Simulation · Biology · Class 12

The two-host life cycle of Plasmodium

From the lesson Malaria and amoebiasis in Human Health and Disease. Change the values and watch what happens.

The idea behind it

NCERT §7.1

Malaria is caused by the protozoan Plasmodium. Different species (P. vivax, P. malariae and P. falciparum) cause different types; malignant malaria, caused by P. falciparum, is the most serious and can be fatal.
Plasmodium enters a person as sporozoites, the infectious form, through the bite of an infected female Anopheles mosquito.
The parasites first multiply inside liver cells, then attack red blood cells and make them burst. Each burst releases a toxic substance, haemozoin, which causes the chill and high fever that return every three to four days.
In the human, the parasites reproduce asexually in liver cells and in RBCs; some become gametocytes, the sexual stages, inside RBCs.
A female Anopheles biting an infected person takes up these stages. Fertilisation and further development happen in the mosquito, and the new sporozoites are stored in its salivary glands, ready for the next bite.
The malarial parasite needs two hosts, human and mosquito, to complete its life cycle; the female Anopheles is also its vector (transmitting agent).
Amoebiasis (amoebic dysentery) is caused by Entamoeba histolytica, a protozoan in the large intestine. Symptoms: constipation, abdominal pain and cramps, and stools with excess mucous and blood clots.
Houseflies act as mechanical carriers, moving the parasite from an infected person's faeces to food. Drinking water and food contaminated with faecal matter are the main source of infection.

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