Malaria parasites and red blood cells: from anaemia to transmission.

Malaria parasites, Plasmodium spp., invade and exploit red blood cells during their asexual expansion within the vertebrate host. The parasite has evolved a suite of adaptive mechanisms enabling optimal exploitation of the host blood cell environment, avoiding host destruction, maintaining a parasite reservoir of infection and producing sexual transmission stages to infect mosquitoes. The highly variable nature of the host blood environment, both over the course of an infection and as a result of other parasitic infections, has selected for the evolution of considerable phenotypic plasticity in the parasite's response to its environment, particularly those phenotypes concerning transmission of the parasite to mosquitoes. With the evolution of human society, human malaria disease is becoming an increasingly urban problem. This imposes different selection pressures on the parasite. The extent to which the parasite is truly plastic over the short term rather than adaptive over the long term will determine the urban epidemiology of malaria and is essential for developing appropriate control methods. Understanding the adaptive nature of malaria parasites is thus vital for anticipating the future visage of urban human malaria.