Vic Rail, a leading horse trainer, died Tuesday, a week after he was stricken by a virus with symptoms similar to one that has killed 14 racehorses. He was 49.
Rail died of a heart attack in Mater Hospital, where he was in the intensive care unit, the hospital said.
All racing in the south of Queensland state has been halted while authorities try to find the cause of the illness that has struck two suburban stables the past week--those of Rail and the adjoining stables of John Fitzgerald.
Doctors have been unable to establish a link between Vail's illness and the mystery horse virus.
Rail was best known as the trainer of Vo Rogue, who won more than $2.3 million between 1987 and 1991.
Poisoning has been ruled out as the cause of the horse deaths.
Ian Douglas, exotic diseases director for the Department of Primary Industries, said veterinary experts have agreed a virus was the cause of the deaths, but no known condition has been revealed by tests.
Douglas said the disease did not appear to have spread beyond the two stables.
He has ruled out African horse sickness, equine flu, equine herpes and three types of encephalitis as possible causes.