Blood Parasites Principal Causative Organisms of Tropical Diseases

Abstract

The causative Plasmodium organisms are transmitted to man as sporozoites in the saliva of the feeding anopheles mosquito. The organisms travel in the bloodstream from the capillaries to the liver, where they undergo further development. They enter the liver cells (primary tissue forms) in the “pre-erythrocytic phase” of their life cycle, and after a variable period they are released into the peripheral blood as schizonts. There they attack the erythrocytes in a process which incites episodes of fever. Inside the red cells the schizonts mature through several stages, culminating in the discharge of merozoites from the remains of the erythrocyte; these then proceed to infect fresh erythrocytes. This process takes about 48 h for the parasite of tertian malaria (Plasmodium vivax and Plasmodium ovale) and malignant tertian malaria (Plasmodium falciparum) and 72 h for the parasite of quartan malaria (Plasmodium malariae).

Contributed by Prof Dr. W. Mohr, Hamburg