- 92 Downloads
Four species of the protozoan genus Plasmodium (P.vivax, P.ovale, P.malariae and P.falciparum) infect humans, and give rise to malaria. One hundred million people are infected annually, and the disease is very widespread in tropical and warm temperate regions where the appropriate anophiline mosquito vectors are found. Malaria is transmitted to humans by sporozoites from mosquito salivary glands. After inoculation, sporozoites enter liver parenchymal cells and undergo asexual multiplication (tissue schizogony) to form merozoite-filled tissue schizonts. Schizont rupture releases merozoites which then invade red cells by means of attachment to specific binding sites. The merozoites divide asexually forming trophozoites which subdivide to form red cell schizonts. The asexual replication cycle then recurs at regular intervals until treatment, acquisition of immunity or death supervenes. With the relapsing malarias, due to P.vivax and P.ovale merozoites may also be released from long-term persisting liver forms called hypnozoites (which are dormant sporozoite forms); these are responsible for late relapses.
KeywordsPlasmodium Species Late Relapse Blood Transfusion Product Label Component Parasite Life Cycle
- Krogstad DJ. Plasmodium species. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases, 4th edn. New York, Edinburgh, London: Churchill Livingstone. 1995: 2415–27.Google Scholar