It does, however, cause severe diarrhoea in humans. This is a unique group because all members are parasitic. The group includes parasites causing malaria, cryptosporidiosis and toxoplasmosis. The common feature of all members is the presence of an apical complex in one or more stages of the life cycle. Although the exact components of the apical complex varies among members, it contains enzymes used to penetrate host tissues.
Plasmodium species cause malaria.
The four principal species are P. falciparum, P. vivax, P. ovale and P. malariae. The disease is in fact transmitted by the female Anopheles mosquito that inhabits such environments. This in turn forms a motile ookinete that penetrates the midgut wall and develops into an oocyst within which are many thousands of sporozoites. When mature, the sporozoites rupture the oocyst and penetrate the salivary glands. When the mosquito next feeds on man, the sporozoites are passed via the blood stream to infect parenchymal cells of the liver.