Unwanted mosquito suspected in Central Hawke's Bay

3 November 2000

Southern saltmarsh mosquito suspected in Central Hawke's Bay

The discovery of mosquito larvae and an adult mosquito in Porongahau, Central Hawke's Bay suspected to be the southern saltmarsh mosquito, has prompted an extensive survey from Cape Kidnappers in Hawke's Bay to Cape Palliser in Wairarapa.

Three larvae and one adult mosquito were found yesterday at two small sites near the Porongahau Estuary - approximately 85 kilometres south of the most southerly positive southern saltmarsh mosquito site in Hawke's Bay. The samples have been sent to Australia for official confirmation.

Chief Technical Officer (Health) Dr Lynne Lane said the early discovery vindicates the national surveillance programme which has been in place since the mosquitos were first identified in Hawke's Bay in December 1998. Surveillance measures were enhanced last month following the discovery of mosquitos in Gisborne.

Dr Lane said to date, the surveillance programme has been based on the fact that the southern saltmarsh mosquito, Aedes camptorhynchus, has a 5 kilometre flight range and the potential locality to ports and airports.

"However, the suspected find at Porongahau which is 85 kilometres south of the most southern positive site in Hawke's Bay, and the fact Porongahau has no port or airport raises questions as to how it may have arrived.

"Wind dispersal could be a factor, and as a result the Technical Advisory Group to the Ministry of Health has recommended an extensive survey between Cape Kidnappers and Cape Palliser to identify potential breeding sites.

"Samples will also be taken, however some potential breeding sites may have dried up recently due to the warm weather. As a precaution, additional sampling will occur after the next heavy rainfall to determine if there is any new evidence of the mosquito."

Dr Lane said in the meantime, the eradication programme in Napier will continue, as will the containment programme in Gisborne. Sites in the Porongahau area returning positive samples will be treated until there is sufficient information to make a decision on future management of the mosquito.

END

For more information contact: Selina Gentry, Media Advisor, ph: 04-496-2483 or 025-277-5411 Internet address: http://www.moh.govt.nz/media.html

Background Information

The southern saltmarsh mosquito has been declared an unwanted organism in New Zealand. In Australia it is thought to be the main carrier of the Ross River Virus. To date there have been no confirmed cases of Ross River Virus in Napier or Gisborne.

An eradication programme is currently underway in Napier, Hawke's Bay. It is estimated that this will cost approximately $6-million over four years. A treatment programme is underway in Muriwai and Sponge Bay in Gisborne. This involves ground spraying any sites returning positive samples, as well as disinsection of all aircraft departing Gisborne.

Selina Gentry Media Liaison Communications DDI: 496 2483 Fax: 496 2010 mailto:selina_gentry@moh.govt.nz Ministry of Health

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