Question

Name the protozoan which causes malaria.

Answer 1

When the functioning of one or more organs or systems of the body is adversely affected, characterised by various signs and symptoms, we say, that we are not healthy, i.e., we have a disease. A wide range of organisms could cause disease in man. They are called pathogens. Malaria is caused by protozoa.

Complete answer:
Malaria is a protozoan disease which is caused by Pathogen: Malaria is caused by Plasmodium, a tiny protozoan. Different species of Plasmodium which attack humans are Pvivax, P. malariae, P. ovale and P. falciparum.

Mode of transmission: Malarial parasite (Plasmodium) requires two hosts to complete its life cycle Human, and Mosquito (female Anopheles) which is the vector/transmitting agent too. Plasmodium eget pierce in the human body as sporozoites (infectious form) through the bite of infected female Anopheles.
Life-history: When an infected female Anopheles bites a human to suck blood, it also injects the malarial parasites into the human blood with its saliva.
This infective stage of Plasmodium is a minute sickle-shaped sporozoite. Sporozoites are inoculated in thousands into the human blood. In about half an hour the sporozoites disappear from the bloodstream and enter the parenchymatous cells of the liver to escape from phagocytic white blood corpuscles and multiply their own number.
Schizogony: Each sporozoite grows in the liver cell to form a large and rounded schizont, which divides to form about 1,000 small spindle-shaped merozoites.
The multiple fission is called schizogony. The schizont ruptures and merozoites are liberated into liver venous passages (sinusoids). This phase of reproduction is termed as the pre-erythrocytic phase and in this the merozoites are also called cryptozoites, they are immune to medicines and also to the resistance of the host.
The cryptozoites (merozoites) enter new liver cells, grow into schizonts which again divide to form merozoites. These merozoites of the second generation are termed meta cryptozoites and their formation is called the exo-erythrocytic phase.
The exo-erythrocytic cycle may continue in more liver cells to form a reservoir of parasites, or some merozoites after two or more cycles in the liver may re enter the bloodstream. The merozoites which reach the bloodstream start to attack healthy erythrocytes that are red blood cells these are called phanerozoic or meta crypto merozoites.
Pre-patent period is the duration between the initial sporozoite infection and the first appearance of the parasites in blood. It is 8 days in Plasmodium vivax. Incubation period is the duration between the initial sporozoite infection and the first appearance of malarial symptoms. It is about 14 days in P. vivax, 30 days in P. malariae, 14 days in P ovale and 12 days in P. falciparum.

Note:
Plasmodium, the causative agent of malaria, was discovered by Charles Laveran in 1880. Lancisi first suspected a relationship between mosquito and malaria. Ronald Ross (1897) discovered a (confirmed) relationship between malaria and mosquito. In 1897 Ross discovered oocytes of Plasmodium in the stomach of mosquitoes.