Describe the life cycle of Plasmodium in humans and in the mosquito. How can malaria be controlled?
How to lay out the answer. Follow the frame, then write it in your own words.
1 · Name the parasite and vector. Malaria is caused by Plasmodium (P. vivax, P. malariae, P. falciparum) and spread by the female Anopheles mosquito.
2 · Stages in humans.
Sporozoites injected by the bite.
Asexual multiplication in liver cells.
Asexual multiplication in RBCs; RBCs burst; haemozoin causes chills and fever every 3 to 4 days.
Gametocytes form in the blood.
3 · Stages in the mosquito. Gametocytes taken up with blood; fertilisation and development in the gut; sporozoites stored in salivary glands.
4 · Draw the cycle. [Diagram: cycle with human liver, RBCs, gametocytes, mosquito gut, salivary glands, sporozoites]
5 · Control. Remove stagnant water, mosquito nets and wire mesh, Gambusia in ponds, insecticide spraying.
6 · Close in one line. So Plasmodium needs two hosts, and breaking the mosquito link controls malaria.
Scoring tip: Say clearly which stages are in the human and which in the mosquito, and name haemozoin. A neat labelled cycle earns a full mark on its own.
