EVOLUTION OF MALARIA IN AFRICA FOR THE PAST 40 YEARS - IMPACT OF CLIMATIC AND HUMAN-FACTORS

Different malarial situations in Africa within the past 40 years are d iscussed in order to evaluate the impact of climatic and human factors on the disease. North of the equator, more droughts and lower rainfal l have been recorded since 1972; and in eastern and southern Africa, t here have been alternating dry and wet periods in relation to El Ni (n ) over tilde o. Since 1955, the increase in human population from 125 to 450 million has resulted in both expansion of land cultivation and urbanization. In stable malaria areas of West and Central Africa and o n the Madagascar coasts, the endemic situation has not changed since 1 955. However, in unstable malaria areas such as the highlands and Sahe l significant changes have occurred. In Madagascar, cessation of malar ia control programs resulted in the deadly epidemic of 1987-88. The sa me situation was observed in Swaziland in 1984-85. In Uganda, malaria incidence has increased more than 30 times in the highlands (1,500-1,8 00 m), but its altitudinal limit has not overcome that of the beginnin g of the century. Cultivation of valley bottoms and extension of settl ements are in large part responsible for this increase, along with abn ormally heavy rainfall that favored the severe epidemic of 1994. A sim ilar increase in malaria was observed in neighboring highlands of Rwan da and Burundi, and epidemics have been recorded in Ethiopia since 195 8. In contrast, in the Sahel (Niayes region, Senegal), stricken by dro ughts since 1972, endemic malaria decreased drastically after the disa ppearance of the main vector, Anopheles funestus, due to the destructi on of its larval sites by cultivation. Even during the very wet year o f 1995, An. funestus did not reinvade the region and malaria did not i ncrease. The same situation was observed in the Sahelian zone of Niger . Therefore, the temperature increase of 0.5 degrees C during the last 2 decades cannot be incriminated as a major cause for these malaria c hanges, which are mainly due to the combination of climatic, human, an d operational factors.