 During World War I he was a doctor of colonial troops, receiving the Croix de Guerre in 1916.From 1917 to 1920 he was a physician in charge of the bacteriology laboratory at the hospital in Diego-Suarez.In 1922 he was appointed director of the Institute of Bacteriology of Madagascar (Institut Pasteur of Antananarivo), a position he maintained until 1940..

During his tenure in Madagascar, Girard conducted studies of typhoid, tuberculosis, leprosy and especially bubonic plague.