Mosquitoes & Arboviruses

Mosquitoes

Please take extra care when outdoors due to the massive increase in mosquito borne infections.

Water is an important component of human lifestyle and economy, but unfortunately it is also important for mosquitoes to complete their life cycles.

There are many species of mosquitoes, but the ones that are considered pests are the species that suck blood. With these species, the female requires a blood meal to gain the protein required to lay eggs. The itching sensation often experienced with mosquito bites can cause restless sleep, inflammation and infection.

However, the major problem with mosquitoes is not so much the annoyance of itching after being bitten my them but their role in the transmission of diseases. Mosquitoes themselves do not cause disease but act as a 'vector' in the transmission of disease between vertebrate hosts. The diseases spread include filarial worms (a type of nematode), malaria, and arboviruses. Of these, arboviruses (a type of virus that lives in insects like mosquitoes and is passed onto humand through insect bites) are of the most concern in Australia, and the most common in the Riverina region is the Ross River Virus. See below for more details on arboviruses.

It is therefore important to minimise contact with mosquitoes to avoid catching these diseases.

How to avoid getting bitten by mosquitoes:

Avoid going outside when mosquitoes are around - mosquitoes are most active just before dusk and two hours afterwards. In coastal regions they may also be active during the day.
Cover up and wear light-coloured, long, loose fitting clothing. Mosquitoes are attracted to dark colours and can bite through tight clothing.
Use a repellent - especially at high risk times. However, do not use repellents for prolonged periods and only use sparingly on children. Keep repellent away from the eyes and mouth, and follow the instructions on the label.
Ensure that all windows, doors, chimneys, vents and other entrances are covered with a suitable insect screen.

Creating a mosquito-free zone at home:

Eliminate sources of still water where mosquitoes can breed.
Dispose of all tins, tyres and other rubbish containers that may hold water.
Don’t let water sit in pot plant saucers - empty them once a week or use sand in the saucer to absorb excess water.
Keep pools chlorinated or salted at recommended levels or empty them when not in use for prolonged periods. This includes children’s paddling pools.
Overturn boats and dinghy's or remove the drain plug when not in use so that they do not hold water.
Ensure children's play equipment such as swings and tyres have holes drilled in them to drain water.
Keep ponds stocked with fish. Fish like to feed on mosquito larvae.
Keep gardens maintained so they do not provide shelter for adult mosquitoes.
Ensure water tanks are screened to prevent mosquitoes laying their eggs or the adults escaping.
For more information download the Better Health brochure on Mosquito Control Around the Home

Take a look at this NSW Health flyer for more information on mosquitoes and taking precautions against them.

Creating a mosquito-free zone on the farm:

Keep dams, irrigation channels and ground pools free of vegetation.

Check dam walls and irrigation bays for water leaks.
Be careful not to over-irrigate and avoid water from collecting in low lying areas such as table drains and potholes for long periods of time.
Ensure water does not collect in disused machinery, water troughs or tyres.
Keep water pipes in good repair and avoid leaks.
Keep septic systems well maintained.
In rice fields, avoid creating shallow water areas and control weeds around the edges.

For more information, see the University of Sydney website on irrigation and mosquito control.

Arboviruses

Arboviruses are a type of virus that lives in insects like mosquitoes and is passed onto humand through insect bites. The most common occurring arboviruses in New South Wales are Ross River Virus, Murray Valley Encephalitis, Barmah Forest Virus, and Kunjin Virus. All are notifiable diseases.

Ross River & Barmah Forest Virus

Most commonly occurs during summer and autumn.
Symptoms may include fever, rashes, and arthritis.
No fatalities have been recorded from these diseases.
Symptoms may last from several weeks to several months or years resulting in reduced productivity and reduced quality of life.
Diagnosis is by blood test.
There is no specific cure or vaccine available.
For more information see the Ross River & Barmah Forest website.

Murray Valley & Kunjin Encephalitis

Outbreaks often linked to extreme rainfall and flooding.
Symptoms may include a sudden onset of fever; anorexia and headache are common, while vomiting, nausea, diarrhoea and dizziness may also be experienced.
Severe cases may include lethargy, irritability, drowsiness, confusion, convulsions and fits.
May result in coma and death.
Diagnosis is by blood test.
There is no specific cure or vaccine available.
For more information see the Murray Valley & Kunjin Encephalitis website.

Vector-borne diseases

Japanese encephalitis

Most people who get Japanese encephalitis do not have any symptoms.

Some people may get symptoms such as:

fever
headache
vomiting

People with a severe infection (1 in every 250 people) may get symptoms such as:

neck stiffness
disorientation
tremors
coma
seizures
paralysis

If you get any of these symptoms contact a doctor right away, or in an emergency call Triple Zero (000) or visit your nearest emergency department.

Among those who get a serious illness, some may have lifelong neurological complications or even death.

If you get symptoms, they can appear 5 to 15 days after getting bitten by infected mosquitoes.

More information available here:

NSW Arbovirus Surveillance & Vector Monitoring Program

This program monitors mosquito populations around the state during their breeding season. Griffith is currently monitored as part of this program. There are two parts to the testing. One is the collection of mosquitoes and establishing population numbers. The other part is the use of 'sentinel chickens' whose blood is tested on regular intervals for the presence of Murray Valley encephalitis and Kunjin as well as some other viruses. These results alert NSW Health to any increasing number in mosquito numbers or the occurrence of diseases. The results and further information are available from NSW Health’s Arbovirus Monitoring site.

For more information about Council's NSW Arbovirus Surveillance and Mosquito Monitoring Program please contact the Environment and Health Department on 1300 176 077.