Malaria

About malaria

Malaria is an infection characterised by fever, shivering, chills, generally feeling unwell, headache and sweats, but it can present as a respiratory or gastrointestinal illness. It is caused by any of 4 different species of the Plasmodium parasite, passed on by the bite of an infected mosquito. Malaria caused by Plasmodium falciparum is life threatening. Infants, the elderly and those with lower levels of immunity are at greater risk.

The incidence of malaria is on the rise. Around 311 million new infections and 900,000 deaths occur 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, East Timor and Indonesia.

Effective treatment relies on early diagnosis and specific anti-malarial medications.

Symptoms of malaria

Symptoms include:

• slow rising fever that escalates to a rapid temperature rise and fall
• headache
• nausea
• chills
• shivering
• excessive sweating
• diarrhoea
• generally feeling unwell
• anaemia and associated symptoms.

Four species of parasite

Malaria is caused by infection by one of 4 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 following infection but reactivate and cause symptoms years later. 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 6 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, suggested precautions against mosquito bites 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 windows don't have flyscreens.

Anti-malarial drugs

Travellers who visit malarial locations should avoid mosquito bites and take anti-malarial medications. Unfortunately, medications are becoming increasingly ineffective as the parasites develop resistance.

The choice of medication depends on several factors, including:

• age, health and medical history of the traveller
• the type of malaria parasites present at the intended location
• the parasites' drug resistance status (parasites in many areas are now resistant to chloroquine, and in some areas also to mefloquine)
• length of intended stay
• local healthcare 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. Fetal development may also be affected. Treatment options for malaria in pregnant women are limited.

Diagnosis of malaria

If you experience symptoms of malaria, 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 found during a physical examination. Malaria is usually diagnosed with a blood test that screens for the presence of malaria parasites.

Treatment of malaria

Treatment consists of anti-malarial medications. The particular medication used depends on the species of parasite and any associated medication resistance. In most cases, urgent hospital assessment and management is indicated.

Where to get help

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