Kaipara Harbour Mosquito Programme
6 August 2002
Kaipara Harbour Mosquito Programme
Public education on the Kaipara Harbour exotic mosquito programme has begun, as the Ministry of Health has been contacting local property owners, iwi, government agencies and regional and local authorities.
Associate Biosecurity Minister Marian Hobbs recently announced Cabinet had agreed to a $30 million four-year programme to eradicate the southern saltmarsh mosquito in the Kaipara Harbour area. The eradication will begin later this year.
Ministry of Health Public Health Programmes Manager Graeme Gillespie said the southern saltmarsh mosquito is a known vector of the Ross River virus and bites during the day.
"We have not had a case of New Zealand-acquired, mosquito-borne disease in this country and the eradication programme will help to keep it that way," said Mr Gillespie.
"Most of the treatment will be on private property and our contractors, New Zealand Biosecure, will be contacting the property owners to inform them about the programme before it begins."
The programme will involve several control techniques including the aerial and ground delivery of S-methoprene, an insect growth regulator that stops the mosquito pupae hatching into adults.
"S-methoprene has been proven to be very effective and we are confident it is environmentally safe. S-methoprene is not a spray and does not drift. The active ingredient of the product is coated onto sand granules and it is biodegradable. The mosquito is especially sensitive to this product and it is safe to handle," said Mr Gillespie.
"S-methoprene has been used against mosquitoes throughout the world and has undergone a full health impact assessment in New Zealand. Studies of the impact on non-target species where it has been applied in the Hawke's Bay have shown there has been no adverse impact."
The mosquito lays its eggs in tidal areas on vegetation just above the waterline. The eggs need to be wetted before hatching can be initiated. This requires a major weather event or a very high tide.
For more information
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What is Ross River virus? Ross River virus disease is known as epidemic polyarthritis (inflammation of the joints). Symptoms can be wide ranging, from pain and tenderness in the muscles and joints to flu-like symptoms of chills and fevers. Most people fully recover within a month of the onset of symptoms. No locally acquired cases of Ross River virus disease have been reported, however, people carrying Ross River Virus will be in New Zealand regularly (eg tourists or travelers returning from Australian states where Ross River Virus is endemic). Ross River virus disease can only be transmitted by mosquitoes, it cannot spread from person to person.
What is S-methoprene? S-methoprene is an insect growth regulator that stops the mosquito pupae hatching into adults. It has been used extensively overseas to control mosquitoes and has undergone a full health impact assessment. S-methoprene breaks down quickly in the environment and is believed to be environmentally safe for use in New Zealand. It is most effective for eradication programmes because it is a slow-release product that works over several days. Studies of the effect on 'non-target' species in Hawkes Bay have shown no impact.
What spray is currently being used to control the mosquito in Kaipara? Sites are being treated with the biological spray Bti - already being used in eradication programmes in Hawke's Bay and Tairawhiti. This product has been extensively used in control programmes in Australia, Africa, the United States and Germany. Bti has undergone a full health impact assessment and is not allergenic. It leaves no long-term residue but is not considered adequate to achieve eradication. It will continue to be used in some areas to supplement the use of S-methoprene along with some habitat management techniques to eliminate larval breeding sites.
When and where were mosquito larvae first found in the Kaipara area? Sampling was taken in the Kaipara Harbour area on 18 February 2001, nine days after heavy rain and high tides were reported in the area. On February 20, the Ministry of Health was told seven of the larvae found in the Rodney District of Kaipara Harbour were unconfirmed southern saltmarsh mosquito larvae. The samples were then sent to Australia for confirmation. Since then, adult mosquitoes have also been found in the area. After the larvae was discovered, surveying to find out the extent of their presence was carried out, followed by a control programme using the biological spray Bti. When the eradication programmes cease, there will need to be continued surveying to ensure that the eradication has been successful.
Where will the operation be carried out in the Kaipara Harbour area? The infested area in the Kaipara region is the largest incursion of the southern saltmarsh mosquito in New Zealand. The major area of eradication activity will be around the Kaipara coastline. A further two smaller eradication sites are in the Mangawhai and Whitford areas. The total area that may need to be treated is nearly 3000 hectares.
Have there been any other eradication programmes in New Zealand? Yes. A similar eradication programme has been running for three years in the Hawke's Bay and has been very successful. Napier, the first area in New Zealand where the exotic mosquito was discovered, has had no sign of these mosquitoes for two years.
How much funding did the Government allocate to controlling and eradicating exotic mosquitoes in 2001? $5-million was approved for spending over four years to eradicate the exotic mosquito in Napier, Gisborne, Mahia and Porangahau and to contain and control the spread of the mosquito in the Kaipara and Mangawhai areas. The Government has now decided that the response in the Kaipara area will move to full eradication and the other eradication programmes will continue as planned. The Government recently announced a further $30-million for the attempted eradication of the southern saltmarsh mosquito from Kaipara (and including Mangawhai and Whitford).