Probe into shock death of 10 horses in Melbourne’s southeast

Three more horses have died in mysterious circumstances as authorities continue to probe what has caused a “very unusual” cluster of horse deaths across Victoria.

Authorities are undertaking a “complex investigation” into what has caused a concerning cluster of horse deaths across Victoria

Vets still don’t know what is causing horses to mysteriously drop dead across Victoria as three more properties come under investigation.

Three more horses have suddenly died, bringing the total cluster of dead horses to 13 across five locations, as of July 18.

The reported properties include one located on the Mornington Peninsula, two in Cranbourne and others near Ballarat and Colac in the state’s west.

Agriculture Victoria said the investigation was still in its “very early days” and many possible causes – including feed, environmental factors and disease – were being examined.

Authorities have yet to officially rule out whether the horses may have been poisoned.

In a statement, Agriculture Victoria on Wednesday said it was working with private vets and industry experts to respond to calls and build a “bigger picture of the situation”.

“Agriculture Victoria’s investigation into a number of sudden horse deaths is continuing,” it said in an update posted to its website on Wednesday.

“It is not yet known what has caused these deaths. It is therefore possible they are not related and are different causes on each property.

“The investigation is in its early stages and surveillance and testing is being undertaken to assist determine possible causes.”

Early testing for a variety of infectious diseases, including Hendra virus and anthrax, has been negative.

But experts said it may be difficult to determine a cause of death in all cases due to a lack of samples for testing.

On Monday, Victoria’s chief vet said he was at a loss as to what has caused a concerning cluster of horse deaths, as authorities continue to probe the “very unusual and significant event”.

Dr Graeme Cooke is at a loss as to what has caused the deaths. Picture: Zoe Phillips

Dr Graeme Cooke confirmed initial tests suggested an infectious disease was not to blame, with experts investigating whether food staphs and environmental factors could be causing the mysterious deaths.

“This means this is a very complex investigation,” he said.

Since the beginning of July, 13 horses — on properties located on the Mornington Peninsula, southeast Melbourne and southwest Victoria — died rapidly within six to 24 hours of falling ill.

“Multiple horse deaths within that time frame is a significant event,” Dr Cooke said.

“Between all the premises, the only commonality is rapid deterioration. At this stage in the investigation, and it’s very early days, there are no other commonalities that immediately become apparent.

“It’s very good that we’ve had initial infectious disease samples saying that everything we tested for is negative, now we’re entering into this longer, more complex area … It’s not an easy area to be in.

“We really are looking to bring together all the expertise that is available … to look down how far we can take this but it’s become very complex.”

Dr Cooke said while testing for infectious diseases will continue, there is no advice to suggest that horses should be separated.

The horses that died were all housed on properties with other horses, including many that haven’t fallen ill.

“It’s very important to emphasise that remaining horses on these sites … remain healthy and there’s no indication of any transmissible disease,” he said.

Dr Cooke said there was no need for horse owners to take drastic action including locking down stables or closing their businesses to the public.

“There is no evidence that justifies that as an approach at this point,” he said.

“We understand that the horse community is very concerned about this but it’s very early days.”

Authorities say the number of horse deaths across Victoria is “significant”

Dr Cooke said he has spoken with counterparts in other states, but said there is no advice of similar deaths across state borders.

On Sunday, Agriculture Victoria confirmed it is working with local vets and experts to investigate the deaths.

“The investigation is in its very early stages and extensive information gathering and testing is underway to understand the possible causes of the illness and deaths,” an Agriculture Victoria spokesman said.

Equine specialist John Russell, who works at the Woodgrange Equine Hospital in Bayles, said a colitis outbreak may be to blame for the deaths, but that was still being examined.

Dr Russell told the Herald Sun his clinic had been bombarded with calls from concerned horse owners worried about the deaths.

“We are getting calls from all around the state,” he said.

“There are a lot of sick horses that have been reported to us. It is still very early days.”

Colitis is often caused by an infection in the gut or from eating a toxin.

The main symptom is diarrhoea.

“The big concern is that horses can lose such a large volume of water through their gut from the diarrhoea that they simply can’t drink enough water to maintain their fluid levels,” he said.

“It can get to the stage where they’re losing fluid so quickly that we can’t give them an intravenous drop in time because they’re in really serious distress and they die really quickly.”

Dr Russell said while the disease is “very serious”, it isn’t necessarily abnormal to have a colitis outbreak.

“There were some initial concerns that there might be a toxin in the food causing this. That is still being looked at, but we don’t see any reason for people to be worried about giving their horses their normal feed,” he said.

In a letter to its members, the Australian Veterinary Association said it had been informed of a number of horses having died unexpectantly — including five from one property.

“In a case that was examined prior to death, the significant clinical sign was pyrexia with a core body temperature greater than 40C,” the letter stated.

Dr Russell urged concerned owners to check their horse’s rectal temperature.

“A normal range should be between 37.0 degrees to 38.3 degrees,” he said.

“If it gets above 38.5 — that is officially an elevated temperature and you should contact your private vet.”

Authorities said they are aware of several other non-confirmed reports of horse deaths through social media.

Horse owners should monitor their animals and report any sudden deaths or onset of illness in their horses immediately to their local vet, Agriculture Victoria, or via the emergency animal disease hotline on 1800 675 888.