Harvey S. Purchase was born in Fort Jameson, Northern Rhodesia (now Chipata, Zambia). He was educated at Mill Hill School, London, and then obtained the BSc (Vet) degree and qualified as a veterinarian (MRCVS) at the Royal Veterinary College, London, in 1928. After qualifying he spent a year at the Weybridge Veterinary Research Laboratories in Surrey, England (1929-1930), followed by a year on a Colonial Fellowship at the Molteno Institute, Cambridge, where he studied tropical diseases.
In 1931 he was awarded the FRCVS for a thesis entitled Some diseases of domestication and their prevention. That same year he joined the Veterinary Department of the Northern Rhodesia Goverment as district veterinary officer - the first Rhodesian-born to hold such a post. In 1938 he obtained a PhD degree from London University with a thesis on Bovine Pleuropneumonia. That year he went to Kenya as a veterinary research officer (1938-1948). In 1948, as member of a committee of the Food and Agricultural Organisation of the United Nations, he visited China and Thailand in connection with rinderpest control in those countries. In the same year he was promoted to chief veterinary research officer of the laboratory at Kabete. He had a knowledge of several African languages and in his youth was as fluent in Chinyanja as in English.
Purchase resigned from the Colonial Service in 1952 and that same year was honoured as an Officer of the Order of the British Empire (OBE) for his services. He then joined the firm Cooper and Nephews (SA) as Technical Manager in Johannesburg, remaining in this post until his death. Meanwhile he was also a director of Vitamin Mineral Products (Pty) Ltd., and St O'Gormans Chemical Company Ltd.
Purchase was a kind and friendly person, well liked by the many veterinarians with whom he came in contact. He married Vera M. Cooper in 1934 and they had two sons, both of whom qualified as veterinarians at Onderstepoort.