[1][2] After qualifying as a physician, Das Gupta was appointed in 1921 to a position as a researcher and assistant surgeon at the Calcutta School of Tropical Medicine.
[3] At the Calcutta School of Tropical Medicine, in 1931 H. G. M. Campbell detected the Plasmodium species now known as P. knowlesi in a macaque imported from Singapore.
Campbell showed his discovery to his supervisor Lionel Everard Napier, who injected the strain into three monkeys, one of which developed symptoms of malaria.
Das Gupta maintained the Plasmodium species by serial passage in monkeys until Knowles returned from leave.
[1] Das Gupta was the director of the Calcutta School of Tropical Medicine from 1943 until his death in 1945.