Explanation

Plasmodium malariae antigen: what is measured?

Plasmodium malariae is a malaria parasite that usually causes a mild but long-lasting illness. According to the LCI guideline (RIVM) on malaria, the time between the mosquito bite and the first symptoms can be weeks to years, and the parasite can remain in the blood for a long time. Unlike Plasmodium vivax and ovale, this species does not leave dormant forms in the liver. The rapid test looks in a drop of blood for a protein (antigen) of the parasite; the thick blood smear under the microscope remains the test that establishes the species and the number of parasites.

What can it detect?

A current infection with Plasmodium malariae
A long-standing infection that only causes symptoms weeks to years after infection

Result

What does the result mean?

Positive result

A protein was found that fits an infection with Plasmodium malariae. This species usually runs a milder course than Plasmodium falciparum, with fever attacks that classically return every three days, chills, headache and muscle pain. Without treatment, the infection can persist for a long time and still cause symptoms years later; treatment is therefore needed even with few symptoms. Rarely, a long-lasting infection with this species causes a kidney problem with protein loss.

Negative result

No protein of Plasmodium malariae was found. This does not rule out malaria; the rapid test is not very sensitive for this species, partly because there are often few parasites in the blood. The LCI guideline (RIVM) considers rapid tests not sensitive enough to detect species other than Plasmodium falciparum. Microscopic examination of a thick blood smear remains necessary with fever after a stay in a malaria area and is repeated if the suspicion persists.

After an abnormal result

Fever during or after a stay in an area where malaria occurs is an emergency and should be assessed by a doctor the same day; you do not wait for the result of a self-ordered test. A negative rapid test does not rule out malaria: if the suspicion persists, microscopic examination of a thick blood smear follows, repeated if needed. If an infection is confirmed, treatment follows, even if the symptoms are mild, because otherwise the infection can persist for a long time. Malaria is notifiable (group C): a confirmed infection is reported to the GGD (municipal public health service) within one working day.

Reliability

How reliable is the test?

According to the LCI guideline (RIVM) on malaria, rapid tests are not sensitive enough to detect species other than Plasmodium falciparum. Microscopic examination of a thick blood smear is the standard test; it also determines the species and the share of infected red blood cells. With this species, a negative rapid test says little and does not rule out malaria. A positive result fits an infection, but the species is confirmed with microscopy or PCR. This applies even more strongly to Plasmodium malariae: with this species there are often few parasites in the blood, so rapid tests regularly miss the infection.

What can affect the result?

Rapid tests regularly miss Plasmodium malariae, especially when there are few parasites in the blood; microscopy or PCR is needed to establish the species.
The time between infection and symptoms can be weeks to years, so the link with a trip is not always made.
A simultaneous infection with Plasmodium falciparum can be missed if only this species is tested for.
The proteins of the different Plasmodium species are similar; the species identification is confirmed with microscopy or PCR.

Who it is for

Who is the test useful for?

Useful for

Intended for people with fever or flu-like symptoms during or after a stay in an area where malaria occurs. With this species, a long time can pass between infection and the first symptoms, from weeks to years, and symptoms can still develop long after a trip. Without a stay in a malaria area, the test has no meaning.

How common is it?

Between 2014 and 2024, 72 to 343 cases of malaria were reported in the Netherlands each year; in 2023 there were 249 and in 2024 there were 217. About 90 in 100 reports concern an infection acquired in Africa, often during a visit to family or friends. Malaria is not transmitted in the Netherlands itself. Plasmodium malariae is one of the less commonly found species.

RIVM/LCI guideline on malaria (reports 2014 to 2024)

Drawbacks and risks

A negative rapid test can give false reassurance: this species is often missed by rapid tests and requires microscopic examination.
A test aimed only at this species can miss a simultaneous infection with Plasmodium falciparum, while that species becomes severe most quickly.

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