Malaria and ecosystems: from prehistory to posteradication.

Human malaria originated in tropical areas of the Old World but the Pleistocene glaciations delayed its spread in the Northern Hemisphere. The last glaciation produced temperatures 9 degrees C lower than those prevailing today in Southern Europe, making the transmission of malaria there virtually impossible. When temperatures approximately equal to those of today were reached 10,000 years ago, the disease and some of its most effective vectors, Anopheles labranchiae and A. sacharovi, spread to the North although the refractoriness of the European vectors to Pasmodium falciparum probably delayed the spread of the malignant tertian parasites. Malaria may have spread earlier in the Levant and parts of Asia, due to a less marked drop of temperature during the last glaciation but we have witnessed in contemporary times the spread of A. stephensi, one of the most effective vectors in the area. The first noticeable decline of malaria was seen in Europe during the nineteenth century due to new agricultural practices and changed social conditions. The final disappearance of the disease in Europe and North America was due more to those changed conditions than to the use of DDT and other residual insecticides which were going to fall in so-called eradication campaigns in the Third World.