1890s African rinderpest epizootic
In the 1890s, an epizootic of the rinderpest virus struck all across Africa, but primarily in Eastern and Southern Africa. It was considered to be "the most devastating epidemic to hit southern Africa in the late nineteenth century." It killed more than 5.2 million cattle south of the Zambezi, as well as domestic oxen, sheep, and goats, and wild populations of buffalo, giraffe, and wildebeest.
Source: Wikipedia — 1890s African rinderpest epizootic (CC BY-SA 4.0)