Malaria is caused by a protozoan parasite, Plasmodium, and is carried and spread to various persons and places by the female mosquito, Anopheles.
History of Discovery: In older times it was supposed that malaria disease was caused by poisonous gases. The plasmodium germ as the causative agent of malaria was discovered in 1880 by Charles Laveran. Sir Patrick Manson suggested that malarial parasites are probably introduced into our blood by the bite of mosquito. Dr. Ross (1897) finally discovered the presence of malarial parasites in the body of female mosquito which had fed on the blood of malarial patient. He was awarded Nobel Prize in the year 1902 for working out the complete cycle of malarial parasites. It was Grassi in 1917 who studied the cycle of human malaria in Anopheles.
Species of Plasmodium: About 4 species are known to infect man and cause different kinds of malaria.
(a) Plasmodium malariae– causes Quartan malaria.
(b) P. vivax- causes Benign tertian malaria.
(c) P. falciparum– causes Malignant tertian malaria.
(d) P. ovale– causes mild tertian malaria.
Of these four species, P. vivax is the most widespread and prevailing species of the temperature region; and P. falciparum is confined to warmer countries only.
Life Cycle: The life cycle of Plasmodium consists of an exogeneous sexual phase called sporogony which multiplies in female mosquito and an endogeneous asexual phase called schizogony which takes place in man. Thus, it is genetic, i.e., life cycle is completed in two different kinds of hosts- one vertebrate (man) and the other invertebrate (mosquito). Mosquito is termed the primary or final host while man, the secondary or intermediate host.