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10 February, 2010

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Malaria

Malaria is an infection characterised by fever, shivering, chills, malaise, headache and sweats, but it can present as a respiratory or gastrointestinal illness. It is caused by any of four different species of the Plasmodium parasite, passed on via the bite of an infected mosquito. Malaria caused by Plasmodium falciparum is life threatening. Infants, the elderly and those with comprised immunity may be at greater risk. The incidence of malaria is on the rise, with around 220 million new infections worldwide every year. Australia is free of endemic malaria, but Australians can catch the disease when travelling to tropical regions in Asia, Africa, and Central or South America. Most Australian cases of malaria are contracted in Papua New Guinea. Effective treatment relies on early diagnosis and specific anti-malarial medications.

Symptoms
Symptoms of malaria include:

A slow rising fever that escalates to a rapid temperature rise and fall
Headache
Nausea
Chills
Shivering
Excessive sweating
Diarrhoea
General malaise
Anaemia and associated symptoms.

Four different species of parasite
Malaria is caused by infection by one of four different species of the Plasmodium parasite: P. vivax, P. ovale, P. malariae and P. falciparum. The most common infections are those caused by P. vivax and P. falciparum. The P. vivax and P. ovale parasites can lie dormant in the body, only to reactivate and cause symptoms after a number of years. Falciparum malaria can be life threatening without prompt medical treatment.

Falciparum malaria can be fatal
The typical symptoms of malaria described above can lead to further symptoms and complications in the case of P. falciparum infection, including:

Jaundice
Coagulation defects (blood doesn't clot)
Rupture of the spleen
Haemolytic anaemia (the red cells don't live a normal life span)
Shock
Kidney failure
Liver failure
Pulmonary oedema
Cerebral malaria, producing coma
Death.

Modes of transmission and incubation periods
Malarial parasites are carried by the female anopheles mosquito, which tends to be active at dusk and early evening. When an infected mosquito bites a human, the parasites roam in the bloodstream for around one hour before entering the liver and multiplying. After six to 16 days (depending on the species), the parasites return to the bloodstream to invade and multiply inside red blood cells until they burst. The released parasites then invade fresh red blood cells and the destruction continues. The incubation period (the time between the mosquito bite and the onset of symptoms) ranges from 8 to 30 days, once again depending on the parasite species. Other less common modes of transmission include blood transfusion, sharing needles or syringes, and congenital infection.

Avoid mosquito bites
When in malarial areas, suggestions include:

Avoid outdoor activity around dusk and dawn when mosquitoes are most active.
Wear loose, long, light-coloured clothing.
Use mosquito repellents on exposed skin and clothing.
Don't wear perfumes, colognes or aftershave.
Use 'knockdown' sprays, mosquito coils and plug-in vaporising devices indoors.
Sleep under mosquito nets treated with repellents or insecticides if you don't have fly-wire screens on windows.

Anti-malarial drugs
Travellers who visit malarial locations should avoid mosquito bites and take anti-malarial drugs. Unfortunately, drugs are becoming increasingly ineffective as the parasites develop resistance. There are different drugs available, such as chloroquine, mefloquine and doxycycline. The choice of drug used depends on a number of factors, including:

The age, health and medical history of the traveller
The type of malaria parasites present at the intended location
The parasites' drug resistance status (the parasites in many areas are now resistant to chloroquine)
Length of intended stay
Local health care facilities.

Pregnant women are at risk
Pregnant women are advised to avoid malarial areas. While it is relatively rare for malaria to pass from infected mother to unborn child, the disease increases the risk of miscarriage or premature labour. Foetal development may also be affected. Treatment options for malaria in pregnant women are limited.

Diagnostic methods
If you experience symptoms, seek prompt medical treatment, even if you took all precautions against mosquito bites and used anti-malarial medications. Enlargement of the liver (hepatomegaly) and spleen (splenomegaly) may be apparent during a physical examination. Malaria is principally diagnosed with a blood test that screens for the presence of malaria parasites.

Treatment options
Treatment consists of anti-malarial medications; the particular medication used depends on the species of parasite and any associated drug resistance. In severe cases, hospitalisation and intravenous treatment may be needed.

Where to get help

Your doctor
Travel Clinics Australia Tel. (03) 9528 1222 or 1300 369 359

Things to remember

Malaria is an infection characterised by fever, shivering, chills and malaise, but may also present in a less typical manner.
It is caused by any of four different species of the Plasmodium parasite, passed on via the bite of an infected mosquito.
Australia is free of endemic malaria, but Australians can catch the disease when travelling to tropical regions in Asia, Africa, and Central or South America.
Malaria can be life threatening - early treatment is paramount.
Treatment consists of anti-malarial medications; the particular medication used depends on the species of parasite and any associated drug resistance.

You might also be interested in:
Dengue fever.
Mosquitoes can carry diseases.
Ross River virus disease.
Travel health - yellow fever vaccine.
West Nile virus.

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