In horses, the benzimidazoles are characterized by effective removal (90-100%) of almost all mature strongyles, High levels and repeated administration may be necessary for extraintestinal migrating stages of large strongyles and for small-strongyle larvae embedded or encysted in the wall of the Intestine.. Ascarid removal in horses varies with various members of the benzimidazole group. Oxyuris equi is usually removed by any of the benzimidazoles at the recommended dose.