Plasmodium

Plasmodium
Disease Malaria is caused by four plasmodia:
- Plasmodium Falciparum ( most common causes of malaria)
- Plasmodium vivax
- Plasmodium ovale
- Plasmodium malariae
Important properties
? The vector and definitive host is the female Anopheles mosquito.
? There are two phases in the life cycle: the sexual cycle (in mosquitoes) & the asexual cycle (in humans, the intermediate hosts).
? The sexual cycle is called sporogony (sporozoites are produced). & the asexual cycle is called schizogony (schizonts are made).
Pathogenesis &Epidemiology
? Destruction of red blood cells by release of merozoites& the action of the spleen to first sequester the infected red cells & then to lyse them.
? The enlarged spleen is due to congestion of sinusoids with erythrocytes, coupled with hyperplasia of lymphocytes & macrophages.
? Malaria caused by P. falciparum is more severe than that caused by other plasmodia:
1. It is characterized by infection of far more red cells than the other species & by occlusion of the capillaries with aggregates of parasitized red cells. This is lead to hemorrhage and necrosis particularly in the brain (cerebral malaria).
2. P. falciparum is chloroquine resistance. These strains now predominate in most areas of the world where malaria is endemic. This resistance is mediated by a mutation in the gene encoding the chloroquine transporter in the cell membrane of the organism.
3. P. falciparum causes a high level of parasitemia, because it can infect red cells of all ages.
? Extensive hemolysis and kidney damage occur, with resulting hemoglobinuria. The dark color of the patient’s urine has given rise to the term (black water fever). The hemoglobinuria can lead to acute renal failure.
? The timing of the fever cycle is 72 h. for P. malariae & 48 h. for the other plasmodia