Rabbits’ viral expansion

January 26, 2015

The Invasive Animals CRC is seeking improved methods of biological control to effectively manage rabbit populations.

The British colonies of the South Pacific called an inter-colonial commission in 1883 to consider matters of common interest. German and French intentions in the Pacific, quarantine and trade issues loomed large. So too did the rabbit, which less than 25 years after its introduction to Australia from Europe was considered “so serious a national evil” it could not be left “to the efforts of individuals for its remedy”.

200115_rabbits_box1 Within five years, Henry Parkes had sponsored an international competition offering the astounding sum of £25,000 to fix the problem. This sparked an ongoing quest for biological controls for Australia’s number one vertebrate pest. Where Louis Pasteur and others had tried and failed, the CSIRO succeeded, twice, with new viral controls: myxoma virus in the 1950s and rabbit haemorrhagic disease virus (RHDV, also known as rabbit calicivirus) in the 1990s. Myxoma received a boost in the 1960s when a new carrier for the virus, the European rabbit flea, was introduced.

The Invasive Animals CRC (IA CRC) is hoping to mirror that success with a new program aimed at improving the impact of RHDV. “When we brought RHDV to Australia, only one strain, a Czech strain, was available to us,” said Dr Brian Cooke, from the IA CRC and the University of Canberra, who has spent his career battling rabbits using biological controls.

“We now understand that another strain – RCV-A1, which doesn’t cause the disease – was already here. This immunises some rabbits, which is why RHDV was less effective in wetter, higher production areas where it is more prevalent. In arid Australia, generally without RCV-A1, around 85% of rabbits died.”

Under the RHD-Boost Program, the IA CRC searched the world for more effective RHDV strains, eventually importing and screening 38 naturally varying strains. After additional tests, six were further investigated, and two virus strains – both from South Korea – demonstrated advantages over the existing Czech strain. One also showed an ability to overcome the partial protection from the problematic RCV-A1 calicivirus.

200115_rabbits_box2 CEO of the CRC, Andreas Glanznig, said the discovery is encouraging but there are more steps to take before a new RHDV strain can be released. “Myxoma and RHDV are the only two examples of wide-scale viral biocontrol for vertebrate animals – ever.”

The rewards are “potentially huge”, he said. “These two viruses have so far delivered more than $70 billion in value to Australia and prevented untold environmental damage.” Myxoma still kills about half the rabbits born in Australia today, at zero cost.

With rabbit numbers on the rise, Australia needs to stay on the front foot. “It is imperative that we have a pipeline of new RHDV strains to keep rabbit biocontrol effective. The alternative will undo decades of management of Australia’s most costly vertebrate pest,” said Glanznig.

Tony Peacock

www.invasiveanimals.com

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