Introduction
Each year approximately 500 million cases of malaria occur worldwide. This constitutes a health problem for 2.4 billion people representing 40% of the world population in over 40 countries in the southern hemisphere. Malaria causes from 1.5 to 2.7 million deaths annually [65]; over 90% of the deaths from malaria occur in Africa, mainly among children under 5 years of age. Those who survive may suffer mental retardation and impaired development. Another category of people highly exposed to the disease is pregnant women, who often suffer miscarriages or give birth to low-weight babies affected by anemia. In Africa, around 100,000 newborn infants die each year due to low birth weight caused by malaria infection during pregnancy [27]. Nearly all deaths are attributable to Plasmodium falciparum, one of the four species of plasmodium that infect humans. Almost 10% of the world population suffers at least one malaria attack per year (Table 1); fortunately, the majority survive, but during the period of illness these people are no longer able to perform normal job duties or attend school, resulting in a decline in productivity and impaired learning. Drug resistance of the parasite is a serious problem; Chloroquine, an extremely safe, inexpensive and effective drug, has widespread resistance in most parts of the world. Mosquitoes of the genus Anopheles, the transmission vectors of malaria, have likewise developed resistance to the majority of insecticides used in control programs. Population increases, wars and demographic changes have led to mass migrations across areas where malaria is endemic. As a consequence, people who lack natural immunity have become exposed to the risk of malaria epidemics characterized by elevated mortality. The building of new roads, exploitation of subsoil, deforestation of new areas and new irrigation projects have had the effect of creating new vector breeding sites. Funding for malaria research and control projects has declined significantly in recent decades: public health issues are often at the bottom of the list when it comes to allocating funds. Wars and the presence of refugees constitute ideal conditions for the aggressive spread of malaria. What does the future hold in store? Many hypotheses have been formulated concerning the effects caused byincreasing urbanization, migrations and climate change, but one thing is certain: unless developed nations make a strong political commitment to providing scientific, technical and economic support, malaria will continue to represent a major health problem in countries in the southern part of the globe.