Malaria

Malaria is an parasitic disease transmitted by Anopheles mosquitoes.

There five types of parasites that cause malaria, such as:

• Plasmodium ovale
• P. malariae
• P. knowlesi
• P. vivax
• P. falciparum.

The last two are the most common.

Where it's found

Malaria is found throughout the tropical and subtropical regions of the world.

Areas of high transmission are found predominantly in rural areas in:

• South America (e.g. Brazil)
• south-east Asia (e.g. Thailand, Indonesia and East Timor)
• Western Pacific (Papua New Guinea, Solomon Islands and Vanuatu)
• sub-Saharan Africa.

Australia was declared free of malaria by the World Health Organisation (WHO) in 1981.

The last case of locally-acquired malaria in the NT was in 1962.

However, Anopheles mosquitoes do exist in the NT so it could be re-introduced if infected overseas travellers are bitten here.

Malaria could become established anywhere in the Top End, down to a latitude of 19 degrees which is just north of Tennant Creek.

Symptoms

Symptoms appear about 9 to 14 days after a bite from an infected mosquito, and coincide with the rupture of the red blood cells.

They are often delayed in people who have lived in malarious areas and who may have developed some immunity.

Typically malaria produces:

• sudden fever
• rigors (shakes)
• sweating
• headache
• vomiting
• other flu-like symptoms.

Sometimes, there is a 2 or 3-day period of reduced symptoms before a recurrence on the third or fourth day.

If untreated, infection can progress rapidly and become life threatening.

Malaria can kill by destruction of red blood cells (anaemia) and by altering the function of vital organs.

These organs include the brain, (cerebral malaria) lungs or kidneys.

If you return from a malarious area and develop symptoms

Contact your GP or hospital emergency department immediately for an urgent medical assessment.

Remember to inform them of where you have travelled as this will help determine:

• your risk of malaria
• the type of treatment required.

If you have malaria, the people you have travelled with should also be tested.

Diagnosis

Malaria is diagnosed by a blood test.

The blood is examined under a microscope looking for malaria parasites inside the red blood cells.

All travellers from malarious areas who become ill or develop a fever should be tested.

Treatment

Treatment must be given in consultation with specialist physicians.

All cases of P. falciparum malaria in the NT are admitted to hospital because it can rapidly become life threatening.

Other cases of malaria can sometimes be treated at home if the:

• house is adequately screened
• patient agrees to stay indoors between dusk and dawn.

This is to avoid any risk of transmission of the parasite to the local Anopheles mosquitoes.

Recurring episodes

• P. vivax and P. ovale exist as dormant forms that remain in the liver for months or years before producing the disease.
• P. falciparum can reoccur after apparent recovery, due to inadequate treatment or infection with a drug resistant strain.
• P. malariae can rarely persist with very low levels of parasite in the peripheral blood for decades.
• P. knowlesi produces acute illness but does not cause relapse.

Prevention

Check whether the countries you are travelling are affected by malaria by:

• contacting your GP or travel health clinic
• going to the WHO or US Centers for Disease Control and Prevention websites.

If you are travelling to an affected country, you will often need anti-malarial medication.

Contact your GP or travel clinic to organise this for your trip.

Some medication must be started 1 week prior to entry.

How to protect yourself from mosquito bites

To reduce the risk of mosquito bites in affected areas, you should:

• avoid being outdoors between dusk and dawn, particularly in poorly lit areas, rural areas, or the outskirts of large towns
• sleep inside mosquito netting or use insecticide-treated bed nets and clothing in high-risk areas - if accommodation is not well screened
• avoid scents on your body e.g. perfume, deodorants, and sweat, since these can attract mosquitoes
• use protective clothing in outdoor situations including covering feet, legs and arms - loose, light coloured clothing is best
• use personal repellents containing DEET or picaridin on areas of exposed skin in combination with protective clothing
• use electric insecticide devices using repellent treated pads in indoor or enclosed areas
• use mosquito coils, or candle heated or gas operated devices using insecticide treated pads for patio and veranda or relatively sheltered or low wind outdoor situations.

Read more about personal protection from mosquitoes.

Information for health professionals

To find out more, go to the NT Health website.

Contact

Contact your nearest Centre for Disease Control on the NT Health website.