Our deworming arsenal

Three major classes of deworming chemicals (anthelmintics) are used in horses:

Macrocyclic lactones, including:

• Ivermectin, which works against most of the common equine parasites except for tapeworms. It does not work against encysted small strongyles, however.

• Moxidectin, which is similar to ivermectin but also acts against encysted small strongyles.

Benzimidazoles including:

• Fenbendazole, which kills large strongyles, pinworms and ascarids.

• Oxibendazole, which kills large strongyles, pinworms, ascarids and threadworms.

• Oxfendazole, which kills large strongyles, roundworms and pinworms.

Tetrahydropyrimidines, also called pyrantel salts, including:

• Pyrantel pamoate, which kills large strongyles, pinworms, ascarids and some tapeworms in a standard dose. When used at a double dose it kills 85 to 95 percent of tapeworms.

• Pyrantel tartrate, which is used for daily feed-through dewormers. It controls large strongyles and ascarids.

• Praziquantel, which works specifically against tapeworms