Hans Sieber was recruited by Arnold Theiler* from the Institute for Tropical Medicine in Hamburg, Germany, in 1910, to replace W. Frei* as assistant veterinary bacteriologist at the Onderstepoort Veterinary Research Institute. Sieber worked on Anaplasma marginale infection (tick-borne gall sickness) in cattle and reported on his work in "Anaplasma marginale (Theiler)" (Report of the Government Veterinary Bacteriologist of the Transvaal, 1909/10, pp. 104-116). However, his health appears to have been poor at this time, as he applied for six months sick leave during 1910. The next year he moved to German South West Africa (now Namibia) as director of the Gammams Veterinary Research Institute, originally established as a lung sickness station near Windhoek in 1895. Following a visit to the territory by Professor R. von Ostertag* the authorities decided to develop the institute into a research centre comparable to that at Onderstepoort and entrusted Sieber with the task. His work included the investigation of African stock diseases, serum production, the preparation of a serum against snake venom, and vaccines against human smallpox and typhus fever. The institute was dissolved in 1915, during World War I, when the territory came under South African control. By 1918 Sieber was living in Swakopmund.