A carpageddon is coming. The government has announced a $15 million plan to release a herpes virus into the rivers, in a bid to wipe out our country’s most notorious fish pest.
Carp have decimated native Australian fish populations since their introduction in 1859, particularly in the Murray-Darling river system, where they now make up 80% of fish numbers.
Scientists at CSIRO have spent the last seven years investigating the potential of a carp-specific herpes strain – cyprinid herpesvirus 3 – to fight off the invaders. Rigorous testing has shown that the virus kills between 70 and 80 per cent of carp populations, but does not harm native fish species or yabbies, eels, chickens, mice, frogs, turtles or water dragons.
The government announced on Sunday that cyprinid herpesvirus 3 will be released into the Murray-Darling river system by the end of 2018.
“As you can imagine there is a lot of work to be done in preparation,” science minister Christopher Pyne told a press conference on Sunday. “Because suddenly, there will be literally hundreds of thousands, if not millions of tonnes, of carp that will be dead… So we have to have a clean-up programme.”
The herpes virus is fatal to carp because it attacks their kidneys, skin and gills, and makes it difficult for them to breathe, says Ken McColl of CSIRO. “The virus multiplies in the fish for about seven days, and then it takes about 24 hours from the first signs of disease until they die,” he says.
However, as with any virus, resistance is likely to build up over time, he says. “We’ll probably have a window of about two to four years to really take advantage of it.”
The carp control plan will be the first example of a biocontrol strategy that uses a herpes virus, but the potential risks to humans are small, says McColl. Cyprinid herpesvirus 3 has not caused any adverse effects in carp farmers in countries like China and Vietnam, where many native carp populations have been infected since the virus first appeared in the late 1990s, he says.
The virus also has a low risk of mutating and jumping to other species because it is a complex DNA virus, rather than an RNA virus like Ebola or influenza, McColl says. In this way, carp herpes is similar to myxomatosis, another complex DNA virus that has been used successfully and safely in Australia to control rabbit numbers, he says.
Nevertheless, even the most comprehensive testing cannot rule out the unforeseeable problems, says Richard Kingsford of the University of New South Wales. “I think it’s a great idea, but I guess it’s like a lot of these tricky biological control approaches – there are always risks.”