Understanding Malaria: Should Australians be Concerned?

At least 200 million people are infected with malaria every year. In 2021, there were 619,000 malaria deaths worldwide (WHO 2023).

What is Malaria?

Malaria is an infectious disease caused by the parasite Plasmodium, which is transmitted through the bite of a female Anopheles mosquito. In rare cases, it is transmitted congenitally, via blood transfusion or through shared injecting equipment (WHO 2023a; NSW Heath 2022).

When female Anopheles mosquitoes feed on blood to nurture their eggs, they can pick up Plasmodium parasites from humans infected with malaria. These mosquitoes will then become vectors (carriers) and transmit Plasmodium to other people they bite. You can not contract malaria directly from another person (CDC 2022).

Should Australians be Worried About Malaria?

Australia was certified as being malaria-free by the World Health Organisation in 1981 (WHO 2023b).

Despite this, there are still reasons to be vigilant:

• Every year, several hundred imported cases from travellers are recorded in Australia.
• If you travel to areas where malaria occurs, you are at risk of being infected if you do not take appropriate precautions. Areas of particular risk to Australians include:
  • The south-west Pacific (Solomon Islands, Papua New Guinea and Vanuatu)
  • Parts of Asia (particularly parts of Thailand, Myanmar, Sabah, Vietnam and India)
  • Parts of Africa (particularly East African countries).
• Local cases are occasionally reported in the Torres Strait in Australian territory.
• The Anopheles mosquito lives in parts of the Northern Territory.

(QLD DoH 2022; Healthdirect 2022; Canna 2019)

If Australia is to remain free of malaria, it is imperative that all cases are diagnosed and treated appropriately. Anyone who has been in an area where malaria has occurred within the previous 12 months and who develops a fever should be checked for malaria, both for their own sake and to prevent malaria from getting into the community.

Types of Plasmodium

There are five main species of Plasmodium that cause malaria in humans. They differ somewhat in areas where they mainly occur, the symptoms they cause, and treatment required.

1. Plasmodium falciparum causes the most serious and life-threatening illness, potentially resulting in liver or kidney failure, convulsions or coma.
2. Plasmodium vivax generally causes a less serious illness but is able to lie dormant in humans for months or years. It causes many cases of malaria in the Asia-Pacific region.
3. Plasmodium ovale generally causes a less serious illness but is able to lie dormant in humans for months or years.
4. Plasmodium malariae generally causes a less serious illness.
5. Plasmodium knowlesi usually only causes malaria in monkeys, but there have been some human cases.

(MyDr 2018; Stanford Health Care 2019; WEHI 2023)

Malaria Symptoms

After being bitten by an infected mosquito, Plasmodium parasites enter the person’s liver, where they begin to multiply. After a number of days (depending on the type of Plasmodium), the parasites re-enter the bloodstream, invade red blood cells and repromalaria duce (WEHI 2023).

The initial flu-like symptoms are likely to include:

• Feeling hot and shivery
• Fever, which may be constant or come and go
• Headache
• Nausea and vomiting
• Muscle and joint pains.

(NSW Health 2022; SA Health 2022)

P. malariae may persist for several years and has been associated with nephrotic syndrome in children (Langford et al. 2015).

Severe malaria may cause symptoms such as:

• Impaired consciousness or coma
• Prostration (inability to sit up without assistance)
• Convulsions
• Pulmonary oedema
• Shock
• Acidosis
• Hypoglycaemia
• Severe anaemia
• Renal impairment
• Jaundice
• Recurrent or prolonged bleeding (e.g. from nose or gums)
• Hyperparasitaemia.

(UpToDate 2023)

Diagnosing Malaria

Laboratory diagnosis of malaria is by microscopy. A blood specimen is spread as a smear and examined to confirm the presence of Plasmodium and calculate the percentage of red cells containing the parasites (PHLN 2018).

Treating Malaria

Malaria is treated with antimalarial medicines to kill the Plasmodium parasites. The exact medicine will depend on factors such as the species of Plasmodium involved, the severity of symptoms, the age of the patient and pregnancy (Mayo Clinic 2023).

Note that there is increasing resistance to antimalarials, so it’s recommended that treatment is overseen by an infectious disease specialist or other expert (SA Health 2022).

Cases of severe malaria require intravaneous administration of antimalarials. If the attack is not classified as severe, oral medications may be used (Buck & Finnigan 2023).

P. vivax and P. ovale may have dormant stages (hypnozoites) that persist in the liver and are not killed by the medication used for the acute attack. The patient may need to take primaquine to eradicate these dormant parasites (Buck & Finnigan 2023).

Preventing Malaria

Anyone travelling to a malarious region should take precautions. This includes consulting a physician to prescribe preventative antimalarial drugs (NSW Health 2022).

No antimalarial drug is 100% effective, so taking precautions to avoid mosquito bites is also crucial. These include:

• Being vigilant if spending time outdoors around dawn and dusk and into the evening
• Wearing loose, light-coloured, long-sleeved shirts and long pants when outdoors
• Wearing socks and covered shoes when outdoors
• Applying mosquito repellent to exposed skin and on clothing
• Avoiding perfumes, colognes or aftershaves, which may attract mosquitoe
• Sleeping in screened or air-conditioned rooms if possible, and using a mosquito net if not
• Using ‘knockdown’ sprays, mosquito coils and plug-in vaporising devices.

(NSW Health 2022; Better Health Channel 2015)