Stages of malaria

Infection begins with the female Anopheles mosquito, the carrier and transmitter of malaria. When the mosquito bites and consumes the blood of someone with malaria, the malaria parasites enter the mosquito’s body. They develop in the mosquito for eight to 35 days, before travelling to its saliva glands. The next time this mosquito bites someone, the parasites are released into that person’s bloodstream. The mosquito itself is not affected by the parasites.

Inside a human host, the malaria parasites travel to the liver. Here the parasites multiply before re-entering the bloodstream. The amount of time that the parasites spend in the liver will depend upon the specific parasite; some re-enter the bloodstream within a week, while others can take months.

Once in the bloodstream, the malaria parasites begin to multiply in red blood cells. The affected cells eventually burst, releasing more parasites into the bloodstream. This occurs every 48 to 72 hours, which is why malaria is sometimes diagnosed through bouts of symptoms that repeat every two or three days.

After you have been bitten by a mosquito carrying malaria, it will normally take at least one week for symptoms to develop. P. falciparum typically causes symptoms within the shortest time, while p. malariae takes the longest to present.

Often, malaria symptoms are relatively mild and may be confused for another illness.

They include:

Malaria is more easily diagnosed when it comes in cycles. P. falciparum, p. vivax and p. ovale can cause the onset of symptoms every two days (when red blood cells burst, releasing more parasites). P. malariae is thought to cause the onset of symptoms every three days. The symptoms come on over a period of hours and start with chills, followed by a fever, and lastly sweating.

The problem is that malaria symptoms don’t always come in cycles, which means that diagnosis is not always easy – particularly in a country where malaria is not high risk.

If you have travelled from a malaria zone to a non-malaria zone and develop the kinds of symptoms described above, be sure to tell your doctors that you could be at risk of the disease. Remember that symptoms can take months to develop.

Of all the malaria parasites, p. falciparum is the most fast-acting and dangerous. It multiples rapidly in the bloodstream, which means it can lead to anaemia. This is a condition in which the red blood cells cannot carry enough oxygen, causing drowsiness and fainting. This type of malaria parasite is also associated with cerebral malaria, in which the brain swells. This can cause seizures, brain damage and coma.

Plasmodium falciparum is particularly prevalent in sub-Saharan Africa. If you are travelling through countries in this region and you develop any of the symptoms described above you should visit a doctor immediately, even if you have been taking antimalarials. Infection with this type of the parasite requires swift treatment to avoid serious complications.

Although these two malaria parasites are not as dangerous as P. falciparum, they can stay in the liver for many months, or even years. If you become infected with one of these parasites, you may experience a bout of initial symptoms, followed by months or years of no symptoms at all. After this dormant stage you may experience relapses.

P. vivax is usually found in Asia and Central and South America; P. ovale is usually found in West Africa. If you travelled through countries in these parts of the world and became sick with malaria in the past, be aware that symptoms could recur in the future. It’s important therefore that you are treated with a specific drug which prevents these relapses.

If you are going to travel through a malaria zone you will need to take antimalarials and protect yourself from mosquito bites.

To find out which antimalarials you will need, visit the NHS site NaTHNaC. To learn about insect bite avoidance, read this guide.

You can obtain a prescription for malaria tablets from your GP. Alternatively, visit the LloydsPharmacy Online Doctor malaria clinic.

This type of plasmodium parasite is the most common and deadly. It is responsible for most malaria deaths and is most prevalent in sub-Saharan Africa. In 2018, p. falciparum accounted for 99.7% of estimated malaria cases in the WHO African Region.*

Malaria caused by p. falciparum often leads to severe symptoms such as anaemia, as this type of parasite multiples rapidly in the blood. Falciparum malaria requires swift treatment, preferably within 24 hours of the onset of symptoms, otherwise the infection can become very severe and even life threatening.

The plasmodium falciparum parasite enter the bloodstream via a mosquito bite, where they travel to the liver and incubate for a period of days or weeks. After this incubation period, the parasites then enter the bloodstream, at which point symptoms begin, sometimes occurring in cycles of two or three days.