Know What’s in Your Wormer

Four key chemical groups used for worming.

1. MLs or “mectins” include:

• Avermectins (abamectin, ivermectin)
• Milbemycin (moxidectin)

Macrocyclic lactones or mectins are the most widely used chemical class of anthelmintics. They are very useful to control a wide range of parasites of the horse but not tapeworms. Compared to other chemicals they are able to control younger stages of many worms and also persist in the body to give a longer control period.

There are two types of mectin: avermectin is one of them. At the present time the only avermectin chemicals on the market in Australia for horses are ivermectin and abamectin. Milbemycin is the other type of mectin. Moxidectin is currently the only milbemycin sold for horses. Unfortunately roundworm, the major threat to young horses, is commonly resistant to mectins. A wormer only containing a mectin +/- a tapewormer should not be used in horses less than two years of age. This makes most wormer products currently sold not suitable for treatment of the young horse. Mectins are also being overused in adult horses which necessitate the strategic use of other chemicals.

2. BZs include drenches ending in “azole”:

• Oxfendazole
• Oxibendazole
• Fenbendazole

BZs include wormer chemicals ending in ‘azole’, treat the majority of worm species, but have no efficacy against tapeworms or bots. There are several forms of BZs available, including oxfendazole, fenbendazole and oxibendazole. Small stronglyes have become widely resistant to BZs when used on their own. However when used in combination with other chemicals the BZ class of chemicals can help treat worms that are developing resistance to mectins.

3. Tetrahydropyrimidines, known as THPs, these include:

• Pyrantel
• Morantel

Tetrahydropyrimidines, or THPs, treat the majority of worm species, including some tapeworms, but have no effect on bots. There are only two types of THP – pyrantel and morantel. It is essential that all horses less than two years of age include a THP in their worming program because mectins and BZs used on their own are not reliable enough against ascarids. EQUIMAX^® ELEVATION and STRATEGY-T^® is highly suitable for the current resistance status of roundworm in Australian foals.

4. Isoquinolines, this class includes praziquantel only

Praziquantel is a member of the chemical family called the isoquinolines family. It’s highly effective against tapeworms.

No single worming compound is effective on all parasites, especially with developing resistance. STRATEGY-T and EQUIMAX ELEVATION are leading examples of combination wormers. Leading parasitologists recommend that the use of unrelated chemical actives on the same day is an effective strategy to delay chemical resistance. Unlike any other wormers they combine a BZ or mectin respectively with pyrantel. Strategic use of STRATEGY-T and EQUIMAX ELEVATION provides you with a complete solution to the worming needs of horses of all ages.