It is not uncommon for horses let out to pasture to pick up intestinal parasites. Quest Plus Equine Paste Wormer kills strongyles and tapeworms. Each dose of Quest also helps to prevent re-infestation for a period of 84 days. This product is appropriate for horses that are over six months of age. The syringe contains enough medication to adequately treat a horse that weighs no more than 1,250 pounds.