Explanation

Plasmodium ovale antigen: what is measured?

Plasmodium ovale is a malaria parasite that occurs mainly in West Africa. Like Plasmodium vivax, this species leaves dormant forms (hypnozoites) in the liver, so that according to the LCI guideline (RIVM) on malaria, the disease can flare up again up to about five years after returning. The rapid test looks in a drop of blood for a protein (antigen) of the parasite. The test is part of the same examination as the thick blood smear, which shows the species and the number of parasites.

What can it detect?

A current infection with Plasmodium ovale
A flare-up from dormant liver stages, up to about five years after returning from a malaria area

Result

What does the result mean?

Positive result

A protein was found that fits an infection with Plasmodium ovale. This species usually causes a milder illness than Plasmodium falciparum, with fever in attacks, chills, headache and muscle pain; the symptoms start on average 12 to 17 days after the mosquito bite and sometimes only months later. The infection should be treated. Because this species leaves dormant forms in the liver, the treatment of the infection in the blood is followed by an additional treatment that clears those liver stages.

Negative result

No protein of Plasmodium ovale was found. This does not rule out malaria; the rapid test is particularly insensitive for this species. 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. Dormant forms in the liver cannot be seen with any blood test.

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 with this species is confirmed, the treatment should be followed by an additional treatment against the dormant liver stages. 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 ovale: this species often causes few parasites in the blood and is regularly missed by rapid tests. The dormant liver stages that go with this species cannot be detected in blood.

What can affect the result?

Rapid tests regularly miss Plasmodium ovale, especially when there are few parasites in the blood; microscopy or PCR is needed to establish the species.
Dormant liver stages cannot be detected in blood; a negative result says nothing about the chance of a later flare-up.
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, especially West Africa. With this species, the first symptoms can appear only months after returning, and the disease can flare up again up to about five years later. 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 ovale is one of the less commonly found species and is mainly acquired in West Africa.

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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