Answer:
Malaria is caused by any one of five types of Plasmodium parasite, transmitted via female Anopholes mosquito bites. Of these five types, Plasmodium Falciparum causes the most extreme and potentially fatal illness.
A mosquito feeding upon the blood of an infected host can ingest a number of these parasites. They develop within the mosquito and are secreted through its saliva to infect other potential hosts when bitten.
Once inside a human host, they can spend a protracted period (from weeks or months to, potentially, years) inside the liver before eventually reproducing in the blood (specifically, within the red blood cells).