Information about the Malarial Parasite - PLASMODIUM
The malarial parasite,Plasmodium,was first discovered in blood by a French scientist,Laveran in 1880.
Four Human malarial parasites can cause malaria
- Plasmodium vivax
- Plasmodium falciparum
- Plasmodium malariae
- Plasmodium ovale
Life cycle of Plasmodium occurs both in Man and in Mosquito vector:
Life cycle in man – Exo-erythrocytic cycle or Tissue phase:
- When a person is bitten by an infected female Anopheles mosquito, sporozoites of malarial parasites are injected into the blood stream.
- Inside the blood, the sporozoites circulate before entering the reticulo-endothelial cells of the liver.
- Inside the liver cells the sporozoites develop in to feeding stage called cryptozoite which feeds on the liver cells.
- Asexual division occurs resulting in cells known as Crypto-merozoites, which are released into blood streams.
- This stage is called as Prepatent period and lasts for 7 to 17 days and is considered as a period of incubation.
Endo-erythrocytic cycle or Schizogony cycle:
- The tissue phase plasmodium enters into the Red cells and develops into a trophozoite.
- From the trophozoite numerous merozoites are liberated into the blood stream.
- Each merozoite liberated attacks Red blood cells and continuous independent cycle and multiplication.
- The liberation of merozoite corresponds to clinical symptoms of shivering and fever in a malaria patient.
Life cycle in the Mosquito:
The life cycle in mosquito is called as sexual cycle or sporogony cycle.
- When another anopheles mosquito feeds on the blood of a malaria patient, the plasmodium enters the stomach of the mosquito.
- The plasmodium then develops into gametes or germ cells, which fuse to form Syngamy, resulting in the formation of zygote or egg cell.
- The egg develops into sporozoites. These sporozoites are motile and enter the salivary gland of the mosquito. In this stage the mosquito is called as infective mosquito, and it is ready to transmit the infection.
- When the infected mosquito bites a human host, the sporozoites enter the blood stream to form Tissue phase and the life cycle continues.
- In the human body, the malarial parasite shows asexual development and therefore man is the intermediate host. Inside the female anopheles mosquito the parasite shows sexual development and hence the mosquito is a definitive host.