Threat of exotic vector-borne diseases worsening with climate change, scientists say

Academics and farmers are growing increasingly worried about the spread of exotic diseases due to rapidly changing weather patterns.

CSIRO principal research scientist Prasad Paradkar said there had been a spike in the number of vector-borne diseases detected in South-East Asia, in large part because of the direct and indirect impacts of climate change.

Direct effects include extreme weather events like cyclones and strong storms that can blow insects over large distances.

“Indirect effects include things like increased average temperatures,” Dr Paradkar said.

Warmer temperatures allow the vectors of these diseases to inhabit a wider geographical range and help pathogens to reproduce.

In on the wind

Japanese encephalitis (JE) is thought to have been brought to Australia from Asia by migratory birds flying further south than usual.

The birds are bitten by mosquitoes, which spread the disease to animals and humans.

Six people have died from JE in the past year.

Edwina Beveridge, a pork producer and director of Blantyre Farms in Young, New South Wales, said she was shocked by the incursion.

She said more cases were likely given the wet weather and that she was taking preventative action.

“We’ve [brought] excavators in to improve the drainage around our shed to stop water pooling and becoming a mosquito breeding ground,” Ms Beveridge said.

But there are other diseases near our borders that we have not seen in Australia yet.

LSD and bats

Lumpy Skin Disease (LSD), if it spreads any further south or east in the Indonesian archipelago, could be blown to Australia by a strong cyclone that brings biting insects with it.

African horse sickness could also spread to Australia this way, but it has not been found in Indonesia yet so the threat is relatively lower.

Bats could present another risk.

University of Sydney chair of Veterinary Public Health Michael Ward said the Hendra virus was moving south as the distribution of flying foxes changed.

“It could be land clearing, or El Niño impacts, drought impacts that shift the bat distribution, and then we get that spillover occurring,” he said.

The virus has killed more than 50 per cent of the people infected, though infection has been rare so far.

‘Not if, but when’

Fruit bats can also spread Nipah virus.

In 2010 scientists satellites were used to track bat movement and found several instances of migration between Australia and Papua New Guinea, as well as Papua New Guinea to Indonesia.

Bats are also known to move to Indonesia from Malaysia, which has seen a serious outbreak of Nipah virus.

Nipah virus killed more than 100 people in 1998 and more than one million pigs were destroyed to control it.

Another paper found evidence of Nipah in fruit bats within 500 kilometres of Australia.

While there is no immediate threat from many of these diseases yet, Dr Ward said the pattern of spread had been rendered unpredictable by climate change and farmers that should be prepared for anything.

Dr Paradkar said it was all but inevitable that one of the diseases would arrive in Australia eventually.

“It does appear to be a matter of not if, but when,” he said.