Aetiology of malaria

Malaria is caused by Plasmodium parasites that are transmitted to humans through the bites of infected mosquitoes. Of the five Plasmodium species that infect humans (P. falciparum, P. vivax, P. knowlesi, P. malariae and P. ovale), P. falciparum and P. knowlesi are the most pathogenic and P. falciparum is the most resistant to standard antimalarials. P. knowlesi is increasingly a cause of malaria in parts of Southeast Asia; it has a similar appearance on microscopy to P. falciparum (ring stages) or P. malariae (mature stages).