A Deadly Parasite Outbreak Is Killing Off Australian Wombats

Narawntapu is a national park on Tasmania's northern coast. Despite once being named "Asbestos Ranges" it's actually a really beautiful place—rocky coastline stretching into grasslands teeming with kangaroos, wallabies, Tasmanian devils, and wombats. Or at least it used to be that way. Over the past six years, 94 percent of Narawntapu's wombats have died.

Wildlife ecologists from the University of Tasmania started noticing something was wrong during an annual survey of the park by undergraduate students. The wombats they found showed troubling signs: hair loss, thickened skin; the animals were moving slowly, spending four times as long doing simple things like feeding.

The disease is called sarcoptic mange, explains Dr Scott Carver, a lecturer in wildlife ecology at the University of Tasmania. For the past three years, Carver and his team have been working to save Narawntapu's wombats with little success. While individual animals can be nursed back to health, once they are released back into Narawntapu, the chance of getting infected again is very high.

Sarcoptic mange is caused by a mite called sarcoptes scabiei, which burrows into the skin of the wombat. In humans and dogs, the mite is what causes scabies but it's not known why mange affects wombats so badly, or why their immune systems can't fight it off. What's known is that left untreated, wombats with sarcoptic mange can become blind and deaf as their skin thickens over their eyes and ears. They eventually become too weak to sacavange for food.

Irritated by the mite under its skin, wombats with mange will scratch incessantly, clawing at their skin, causing deep lacerations. It's these wounds that usually kill the animal because they get invaded by a secondary infection. It's a slow, painful death that can take months.

"It's catastrophic," Dr Carver says. "At Narawntapu National Park our research indicates that there is a reasonable probability mange may cause the population to go extinct in the next 12 months."

Dr Carver and his team don't know why the mange outbreak in Narawntapu has become so bad. It may be climatic factors, which make it easier for the mite to breed and spread. It's also thought foxes using wombat burrows as dens may help the spread. However, sarcoptic mange isn't by any means limited to this small national park on Tasmania's northern coast.

"This is the number one disease for wombats nationally," Dr Carver says. There is anecdotal evidence of other smaller outbreaks across Tasmania, and also in South Australia. However, the Wombat Protection Society of Australia argues the problem is even worse than that. "Mange is widespread throughout all populations of wombats in Australia with the exception of the Northern Hairy Nosed Wombat," says Amanda Cox, the society's public officer.

In Narawntapu National Park, Dr Carver and his team have tried to treat sarcoptic mange at a population level, using a method that's "genius in its simplicity" called a burrow flap. Essentially, it's an ice cream container hung above the entrance to a wombat burrow, which douses the animal with a chemical treatment called cydectin as they climb out.

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Back in 2015, the scientists installed hundreds of these throughout the park, meticulously refilling the treatment every week. But it didn't work. "These were perfect conditions… ocean on three sides and even there we weren't able to control it," Dr Carver says.

So now Dr Carver and other wombat researchers are going back to basics, trying to get some good baseline data around how bad this outbreak really is. They are also calling on the help of the public, asking people to log wombat sightings using an online system called WomSAT. Already, more than 4,500 wombats have been logged across Australia.

There are challenges with resourcing… But certainly not for lack of will," Dr Carver says. "One of our biggest limitations is that there isn't a lot of survey information… around Tasmania or Australia more broadly."

Not far from Narawntapu, in Tasmania's north west, there's been hopeful reports for another native species fighting off a decimating outbreak. Over the past 20 years, the parasitic cancer facial tumour disease has killed off at least 70 percent of the state's Tasmanian devils.

But researchers from the University of Tasmania recently discovered six Tassie devils that had successfully cured themselves of the cancer. Its not yet known how; however, one hypothesis is the animals may have evolved an immune response to protect themselves from the disease.

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