About half the thoroughbreds confined to a locked-down Randwick Racecourse are now believed to have the equine flu virus, as the total number of horses likely to be exposed across New South Wales and Queensland approaches 3000.
However, there are predictions the number of cases should plateau this week as a result of the movement bans and massive containment measures across the two states.
Randwick was locked down after horses were found with the disease in a trainer's stables. It is expected that most of the horses housed at the course will contract the disease. The track is likely to remain closed for at least two months.
Horse-movement bans remain in place in New South Wales and Queensland, but South Australia lifted its ban at 12.30pm yesterday. However, the SA government says horse movements should be kept to a minimum, and permits are required for any gatherings of 10 or more horses from more than one property.
The government's preference is that events should be postponed, but if they must go ahead then a permit must be obtained.
"Basically, horses should stay at home wherever possible," a government spokeswoman said.
New South Wales deputy chief veterinary officer, Steve Dunn, said a total of 835 horses were infected on 119 properties in the state, while another 2900 horses were considered suspect on a total of 319 properties.
Mr Dunn said reporting sick horses is a vital component of the ongoing effort to eradicate equine influenza.
"The battle to contain the disease is still going ahead with a strong resolve that it can be beaten," he said. "We cannot afford to become blasé in communities that have a high incidence of the disease.
"It's becoming clear to many people in high incidence areas whose horses have not yet become sick that their animals will probably get horse flu. But it is still important that horse owners and vets report the problem and follow the correct procedures so that the Department of Primary Industries has every chance to plot the spread and transfer path of the disease.
"Even if your horses are well and you do not think they could have horse flu, do not attempt to move them even if you think there is a safer, a better or a more convenient place to keep them.
"Horse flu is so infectious that you can safely assume that if one horse in your stable has the disease, all the horses will get it," he said.
Across Australia, respiratory infections in horses raise the spectre of flu. There are nervous periods while test results are awaited. In Tasmania, five horses have undergone testing. It is understood two horses have been tested near Geelong in Victoria.
Five standardbred horses have tested positive for the disease at Eagelton, New South Wales. A total of nine horses in the stables have caught the disease, which is understood to have been brought in by a horse which returned there after competing in a one-day event at Maitland in the Hunter Valley.
This was the location from where the disease is understood to have spread when horses returned to their homes in NSW and Queensland.
In other news:
Horses in both countries are not vaccinated against the disease, and animals have no natural resistance to the infection.
In Britain, all racehorses are required to be vaccinated against it.
The British Horseracing Authority said the vaccination requirement meant "that in the event of cases of infection with the virus, both the severity and spread of the disease would be minimal."
"There is round the clock activity in Australia to trace all potentially infected horses and identify the exact strain of the virus as quickly as possible," the authority said. "Once the exact strain is known, a proper assessment of the possible effect of this outbreak on British horses entering, and more significantly returning from, Australia can be made.
"As was evidenced in 2003 with the last outbreak involving a number of horses in training, the British Horseracing Authority does not anticipate a requirement for restrictions within Great Britain in relation to this virus."