Phylum - Protozoa
Class - Sporozoa
Order - Haemosporidia
Members of the genus Plasmodium are collectively known as ma-larial parasites. They cause a febrile disease called malaria. Malaria as a chill and fever disease is known to mankind for a long time. Eradication of malaria is an important problem in public health. For a long time it was believed that malaria was caused by harmful vapours produced in marshy land (Gr. Malo-bad+air). Charles Laveran, a french military surgeon, for the first time, noticed Plasmodium in the blood of a malarial patient, in 1880. Its connection with the intermediate host and the modes of transmission were experimentally worked out in Calcutta by Sir Ronald Ross in 1889. For this discovery he was awarded the nobel prize for medicine in 1902. Grassi (1890) provided absolute scientific proof for the specific relationship between Anopheles mosquito and the human malarial parasite.
Plasmodium : The plasmodium is an intracellular sporozoan blood parasite. For the completion of life cycle it requires two hosts, a vertebrate and a blood sucking invertebrate. Transference of the parasite is effected by the inverte-brate host. In man, the infection takes place by the inoculation of the slender, sickle shaped nucleated sporozoite in the blood by the bite of an infected female mosquito belonging to the genus Anopheles. At least four species of Plasmodium, P. vivax, P. falciparum, P. malariae and P. ovale, are known to attack man causing different kinds of malaria.
The life cycle of the malarial parasite involves two hosts, the man and the mosquito. The modes of development in these two hosts are different. In man the mode of reproduction is asexual and in mosquito it is sexual. Man is the intermediate host and the mosquito is the definitive host.