Definitions

Plasmodium malariae

Plasmodium malariae

Plasmodium malariae is a parasitic protozoa that causes malaria in humans and animals. It is closely related to Plasmodium falciparum and Plasmodium vivax which are responsible for most malarial infection. While found worldwide, it is a so-called "benign malaria" and is not nearly as dangerous as that produced by P. falciparum or P. vivax. P. malariae causes fevers that recur at approximately three-day intervals (a quartan fever), longer than the two-day (tertian) intervals of the other malarial parasites.

Signs and symptoms

Plasmodium malariae causes a long-lasting, chronic infection that in some cases can last a lifetime. In some patients P. malariae can cause serious complications such as the nephrotic syndrome.

Due to a similarity in the appearances of the pathogens, P. knowlesi infections are often misdiagnosed as P. malariae infections. Molecular analysis is usually required for an accurate diagnosis .

Biology

Life cycle

P. malariae is the only human malaria parasite that causes fevers that recur at approximately three-day intervals (therefore occurring evey fourth day, a quartan fever), longer than the two-day (tertian) intervals of the other malarial parasites.

Human Infection

Liver Stage

Within the hepatocytes, the exoerythrocytic schizogony stage of P. malariae has a minimum duration of roughly 15 days.

Erythrocytic Cycle

The total length of the intraerythrocytic development is roughly 72 hours for P. malariae.

At the schizont stage, after schizogonic division, there are roughly 6-8 parasite cells in the erythrocyte.

Sexual Stage

Mosquito Stage

Laboratory considerations

P. vivax and P. ovale that has been sitting in EDTA for more than half-an-hour before the blood film is made will look very similar in appearance to P. malariae, which is an important reason to warn the laboratory immediately when the blood sample is drawn so they can process the sample as soon as it arrives.

Microscopically, the parasitised red blood cell (erythrocyte) is never enlarged and may even appear smaller than that of normal red blood cells. The cytoplasm is not decolorized and no dots are visible on the cell surface. The food vacuole is small and the parasite is compact. Cells seldom host more than one parasite. Band forms, where the parasite forms a thick band across the width of the infected cell, are characteristic of this species (and some would say is diagnostic). Large grains of malarial pigment are often seen in these parasites: more so than any other Plasmodium species. 8 merozoites

References

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