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Chapter 1 : The Life of Plasmodium: An Overview
Historical records, some >3,000 years old, attest to the antiquity of the disease malaria. Using a light microscope, Alphonse Laveran noticed some crescent-shaped bodies among the red blood cells that were almost entirely transparent, save for some pigment inclusions. He recognized that these bodies were alive, and that he was looking at an animal parasite, not a bacterium or a fungus. Subsequently, he examined blood samples from 192 malaria patients: in 148 of these, he found the telltale crescents. Where there were no crescents, there were no symptoms of malaria. He named the parasite Oscillaria malariae and communicated his findings to the Societé Medicale des Hopitaux on 24 December 1880. Although malaria can be induced in a host by the introduction of parasites (called sporozoites) through the bite of an infectious female mosquito, the parasites do not immediately appear in the blood. This was surprising in view of the fact that in 1903 Fritz Schaudinn claimed to have seen sporozoites directly invade erythrocytes. All human malarial agents (Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae) are transmitted through the bite of an infected female anopheline mosquito when she injects sporozoites from her salivary glands during blood feeding. Investigations at the molecular level of enzyme structure, gene sequences, chromosomal arrangements, and transcriptional control will permit an uncovering of the adhesive molecules that mediate cell-cell interactions, determine the mechanisms of protein trafficking, and identify putative drug targets and vaccine candidates.