of active ingredient is important for two reasons. Firstly, not all types of worm are killed by all chemicals. Secondly, worms can become resistant to a chemical after repeated exposures. For these reasons it is important to have a horse worming schedule in which the active ingredient, not just the brand name, is rotated.
More recently, some experts are recommending having a faecal egg test done on horses, and only worming as and when needed. This avoids unnecessary worming with the aim of preventing further wormer resistance.
The following are the most common active ingredients.
Pyrantel Pamoate Horse Wormers (also known as Pyrantel Emboate)
Examples of brand names are Strongid, Pyratape-P, Exodus and Tapecare plus. Apart from Praziquantel, Pyrantel is the only drug effective against tapeworm. Double dosage is needed to treat tapeworms. It is not effective against worm eggs, encysted small redworm larvae, migrating large redworm larvae or bots.
Ivermectin Horse Wormers
Brand names includes Eqvalan, Furexel, Iverease, Ivercare, Rotectin, Zimectrin, Equell, Bimectin and Equmectrin. Ivermectin is a very effective drug, active against most parasites and migrating larvae at normal doses.
It is effective against bots and should be administered in December (northern hemisphere) when the frosts have killed the flies and the bot larvae have reached the stomach. Ivermectin is not effective against worm eggs or tapeworm.
Fenbendazole Horse Wormers
Fenbendazole is found in Panacur, Telmin, Bayverm and Safe-guard. It kills eggs, adults and larval stages of large and small strongyles. Panacur Equine Guard or Safe Guard power dose are the only wormers able to remove encysted small redworm larvae. To do so they are given for five consecutive days. Fenbendazole has limited tapeworm control, does not control bots and resistance occurs in adult small redworm.
Moxidectin Horse Wormers
Equest/Quest is the only major brand name currently available. Moxidectin is released slowly into the horse's bloodstream so is effective for longer than other drug types. It is broadly similar to Ivermectin. It is effective against migrating large redworm and bots, but not against eggs, tapeworm or inhibited redworm larvae. Not recommended for use in foals under the age of four months.
Praziquantel
This is used to control tapeworms. Wormers such as Zimectrin Gold or Equimax combine it with Ivermectin or Moxidection.
Horse Worming Schedule
A schedule should be created to worm regularly and include extra doses to target tapeworm, encysted small redworm larvae, and bots, which are not killed by all wormers. Rotate the active ingredient for the routine worming annually.
As mentioned above, some people are now choosing instead to do faecal egg tests and target their worming program to the worm burden of each specific horse.
Kirsty Jenkins - I came across horses as a young child and have been around them ever since. My experiences have varied: schooling naughty riding school ...
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