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Exotic Mosquitoes Found in the Coromandel

11 May 2006

Exotic Mosquitoes Found in the Coromandel

The national surveillance programme to identify incursions of salt marsh mosquito species has detected southern saltmarsh mosquitoes breeding at three discrete sites in a remote area of the Coromandel Peninsula, just north of Colville.

The findings were made by the saltmarsh mosquito surveillance teams that had deployed to the area following the recent heavy rainfall that has enhanced breeding conditions for salt marsh species.

“As soon as the samples were found a delimitation survey was commenced and breeding was confirmed at three very small sites”, said John (JR) Gardner, Deputy Chief Technical Officer (Health).

“The findings demonstrate the efficiency of the surveillance programme, but it is of course a real disappointment to find these mosquitoes here.” said JR Gardner “The next few days and weeks are important as this finding will be followed up by intensive surveys to clearly delimit the size of the incursion."

"We will also be responding by engaging with local stakeholders and conducting limited treatment of identified breeding sites to suppress the mosquito biomass. This will buy some time by containing the incursion whilst officials and technical experts analyze the collection data. Once all the information is processed the officials will develop options for dealing with this event that will meet the rigorous science based standards maintained throughout the programme.”

Mr Gardner said if anyone had seen unusual mosquitoes or had experienced unusual biting that they ring 0800 Mossie (0800 669943) to report this, or call the Ministry of Agriculture and Forestry exotic pest and diseases hotline 0800 809966.

-- mosquitoes

Background Information

Ochlerotatus (ochlerotatus camptorhynchus) formerly Aedes camptorhynchus is commonly referred to as the Southern Saltmarsh Mosquito (SSM) in Australia due to its distribution throughout the southern coastal portion of Australia. This mosquito was discovered in Napier in December 1998; Muriwai, Mahia and Porangahau in October and November 2000; and the Kaipara and Mangawhai harbours in February and April 2001 respectively. Sites were discovered at Whitford and Whangaporoaoa in 2002 and 2004 respectively. Further infestations were discovered in Wairau in 2005.

The mosquito is an aggressive biter with the potential to cause significant nuisance effects for people, livestock and birds and is a confirmed vector of Ross River Virus (RRV) in Southwest Western Australia. If the SSM mosquito population is left unchecked a future risk exists for the introduction of RRV to susceptible human populations with the potential for an epidemic of the disease.

If left unchecked and under favourable weather conditions the mosquito will colonise further areas of habitat with the potential for spread to other neighbouring harbours and to other parts of New Zealand.

Where were the mosquitoes found.
They were found in three sites just north of Colville on the Coromandel Peninsula. Mosquitoe larvae was found.

How big is the initial infestation area (size of area)
An initial survey is being conducted to determine the extent of the spread of the mosquito. At this point it is thought to be about 10 hectares

Why is it so important to do a survey of possible habitats.
It is only possible to identify breeding habitat when the site has been deluged with water. Some sites may need to be resurveyed following rain, rises in river levels or spring tides.

What monitoring has occurred in the area within the past two years.
Intermittent routine monitoring by the regional public health service has not detected the mosquito prior to this find.

What biosecurity efforts have been directed at preventing the spread.
At the moment efforts are being concentrated on determining the extent of the problems.

What should people do.
If people need to go into this area they should wear long loose clothing and use insect repellent to prevent getting bitten.

What is the lifeycle of the SSM
The mosquito life cycle has four stages, these being
Southern saltmarsh mosquitos lay their EGGS above the surface of the water and the eggs do not hatch until there is a water event such as spring tide or heavy rainfall to wet them.
The LARVAE hatch out and swim in water. The larval stage is when the mosquito is easiest to detect and is vulnerable to eradication measures
The PUPAE is the resting stage between LARVAE and ADULT.
The ADULT is the flying stage of the insects life cycle. Breeding and egg laying occur. An adult female SSM requires a blood meal before laying eggs. Adults can fly up to 5km from their breeding sites.

What is Ross River virus (RRV) disease.
Ross River virus disease is a viral infection that is endemic in Australia, and has affected people from Papua New Guinea, the Solomon Islands and some Pacific Islands. All cases that have so far been reported in New Zealand have acquired the infection from travel overseas.

What are the symptoms?
People infected by Ross River virus may develop a wide range of symptoms. Many people do not become ill but those who do may complain of pain and tenderness in muscles and joints. Joints most commonly affected are the wrists, knees and ankles. Flu like symptoms are also common and include fever, chills, sweating, a headache and tiredness. A rash may also occur on the trunk and limbs for a short time.

The symptoms may be similar to some rheumatic diseases and can only be diagnosed by a special blood test.

Symptoms occur three to 21 days (average nine days) after being bitten and may persist for months to years. The symptoms subside eventually and leave few or no after-effects.

Symptoms occur most commonly in adults. The disease is usually milder and runs a shorter course in children.

How is it spread?
The only way that people can catch Ross River virus is by being bitten by a virus-carrying mosquito. The virus cannot be spread from person to person.

A number of different mosquitoes can spread the virus to humans. The mosquito has been shown to transmit Ross River virus disease in Australia but there is no evidence that this has occurred in New Zealand.

How is Ross River virus treated?
Treatment is aimed at relieving symptoms. Your doctor may recommend rest and pain-killers, like aspirin or paracetamol to relieve the pain and swelling of joints. Sometimes stronger medications are required to ease the inflammation.
Most people fully recover within a month of the onset of symptoms but these can last for longer and be quite severe.

How can infection be prevented?
Ross River virus is not contagious. If people can avoid being bitten by mosquitoes, they cannot get infected.
There are a number of things people can do to avoid mosquito bites:
- wear loose fitting clothing that covers the skin as much as possible - mosquitoes can bite through tight clothing - and avoid dark colours which attract mosquitoes.
- use an effective insect repellent when outdoors. A repellent that contains the chemical DEET (diethyl toluamide) or DIMP (dimethyl phthalate) is recommended.
- doors and windows can be screened to stop mosquitoes from getting inside
- aerosol sprays and mosquito coils may be used indoors


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