The horses, collectively worth more than $US2 million, fell seriously ill as they arrived at the International Polo Club of Palm Beach to play in a fixture as part of the United States Polo Open in April 2009.
The incident brought to light the absence of drug policies in the sport.
Since then polo officials spent time reviewing drug-testing regimes in other horse-related sports, including the Hurlingham Polo Association, which oversees polo in the UK and Ireland. In October 2009, the USPA's Board of Governors approved a pilot programme to engage the services of the USEF's Equine Drugs and Medications Program, in time for the annual 2010 polo season that includes the annual USPA US Open Polo Championship. The US Open runs from March 29 to April 18.
At their annual meeting in October 2009, the USPA Board of Governors unanimously approved a by-law change that requires individual members of the USPA to submit his or her horses for random blood and/or urine testing. The association has also amended by-laws to include disciplinary action against any member convicted of a civil animal-abuse violation.
"As we reflect on the importance of equine safety and welfare in the sport of polo, I am proud to see such an outpouring of national support regarding our new Equine Drugs and Medications Program (EDMP), said USPA Executive Director Peter Rizzo.
"We at the USPA feel it's important that polo players and the general public alike know we uphold the welfare of our animals to the highest degree and will take the measures necessary to ensure animal safety in our sport."
The new USPA program includes detailed information about permitted, restricted and prohibited drugs, medications and substances, as well as rules regarding enforcement and sanctions for EDMP Rules violations. The rules also include dosing recommendations for restricted medications. Random testing will be conducted field-side after the game.
Dr Stephen Schumacher, Chief administrator of the USEF Drugs and Medications, said the USPA should be commended for taking this "monumental step for horse welfare".
"It's been exciting to work with the USPA leadership over the past year in developing a program to address their concerns," Dr Schumacher said.
During the 2010 calendar year, there will be no adjudication for violations of the USPA Equine Drugs and Medications Rules. If a horse tests positive for prohibited drugs and medications in 2010, the owner and the player of the horse will be contacted by the USPA.
Commencing 2011 and thereafter, upon finding of a positive test under the USPA Equine Drugs and Medications Rules, the owner, and /or the player who competed the horse (who may, or may not, be the same person) as well as the sponsor of the team for whom the horse competed (if the horse is owned by a corporate entity) could be charged with a Conduct Violation according to USPA Rules and/or By-Laws.
Such violation, depending upon the severity, may result in suspension or termination of USPA membership and exclusion from USPA competition and Member Clubs, monetary fine and retroactive disqualification from a competition.