Less than a month away from the World Championships in Moscow, sprinting has succumbed once again to the shame of doping as American Tyson Gay and Jamaican Asafa Powell were caught out.

The 30-year-old Gay insisted he made a mistake in erroneously trusting someone he shouldn't have.

Powell confirmed he too had failed a dope test, one of five Jamaicans reportedly to have done so at their country's national trials.

The 2007 world champion Gay would have gone into the worlds not as favorite, but as close a fancied challenger to Usain Bolt as anyone could be.

He had posted the fastest 100m time of the year with 9.75sec, almost two tenths quicker than Bolt's best effort in 2013.

Alongside Yohan Blake, who has been suffering with a thigh injury this season, Gay is the second fastest man of all time with his 9.69sec managed in Shanghai in 2009 bettered only by Bolt himself.

Powell had not qualified for the worlds but had the third fastest 100m time this year and is the fourth fastest man in history, behind Bolt, Gay and Blake.

Gay was majestic in cruising to a 100m and 200m double at the American World Championship trials in June.

Yet following fast on the heels of Jamaica's double Olympic 200m champion Veronica Campbell-Brown's own failed dope test, this latest news is another crushing blow to the credibility of sprinting.

There was yet more bad news to come from the Caribbean.

Powell and Sherone Simpson, the 2008 Olympic women's 100m runner-up, and member of the sprint relay gold-medal winning team in 2004, were immediately identified.

"I want to be clear that I have never knowingly or willfully taken any supplements or substances that break any rules. I am not now nor have I ever been a cheat," insisted Powell.

With a host of eastern European athletes failing tests this year, including Bulgaria's European indoor 60m champion Tezdzhan Naimova, Russian European 800m winner Yelena Arzhakova and Russian Olympic discus silver medalist Daria Pishchalnikova, athletics is reeling.

Not that athletics, and in particular sprinting, have ever been strangers to the scourge of drug use.

The impact of Gay's doping case will be wider ranging, though, not least because one of the favorites to challenge Bolt in his absence will be his US compatriot Justin Gatlin, who has already served two drug suspensions during his career.

The credibility of the sprint disciplines in track and field will now be hanging by an even thinner thread than ever before.

Such high-profile cases in the past have seen Ben Johnson stripped of his Olympic 100m title with Marion Jones suffering the same fate. Kelli White lost her 100m and 200m double success in the 2003 World Championships after she was later caught doping.

Other big names in the not too distant past such as Linford Christie and Dennis Mitchell have been banned while Kostas Kenteris, the Sydney 200m Olympic champion, and his countrywoman and 100m Olympic silver-medalist Ekaterina Thanou were prevented from competing at their home Games in Athens and subsequently banned for faking a motorcycle accident in order to skip a dope test.

With so many of the finest sprinters of the current generation, and indeed others from recent generations, having been exposed as drug cheats, athletics, in particular sprinting, runs the risk of seeing the whole profession tarnished in the way cycling has been in the wake of its own high-profile revelations.

With the likes of Tour de France winners Lance Armstrong, Jan Ulrich, Bjarne Riis and Floyd Landis all having finally admitted to doping after being banned for doing so, cycling suffers from a serious lack of trust and credibility.

Yet with the Tour de France going on at the moment and no doping stories having come out so far, athletics has stepped into the scandal breach in spectacular fashion. (AFP)