Some invasions of Australian mosquitoes have been eradicated on parts of the North Island's east coast, but biosecurity officials are still facing problems in the Kaipara region.
Associate Biosecurity Minister Marian Hobbs yesterday warned that the eradication battle was not over.
The Government is spending $30 million to combat the southern saltmarsh
mosquito which established itself at Napier in 1998, and has since spread to Gisborne, Mahia, Porongahau, Kaipara and Mangawhai.
The variety is a particularly aggressive daytime-biting mosquito and is a carrier of the debilitating Ross River virus.
Authorities fear a "virgin soil epidemic" if a mosquito picks up the virus from an infected Australian tourist because the disease would quickly get into animal populations and severely damage the economy.
Ross River virus is not fatal, but it can cause a disease known as epidemic polyarthritis, which can cause chronic fatigue for up to a year.
An estimate done in 2001 put the cost to the taxpayer of an outbreak in Auckland alone at more than $38 million.
Ms Hobbs said no adults or larvae of the saltmarsh mosquito had been detected in the Mahia Peninsula for two years and it was now officially regarded as eradicated from there and Napier. But spraying continues in nearby Porongahau, the last remaining Hawkes Bay site where the mosquito has been detected.
This area is expected to be cleared in August and Tairawhiti cleared a month after that.
In the Kaipara region, where the mosquito has spread into a potential habitat of 2700ha, the mosquitoes are under a two-pronged attack from spreading of an insect growth regulator and the spraying a bacterial agent.
A base has been built in the region with a helicopter landing pad, screening laboratory and operations centre.
Sampling sites have been established around Kaipara, at 31 locations. They are visited twice weekly and sampled for adults and larvae. Only single adults were found in August and September checks and no adults were found in October.
Ross river virus
* The disease can be spread only by specific mosquito species.
* It can cause symptoms such as pain and tenderness in muscles and joints, fever, chills, sweating, a headache and tiredness
- NZPA
Herald Feature: Conservation and Environment
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