Tsetse were absent from much of southern and eastern Africa until colonial times. The accidental introduction of rinderpest in 1887 killed most of the cattle in these parts of Africa and the resulting famine removed much of the human population. Thorny bush ideal for tsetse quickly grew up where there had been pasture, and was repopulated by wild mammals. Tsetse and sleeping sickness soon colonised the whole region, effectively excluding the reintroduction of farming and animal husbandry. Sleeping sickness has been described by some conservationists as "the best game warden in Africa".