- plasmodium
-
—plasmodial, adj./plaz moh"dee euhm/, n., pl. plasmodia /-dee euh/.1. Biol. an ameboid, multinucleate mass or sheet of cytoplasm characteristic of some stages of organisms, as of myxomycetes or slime molds.2. any parasitic protozoan of the genus Plasmodium, causing malaria in humans.[1870-75; < NL; see PLASM-, -ODE1, -IUM]
* * *
Any of the parasitic protozoans that make up the genus Plasmodium, the cause of malaria.Infecting red blood cells in mammals, birds, and reptiles, plasmodia occur worldwide, especially in tropical and temperate zones. They are transmitted to humans by the bite of the Anopheles mosquito. From the bloodstream, young plasmodia enter liver cells, where they divide and form an adult stage that is then released back into the bloodstream and infects red blood cells. Rapid division of the parasites results in the destruction of the red blood cells, which release toxins that cause the periodic chill and fever cycles typical of malaria.* * *
▪ protozoan genusa genus of parasitic protozoans of the sporozoan subclass Coccidia that are the causative organisms of malaria. Plasmodium, which infects red blood cells in mammals (including humans), birds, and reptiles, occurs worldwide, especially in tropical and temperate zones. The organism is transmitted by the bite of the female Anopheles mosquito. Other insects and some mites may also transmit forms of malaria to animals.Four species cause human malaria: P. vivax (producing the most widespread form), P. ovale (relatively uncommon), P. falciparum (producing the most severe symptoms), and P. malariae. Plasmodium species exhibit three life-cycle stages—gametocytes, sporozoites, and merozoites. Gametocytes within a mosquito develop into sporozoites. The sporozoites are transmitted via the saliva of a feeding mosquito to the human bloodstream. From there they enter liver parenchyma cells, where they divide and form merozoites. The merozoites are released into the bloodstream and infect red blood cells. Rapid division of the merozoites results in the destruction of the red blood cells, and the newly multiplied merozoites then infect new red blood cells. Some merozoites may develop into gametocytes, which can be ingested by a feeding mosquito, starting the life cycle over again. The red blood cells destroyed by the merozoites liberate toxins that cause the periodic chill and fever cycles that are the typical symptoms of malaria. P. vivax, P. ovale, and P. falciparum repeat this chill-fever cycle every 48 hours (tertian malaria), and P. malariae repeats it every 72 hours (quartan malaria).* * *
Universalium. 2010.
