20 May 2004

Want to be a human mosquito trap? Let the Public Health Unit know if you are being bitten by mosquitoes

Hawke’s Bay District Health Board’s public health unit is making a special plea to the public, and especially those such as duck shooters, farmers, and others who visit and spend time in swampy areas close to the coast to let them know if they are being pestered by biting mosquitoes.

This request comes in light of the recent discovery of the Southern Saltmarsh Mosquito at the Wairau Lagoons, close to Blenheim in the South Island. This aggressive day-biting mosquito, known to transmit Ross River fever in Australia, was brought to the attention of authorities by duck shooters and vineyard workers who were being bitten by them. The Southern Saltmarsh Mosquito’s habitat is saltmarshes and drains with a coastal saline (sea water) influence.

The Southern Saltmarsh Mosquito was first discovered in New Zealand at Napier and Haumoana/East Clive in late 1998-early 1999, after complaints about mozzie bites from residents were received by the Public Health Unit, and the Napier City Council.

This was the first discovery of the mosquito in New Zealand and ultimately resulted in a Ministry of Health eradication plan being put into place. The plan was implemented by the Public Health Unit in 1999. Since then the mosquito has also been found in Hawke’s Bay at Mahia, and Porangahau, and outside Hawke’s Bay at Gisborne, Kaipara, Mangawhai, Whitford, and Whangaparoa. Eradication programmes have been put in place at all these sites.

The Napier, Haumoana/East Clive, and Mahia areas were declared eradicated of the Southern Saltmarsh Mosquito, under the World Health Organisations eradication criteria in July 2002, and September 2003 respectively. The Porangahau area will likewise be declared eradicated in September this year should no more larvae/pupae or adult Southern Saltmarsh Mosquitoes be found by the Ministry of Health’s contracted eradication team, New Zealand BioSecure.

Once deemed eradicated from an area it is handed back to the local Public Health Unit for on-going post-eradication surveillance. The Public Health Unit, Napier currently undertakes such surveillance in Napier, Haumoana/East Clive and Mahia.

The surveillance is timed around tide and rainfall events, as rising water levels cause the eggs to hatch. Surveillance takes the form of a combination of trapping adult mosquitoes and taking water samples from saltmarsh waters.

The major attractant for adult mosquitoes is the carbon dioxide ‘plume’ that humans and animals exhale in our breath, therefore the adult traps work by mimicking this plume.

“There is nothing like the real thing to a mosquito though and this is why we are keen to get the “let us know if you are being bitten” message out to the public, and especially those who spend time in the saltmarsh habitat,” said Noel Watson, Health Protection Officer.

If you have any information, or even better, are able to capture some of the mosquitoes in a container, then we would be very keen to hear from you. You can call the Public Health Unit on (06) 834-1815.

ENDS

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