First Reports On Mosquito Response Positive

The rapid response to the discovery of the southern saltmarsh mosquito appears to have been effective, said Ministry of Health spokesperson Graeme Gillespie.

Treatment began on Friday near Whitford after the southern saltmarsh mosquito was identified as part of the routine surveillance programme.

"Early indications have been promising. Of the 17 sites surveyed on the ground, only three sites within an area of less than one hectare were found to have larvae identified as being from the southern saltmarsh mosquito," said Mr Gillespie.

"These sites have been treated with s-methoprene, an insect growth regulator that stops the mosquito pupae hatching into adults.

"The aerial survey of sites with potential mosquito habitat also produced promising results. None of the 20 sites surveyed between Miranda and Whitford, or the two sites checked on Waiheke Island, showed any evidence of larvae from the southern saltmarsh mosquito."

Mr Gillespie said the response to the initial finding was very quick and effective.

"The team working on the operation is very experienced and there has been excellent co-operation between all parties involved."

Extensive efforts were made to contact affected landowners and close neighbours before treatment began. Consultation has occurred with the Department of Conservation, Whitford Residents and Ratepayers' Association, Auckland Regional Council, and Manukau City Council environmental staff being notified of the treatment programme. Consultation with other interested groups is underway.

"Trapping for adult mosquitoes will continue this week. This will tell us if any adults have emerged from the larval population found last week and show us what impact the treatment has had on the mosquito population. The results of the adult trapping are needed to enable future work planning."

The southern saltmarsh mosquito, Ochlerotatus camptorhynchus, can spread Ross River virus disease.

For more information contact: Zoe Priestley Media Advisor ph: 04-496-2483
http://www.moh.govt.nz/media.html

BACKGROUND

Why is it important the initial survey is completed within 48 hours before any larvae that may have hatched following the recent king tide become pupae? The mosquito life cycle has four stages, these being The EGGS are laid in water. Southern saltmarsh mosquitos lay their eggs above the surface of the water and the eggs do not hatch until there is a king 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 pupa is difficult to detect The ADULT is the flying stage of the insects life cycle. Breeding and egg laying occur. An adult female southern saltmarsh mosquito requires a blood meal before laying eggs.

What is s-methoprene? S-methoprene is an insect growth regulator that stops the mosquito pupae hatching into adults. It is not a spray and does not drift. Sand granules are coated in 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 in the environment and is believed to be environmentally safe for use in New Zealand. Studies of the impact on non-target species where it has been applied in the Hawke's Bay have shown no impact.

What is Ross River virus (RRV) disease? Ross River virus disease is a viral infection which has been reported from Australia, as well as 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 recently discovered in Napier has been shown to transmit Ross River virus disease in Australia but there is no evidence that this has occurred yet, 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 check your home and garden for areas where mosquitoes can breed, such as garden rubbish or blocked gutters and drains which hold water and ensure that these are kept dry.

For further information concerning Ross River virus disease prevention contact your local public health service.

How much funding did the Government allocate to controlling and eradicating exotic mosquitos in 2001? There has been $5-million approved for spending over four years to eradicate the exotic mosquito in Napier, Gisborne, Mahia and Porangahau and to contain and control the spread of the mosquito in the Kaipara and Mangawhai areas, as phase one of a possible eradication programme.

Zoe Priestley Media Advisor Communications Corporate & Information Directorate Ministry of Health DDI: 04 496 2483 Fax: 04 496 2010

http://www.moh.govt.nz mailto:zoe_priestley@moh.govt.nz

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