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Rabbits are appearing in big numbers around Bridgetown in a phenomenon that’s being repeated throughout the southwest.

However, Blackwood Biosecurity thinks help may be at hand with the release of the K5 strain of calicivirus which has been shown to reduce rabbit populations by up to 36% when it’s released.

A controlled release of the K5 strain is essential to prevent immunity, because rabbit control in Australia has long been a biological arms race between the rabbits and the viruses that afflict them.

When myxomatosis was introduced to Australia in 1950 it initially cut a swathe through the millions of rabbits that were devastating Australian agriculture and damaging the natural environment. But its effectiveness gradually declined as surviving rabbits passed on their immunity to future generations. 


The next biological weapon was calicivirus, which escaped from its initial field trials on South Australia’s Wardang Island and spread rapidly across the country, where it initially reduced rabbit numbers to 10-15 per cent of their previous population.

The K5 strain of calicivirus is from Korea, but one strain of the disease showing even greater promise is RHDV2. It’s endemic in Europe and has entered America, where unfortunately it’s devastating native rabbit species across the country.

RHDV2 is already present in Australia and is proving particularly virulent against young rabbits. A combination of the RHDV2 and K5 is thought to be particularly effective because they affect rabbits at different life stages.

Arms race

The evolutionary arms race between virus and rabbits is never ending, however, and new biological controls are needed every 8 to 10 years.

Locally, Blackwood Biosecurity is carrying out the war on the hopping horrors and now is a good time to release it.

Pre-feeding them with oats is essential to encourage them to take the bait, which is oats laced with the virus.

The good news for landholders with one hectare or more is that Blackwood Biosecurity’s service is free. Smaller landholders pay a small fee.

Owners of pet rabbits need not fear the virus as long as they take their pets to a vet, because a vaccine to protect them from it is available.