Malaria - including symptoms, treatment and prevention

25 April every year: Raising awareness of malaria as a curable and preventable disease. The aim of World Malaria Day is to provide education and understanding of malaria as a global scourge that is preventable and a disease that is curable.

Malaria is caused by a parasite called Plasmodium. There are 5 species of Plasmodium which infect humans:

Plasmodium vivax
Plasmodium falciparum
Plasmodium malariae
Plasmodium ovale
Plasmodium knowlesi which is less common.

Of these, Plasmodium falciparum infection is the most severe and can cause death in up to 10% of cases. It can be rapidly fatal. Pregnant women and children are especially at risk. Other types of malaria are less severe, but still may cause death.

How malaria is spread

The parasite is transmitted to humans by the bite of infected female Anopheles species mosquitoes.

The parasites multiply in the liver and the bloodstream of the infected person. The parasite may be taken up by another mosquito when it bites an infected person. The mosquito is then infected for the duration of its life and can infect other humans when it bites them.

Occasionally malaria is transmitted by blood transfusion. For this reason, people who have travelled to countries where malaria occurs may be deferred from giving blood for a short period. Malaria can also be transmitted from a mother to her fetus.

Malaria occurs in most tropical and sub-tropical areas of the world, including:

Africa
Central and South America
Asia (including southeast Asia)
Papua New Guinea
western Pacific islands.

Over 600,000 people living in these countries die from malaria each year. Many thousands of tourists also get malaria during their travels to countries where malaria is present. Tourists often get severe illness because they have had no previous exposure to malaria and have no resistance to the disease.
Signs and symptoms

Symptoms of malaria may include:

fever, which may come and go, or may be constant
chills
profuse sweating
malaise (feeling of unwellness)
muscle and joint pain
headache
confusion
nausea
loss of appetite
diarrhoea
abdominal pain
cough
anemia.

Plasmodium falciparum may cause cerebral malaria, a serious complication resulting from inflammation of the brain that may cause coma.

Diagnosis

Diagnosis is made by a blood test – sometimes it is necessary to repeat the test a number of times, as the parasites can be difficult to detect.
Incubation period

(time between becoming infected and developing symptoms)

Varies with the type:

P. falciparum: 9 to 14 days
P . vivax: 12 to18 days but some strains may have an incubation period of 8 to 10 months or longer
P. ovale: 12 to 18 days
P. malariae: 18 to 40 days
P. knowlesi 9 to 12 days.

These periods are approximate and may be longer if the person has been taking drugs taken to prevent infection.

Infectious period

(time during which an infected person can infect others)

Direct person-to-person spread does not occur.

A person remains infectious to mosquitoes as long as the parasites are present in the blood. This may be several years if adequate treatment is not given. Parasites disappear from the blood within a few days of commencing appropriate treatment. Mosquitoes remain infected for life.

Treatment

Specific antimalarial treatment is available and must always be started as soon as malaria is diagnosed. There is increasing resistance to currently available drugs and treatment should be carried out by an infectious diseases specialist or other expert in the field.

Prevention

Exclusion from childcare, preschool, school or work is not necessary but cases should avoid being bitten by mosquitoes while they are unwell. Travellers to areas with malaria are usually advised to take preventative anti-malarial drugs.
There is no vaccine to prevent human infection by this parasite.
Personal protection and the environmental management of mosquitoes are important in preventing illness. See Fight the Bite for tips to on how to protect yourself.

Travel in countries where there is malaria

Extensive international programs are undertaken in malarious countries to try to control this disease. For travellers, the following advice is given:

See a travel medicine expert before you go to get specific advice for the places you will be visiting.
Always take malaria prophylaxis drugs exactly as prescribed and take the full course. Be aware of their potential side effects.
Protect yourself from mosquito bites. Travel medical centres have good information on how to do this.
Be aware that no preventive measures are 100% effective, so always seek medical attention immediately if you develop a fever while travelling in, or after return from, a country where malaria occurs.
Always give your doctor the information about your travel if you become sick.