Casimir Davaine (March 19, 1812 – 14 October 1882) was a French physician known for his work in the field of microbiology. He was a native of Saint-Amand-les-Eaux, department of Nord.
In 1850, Davaine along with French dermatologist Pierre François Olive Rayer (1793–1867) discovered a certain microorganism in the blood of diseased and dying sheep. In the diseased blood, Rayer and Davaine observed the bacillus which is known as Bacillus anthracis, the causative bacterium of anthrax. Soon afterwards, Rayer published an essay on anthrax, which contained the first description of Bacillus anthracis.
In 1863 Davaine demonstrated that the anthrax bacillus could be directly transmitted from one animal to another. He was able to identify the causative organism but was unaware of its true etiology. Later, German microbiologist Robert Koch researched the etiology of Bacillus anthracis, and discovered its ability to produce "resting spores" that could stay alive in the soil for a long period of time to serve as a future source of infection.
Casimir Davaine is also credited for pioneer work in the study of septicemia (blood poisoning).