Southern saltmarsh mosquito
Ochlerotatus camptorhyncus
Southern saltmarsh mosquito
Questions and Answers about the Southern saltmarsh mosquito 
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The Southern saltmarsh mosquito (Ochlerotatus camptorhyncus) appears similar to other mosquitoes to the untrained eye, but is distinctive in that it is an aggressive day-time daytime biter (unlike most other mosquitoes). This mosquito presents a biosecurity concern as it is known to carry the debilitating human illness Ross River virus. The virus produces severe flu-like symptoms in humans. There is no vaccine for this virus.
As its name suggests, the southern saltmarsh mosquito’s (SSM) preferred habitat is in saltmarshes. These are inter-tidal waterways where salty sea water mixes with fresh water, and they are commonly found in estuaries, sounds, drains and coastal areas where rivers meet the sea. SSM requires occasional floods to trigger egg hatching. It does not tolerate regular daily tidal flows.
SSM history in New Zealand
Following the first detection of SSM in Napier in 1998, the mosquito was subsequently identified and progressively eradicated from ten other coastal locations around the North Island, and in Wairau at the top of the South Island. The last adult mosquito was detected in Wairau in October 2006 and the last mosquito larvae were found in June 2008.
SSM was declared eradicated from New Zealand by Minister for Biosecurity, David Carter and Minister of Health Tony Ryall on 1 July 2010.
What success means
Had it not been successfully eradicated, SSM was likely to have had considerable impacts on human health, social and cultural wellbeing. The likely economic cost of this mosquito establishing permanently was estimated at over $120 million for direct health costs alone, not counting the impact on lifestyles, lost productivity, reduced tourism and the costs of mosquito control, screens and repellents.
The eradication programme
The eradication programme was started by the Ministry of Health when it was the government agency responsible for responding to biosecurity pests of public health significance. The programme was supported by considerable advice from international experts from Australia and the USA. Local councils, landowners, residents, iwi and hapu, environmental groups and other Government departments assisted in various ways with the eradication programmes in their areas.
In July 2006 responsibility for the programme was passed on to MAF Biosecurity New Zealand, the biosecurity division of the Ministry of Agriculture and Forestry.
Eradication methodology
Over the 11 years of the eradication programme, work involved helicopter and ground treatments, trapping and sampling. Treatment in infested areas was carried out every 21 days using s-Methoprene granules. Spraying with Bti (Bacillus thuringiensis israelensis) was used in instances where live larvae were found.
S-methoprene
S-methoprene is an insect growth regulator that stops mosquito pupae from hatching into adults. It is a solid granule; so it does not drift. The granules are coated with the active ingredient. S-methoprene is used against mosquitoes throughout the world. It has undergone a full health impact assessment in New Zealand. S-methoprene breaks down quickly and is considered to be environmentally safe for use in New Zealand.
Bti
Bti spraying has been used extensively in mosquito control programmes world wide. Bti has also undergone a full health impact assessment. It is not allergenic and has no reported impact on the environment.
Future Surveillance
From 1 July 2010, MAF Biosecurity New Zealand assumes responsibility from the Ministry of Health for the surveillance of mosquitoes that may be found in salt marshes around New Zealand. The programme will ensure that any new invasions of saltmarsh mosquito species are detected quickly. Early detection means eradication is more feasible as it can be carried out before any populations can become established, meaning the cost of eradication is kept as low as possible. The Ministry of Health remains responsible for mosquito surveillance at New Zealand’s ports and airports.
Link to Ministers' release on www.beehive.govt.nz 
Page last updated: 1 July 2010