The American racing industry is rife with speculation that injured horses are illegally receiving extracorporeal shock wave therapy (ESWT) to boost their performance.

ESWT is an established veterinary treatment, which stimulates blood flow to injured areas and speeds up recovery. However, it also numbs pain for several days and suspicions are growing that unscrupulous owners may be abusing it to make injured horses race despite their condition.

The treatment became common in American racing a few years ago. Between late 2002 and early 2003 many state jurisdictions required owners to record ESWT usage and introduced rules banning horses from the track for seven to 10 days after receiving treatment.

However, ESWT devices can easily be bought on the Internet — HHO found a used one for sale for just £4,850 — and it is virtually impossible to detect whether the therapy has been applied on a horse, unless it has been shaved and sedated, which is not always the case.

So owners can illegally administer the therapy themselves and then race the horse before the seven or 10 days’ enforced rest is completed. It is unlikely that individuals would risk a winner, but they may take their chances with a lesser horse.

The extent of illegal ESWT use, however, is unclear. “It is pretty speculative as to whether shock wave [therapy] is continuing in an improper manner,” says Mike Marten of the California Horse Racing Board (CHRB).

“Prior to the board requiring registration of [ESWT] machines and recording of treatment, it could have been done by anyone without any punishment, without violating any rules. We declared it an analgesic and you can’t administer it within 10 days of the race, and this has largely stopped [ESWT abuse].”

But, he adds, “as with any activity, it doesn’t stop 100%.” To close “these last loopholes,” the CHRB are thinking of monitoring the movements of horses from and to a racecourse as part of a broader security push.

ESWT cannot be administered on a racecourse undetected because the machines make a lot of noise. But horses could be shipped off for a quick treatment and brought back to run the race, so keeping a closer eye on those that seem to go in and out too frequently would help curb the abuse.

“One of the steps we’d like to do is be able to monitor horses coming and going,” says Marten. “Not that there is any rule forbidding that, but if you knew who was doing that often you’d be putting some form of control.”

However, accurate monitoring would require checking horses IDs and the CHRB haven’t yet found a practical way of doing this. “What we are looking at now is the practicality of inserting microchips but it is more of a long term plan,” says Marten. “There are many reasons to look at microchips and this [ESWT control] can be one more to make the industry go that way.”

So could ESWT abuse happen in the UK? “We reviewed this is the past and our assessment at the time was that this was not a problem with racehorses in Britain,” says Peter Webbon, the Jockey Club’s chief vet. “There is no indication at the moment that [ESWT] is misused here.”

For this reason, no formal rule currently prevents a treated horse running a race in Britain. “If there is a problem, we will put a rule in place,” says Webbon. But, he adds, “it will be an exceptionally difficult rule to police.”