Graziers are being urged to vaccinate their cattle as an unseasonal outbreak of a flu-like virus spreads through north Queensland.
Bovine ephemeral fever is often called three-day sickness because usually that was how long symptoms last.
Hughenden based-vet Libby Harriman said the current outbreak was one of the worst she's seen in a decade.
"Cattle have died over a 24 to 48-hour period, which is quite unusual for three day sickness,"
she said.
"They lie down, they get muscle aches and pains, they can go off their feed and drool and shiver, or they can look like they're laying with a broken leg."
There is no risk to humans, meat safety or supply.
Three day sickness is common in northern Australia, with cases usually peaking in March. (ABC News: Curtis Rodda)
Since first identified in September, Dr Harriman said there had been several cases in Hughenden and Charters Towers, a significant cattle-selling centre about 135 kilometres south-west of Townsville.
"Particularly Charters Towers is very badly hit. I've had a couple of clients there with significant losses," Dr Harriman said.
"Normally we only expect to see deaths in heavier cattle — they get down and they can't get up.
"But we've had losses in heifers and young stock … succumbing to the virus within a couple of days."
Outbreaks can occur in northern Australia and along the eastern seaboard as far south as the Victorian border, although industry research body Meat and Livestock Australia notes it is more sporadic in cooler regions.
The peak of cases is usually in March, and cattle that survive the illness are immune to future infections.
Both Charters Towers and Hughenden received average to below average rainfall in September. (Supplied: Bureau of Meteorology)
Shane McCarthy, president of farm lobby AgForce Queensland, said the severity of the symptoms at this time of year had some questioning if the virus had changed.
"It seems to be more virulent … and there is a little bit of a higher mortality rate,"
he said.
"We just need to be wary that it is out there, it is [the three day sickness], and there are some anti-inflammatory and drugs available from your local vets."
New strain unlikely
Bovine ephemeral fever was first reported in Australia in 1936, and all known strains present in Australia can be traced to a 1955–56 outbreak.
It's believed the out-of-season virus may have been spread into the west by mosquitoes from central Queensland. (ABC Rural: Melanie Groves)
Despite there being no mutations recorded in 70 years, Queensland's Department of Primary Industries said it was testing samples to confirm the strain.
"The Department of Primary Industries is aware of some reports of higher than usual impacts of three day sickness in central and western Queensland and producer concerns that a new strain of virus may be involved, " a spokesperson said.
Dr Harriman said the current outbreak was most likely started by mosquitoes blown in from the east coast, and the increased virulence could be attributed to a lack of herd immunity.
"When we haven't seen it for a number of years the population immunity declines. When we see it as a fresh outbreak, like what we're seeing this year, it tends to be much more severe," she said.
"Over the next couple of years there'll be a good herd immunity so symptoms won't be as bad."
It's unusual for an outbreak of cattle fever to spread to Hughenden during the dry season. (ABC North Queensland: Meghan Dansie)
About 700km south at Baralaba, cattle breeder Allan Trail recently withdrew from the Brahman Week sale due to the sudden onset of the virus in one of his bulls.
"On Saturday morning they were fine, we fed them up on Saturday afternoon, they were fine," he said.
"We went out fed the bulls on Sunday morning [and] he was crook."
Vaccinate early
He said the virus was becoming unpredictable and was arriving months earlier in August, instead of October or November.
"I think a lot more people are using the vaccine than they used to, particularly in the bull breeding game,"
he said.
"Obviously it doesn't protect them 100 per cent, but it does make a huge difference."
Charters Towers is a major cattle grazing centre in northern Australia, situated about 135km inland. (ABC Rural: Tom Major)
Dr Harriman urged others to consider vaccination as there were few treatment options available.
"The mainstay of treatment is good nursing and anti-inflammatory, same as if you had the flu yourself," Dr Harriman said.
"Pain relief options … it's basically all we can do for them other than providing shade, feed and nursing."