Mosquitoes to watch out for

Mosquitoes which have previously arrived at New Zealand borders by means such as shipping containers include the Asian tiger mosquito and the Southern saltmarsh mosquito. Both could spread disease if they became established here. An eradication programme was carried out when the Southern saltmarsh mosquito was found in coastal areas, and it was declared eradicated in 2010. However, the threat of exotic mosquito species finding their way into New Zealand remains, and biosecurity measures and surveillance are ongoing.

Mosquitoes resident in New Zealand

New Zealand has 12 native (endemic) mosquito species and another four "exotic" (ie, introduced) species. In fact, three exotic mosquito species (Aedes notoscriptus, Culex quinquefaciatus and Aedes australis) have been here so long, they are now considered endemic but remain potential carriers of disease (a carrier is known as a vector).

New Zealand mosquitoes as vectors

Aedes notoscriptus (first collected here in 1916 and probably accidentally imported from Australia) and Culex quinquefaciatus (native to warmer parts of the Americas and collected here prior to 1848) are vectors for Ross River virus and Murray Valley encephalitis. Both are found in warmer climates of the North Island and have been reported in Nelson.

Aedes australis (first found on Stewart Island in 1961 and also found in the southern-most parts of the South Island) has the potential to transmit Ross River virus.

Asian tiger mosquito

The Asian tiger mosquito (Aedes albopictus), is a prime vector for Ross River virus, yellow fever, dengue fever and possibly other diseases. A permanent resident visa for this mosquito would be an unwanted occurrence as its performance as a vector is so much better than the other endemic species.

In 2007 a single Asian tiger mosquito was found at the Ports of Auckland as part of a routine mosquito surveillance programme. Further surveillance was carried out, as well as treating mosquito habitat within a 1km area and using mosquito traps, but no further Asian tiger mosquitoes were detected. 

In December 2011 the Asian tiger mosquito (Aedes albopictus) and a second species Culex quinquefasciatus were discovered on a ship docked at Auckland Port. The ship had come from Vanuatu and docked in Tauranga prior to Auckland. The discovery was made by Ministry of Agriculture and Fisheries (MAF) staff during routine biosecurity checks and all mosquitoes detected on the ship were treated and killed. The species Culex quinquefasciatus is already present in New Zealand and is mostly considered a nuisance pest at present, but the Asian tiger mosquito is of particular concern.

The Ministry of Health (MOH) advised, in a media release dated 8 December 2011, that checks of the vicinity were made and traps set locally in both ports. Sally Gilbert, the MOH’s manager of border and environmental health says, "Border health protection officers are maintaining close surveillance around the areas and are conducting further searches for mosquitoes.”

Public hotlines to report exotic pests

In addition, the MOH requests [Dec 2011] anyone living or working in the vicinity of the Auckland or Tauranga wharves who notices any mosquito activity such as insect biting or ‘wrigglers in pooled water’ should contact the hotline 0800 MOZZIE or 0800 669 943.

Biosecurity agencies ask that cargo handlers and members of the public who note anything unusual on imported goods to "see it, contain it and report it''.  This could mean closing off the vehicle, container, package or room, and reporting it to the MAF exotic pest hotline 0800 80 99 66.

Southern saltmarsh mosquito

The Southern saltmarsh mosquito, Aedes camptorhynchus, is a competent vector of Ross River virus and was the most recent exotic to take up temporary residence here [see below]. The main concern about the arrival of these more potent vectors is their effect on the endemic mosquito species' potential to carry the viruses.

Eradication programme declared a success

After the Southern saltmarsh mosquito was detected in New Zealand in 1998 (in Napier), it was subsequently found in 10 other coastal locations in the North Island and one in the South Island (Wairau). An extensive eradication programme was carried out, at a cost of approximately $70 million over an 11-year period. The Southern saltmarsh mosquito was declared eradicated from New Zealand by Minister for Biosecurity, David Carter, and Minister of Health, Tony Ryall, on 1 July 2010.

Ongoing surveillance

From 1 July 2010, MAF Biosecurity New Zealand assumed responsibility from the Ministry of Health for the surveillance of mosquitoes that may be found in salt marshes around New Zealand. The Ministry of Health remains responsible for mosquito surveillance at New Zealand's ports and airports.

While the eradication of the Southern saltmarsh mosquito from New Zealand has been confirmed, MAF Biosecurity NZ requests the public to report any suspected future sightings of this mosquito by phoning 0800 80 99 66. This number also applies to report suspected exotic disease or pests in animals, plants, fish or bees. The Southern saltmarsh mosquito is an aggressive daytime biter and its preferred habitat is inter-tidal waterways where salty sea water mixes with fresh water.

Also see: Diseases spread by mosquitoes

Exotic mosquito species known to have landed in New Zealand

New Zealand has had a visit from around 15 other species, some shipped in dead, others landing for a brief period before being discovered and killed (some of these are listed below).

What's a vector? In medicine, vector means carrier. In this case, certain tyes of mosquito have the ability to carry different viruses to greater or lesser degrees.

Vector: Aedes camptorhynchus (S. saltmarsh mosquito - a daytime biter)
Disease: Ross River virus, possibly Barmah Forest virus

Vector: Culex annulirostris
Disease: Ross River virus, Barmah Forest virus, Murray Valley encephalitis, Japanese encephalitis

Vector: Aedes albopictus (Asian tiger mosquito)
Disease: Dengue fever, Japanese encephalitis, Ross River virus, yellow fever and numerous others

Vector: Aedes Japonicus (Rock pool mosquito)
Disease: Japanese encephalitis

Vector: Aedes aegypti (Yellow fever mosquito)
Disease: Dengue fever, Ross River virus, Barmah Forest virus and yellow fever

Aedes polynesiensis, Ochlerotatus vigilax, Culex gelidus and Culex pipiens pallens have also been found arriving in New Zealand and can carry one or more of the diseases mentioned.

Photos

The Medical Entomology Department, University of Sydney has an extensive online collection of mosquito photos. 

Related topics

See also Mosquitoes - the threat of new disease in NZ

Mosquitoes - how could a disease outbreak occur in NZ?

Original material provided by New Zealand Doctor magazine, February 2004. Reviewed and edited by everybody, December 2011.