Thoroughbred racing was banned indefinitely on Monday in Australia's most populous state of New South Wales, as an outbreak of equine flu spread to 60 horses and another 450 horses were suspected of being infected.A three-day national ban on horse movements was extended until Friday in an attempt to contain the outbreak, national Agriculture Minister Peter McGauran said on Monday."This standstill applies to all horses, donkeys and mules, not just racehorses, and in effect, it means horses should not be leaving their property, not even when being ridden or led," McGauran said in a statement.Horses due to be used by police as part of security at next week's APEC summit in Sydney have also been confined to stables due to the outbreak.Shares in Australian betting firms fell, with top wagering group Tabcorp Holdings Ltd saying it expected to lose about A$150 million ($124 million) in turnover after racing across the country was cancelled last weekend.Authorities in the state of Victoria, where there has been no outbreak, said they expected racing to resume on Saturday, while Queensland state officials said they did not expect racing to start again for a week.The national racing shutdown was costing the industry tens of millions of dollars every day."When you take into account breeders, trainers, jockeys and race meetings, the outbreak will affect the economy," warned Australian Treasurer Peter Costello.The highly contagious disease is not infectious to humans but has the same debilitating effect on horses as influenza has on people; causing high fevers, coughing, sneezing and lack of appetite. In rare cases, it can be fatal to horses.Australia has some of the toughest quarantine rules in the world, but officials suspect the nation's first outbreak of equine flu may have come from Japan, which has just been hit by a much larger outbreak.Racing was cancelled in Japan last weekend for the first time in more than 35 years after almost 100 horses tested positive.RACING SUSPENDEDNew South Wales authorities said on Monday that all racing and the movement of horses in the state, where the majority of infected horses have been diagnosed, had been suspended indefinitely and the situation will be reviewed on September 3."The industry has come to a screaming halt," leading Sydney horse trainer Gai Waterhouse told reporters.Sydney's premier racetrack, Royal Randwick, was locked down on Monday after four horses displayed high temperatures, sparking fears an outbreak of equine flu may have spread to the multi-billion dollar racing industry.The horses tested negative to the virus late on Monday. No racehorses have yet tested positive to equine flu.The outbreak of equine flu has occurred on the eve of Australia's thoroughbred breeding season, when some of the world's top stallions arrive from the northern hemisphere.Some 40 international stallions have been quarantined in Australia and the New Zealand government has closed its borders to horses from Australia, including dozens of top American, European and Asian stallions worth an estimated $500 million.The outbreak is also threatening Australia's premier spring racing season, which includes the country's top race, the Melbourne Cup, run in November.Racing officials said they believe the 2006 winner of the Melbourne Cup, Japanese horse Delta Blues, will pull out of the cup due to equine flu outbreaks in Australia and Japan.Australian bookmakers have frozen all betting markets on the Melbourne Cup and other major spring carnival races."We have always been concerned about the possibility of equine influenza entering the country. We planned against it, we hoped it would never happen, and now the nightmare is here," said Andrew Harding, chief of the Australian Racing Board.