Why do plasmodium multiply only in liver cells and RBC?
The answer lies in the evolutionary significance of this parasite. Current theory suggests that the genera Plasmodium, Hepatocystis and Haemoproteus evolved from one or more Leukocytozoon species. Parasites of the genus Leukocytozoan infect white blood cells (leukocytes), liver and spleen cells and are transmitted by ‘black flies’ (Simulium species) — a large genus of flies related to the mosquitoes. It is thought that Leukocytozoon evolved from a parasite that spread by the orofaecal route and which infected the intestinal wall. At some point this parasite evolved the ability to infect the liver. This pattern is seen in the genus Cryptosporidium to which Plasmodium is distantly related. At some later point this ancestor developed the ability to infect blood cells and to survive and infect mosquitoes. Once vector transmission was firmly established the previous orofecal route of transmission was lost. Leukocytes, hepatocytes and most spleen cells actively phagocytose particulate matter
