LOAD OF CARP: A national plan to control carp through the delibate spreading of a virus could be implemented in southeast Queensland.
LOAD OF CARP: A national plan to control carp through the delibate spreading of a virus could be implemented in southeast Queensland. Lyndon Keane

A load of carp? Virus to kill pest has community divided

THE PROPOSED introduction of a specialised herpes virus to dramatically reduce the numbers of European carp in Australia could include the Albert and Logan River systems.

The Fisheries Research and Development Corporation is in charge of the $15million planning process for the possible introduction of the virus CyHV-3 - also known as cyprinid herpesvirus-3.

The plan has divided opinion among scientists and the wider community, with a range of opinions on the potential risks of introducing an irreversible strain of herpes to waterways.

The QT was contacted by several Scenic Rim residents who attended a community consultation forum hosted by those in charge of preparing the National Carp Control Plan.

The meeting was held in Beaudesert on March 6 and aimed to provide the public with the most up to date information, however some of those who attended the meeting came away with questions and concerns about the implications of the plan, if it is allowed to go ahead.

NCCP co-ordinator Matt Barwick said research was being undertaken in the Albert and Logan system to discover how prevalent carp are.

"We are right in the midst of our research," Mr Barwick said.

"One of our biggest challenges is in finding out how many tonnes of carp are in the various waterways.

"That then affects how effectively the virus would transmit from fish to fish, and the cost of the clean-up."

Mr Barwick said it was a complex issue. Water temperature also affects the virus' spread and effectiveness in killing carp. He said the researchers still had "a long way to go" to prove to the public that the virus could be introduced and effectively kill carp while not adversely affecting other animals and the general environment in the long term.

While the Albert and Logan system is known to contain carp in large numbers, the concentrations are relatively modest compared with some of Australia's worst affected river systems, such as parts of the Murray-Darling.

Even in the event that approval is given to proceed with the plan, Mr Barwick said it would be up to each state and territory to decide where the virus is released.

Due to the fact that the virus would not kill 100 per cent of carp, the plan would have to include a multi-pronged approach, involving other forms of control including commercial fishing and genetically altering carp so that they only produce male offspring.

Part of the concerns aired about the NCCP, however, relate to how many carp it could kill episodically.

Kill rates as high as 90 per cent have been mentioned by Mr Barwick himself, but this depends on the local conditions. Mr Barwick stressed that any planned mass carp kill must be accompanied by a proper plan for the retrieval of the dead fish by "paid professionals".

"We know the clean up would neither be easy nor pretty," he said.

"We need paid professionals to make sure it is done safely and effectively, and with that we need to weigh up the benefits and risks of utilising volunteers to assist. There are tremendous opportunities to utilise volunteers to report on large aggregations of carp."

Spreading herpes

If it is introduced, CyHV-3 would be injected into harvested fish, which would then be returned to their natural habitat, where they would then spread the virus through contact with other individuals.

Scientists are still conducting research on how the virus transmits.

An infected fish would show no clinical signs until about day five, when it would develop sores and begin to behave erratically. From there, its life expectancy is only another 24 hours.

The CyHV-3 virus already exists in 33 countries across Asia, Europe, Africa and North America, having been spread accidentally through human transport of carp. Mr Barwick said experience of the virus overseas had shown Australian researchers that no other species had been affected, and that there were no significant environmental impacts.


Dr Tony Piddocke from the National Carp Control Plan, gathering feedback at a community meeting.
Dr Tony Piddocke from the National Carp Control Plan, gathering feedback at a community meeting. Contributed

Virologist: Herpes virus risks outweigh benefits

UNIVERSITY of Queensland virologist Philip Stevenson is one of several experts in the field to have expressed some concerns about the proposal to introduce a virus in order to reduce European carp numbers.

Dr Stevenson said his primary concern was not that the virus may not be effective in the first place.

Interestingly, Dr Stevenson said scientists couldn't even be certain that the virus didn't already make it into Australia.

"CyHV-3 can certainly kill carp in a laboratory setting. But that is very different to killing wild carp," he said.

"There have been instances of large scale deaths in wild carp associated with CyHV-3 isolation. However, that doesn't prove that the virus killed the carp. Herpes viruses generally persist at a low level then re-emerge if their host becomes sick from another cause. So it's just an association, not cause and effect. More importantly, there is plenty of evidence that CyHV-3 can persist in wild carp populations without causing disease."

"So there is no guarantee at all that CyHV-3 release will kill free-living Australian carp. It has never been tested. In fact, they may have the virus already. There haven't been reports of mass death in Australian carp. But death requires virus plus co-factors. One is missing but we don't know which one."

In the event that the virus does kill a lot of carp, as intended, Dr Stevenson said the obvious risk was then to other species.

"Given the problems of distance and accessibility, if CyHV-3 does kill a lot of carp it will be very difficult to remove them from the waterways. This will lead to bacterial overgrowth and hypoxic water, and could have catastrophic effects on other species," he said.

"Carp are well adapted to hypoxic conditions. So genetically resistant or immunised carp will be among the first to repopulate. In other words, killing carp could ultimately make the carp problem worse, by degrading the environment."

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