Germination is at the site of exposure in the macrophages. Locally there is edema and tissue necrosis but no purulence. The organism is easily isolated from the vesicular fluid and is evident on gram stain. The differential diagnosis includes tularemia, plague, cutaneous diphtheria, staphylococcal disease, rickettsial infection and orf, a viral disease of livestock. Antibiotics prevent dissemination but do not affect the natural history of the lesion.
Gastrointestinal anthrax begins with ingestion of contaminated meat.
The spores are transported to mesenteric or regional lymph nodes, where they undergo replication and dissemination. The incubation period is 2-5 days after ingestion. The host subsequently becomes bacteremic with a high mortality rate. A subset of this disease is oropharyngeal anthrax. Virulence depends on the bacterial capsule and the anthrax toxin complex.