Mosquito-born Diseases

Malaria Fact Sheet 

 Background

Malaria is a parasitic disease caused by one or more of four Plasmodium species – P. vivax, P. falciparum, P. malariae and P. ovale. Of the four types of malaria, P. falciparum is the most severe and can result in death in up to 10% of cases. The other types of malaria are generally non-fatal unless the patient is very young, very old, is suffering from other illness. The disease is transmitted between humans by an infected female Anopheles mosquito.

Many thousands of tourists become ill with malaria each year either during their travel, or during the incubation period of 7 and 30 days, after they return home from a malarious area. The illness is characterised by malaise, fever, chills, headache, rising temperature, nausea and profuse sweating. These symptoms may cease only to recur within several days.The incidence and severity of malaria worldwide is increasing and its prevention and treatment is becoming more difficult due to resistance of the parasites to currently available drugs.

Occurrence

Tropical and sub-tropical areas including South & Central America, SE Asia, Asia, the eastern Mediterranean and the Western Pacific. Particularly high-risk areas are found in South America, SE Asia, sub-Saharan Africa and the Western Pacific islands of Papua New Guinea, Vanuatu, and the Solomon Islands. Malaria is rarely present in highly urbanised areas of cities, except on the outskirts near rural areas.

Treatment

Primary treatment is the administration of antimalarial drugs. There is no vaccine available for malaria. You should seek medical advice at the first sign of a fever as early treatment is essential in cases of P. falciparum malaria.

Avoidance

The main way to minimise the risk of malaria infection is to avoid being bitten by mosquitoes through the application of measures such as wearing loose fitting long sleeved clothing, applying personal mosquito repellent to exposed areas and living in mosquito proof accommodation or using a mosquito net over your bed. The Anopheles mosquito is mainly active between sunset and sunrise It is also essential to take appropriate antimalarial drugs strictly in accordance with the prescriber’s instructions. However, no antimalarial drug regime gives complete protection against the disease.

Quarantine measures

Malaria is not a quarantinable disease in Australia. However, as Anopheles mosquitoes are present in many parts of Australia, particularly in northern Australia, action may be taken by public health authorities to minimise the risk of the spread of malaria in local communities when the disease is diagnosed in an overseas traveller and vector populations are significant.

(Table taken from World Health Organisation http://www.wpro.who.int/sites/mvp/data/malaria/2008.htm)

Yellow Fever Fact Sheet

What is yellow fever?

Yellow fever is a viral disease of short duration and varying severity that is transmitted primarily by mosquitoes. The infection is so named because of the yellow skin colour (known as ‘jaundice’) observed in people with a serious case of yellow fever infection.

What are the symptoms of yellow fever?

Symptoms of yellow fever can be mild but often increase in severity with the sudden onset of fever, muscle pain, nausea, vomiting, headache and prostration. The disease may progress to visible haemorrhage (bleeding), jaundice (yellowing of eyes and skin), and kidney and liver failure. The death rate in unvaccinated people who contract yellow fever may be as high as 50 per cent.

How do humans become infected with yellow fever virus?

Yellow fever is transmitted to humans by the bite of infected mosquitoes from a variety of species, principally the Aedes and Haemagogus species. The disease occurs in two forms – urban and sylvatic (jungle) yellow fever. Both forms are caused by the same virus.

In jungle and forest areas, monkeys are the main reservoir of infection, with transmission from monkeys carried out by mosquitoes. The infective mosquitoes may bite humans who enter the forest area, usually causing sporadic cases or small outbreaks. In urban areas, monkeys are not involved and infection is transmitted among humans by mosquitoes.

The symptoms may take 3-6 days to appear. Human blood is infectious to mosquitoes shortly before the onset of fever and for the first 3-5 days of the illness. Some infections do not cause symptoms, but most lead to acute illness characterised by two phases. In the first phase there is a sudden onset of fever, muscle pain, nausea, vomiting, headache and prostration. About 15-25 per cent of those with yellow fever progress to the second phase (visible haemorrhage, jaundice, kidney and liver failure) of which half die within 10-14 days after onset of illness.

How can people protect themselves against contracting yellow fever?

By getting vaccinated

Yellow fever is preventable by a safe and effective (approaching 100 per cent) vaccine. With few exceptions, vaccination is recommended for all travellers to countries or areas where there is a risk of yellow fever transmission.

By taking mosquito avoidance measures

The mosquitoes that transmit yellow fever are usually active during the daylight hours. All who travel to or live in yellow fever endemic countries are advised to take mosquito avoidance measures such as using insect repellents, coils and sprays; using mosquito nets (preferably those that have been treated with an insecticide); and ensuring adequate screening of residential premises.

How is yellow fever infection treated?

 There is no specific treatment for yellow fever, though medicines can be used to relieve the symptoms, and this may improve the outcome for seriously ill patients.

Does yellow fever occur in Australia?

Yellow fever is not prevalent in Australia, but mosquitoes (Aedes aegypti) that can transmit the disease are common in the coastal regions of northern Queensland.

What is the occurrence of yellow fever worldwide?

The World Health Organization (WHO) closely monitors reports of yellow fever infection. Yellow fever is considered to be endemic in 32 African and 13 Central and South American countries.

Australia’s list of yellow fever declared places has been updated to include 24 new countries and the Misiones Province of Argentina. The update will ensure that the list correlates with the World Health Organization’s list of yellow fever endemic countries and takes into account recent outbreaks of yellow fever in South America. The new list will take effect on 1 August 2009 and is provided below:

Table

 
Africa South America & Central America
Angola* Guinea-Bissau Argentina – Misiones Province
Benin* Kenya Bolivia*
Burkina Faso* Liberia* Brazil*
Burundi Mali Colombia*
Cameroon* Mauritania Ecuador excluding Galapagos Islands*
Central African Republic Niger French Guiana*
Chad Nigeria* Guyana
Congo, Democratic Republic of the* Rwanda Panama
Congo, Republic of the Sao Tome and Principe Paraguay
Cote d’Ivoire (Ivory Coast)* Senegal Peru*
Equatorial Guinea Sierra Leone* Suriname
Ethiopia Somalia Trinidad and Tobago
Gabon* Sudan* Venezuela*
Gambia* Tanzania  
Ghana* Togo  
Guinea* Uganda  

(* Denotes countries which are already included in Australia’s list of declared yellow fever places.)

Dengue Fever Fact Sheet

What is dengue fever?

Dengue fever is a viral disease transmitted to humans through the bite of an infected mosquito, usually Aedes aegypti. There are four distinct dengue virus strains. 

What type of illnesses does Dengue cause?

Dengue fever (also known as Break Bone Fever) usually causes the sudden onset of high fevers, severe frontal headache, and strong joint and muscle pains. Often there seems to be a partial recovery after 1 to 2 days before symptoms return. Many people also suffer nausea, vomiting, and rash. The rash appears 3 to 5 days after onset of fever and can spread from the torso to the arms, legs, and face.

The illness typically starts from 4 to 7 days after a person is bitten by an infected mosquito, but it can sometimes take up to 14 days for symptoms to appear.

Can dengue cause more severe illness?

Dengue infection occasionally causes a more severe and potentially life-threatening illness associated with bleeding (Dengue Haemorrhagic Fever/DHF) and or a sudden loss in blood pressure (Dengue Shock Syndrome/DSS).

The risk of these more severe types of dengue infection are more likely if someone has had a previous dengue infection with a different strain. International travellers from non-endemic areas such as Australia are generally at low risk of DHF or DSS.

How do humans become infected with dengue virus?

The main mosquito vector for dengue, Aedes aegypti, becomes a carrier of the dengue virus through biting an infected person. It can then pass the infection on to other people it bites.

This mosquito is most frequently found in or near homes and prefers to feed on humans during the daytime. It has two peak periods of biting activity: in the morning for several hours after daybreak and in the late afternoon for several hours before dark. The mosquito may feed at any time during the day, however, it prefers to feed indoors, in shady areas, or when it is overcast.

Aedes albopictus, a mosquito common in south-east Asia and Papua New Guinea, can also be an important dengue vector.

Where does dengue virus occur?

Dengue is a rapidly expanding disease and is now endemic in most tropical countries of the South Pacific, Asia, the Caribbean, the Americas, and Africa, including urban areas.

Dengue fever is not an endemic disease in Australia but cases are confirmed every year in travellers returning to Australia after visits to dengue-endemic tropical and subtropical areas. Over the last twenty five years, local outbreaks of dengue fever have occurred in north Queensland as a result of infected travellers being bitten by an Aedes aegypti mosquito which then spreads the infection to others in the local community.

It is therefore important to rapidly identify and protect any person with dengue fever in an area where the Aedes aegypti mosquito occurs to prevent local spread.

How is dengue fever treated?

No specific treatment for dengue fever is available. Patients are encouraged to rest and drink plenty of fluids, while paracetamol may be used to relieve fever and aches. Aspirin and non-steroidal anti-inflammatory medicines (such as naproxen or ibuprofen) should be avoided because of their anticoagulant properties.

Infected persons should be protected from further mosquito exposure by staying indoors and sleeping under a mosquito-proof net during the first few days of illness so that they can avoid contributing to the cycle of dengue infection.

What can people do to prevent becoming infected with dengue virus?

There is no vaccine or preventive drug that provides protection against dengue infection. The best way to avoid dengue virus infection is to prevent mosquito bites, particularly during the day.

While most mosquitoes are more active during dusk and night time, Aedes aegypti mosquitoes are daytime biters so precautions against being bitten should also be taken during the day.

Travellers and residents in dengue-prone areas should take the following precautions to reduce their risk of dengue infection:

  • apply insect repellent containing a DEET (diethyl toluamide) on exposed skin;
  • wear long sleeves and pants (ideally treat clothes with permethrin or another repellent);
  • ensure screens on windows and doors are secure and keep mosquitoes out; and
  • remove mosquito breeding sites from around the home.

Mosquitoes can breed in almost any standing water around the home. Common mosquito breeding sites include discarded tyres, uncovered barrels, buckets, flower vases or pots, cans, and cisterns.

(Image taken from World Health Organisation http://www.wpro.who.int/health_topics/dengue/)

Fact sheets taken from Australia’s Department of Health and Ageing

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One response to “Mosquito-born Diseases

  1. Pingback: News article « UQ students design product to eradicate mosquito problem

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