Editor’s Note: This is from Understanding Equine Preventive Medicine by Bradford G. Bentz, VMD. 

Programs that use no rotation involve the continued use of one effective drug until it no longer reduces small strongyle numbers as indicated by fecal egg counts. The intervals of administration depend on the dewormer used, but this program is limited to the use of ivermectin or the daily administration of pyrantel tartrate (Strongid C).

One benefit is that such a program is easily implemented and provides maximal reduction of parasite burdens. Rapid resistance has not been seen to develop with such programs. Horses raised on no-rotation programs will acquire resistance more slowly. The administration of 2-3x pyrantel to control tapeworms would be necessary with either the use of ivermectin or pyrantel as the anthelmintic. This is necessary even with the use of pyrantel tartrate, as the daily dosage is well below the required 2-3x dosage. If pyrantel tartrate is used, ivermectin would be necessary at the appropriate times (May and November) to control stomach bots. It has been suggested that daily administration of pyrantel tartrate may aid in preventing infection with Sarcosyctis neurona, the causative organism of equine protozoal myeloencephalitis (EPM).