Plasmodium falciparum protozoan inside red blood cells, illustration. P. falciparum is the causative agent of malignant tertian malaria, also known as tropical malaria, the most severe form of malaria. It is transmitted to humans by the bite of the female Anopheles mosquito. The illustration shows typical morphological features of P. falciparum in the of mature schizont stage, which is used in laboratory diagnosis. The mature schizont of P. falciparum has 8 to 36 merozoites (24 in average) in a cluster arrangement.