Disease Patterns of 15001900

More intensive trade and political contacts with the outside world, especially Europe, developed from the sixteenth to mid-nineteenth centuries. These contacts, accompanied by more extensive long-distance trade within Africa and by widespread patterns of political centralization, helped to spread many infectious diseases.

Europeans and Africans began a long commercial relationship with the arrival of the Portuguese in the fifteenth century. Trade grew rapidly over the centuries, and came to involve most of the states of western Europe and the Americas and, directly and indirectly, most African groups living within a few hundred miles of the sea. Coastal African merchants sold slaves, ivory, gold, dyewood, and other commodities for cloth, guns, metal goods, tobacco, alcoholic beverages, and other manufactured items. African products were obtained by trade networks extending far into the interior. Negotiations between the coastal middlemen and foreigners were often long and complex, providing ample opportunities for exchanges of pathogens; the trade routes provided paths for diseases to spread into the interior.

Among the most important and best documented diseases in early African history was smallpox. Although it was widespread in North Africa by the seventh century, and had almost certainly reached the western Sudan as a by-product of the trans-Saharan caravan trade by about A.D. 1000, smallpox may not have been indigenous to the western coast or the southern half of the continent until the seventeenth century. Ships brought infection from abroad or carried it from place to place along the coast at irregular intervals, after enough time had passed to allow the appearance of a new generation of susceptibles. An epidemic caused great loss of life along the Gold Coast in the 1680s, and by at least 1700 some West African peoples had adopted or invented variolation techniques. Smallpox epidemics were frequent in the eighteenth and nineteenth centuries, and a major shipborne outbreak swept the whole coast as far south as Gabon and Angola in the early 1860s. In South Africa, where the Dutch East India Company had established a colony at Cape

Town in 1652, smallpox epidemics introduced by sea in 1713, 1755, and 1767 had serious demographic consequences for the colonists and were devastating for the indigenous and already hard-pressed Khoi pastoralists. On the east coast, it is likely that smallpox was an early accompaniment of the Indian Ocean trade, but there is little evidence for it in the pre-European period. The Portuguese recorded a major epidemic in 1589. Smallpox diffusion into the East African interior probably occurred later than in West Africa because of weaker trade networks; it may date back only to about 1800.

Measles and chickenpox were probably also introduced by traders from time to time, but there is little documentation. Tuberculosis probably reached coastal West Africa in the early days of contact, but it did not become widespread until after 1900. Venereal diseases were a different story; syphilis and gonorrhea were common among coastal groups by the eighteenth century, and these diseases must have spread inland as well. Gonorrhea may well have been an indigenous disease whose diffusion was facilitated by new conditions; syphilis almost certainly arrived from the outside world.

Trans-Saharan trade had existed for centuries prior to 1000, and no doubt the caravans, like the sailing ships, sometimes were accompanied by infectious diseases. Smallpox could well have reached the Sudanese market towns, either with infected merchants or in goods. Tuberculosis, measles, and gonorrhea no doubt diffused from North Africa with trade, although they may have already existed in the savanna. Similarly, the extensive pre-European trade along the east coast, between the Swahili towns and merchants from India, Persia, and Arabia, must have resulted in some disease transmission.

It is clear, despite the weakness of the data, that contacts with Europeans and other foreigners had serious disease consequences for many African peoples in the precolonial period, especially those along the west and east coasts and in the market centers for the Sudan. However, although some small groups may have suffered heavily, there was no postcontact pattern of mass death in Africa similar to what occurred in parts of the Americas or the Pacific. Africans shared enough of the Old World disease pool to avoid major demographic disaster. Stronger social systems of African peoples may also have played a role in their enduring and recovering from great epidemics. Even with the drain of the Atlantic, trans-Saharan, and Indian Ocean slave traders, Africa was not depopulated. Disease resistance, strong local social and political systems, and the introduc tion of new food crops like maize and manioc helped to sustain populations.

The African disease environment did have very serious consequences for foreigners. We still know relatively little about how Moslem traders fared, but North African visitors to the Sudan did try to finish their business before the rainy season brought malarial fevers, and Omani Arabs suffered severely from falciparum malaria on the Swahili coast.

The fate of Europeans on the west coast is much better documented. "Fevers" and "fluxes" - especially malaria, yellow fever, and the dysenteries -took a frightful toll among sailors, soldiers, traders, missionaries, explorers, and slavers. Studies of British, Dutch, and French experiences have shown that death rates of 50 percent in a year were not uncommon. It is possible that Portuguese death rates were somewhat lower, but they too paid a heavy price for their African commerce. Mortality prevented any serious European military activity in most of West Africa; maintaining weak, sickly garrisons in a few coastal forts was all that they could normally do. Disease not only helped save West Africans from European encroachment, but also gave them a considerable commercial advantage. African merchants could, and frequently did, drag out trade negotiations, knowing that the Europeans were anxious to complete a deal and leave before the fevers began to reduce their numbers. The limited Portuguese expansion in northern Angola, although hampered by disease, took place in a drier area where malaria was not as serious as elsewhere on the western coast. European colonization at the Cape was possible only because the Dutch were operating south of the tropical disease environment.

Africa was more important as a donor than as a recipient in the post-Columbian exchange of diseases. Falciparum malaria and yellow fever reached Europe from time to time, but probably did not have major demographic consequences there. Much more significant was the transfer of African diseases to the New World, mostly as a by-product of the slave trade. Falciparum malaria and yellow fever played a major role in the population history of the warmer parts of the Americas, from the southern United States to southern Brazil. Whites suffered severely, and these diseases were leading causes of deaths among the American Indians, especially in the Caribbean basin. The African hookworm, misnamed Necator americanus, came over in the bodies of enslaved Africans, and was a very serious cause of sickness and death in the southern United States and in much of the West Indies and Brazil well into the twentieth century. Other African diseases, including onchocerciasis, filariasis, Schistosoma man-soni infection, and yaws, also became established in American foci.

Cosmopolitan diseases like dysentery and smallpox were frequently introduced into ports along with cargoes of slaves. In Brazil, slave imports often rose when there was drought and famine in Angola. Drought conditions caused people to migrate in search of food; they tended to congregate, often as defenseless, disorganized refugees, in areas where they could find sustenance. Such aggregations encouraged flare-ups of endemic smallpox as well as the depredations of slavers. The virus was often transported by captives, and there is a strong correlation between smallpox epidemics in Brazil and in its Angolan slave supply territory.

In sum, the biological consequences of the African slave trade included millions of deaths in the Americas, among both Europeans and Indians. African labor was crucial in many New World economies, but the demographic costs were enormous for inhabitants of North and South America and for European sailors on slave ships, as well as for sub-Saharan Africa. Indeed, at least in the United States, the demographic balance was almost certainly unfavorable. About 300,000 Africans were imported, probably far fewer than the number of whites who died of falciparum malaria, yellow fever, and hookworm infection from the eighteenth to the early twentieth centuries. The period of the European conquest of Africa and the consolidation of colonial rule, roughly from 1880 to 1920, was the most deadly period in history for much of the continent. West Africa, perhaps because of its earlier experience with introduced epidemics, did not suffer as severely as portions of equatorial, East, and central Africa. Intensified long-distance trade, warfare, labor demands, and famine characterized this era, as many African peoples found their relative isolation shattered. People, pathogens, and vectors all moved, and there were radical changes in living conditions. Smallpox spread widely, especially in East Africa, where coastal Moslem merchant caravans had begun to operate in the interior from the 1830s. Cholera was introduced several times into East Africa and diffused over the trade routes, with an especially destructive epidemic occurring in the 1850s. Cerebrospinal meningitis epidemics appeared, probably for the first time, in the western Sudan in the 1880s; there were several great epidemics there and in parts of the Anglo-Egyptian Sudan and East Africa during the twentieth century. On a less spectacular but still important level, even short-distance moves might bring people into contact with antigenically novel strains of familiar organisms, such as the protozoa that caused malaria and amebic dysentery.

Tuberculosis, noted in the coastal towns of West Africa around the turn of the century, spread slowly inland. In the Cape Verde Islands migrants returning from the United States facilitated the spread of infection by the 1880s. The rise of the mining industry in South Africa and the Rhodesias was dependent on migrant labor. Poor conditions in the mines in the early twentieth century led to extremely high tuberculosis rates and explosion of the disease among the rural African population as infected miners returned to their homes.

Besides mining, other development efforts of the colonial era often had unexpected and deleterious health consequences. Major infrastructure projects usually depended on migrant labor and sometimes took a heavy toll in lives. For example, thousands of workers conscripted in the savanna country of southern Chad and Ubangui-Chari died from dysentery, respiratory ailments, and other diseases during the construction of the Congo-Océan railroad in French Equatorial Africa in the 1920s. Water projects frequently facilitate disease transmission in tropical climates. The Gezira irrigation scheme in Sudan, for example, as well as the massive Volta Lake in Ghana, has resulted in hyperendemic schistosomiasis. On a smaller scale, dam ponds may also become foci for malaria and guinea worm infection, and, in parts of northern Ghana, dam spillways and bridge pilings provided breeding sites for the vector of onchocerciasis, a worm disease that often causes blindness.

Venereal diseases also diffused rapidly in the late nineteenth and early twentieth centuries, as labor migration and urbanization disrupted social patterns. Equatorial Africa experienced a very destructive gonorrhea epidemic as a direct result of harsh Belgian and French colonial policies; this resulted in widespread sterility, which is believed to be largely responsible for the very low fertility rates in the region even today. Movements associated with the early colonial period were also apparently responsible for great outbreaks of human trypanosomiasis in French Equatorial Africa and the Lake Victoria region of East Africa in the first decade of the 1900s. At least 250,000 died in East Africa alone.

On a more trivial but still significant level was the rapid spread of the burrowing flea Tunga penetrans (chigoes). This insect invades tissues under the nails and may result in secondary infections that cause disability, or a loss of digits or limbs. Native to Brazil, the fleas were introduced into the Senegambia region about 1800, and to the Angolan coast about 1850. From Angola they spread over central and East Africa in a few decades, causing great misery in any given place, until people learned how to remove them.

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