Book Review

James L.A. Webb Jr., Humanity's Burden: A Global History of Malaria. New York: Cambridge University Press, 2009. Pp. xii + 236.  $23.99 (paper)

     Humanity's Burden is a short (190 pages), dense and very interesting discussion of one of the most debilitating and intractable scourges—malaria—that has cursed humanity from its primate ancestry to the present. James Webb, who teaches at Colby College, presents one of history's persistent epidemiological problems that kills children and incapacitates adults in areas where it has been endemic generation after generation.

     Webb begins his work with an introduction describing the disease for the layman.  There are many varieties of malaria, each caused by a different species of parasite belonging to the genus plasmodium, which infects the blood and sometimes the livers of its human hosts. Plasmodia are protozoa that have a complex life cycle in which the parasites reproduce sexually in the gut of female anopheles mosquitoes. These insects then inject the plasmodium organism into human blood streams by biting. In humans, the plasmodia live in the blood and, in some types of malaria, the liver, where they multiply by asexual reproduction. In their human hosts they cause fevers, anemia, weakness and sometimes, especially in children, death.  Of the four varieties of human malaria, two are most common: vivax in temperate and subtropical zones, and falciparum in the tropics. Both of these varieties of malaria can cause debilitation and death, but some Africans have developed mutations such as Duffy negativity, which makes them immune to vivax, and the sickle cell mutation, which provides partial immunity to falciparum.

     After this very important introductory background, Webb discusses the global history of malaria in six roughly chronological chapters. Chapter One discusses malaria's African origin. Our primate ancestors carried the malaria parasites in their blood and in their livers even before the emergence of hominids. These protozoan parasites, together with their mosquito vectors, co-evolved with humans for millions of years. Although vivax malaria probably intermittently and sporadically infected human populations in Africa for tens of millennia, the sparsity of migratory foraging populations prevented vivax from reaching epidemic proportions. When West African peoples began to rely on the paracultivation of African yams and oil palms for sustenance, they settled in larger and more permanent groups on the forest edges and in fire made clearings, creating reservoirs of infectivity. This led to recurrent epidemics in these settlements. Sometime in the deep past "between 97,200 and BP to 6,500 BP" (21), the Duffy negativity mutation developed, which renders 97 percent of West and Central Africans immune from vivax malaria.

     But Duffy negativity did not provide immunity against falciparum, a malaria parasite more deadly than vivax. Falciparum became and remains endemic in tropical Africa. West Africans did develop the sickle cell mutation, which, though it confers partial immunity to the falciparum parasite, can cause deadly anemia if inherited from both parents. Additionally, the West African yam-based diet may have somewhat ameliorated the effects of falciparum. Webb speculates that the cultural practices of the Bantu, together with their partial immunity to falciparum, may have given them a biological advantage in their expansion across the equatorial Central African rainforest.  In the African forest, falciparum became a deadly scourge, made worse because of its companionship with trypanosomiasis—sleeping sickness—the vector of which is the tsetse fly. Sleeping sickness causes extreme suffering among humans, but is deadly to many domesticated animals: cattle, horses, sheep, goats, camels and pigs. In the absence of livestock from which to obtain blood, the female anopheles mosquito specialized in biting human hosts, becoming more efficient in transmitting malaria. It was only after the fourth millennium BCE that Nilotic agro-pastoralists, by using fire and cultivation, created a tsetse fly-free grassland corridor that permitted pastoralism to take hold in East Africa south to the Cape. Among the cattle herding agro-pastoralists, the incidence of falciparum diminished because the mosquitoes had an alternate source of blood meals.

     In Chapter Two, Webb explains that when humans spilled out from Africa into Eurasia, they carried in their blood the vivax parasite. Again, as long as the largest human aggregations were small nomadic bands, malaria did not become the burden that would later afflict these lands. However, when Eurasians began aggregating in permanent villages, malaria, both vivax and falciparum, became endemic. The zone of falciparum infectivity was limited to tropical and subtropical Eurasia, essentially the Mediterranean region as well as south and Southeast Asia, including southern China. The vivax parasite also proliferated in southern Eurasia, but, since it could over-winter in the livers of its human hosts, followed the advance of farming into northern Eurasia. The adoption of the mold board plow, which enabled the spread of peasant villages into the forests of northern Europe where the soils were heavier, also helped create new favorable environments for the anopheles mosquito, the vector of malaria. As the forest retreated, the vivax parasite advanced, until it lodged in southern Scandinavia by the mid-nineteenth century. Malaria in most of Eurasia proved less deadly that it was in the African tropics, principally because the animals that were a significant feature of the Eurasian agriculture reduced the efficacy of the anopheles mosquitoes as vectors of the disease by providing alternate sources of blood. Chinese farmers sometimes kept animals between the villages and the rice paddies and, perhaps unintentionally, lessened the incidence of malaria infection. Eurasian societies also developed dietary and pharmaceutical strategies meant to ameliorate the impact of malaria, including the ingestion of fava beans (in the western Mediterranean region) and a variety of spices.

     Chapter Three, "Into the Americas," begins with the Columbian Exchange. Webb notes that "Explorers who unfurled their sails in the port harbors of Europe carried vivax parasites with them," and Africans transported from Guinea to Brazil brought falciparum (63). As with other European introduced diseases, malaria decimated Native American societies, severely depleting indigenous populations in tropical coastal lowlands. In the temperate regions of North America, vivax—which is debilitating but less often fatal—became common, causing summer fevers or "agues" (74). In the tropical coastlands and the Caribbean islands, falciparum, which is much more often fatal, prevented the development of large European populations in the colonial era. In these hot lands, Africans were preferred to Native American slaves or European indentured servants because almost all African slaves arriving in the New World as adults had suffered bouts of falciparum as children and had acquired lifelong immunity to the disease. They also were protected from vivax by their inherited Duffy negativity.

     In the nineteenth century, as a result of the soaring demand for cotton and wheat, the agricultural frontier raced westward, and with it, malaria. As new lands were settled, new reservoirs of infectivity, particularly for vivax, were created and malaria became common in a broad swath of land stretching from New England to Texas. (Michael Finkel, in the July 2007 National Geographic, reports that President Lincoln, U.S. Grant, and many of the soldiers in the Civil War had malaria.) Malaria—mostly vivax—raged in much of the United States until the twentieth century, when it was gradually eliminated through the use of drugs and insecticides.

     Chapter Four, "Bitter Medicines," discusses the growing use of cinchona bark and its derivative alkaloids to control malaria. The Spanish used cinchona bark ("Jesuit's Bark") in the seventeenth century, but it was only in the early nineteenth century that the mass production of quinine, the principal alkaloid of cinchona bark, became feasible. Webb discusses the effectiveness of quinine and the changing economics of producing it, as well as the geo-political consequences. For example, the European colonization of Africa occurred when it became possible to protect Europeans in Africa from the ravages of falciparum malaria. European officials, soldiers and merchants—unlike native Africans—had no genetic resistance to this deadly pestilence. In India and China, where quinine was too costly for widespread usage, opium was used to sooth the effects of the disease.

     In Chapter Five, "Toward Global Public Health," Webb describes the twentieth-century campaigns to eradicate malaria. In 1897, scientists discovered that malaria is spread by the female anopheles mosquito, so the anti-malaria campaign became a drive to eliminate mosquitoes as well as to produce drugs to cure malaria. The United States and a few other countries, such as Italy, scored notable successes in "landscape sanitation" (136), while the British and Dutch established cinchona plantations in their empires. The League of Nations and the Rockefeller Foundation also made efforts to launch a global campaign to eliminate malaria. The wars and revolutions of the twentieth century made the effort a Sisyphean task, but, because of the development of DDT, some regions, such as the United States, became malaria free by the 1950s.

     The development of DDT and a new more effective drug, chloroquine, led to a great hubris in the anti-malaria community. After World War II, the World Health Organization set a bold goal of global eradication of malaria. The overuse of DDT and other insecticides, as well as chloroquine and similar drugs, at first had enormous success, but ultimately led to the emergence of resistant strains of mosquitoes and plasmodium parasites. In Chapter Six, "Africa Redux," Webb discusses the "mixed success" of the continuing eradication campaign (187).

     Humanity's Burden is a very interesting book and a valuable contribution to the literature of world history. It would serve as worthwhile reading for the educated layman as well as for students of world history.

Wilfred Bisson is a professor emeritus from Keene State College who lives in DeLand, Florida. He can be contacted at bissonmw@cfl.rr.com.