W.B. Leishman. Sir William Boog Leishman (1865- 1926), British bacteriologist. In 1904-09 he tested and improved the typhoid vaccine, leading to its widespread use. In 1900, he discovered the protozoan, Leishmania, which caused a disease called kala-azar (Leishmaniasis). He also devised a test, Leishman's stain, for detecting protozoa in blood. In 1886 Leishman joined the British army as a medic, being posted to the Army Medical School in 1897, where he became a professor in pathology. In 1913 he joined the War Office, becoming director of pathology in 1919 and director general of Royal Army Medical Services in 1923.