A massive killer

To a dweller in a temperate-climate nation, the word tsetse has relevance solely when confronting crossword puzzles. To those living in sub-Saharan Africa, however, it defines a terrible human misfortune and is an alternate name for the devil incarnate. The dipterous insect called the tsetse fly transmits a major African disease of cattle called nagana; and a tragic disease of humans called sleeping sickness, African trypanosomiasis or maladie sommeil.A 14th-century Arabic explorer named A.L. Qualquasandi maintained a journal describing his travels through West Africa. In it he documents the death of the sultan of Mali, Diata II, as follows: "His end was to be overtaken by the sleeping sickness which is a disease that frequently befalls the inhabitants especially their chieftains. Sleep overtakes one of them in such a manner that it is hardly possible to awaken him."John Atkins, a British naval surgeon, wrote the following clinical memoir when he returned from the Guinea coast of Africa in 1734: "The Sleepy Distemper gives no previous notice than a want of appetite two or three days before; their sleeps are sound, and sense and feeling very little; for pulling, drubbing or whipping will scarce stir up sense and power enough to move; and the moment you cease beating, the smart is forgot, and done again they fall into a state of insensibility ... and the Judgment generally pronounced is Death."Colonization of the African continent brought European scientists in closer contact with this strange, and generally fatal, disease. It begins quietly with some fatigue, low-grade fever, a painless chancre formation on one or another arm (representing the site of the tsetse bite) and some swelling of the neck glands. After a further incubation interval of a few days the victim then shows confusion, disorientation, and increasing somnolence. The lethargy then progresses relentlessly to a profound, irreversible coma and, inevitably, death. During the pre-comatose phase of the disease the victim may, at times, become irrationally manic, sometimes randomly attacking others with whatever weapon is available.In 1898 David Bruce identified a microscopic protozoan parasite, called a trypanosome, in the bloodstream of cattle affected with the disease; and four years later he indicted the blood-sucking brown fly of the African savannah, a member of the Glossina genus, locally called tsetse, as the invertebrate vector carrying the infection from cattle to cattle. Bruce suspected that there existed a vast reservoir of the disease in the wild herds of African gazelle, impala, wildebeest and waterbuck. At the turn of the 20th century other British physicians discovered the same trypanosome parasite in the blood of human victims of sleeping sickness. Long before the aggressive European colonization of Africa was undertaken, largely along Africa's west coast, Arab traders had already established commercial probes from Africa's east coast extending as far west as the kingdoms of Ghana and Mali. These trade routes, often using salt as currency, established trading centers and brought Islam to the indigenous populations of western sub-Saharan Africa. Arabic commerce also converted slave trading from a local intertribal transaction to an international enterprise through such eastern ports as Dar-es-Salaam and Mombasa. Arab slave traders were deeply aware of the commercial hazards in purchasing Africans incubating sleeping sickness in its early manifestations. Accordingly, they learned to palpate the necks of the prospective purchase, routinely; and if they felt swollen glands, they then rejected the purchase.Sleeping sickness, however, remained localized to west and central Africa, particularly around the colonies of Gambia, Senegal, Congo and the Ivory Coast. It was not until roads and railroads to the African interior were constructed, mines established and new commercial centers built -- all of this accompanied by massive population displacement, mainly involuntary -- that the disease spread rapidly and was transformed from a handful of endemic epicenters in the west to a coalescent epidemic involving all of equatorial Africa, with a lethal outcome. Around Lake Victoria, during the late 19th century, for example, vast lakeside regions were depopulated by the disease; and in some years the mortality exceeded over a half-million victims. Since the clinical awareness of sleeping sickness at the onset of the colonial era, there have been three major epidemics. The first one, beginning in 1870, was coincident with the major redistribution of indigenous Africans (thus spreading humans with the active disease to new regions where sleeping sickness had not previously taken root). There was another terrible epidemic in 1920 and a third, beginning in 1970, that still has not abated. About 300,000 to 500,000 new cases are now documented annually.The therapies now available to curb tsetse-fly infestation are moderately successful. But these are expensive interventions and must now compete with such medical catastrophes as AIDS, tuberculosis and infantile diarrhea for increasingly restricted funds. Herbert S. Gasser, the Nobel laureate, once said: "From the beginning of Arab and European influence in the hinterland of tropical Africa, trypanosomiasis of man and animals has curbed the realization of human ambitions and the mobilization of the continent's vast resources."(Stanley M. Aronson, M.D., is dean of medicine emeritus, Brown University. E-mail smamd(at)cox.net. For more stories, visit scrippsnews.com.)