Diseases of Sub Saharan Africa to 1860

Disease in Africa, as elsewhere, has been and continues to be intimately linked with the ways that human populations have fed themselves. Throughout most of the evolutionary journey of Homo sapiens on the African continent (again, as elsewhere), the species existed in small bands of hunter-gatherers with generally fewer than 100 members. As such, individuals were constantly on the move, seldom pausing in one place long enough to foul their water supplies or let their garbage and excrement pile up. They were, as a consequence, spared a host of water-borne parasites and insect disease vectors. Because hunter-gatherers did not have domesticated animals, they were also spared the incredible number of ailments that animals pass along to human masters. Moreover, their numbers were too small to support directly transmitted microparasitic diseases such as smallpox and measles. Finally, evidence suggests that hunter-gatherers were essentially free from the predominant noncommunicable diseases of today, such as cancer, heart-related diseases, and diabetes.

This does not mean that they enjoyed perfect health. They were tormented by a variety of arthritic conditions and suffered from accidents connected with hunting and warfare. Those living within the line of 40-inch rainfall would have been infected from time to time by the trypanosome, which is presumably a very ancient parasite of wild animals. When it is transmitted to humans and large animals by the tsetse fly, it causes often-deadly sleeping sickness. Indeed, as William McNeill points out, the disease probably set some limits on the territory in which early humans were able to hunt and gather. Those living close to the forest would also have been infected on occasion by arboviruses (carried by primates) such as dengue and yellow fever, and it would appear that vivax malaria was ubiquitous at some stage of human development in sub-Saharan Africa. Plasmodium vivax is thought to be the oldest of the malaria types that presumably were passed along to humans by their primate cousins. That this occurred quite some time ago is suggested by the fact that the blood of most (95 percent or more) black Africans and those of African descent scattered around the globe lack Duffy antigen, which makes them absolutely refractory to this malarial parasite. Indeed, vivax malaria has died out in Africa, presumably for a lack of hosts.

It is perhaps ironic that, by domesticating plants and animals in the first gigantic effort of humans to control their environment, they created a disease environment over which they had no control, one over which even today only a small measure of control has been gained. We will probably never know with certainty what prompted hunter-gatherers to become sedentary agriculturalists. A good guess, however (for Africa as elsewhere), is that the relatively disease-free environment contributed to population growth, that slowly a band of fewer than a hundred individuals became more than a hundred and divided, and that these bands grew too large and divided again, until at some point there were simply too many people for even the huge expanse of Africa to support in their hunting and gathering.

If this is true, then another factor was the expansion of the Sahara desert, which meant the shrinking of resources. The concept of sub-Saharan Africa is a relatively recent one. Some 50,000 years ago that desert was no desert at all, but rather a region covered by Mediterranean flora, and as late as 4,000 years ago farmers and pastoralists inhabited many regions that are dry and barren today. The effect of the desiccating desert was to split the continent into two subcontinents, cut off most intercourse between the two, and leave the lower subcontinent in relative isolation from the rest of the world. The isolation of eastern Africa, which fronted on the Indian Ocean, was less severe than that of the West, where a hostile Atlantic Ocean formed still another barrier to the rest of the world.

They were Stone Age peoples who found themselves slowly pressed south by the expanding Sahara. At first they lived by harvesting the seeds of wild grasses on its fringes. Then, gradually, they learned how to sow those seeds, which, with repeated effort, would become domesticated sorghums and millets. To the south, on the edge of the forest, dwelled other Stone Age peoples, who fed themselves by trapping small animals and collecting the roots and fruits of the forest, which they also learned to domesticate. To the east, however, hunting and gathering continued, although some cattle were apparently herded in the northern regions.

It was in the south on the eve of the Iron Age, which is to say, the first millennium B.C., probably in the Congo basin, that there developed an agriculturally oriented people who would soon spread over much of sub-Saharan Africa. These were the Bantu. Their language, proto-Bantu, was not a language of hunters, but rather of farmers with words for domesticated animals and plants. It would seem, however, that at first they were not the cereal agriculturalists that most later became, but rather yam and palm oil cultivators who had discovered that these plants grew best in the wetness of cleared-forest areas. While the language was still in a formative stage, it incorporated words for ax and knife and iron and bellows. These agricultural people with a knowledge of ironworking made up the groups that began to expand southward and eastward from their nuclear area to absorb, conquer, and supplant other peoples until the Bantu culture (and agriculture) predominated in almost all of sub-Saharan Africa save for West Africa.

The latter region was, in the meantime, filling up as the expanding desert continued to nudge people, as well as the forest itself, farther and farther south, with the densest populations staying just to the north of the retreating forest. Many of these peoples were perhaps slower than the Bantu to become accomplished agriculturalists, but by the end of the first millennium A.D. most had done so. By this time the region had achieved a good deal of urbanization on the savannas of Sudan, Mali, northern Ghana, and Nigeria, and obviously a well-developed agricultural base was necessary to support the cities.

It is likely that this political consolidation on the savannas, coupled with the advent of the Iron Age, hastened the occupation of the West African forest. For one thing, the forest was a place of refuge from that consolidation, which was based to some extent on slavery, and from mounted slave hunters who were frustrated by the lack of mobility in the forest and whose horses were vulnerable to the tsetse fly and sleeping sickness in many forest areas. Another reason that people gravitated to the forest had to do with both the development of iron tools that were used to clear it and the efficient cultivation of newly imported Southeast Asian food plants such as the Asian and coco yams: These yams were considerably higher yielding than any African food plant and grew well in forest clearings.

Accompanying this conversion to sedentary agriculture for most sub-Saharan Africans were parasite proliferations. They came from herds of domestic animals in the north, they arrived via caravan across the desert as people from the northern subcontinent came to trade, and they developed internally. The hot, rainy, humid portions of Africa harbor a vast and nasty collection of disease-bearing insects, among them some 60 of the world's species of Anopheles mosquitoes. The creation of clearings and slash-and-burn agriculture made fine breeding places for many of them, including Anopheles gam-biae, the most efficient vector for malaria. With stationary humans acting as reservoirs for the disease, human being to mosquito to human being malaria cycles began. Vivax malaria was in recession but was replaced by the new and much more deadly falciparum malaria, which forced populations to build genetic defenses against it, such as sickle trait, glucose-6-dehydrogenese deficiency, and thalassemia traits. In addition, the less lethal but nonetheless debilitating Plasmodium malariae became widespread, and genetic defenses notwithstanding, immunity acquired by suffering a few bouts of malaria and surviving them was doubtless the first line of defense.

With the development of sickle trait, however, African youngsters probably began to develop deadly sickle cell anemia. Although sickle-shaped cells somehow limit the extent of parasitization in the case of Plasmodium falciparum, that protection comes at a very dear price. When both parents of a child have the trait, the odds are 1 in 4 that the child will be born with sickle cell anemia. In the past, an afflicted child would most likely have died. Thus, in the more malaria-ridden regions of Africa, where the frequency of sickle trait reached 40 percent or more, sickle-cell anemia must have been an important killer of the African young.

Permanent villages in and near the forest accumulated human junk, such as broken pottery, which encouraged the breeding of another disease vector, the Aedes aegypti mosquito. As the latter came to depend on closely packed human populations for blood meals, it began to spread yellow fever among them. Depending on location, villages were cursed with dracunculiasis (guinea worm infection), schistosomiasis, and filariasis (elephantiasis) including onchocerciasis (river blindness, craw craw), and loiasis (loa loa). Individuals now living in close proximity to one another in large numbers passed yaws and leprosy back and forth. Fouled water supplies supported endless rounds of typhoid fever and amebic and bacillary dysentery. In addition, the blood of the animals that were domesticated and lived cheek to jowl with their masters attracted the tsetse fly, which infected humans as well with sleeping sickness (sleepy distemper). They also attracted disease-bearing insects with their dung and passed along parasites like tapeworm, ascaris, and trichuris worms. These and other worms, such as the hookworm, became ubiquitous in towns and villages where fecal material was disposed of casually, if at all, and individuals went barefoot. Indeed, for reasons yet to be explained, West Africans, at least, had so much experience with hookworm infection that they developed a natural resistance to hookworm anemia.

If the forest offered protection from human predators, a price of that protection was frequently isolation: Self-sustaining village-states were remote from one another as well as from the larger world outside the forest. One consequence of this was the development of a rigid social structure that guaranteed the social stability so necessary for survival, but at the expense of innovation and change. Another likely consequence was frequently sufficient isolation from the disease pools of the outside world that when epidemics did strike they proved to be of exceptional virulence.

It is important to stress that the shift to sedentary agriculture among both cereal farmers and yam and palm oil cultivators was not an overnight phenomenon (and indeed, Africa today has hunter-gatherers). Rather, the shift was the result of a process in which expanding food supplies created expanding populations, which in turn sought new areas to bring under cultivation. However, as the diet narrowed from the variety of foodstuffs enjoyed by hunter-gatherers to the single crop generally produced by sedentary agriculturalists, nutritional illnesses must have joined the list of new diseases in Africa. A diet that is essentially vegetable in nature and limited to a very few nutriments is low in iron, the vitamin B complex, and essential amino acids. In these circumstances it is the young, just weaned from the high-quality protein in breast milk to a vegetable pap, who suffer the most from protein-energy malnutrition with kwasiorkor and marasmus as its symptomatic poles. Animal milk would have prevented the disease, but as hinted at previously those within the line of 40-inch rainfall could not develop a dairying industry because of the blood-sucking tsetse fly, which seeks out large animals and infects them with African trypanosomiasis. This explains, in large part, the high frequency of lactose "intolerance among those of West African descent. If they did not drink milk after infancy, there was no reason to maintain the lactose enzyme.

Most West Africans, in particular, were limited to raising a few animals such as goats, chickens, dogs, and perhaps a pig or two. But because these animals were slaughtered only on festive occasions, and because of taboos against drinking goats milk and eating eggs, animal protein figured very little in the diet. Moreover, African soils in the tropical belt are heavily acidic, nitrogen deficient, and leached by rains of their mineral content, especially calcium and phosphorus. As a result, crops that grow on them, as well as animals that graze on them, are protein and mineral deficient. That the West African diet was extraordinarily low in high-quality protein is suggested by the fact that slaves from Africa reaching the Caribbean Islands were significantly shorter than island-born counterparts, despite the miserable quality of the slave diet in the West Indies.

In addition to deficiency diseases, sedentary agriculture led to a reliance on crops that could and did fail because of insects, drought, and warfare. Thus, periodic famine, famine-related diseases, and starvation thinned populations that had swelled during good times, and this synergism became another unpleasant fact of African life. In short, in the switch from hunting and gathering to sedentary agriculture, Africans became what Thomas Malthus called a "forced population," meaning that although the population grew, this growth was managed only at a decreased level of subsistence for everybody.

Contact with Europeans and, through them, their American empires brought a second agricultural revolution to sub-Saharan Africa. Cassava (manioc), maize, peanuts, and sweet potatoes, high-yielding plants imported from America, spread throughout Africa until they became much more important than indigenous crops and further stimulated population growth. Ironically, much of that growth was drained off to America via the slave trade. In addition to population growth, however, the new plants stimulated disease. It has been discovered that those Africans whose diets centered on maize very often suffered from pellagra, and those who consumed cassava were assaulted by beriberi. Also, given the vegetable nature of their diets coupled with the parasites that infected them, most sub-Saharan Africans were anemic. Moreover, the tell-tale spongy and bleeding gums of scurvy were not uncommon.

With the Europeans, and with more contact with the outer world, also came increased exposure to contagious diseases. The earliest European report of smallpox in sub-Saharan Africa dates from Angola in the 1620s, but the strong probability exists that it had been present there for several preceding centuries. In fact, August Hirsch pinpointed regions of central Africa along with India as the "native foci" of the disease, and others have also reported that smallpox was a very old disease on the African continent. This was very likely true of measles, chickenpox, and most other Eurasian diseases as well. Evidence for this assumption derives from the fact that, unlike the American Indians or the Pacific Islanders, sub-Saharan Africans did not die in wholesale fashion after contact with the Europeans. The Europeans, however, were extremely susceptible to African illnesses, especially to the African fevers - yellow fever and malaria. Indeed, white sailors on slaving vessels, and especially soldiers stationed in Africa, suffered such horrendous levels of mortality (in some instances soldiers died at a rate of 500 to 700 per 1,000 per annum) as to earn West Africa the sobriquet "the white man's grave." Thus, it was not until the advent of modern medicine that Europeans were able to colonize much of sub-Saharan Africa.

One Eurasian disease that was slow to make inroads in Africa was tuberculosis. There seems no doubt that whereas tuberculosis was a disease of many ancient civilizations and even prehistoric people in Europe, it was unknown in sub-Saharan Africa until the arrival of the Europeans. Because a long experience with this disease appears to confer some ability to resist it, and conversely, because it falls on "virgin-soil" peoples with considerable fury, one might have expected tuberculosis to have become a severe health problem in Africa long before it did in the nineteenth and twentieth centuries. In the latter part of the nineteenth century, Hirsch pronounced the disease "very malignant" in sub-Saharan Africa. Yet eighteenth-century European observers saw little of it and called it rare.

It may be that the observers in question simply did not recognize the disease, because tuberculosis can have atypical symptoms. Certainly the isolation of many African groups and the relative lack of urban life probably also help to account for the phenomenon. Another possibility, however, deserves some attention.

Leprosy and tuberculosis are both caused by bacilli from the genus Mycobacterium and an inverse relationship between the two diseases has been noticed (e.g., where leprosy is prevalent, tuberculosis is not and vice versa). It is generally thought that, although tuberculosis protects against leprosy, the converse is not the case. Yet in Nigeria, in the heart of the leprosy belt, where it is assumed that the disease has been endemic for many centuries, tuberculosis was very slow to take hold. As late as 1936, for example, a British physician reported much leprosy in Nigeria, but made no mention of tuberculosis.

Bacillary pneumonia, like tuberculosis, was brought to Africa by the Europeans, and like tuberculosis it would prove to be of extraordinary virulence among the Africans, at least by the nineteenth century. Observers reported much lung disease around the Bight of Benin; the disease was viewed as one of the most serious to torment the people of Angola; and Hirsch reported pneumonia as "common" on most of the African West Coast and the East Coast as well.

Syphilis was also a late arrival in sub-Saharan Africa and, like tuberculosis, was slow to spread. But here we are on more solid ground in explaining its slow diffusion. The causative agents of both syphilis and yaws are of the same family (the two diseases may be only one illness with different symptoms and means of transmission) and thus provide cross-immunity. Because yaws was endemic to much of sub-Saharan Africa, it would seem that syphilis had much difficulty finding hosts - so much so that David Livingstone was convinced that "pure Africans" could not develop the disease. Earlier, Mungo Park, the great explorer of the Niger River at the turn of the nineteenth century, saw a great deal of yaws but no syphilis. In contrast, Father Giovanni Cavazzi, in his classic treatment of the diseases of the Congo and Angola, writes of the "mal Frances," called "bubas" by the Portuguese, as the most common disease of the region. Though incomplete, his description suggests syphilis racing through a virgin-soil people, which may well have been the case, for the padre was describing people who had been in contact with Europeans longer than had most others. Yet the disease he reported could also have been leprosy, because until well into the twentieth century, physicians have had difficulty differentiating between syphilis and leprosy in Africa.

To the extent that they were successful in making this distinction, reporters indicate that the disease had apparently overcome the resistance of yaws to become common at least in the port cities of West and West Central Africa during the nineteenth century, although it remained rare in Mozambique until the early twentieth century. From the reports of Livingstone and Park, however, the disease was slow to spread inland.

Gonorrhea, the other major sexually transmitted disease of yesterday, was present much earlier in sub-Saharan Africa and probably had been acquired from the Arabs. Unlike syphilis, gonorrhea had no yawslike disease to hinder its spread and quickly became ubiquitous. The disease is usually not life threatening. But it may cause ophthalmia neonatorum, which along with onchocerciasis was probably responsible for much of the blindness reported among the African natives.

Other nonlethal ailments that tormented sub-Saharan Africans include still more eye ailments, which must have been caused by an absence of vitamin A, since night blindness was regularly seen. The skin complaints that seemed to plague almost everyone resulted from riboflavin deficiency as well as from pellagra, yaws, syphilis, onchocerciasis, and a variety of insect pests including the mites that produce scabies, which were widely reported. Ainhum, sometimes called the "dry gangrene of the little toe" by European observers, which involved the constriction and eventual loss of that digit, was another ailment reported with some frequency; and rheumatism and arthritis were rife across the continent. Finally, women and children often ate dirt and clay, presumably in response to mineral deficiencies.

By 1860, then, sub-Saharan Africans were being born into a world teeming with pathogens. Almost all of the major diseases of the rest of the world had been introduced, including cholera, which had already paid visits to East Africa in 1821, 1836-7, and 1858-9, to enrich a disease pool already brimming with tropical ailments that much of the rest of the world had been spared (cerebrospinal meningitis and plague were yet to arrive). The reasons for the abundance of tropical diseases - helminthic, viral, microbial, and protozoal — in sub-Saharan Africa are diverse. The existence of numerous populations of primates that could harbor diseases and pass them on to humans is obviously one. Another has to do with the high average temperatures and humidity that, along with lush vegetation, make tropical Africa a paradise for the myriad insects that are free from the seasonal controls of more temperate climates and thus can abuse humans on a year-round basis. The same, of course, is true of the many helminthic parasites that find the ecology of the African tropics ideal. As a result, Africans were seldom free of disease, and most likely suffered from more than one at the same time.

Moreover, those born into this world were not provided with much good nutrition to combat their illnesses, and in fact illness often worked synergisti-cally with malnutrition. The chief sufferers of both the disease and nutritional environments were, of course, the young. Infants died at horrendous rates, as did children, and it is likely that 50 percent of those born in sub-Saharan Africa did not live until age 5. Yet such high infant and child mortality constitutes a powerful selective mechanism, and it seems clear that, in the face of sickness and malnutrition, Africans adapted to both in ways we know and in ways we have yet to discover.

Kenneth F. Kiple

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