The death toll of a mystery illness affecting horses in Victoria has risen to 13, with five properties now affected.
Agriculture Victoria began investigating the deaths as a significant event on Sunday after receiving reports that five horses had died on one property within the past two weeks.
All deaths occurred within 48 hours of the rapid onset of a severe, unspecified illness.
There are now confirmed deaths at one property on the Mornington Peninsula, two properties near Cranbourne in south-east Melbourne, a property near Ballarat and a property near Colac.
All properties are at least 30km apart and no links between properties have been identified at this stage.
Victoria’s chief veterinary officer, Dr Graeme Cooke, told ABC Melbourne on Monday that affected horses had been tested for “many, many diseases, some of them foreign to Australia, some of them present in Australia”, and all of those tests have been negative.
That includes testing negative for Hendra and anthrax.
“What has happened here is very, very rapid onset of symptoms and rapid death,” Cooke said. “That does lead one to look at a wide variety of causes which could be non-infectious.”
Asked if they had tested feed samples from affected properties, Cookes said: “All these premises where samples have been available, they have been negative.”
Some of the affected horses lived out on pasture and were not receiving any additional food, leading authorities to also investigate possible environmental causes.
The deaths have caused widespread concern among horse owners and trainers, and sparked a significant amount of speculation.
The Equine Veterinarians Australia president, Dr Hadley Willsallen, urged horse owners “not to contribute to any disinformation or the dissemination of misinformation”.
Agriculture Victoria also urged horse owners to be mindful of what they share online.
Willsallen also urged people not to panic and to be conscious of the pressure that local vets were under.
“I know a lot of vet practices’ phones have been ringing nonstop,” she said. “We need to let the vets work on significant cases and not have their phone lines blowing up.
“If you are worried that your horse is not well – significantly not well – it should be looked at by a vet, and you should let the vet know your concerns as they may need to wear personal protective gear.”
Some affected owners have shared the symptoms their horse experienced, listing a high temperature above 38.5C, diarrhoea and lethargy. However authorities have not listed any symptoms other than rapid onset of illness. Willsallen said it was likely that some of the isolated cases reported so far would be unrelated, particularly those involving a longer illness.
“Sudden death is the symptom,” Willsallen said.
She said that autopsies of affected animals should be able to shed light on the issue.
Agriculture Victoria said it was continuing to follow up cases that had been shared on social media but not yet reported to authorities.
Cooke urged people who believed their horse may be affected to report it as soon as possible to both their vet and Agriculture Victoria.
“That will be a major help into the investigation because that will help us get early cases and early samples,” he said.
Suspected cases can be reported to a veterinarian, Agriculture Victoria or to the emergency animal disease hotline on 1800 675 888.
