Safe-Guard Paste Wormer from Merck is a safe and effective treatment and helps control large strongyles, encysted early third stage, late third stage, and fourth stage cyathostome larvae, small strongyles, pinworms, ascarids and arteritis caused by fourth stage larvae of strongylus vulgaris in horses. The apple-cinnamon taste is highly palatable and safe for use in horses, foals, and pregnant mares.