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La Nina brings fears of roo pandemic

A Western Division animal health expert has warned that the chance of another La Nina weather event could create the ideal conditions for a kangaroo pandemic.

Former Department of Primary Industries (DPI) vet and epidemiologist, Dr Greg Curran has urged graziers, national parks staff and roo shooters to be aware of the potential for mass kangaroo deaths, previously seen in similar conditions in 2016-2018 when it’s estimated 4.1 million animals died across New South Wales, Queensland and South Australia.

Having worked in the arid pastoral regions for over 30 years, Dr Curran says confirmation from the Bureau of Meteorology (BOM) that Australia was entering its third La Nina summer in a row meant higher than average rainfall for properties surrounding Broken Hill.

“This creates repeat conditions that we saw in 2016, the 1990s and 2010. In all of those years, kangaroos, and potentially other animals, were heavily impacted by a set of diseases that we are yet to know much about,” says Dr Curran.

“The cause of this disease has not been determined. What we really need is for the experts to get a full understanding of just what happens and how it impacts the ecosystem.”

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Dr Curran said many roo shooters and pastoralists in the Western Division would be aware of the signs to look out for.

“The first thing people see in the paddock is numbers of roos that look like they are asleep under bushes. They look so relaxed, it’s only when you get up close to them that you realise they are dead or dying. With this disease, they die without struggle,” Dr Curran said.

“The other interesting thing is that the bodies of the dead animals don’t decompose as normal. They don’t break down… so months later you could drive around the paddock and see the bodies still in the same position, under the same tree. The scavengers won’t eat these carcasses,” he said.

“In the early days we thought that there were too many bodies for the scavengers to get around. I visited one property though and saw that the scavengers were dying too, in numbers, or they were moving away from the area very quickly.”

Now retired, Dr Curran has sent multiple requests to the Department of Primary Industries (DPI) to investigate previous incidence of the pandemic, and has detailed a hypothesis on what he thinks is happening.  He says it’s essential that experts get to the bottom of what is causing the mass deaths, which may impact sheep and cattle in the long-term.

“I’ve been called to many properties over the years, and have seen things that create concerns that the disease that is affecting the kangaroos, is in fact spreading to other animals.

“One grazier asked me to come and visit his property because his cattle were having reproductive failure. When I got there, I saw mass deaths of kangaroos, dead crows, and the grazier said the remaining crows had just gone.  On this particular property it was the first time I’d witnessed death across cattle, sheep and kangaroos to such an extent, as well as issues with cattle – a dramatic decline in fertility – and then later fertility issues with the sheep.”

Dr Curran said similar issues had been known in the Hawker region in South Australia, where graziers called the disease in cattle, ‘November Disease.’

“In those areas some just can’t run cattle because of the severity of the problem.”

Dr Curran said while the cattle problem is called ‘November Disease’ in South Australia, NSW graziers have dubbed it ‘3D disease.’  “It stands for drooling, diarrhoea, death.”

He said post mortems on cattle in affected areas have found that the disease affects the animal’s oesophagus.

“I worked on a cow at a mass cattle death, looking at the damage done. I left the oesophagus until last and when I opened it up it was putrid. The animal could not swallow in that state.

“The oesophagus in a cow is usually very tough…they can swallow rough, spikey thorny food, and do that easily…but not in this case. Hence, the drooling.”

Dr Curran said it had been difficult for pathologists to understand the disease.

“Often when you opened up the affected animals during post mortem, virtually every tissue was affected.  But when I sent those samples to be examined microscopically, pathologists could see no change.

“With most viruses you can see something obvious.  With this though there were lots of gross changes but nothing microscopically.

“It wasn’t until a pathologist in Camden tried a new way of studying the kangaroo brains that a breakthrough occurred.  Dr Leah Johnson saw similar structures that we see in rabies – called Negri bodies, although it definitely wasn’t rabies.

“The virus in rabies takes over the body’s mechanism to deal with misfolding proteins.   Misfolding proteins in animals cause Chronic Wasting Disease of deer, scrapie, and “mad cow” disease, none of which are found in Australia. Misfolding proteins are also found in pre-eclampsia, a reproductive problem of people, with similarities to pregnancy toxaemia in ewes.”

But Dr Curran said despite this initial breakthrough, there had been no follow up on the research into the disease.

A DPI spokesperson said they would not undertake further research.

“There is no evidence to link kangaroo mortality events in NSW to health issues in other species.

“NSW DPI has previously investigated kangaroo mortality at the request of the Office of Environment and Heritage (OEH). At that time, there was no evidence to incriminate a single novel or existing infectious agent.”

Landholders and members of the community are encouraged to promptly report unusual death or health issues in animals to Local Lands Services staff or Office of Environment and Heritage for investigation.

 

*Suspected disease outbreaks can be reported via NSW DPI’s wildlife disease reporting web page or the Wildlife Health Network’s web page for reporting disease events.

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