Plasmodium malariae

Mature schizont of Plasmodium malariae in stained blood smear

Plasmodium malariae is a protozoan parasite of the genus Plasmodium and the pathogens of quartan malaria in humans, a relatively benign form of the disease that is rarely fatal. Like other malaria parasite Plasmodium malariae is also of Anopheles mosquitoes transmit. The parasite is now mainly found in tropical countries.

Discovery and description

History

Malaria parasites were first described in 1880 by Alphonse Laveran. However, Laveran was based on only one type of pathogen, which he called Oscillaria malariae; it is assumed that Laveran in Algiers both causative agent of malaria tropica, the malaria tertian and the quartan malaria has observed. These different disease processes and agents could only differentiate Camillo Golgi in 1886. 1890 hit Grassi and Feletti after reviewing the literature for the causative agent of quartan malaria the name Haemamoeba malariae before; a number of other suggestions for names of other authors followed. 1885 had already Marchiafava and Celli proposed the generic name Plasmodium. In 1954, the frequent combination was Plasmodium malariae by the International Commission on Zoological Nomenclature declared valid.

Morphology

As with all plasmodia also P. malariae occurs in various stages of development. Sporozoites from the mosquito are 12 micrometers in diameter comparatively large. Leberschizonten reach a diameter of approximately 50 micrometers and containing many thousands of merozoites. With the proliferation of the parasite in erythrocytes, these are usually not enlarged. Maturity Blutschizonten contain 6 to 14, typically 8 merozoites. Immature gametocytes are microscopically indistinguishable from the asexual forms. The mature gametocytes fill the host cell completely. Macrogametocyte show after staining a deep blue cytoplasm with a small, situated on the edge of the core and distributed pigment, while the microgametocyte show a slightly blue cytoplasm with a diffuse core.

Differentiation of various malaria parasite only on the morphology in blood films may be difficult to impossible. In Southeast Asia, Plasmodium knowlesi infections were falsely identified as those with P. malariae. To prevent such errors, molecular DNA techniques are used to differentiate increased.

System

Traditionally, Plasmodium malariae is with many other primates infecting plasmodia in the subgenus Plasmodium classified. Very closely related to or identical with P. malariae, P. brasilianum, a recorded at various New World monkeys in Central and South America parasite that is microscopic and molecular indistinguishable from P. malariae. It is believed that P. malariae in the last 500 years by infected people came to South America and was transferred from these mosquito on monkeys. In West Africa, another parasite has been described in chimpanzees and gorillas with P. rodhaini, which is indistinguishable from P. malariae. General P. rodhaini is regarded as a synonym of P. malariae. Besides these two plasmodia show no other species particularly close relationship to P. malariae. The evolutionary origin of P. malariae is unclear.

Distribution and host animals

Plasmodium malariae is found in tropical and subtropical areas and is widely used in sub-Saharan Africa, but also in Southeast Asia and on islands in the western Pacific and found in the Amazon basin. Originally P. malariae also occurred in Europe and in the Southern United States.

Generally, the person is viewed as a single reservoir host for Plasmodium malariae. Whether infected monkeys represent an epidemiologically relevant reservoir for infection of humans is unclear. In the identified parasites in apes it is probably anthropozoonoses. To research into the disease, among other night monkeys can be infected experimentally.

A number of Anopheles species occur as a vector for P. malariae in question, including in Europe occurring species such as Anopheles Anopheles atroparvus or messeae.

Life cycle

The life cycle of P. malariae is like the other plasmodia substantially. The parasite shows an obligate host alternation. The sporozoites enter by infected mosquitoes in the bloodstream of people who migrate from there to the liver and invade hepatocytes one in which they reproduce asexually. In comparison to other malaria pathogens, the incubation period of the hepatic phase of at least 15 days, is comparatively long. The Leberschizonten each produce thousands of merozoites, which are released and infect red blood cells, where another asexual reproduction takes place. The generation time in the multiplication in the erythrocytes is approximately 72 hours. Since the development is synchronous, there is at the end of each cycle of propagation to a massive release of new parasites, which is connected with a fever. From the periodicity of the fever, the term derives from quartan malaria. A few plasmodia developing in the erythrocytes to generation forms. This microgametocyte and macrogametocyte can be taken up by mosquitoes during a blood meal, and in the intestines of the insect a new development cycle in motion. After a fusion of the gametes new sporozoites are formed in the intestine, which migrate to the salivary glands, from where they can be transferred to a new host. The development time in the mosquito is 15 to 21 days.

A special feature in the life cycle of P. malariae is the appearance of Rekrudeszenzen that are relapses, resulting from persistent erythrocytic forms. In some cases these occur even after decades, when the parasites were not eliminated by appropriate therapy. Recurrences that arise from Hypnozoiten in the liver, there is not in P. malariae, however.