Malaria

Malaria
Malaria is an acute infectious disease of the blood, caused by one of four species of the protozoal genus, Plasmodium, a sporozoan. P. falciparum accounts for some fifteen percent of all malaria cases, and P. vivax for eighty percent of malaria cases. The plasmodial parasite is transmitted to humans through the bite of a female Anopheles mosquito, or by an infected, blood-contaminated, needle. Sporozoans reproduce asexually in human cells by a process called schizogony, in which multiple nuclear divisions are followed by the envelopment of the nuclei by cell walls producing merozoites. These, in turn, become trophozoites. Sexual reproduction occurs in the mosquito, where new spores (sporozoites) are formed.

Pathology and clinical significance:

Plasmodium sporozoites are injected into the bloodstream, where they rapidly migrate to the
liver. There they kind cyst-like structures containing thousands of merozoites. Upon unharness, the merozoites invade red blood cells, using hemoglobin as a nutrient.

Eventually, the infected red cells rupture, cathartic merozoites which will invade alternative erythrocytes.
If massive numbers of red cells rupture at roughly a similar time, a convulsion (sudden onset) of fever may end up from the huge unharness of deadly substances

Plasmodium falciparum is the most dangerous plasmodial species. It will cause a quickly fulminating illness, characterized by persistent high fever and orthostatic hypotension. Infection can lead to capillary obstruction and death if treatment is not prompt.

P. Malariae, P. vivax, and P. Ovale cause milder forms of the disease, probably as a result of they invade either young or previous red cells, but not both. This is in contrast to P. falciparum, which invades cells of all ages. Even today, malarial infection is a common and serious illness, inflicting some three hundred million cases each year, with a death rate of about one percent.

Diagnosis and treatment:

Diagnosis depends on the detection of the parasite inside red blood cells. Thick blood smears stained with Giemsa stain provide the most sensitive visual test.
Thin blood smears, in which more detail can be discerned, are used to determine the species involved, which is important in planning a course of therapy. [Note: Serologic tests are usually too slow for diagnosis of acute disease.] Drug treatment depends on the stage of infection. Primaquine is effective against the exoerythrocytic forms within the liver and blood and additionally against the gametocytes form, but inactive against parasites in red blood cells. Therefore, for the erythrocytic kind, antimalarial is run in conjunction with a blood schizontocide such as chloroquine, quinine, artemisinin, mefloquine, or pyrimethamine. All species may develop drug resistance.