Malaria is not caused by a mosquito but by a parasite in the mosquito. The malaria parasite needs the mosquito to reproduce and spread. The gametocyte is the developmental stage of the parasite that can be transmitted from people to the mosquito. In the mosquito's stomach the gametes are released and fertilisation takes place. The parasite develops further until the final stage (the sporozoite) in the salivary gland. The sporozoite can be transmitted with the saliva to a person if he/she is bitten by this mosquito. There the parasite reproduces rapidly and the person becomes ill.
People who live in areas where malaria is prevalent, can develop a natural immunity that stops the development of the parasite in the mosquito. This prevents the parasite from spreading further. The presence of this immunity, the so-called transmission-reducing activity, is determined using a laboratory test. Van der Kolk discovered that people who are often infected with malaria could quickly acquire this immunity. He also found that people with higher numbers of gametocytes are more frequently immune.
Each year more than 200 million people develop malaria. More than one million people die from malaria each year. In Cameroon, the researchers recorded how often people were bitten by a mosquito that carried malaria parasites. They also examined the number of transmittable parasites in the blood of infected persons. In a neighbourhood of the capital Yaoundé, 34 infectious bites per person per yea
Source:Netherlands Organization for Scientific Research