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Livestock are of enormous importance in Africa, economically, for nutritional and agricultural purposes, and socially. The problem of African animal trypanosomosis1 (AAT), also called “nagana”, was recognized by African stockmen long before the cause of the disease was known, and many pastoralists associated the disease with the presence of tsetse flies. By experience and folk memory, methods of husbandry were evolved whereby domestic livestock could be maintained in strictly defined areas. By a process of trial and error it became known that certain zones were safe from the ravages of the disease, some were death traps and others were seasonally affected and fluctuated between good and bad years.

The impact of the tsetse-associated disease extends in sub-Saharan Africa over some 10 million km2 (a third of the continent). Of these 10 million km2 some 3 million are covered by equatorial rain forest; the remaining area contains some very good grazing areas, which perhaps fortunately have been protected so far by the tsetse fly against (over)grazing. The disease threatens enormous numbers of cattle and other livestock, while some trypanosomes affect humans also directly in most of this area by causing sleeping sickness. Over this vast area the process of development as seen elsewhere has been greatly hindered. Throughout the rest of the world progress has been attended by the increasing use of harnessed power, and the use of draught animals. For centuries trained oxen provided traction for cart and plough, while cattle also provided meat, milk and manure. Their absence over a great part of the African continent meant a constraint to the progress of development of huge proportions.