Anthrax Diagnosis

Information about how the disease is diagnosed.

Sudden death in an animal without prior signs should lead to a suspicion of anthrax. If anthrax is suspected as the cause of death, the carcass should NOT be opened because exposure of the vegetative anthrax bacteria in body fluids to oxygen induces spore formation. The spores will contaminate the environment and present a health risk to personnel and other nearby animals. In the unopened carcass, the putrefactive processes destroy the bacilli.

Diagnosis can be confirmed by collecting a postmortem blood sample aseptically from a peripheral vein (e.g., the jugular vein) and examining a blood smear for the presence of the bacillus capsule using McFadyean's polychrome methylene blue stain or by culturing the bacilli. When a postmortem blood sample cannot be obtained from a peripheral vein, blood can be obtained from a small incision in the ear using a cotton swab. The swab should be allowed to air dry before shipping in order to encourage sporulation and kill other bacteria. B. anthracis competes poorly with putrefactive bacteria and may not be seen in smears after 2 or 3 days; culture is then necessary for confirmation of diagnosis but growth is increasingly unlikely in blood held for more than 3 days.

Potential culture specimens can also be obtained from hemorrhagic nasal, buccal, or anal exudates or from materials contaminated with the exudates.