Delaware, beginning May 11, will join New York and Ontario, Quebec, as jurisdictions with rules to penalize horses that test positive for erythropoietin antibodies.The Delaware Thoroughbred Racing Commission Tuesday unanimously approved a rule that bans a horse with a positive EPO test from racing until the blood-doping agent is deemed clear from its system. Because the drug can stay in a horse's system for up to 120 days, no penalties will be levied against the horse's trainer.Delaware had conducted EPO testing on an experimental since June 1 of last year. A spokesperson for the commission said the results of the pilot program led Delaware to join New York and Ontario as the only jurisdictions to penalize horses for positive tests.The Delaware rule would also allow a trainer or owner to void a claim of a horse if it subsequently tests positive for EPO.Since New York began EPO testing Nov. 1, no Thoroughbreds have tested positive. However, two Standarbreds on the New York harness circuit have tested positive and were placed on the ineligible list.EPO, which was first used in track and field, helps a body produce more red blood cells, which it is believed increases the flow of oxygen through the bloodstream and therefore performance. However, the medical community has found EPO's side effects on horses can be deadly.