The products most commonly used to deworm horses fall into three major categories:
Avermectins and milbemycins (referred to collectively as macrocyclic lactones) are still largely effective against a wide range of parasites, but resistance, especially in ascarids, is growing. This class includes:
• Ivermectin, which works against most of the common equine parasites except for tapeworms. However, it does not work against small strongyles while they are encysted.
• Moxidectin, which is similar to ivermectin but also acts against encysted small strongyles.
Benzimidazoles are effective against many adult parasites, but their efficacy against larval stages and all small strongyles is declining. This class includes:
• Fenbendazole, which kills large strongyles, pinworms and ascarids.
• Oxibendazole, which works against large strongyles, pinworms, ascarids and threadworms.
• Oxfendazole, which kills large strongyles,…