Most people have been bitten by a mosquito at some time in their lives.
Usually this causes no more than an extremely itchy swelling which produces considerable discomfort for a day or so.
But mosquitoes can be the source of a number of serious illnesses. Some of the diseases spread through mosquito bites cannot be treated, and may produce long-term problems or even death.
Malaria is the most well known mosquito-transmitted illness. It is caused by a tiny parasite that lives inside the mosquito and is spread from person to person when the mosquito bites. It is spread only by a particular type of mosquito (the Anopheles mosquito) which is found in certain parts of the world. The most common symptoms of malaria are fever, headache, nausea, and muscle and joint pain. People living in, or visiting, places where the Anopheles mosquito is found can reduce the risk of malaria by taking tablets on a regular basis, and employing measures to avoid being bitten.
Other diseases spread by mosquitoes
There are a number of other less well-known diseases spread by mosquitoes. Several of these diseases can be contracted in Australia.
Ross River virus infection
Occurring widely in Australia, the Ross River virus is spread from animals to humans by several different types of mosquitoes. Although many people infected with this virus have no, or only slight, symptoms, other people may have a fever, joint pain and swelling and a rash. There is no specific treatment but medicines may be taken to help relieve the symptoms.
Barmah Forest virus infection
The Barmah Forest virus is also widespread in Australia and causes a similar illness to Ross River virus infection but the symptoms usually last for a shorter length of time. The virus is spread from animals to humans by mosquitoes. Again, there is no specific treatment for this infection, but medicines may be taken to help manage the symptoms.
Murray Valley encephalitis
Murray Valley encephalitis is a very rare disease involving swelling of the brain tissue. The disease is caused by infection with a virus that is spread by the bite of infected mosquitoes. The mosquito responsible is found throughout Australia and breeds in surface pools of water. Water birds, such as herons, are a natural reservoir of the virus. Most people infected with the Murray Valley encephalitis virus do not develop symptoms, but others may have high fever, severe headache, neck stiffness, irritability, seizures (or fits), and drowsiness. Immediate medical advice should be sought if you have these symptoms.
The mosquito responsible for transmitting the dengue virus is found in most tropical areas of the world, including north Queensland, Australia. The mosquitoes breed in containers that hold water and bite during the day, not mainly at dusk or evening like other types of mosquito. People infected with the virus may have no symptoms, but others may experience high fever, severe headache, muscle and joint pain, rash and extreme fatigue. In rare cases, dengue fever can be severe and even fatal. It is important to seek immediate medical advice if you suspect you have dengue fever.
Japanese encephalitis is an infection of the brain caused by a virus that is spread by infected mosquitoes. The mosquitoes become infected after biting pigs infected with the virus. Japanese encephalitis occurs in parts of Asia and Papua New Guinea. There have also been cases in north Queensland. Most infected people have no symptoms, but a small proportion may have severe symptoms, including headaches, high fever, convulsions and coma. There is no treatment, but a vaccine is available to protect against the infection in people travelling to, or resident in, areas where the virus is found.
Reducing the risk of mosquito bites
Because there is no specific treatment for many of the mosquito-borne diseases, and few vaccines or medicines available to prevent them, the best protection is to avoid mosquito bites. Measures to avoid being bitten by mosquitoes include:
- trying to stay indoors at dusk (when most mosquitoes do their biting);
- wearing light-coloured, long-sleeved shirts, long trousers and covered shoes at this time of the day;
- using effective insect repellents when outdoors;
- when camping, sleeping under a mosquito net;
- at home, screening doors and windows and removing containers that hold water where mosquitoes might breed; and
- using mosquito coils and zappers.
2. Queensland Health. Topic: Ross River virus [website]. Updated May 2010. http://access.health.qld.gov.au/hid/InfectionsandParasites/ViralInfections/rossRiverVirus_fs.asp (accessed Aug 2010).
3. Queensland Health. Topic: Barmah Forest virus [website]. Updated May 2010. http://access.health.qld.gov.au/hid/InfectionsandParasites/ViralInfections/barmahForestVirus_fs.asp (accessed Aug 2010).
4. Queensland Health. Mosquito-borne diseases. Updated Nov 2007. http://www.health.qld.gov.au/goodhealthintnq/topics/mosquito.asp (accessed Aug 2010).
5. Queensland Health. Topic: Murray Valley encephalitis [website]. Updated Jun 2010. http://access.health.qld.gov.au/hid/InfectionsandParasites/ViralInfections/murrayValleyEncephalitis_fs.asp (accessed Aug 2010).
6. Queensland Health. Topic: Dengue [website]. Updated Mar 2009. http://access.health.qld.gov.au/hid/InfectionsandParasites/ViralInfections/dengue_fs.asp (accessed Aug 2010).
7. Queensland Health. Japanese encephalitis [website]. Updated Apr 2010. http://access.health.qld.gov.au/hid/InfectionsandParasites/ViralInfections/japaneseEncephalitis_fs.asp (accessed Aug 2010).