This document focuses on the characteristics of bacillus anthracis (anthrax).
Anthrax occurs in domesticated and wild animals -- primarily herbivores, including goats, sheep, cattle, horses, and swine. Humans usually become infected by contact with infected animals or contaminated animal products. Infection occurs most commonly via the cutaneous route and only very rarely via the respiratory or gastrointestinal routes. Anthrax occurs worldwide; it exists in the soil as a spore. Owing to the infectiousness of anthrax spores by the respiratory route and the high mortality of inhalational anthrax, the military's concern with anthrax is with its potential use as a biological weapon. More than 95 percent of cases of anthrax are cutaneous, appearing as a small lesion with varying degrees of edema around it. Patients usually have fever, malaise, and headache. Inhalational anthrax begins after an incubation period of 1 to 6 days with nonspecific symptoms of malaise, fatigue, myalgia, and fever. There may be an associated nonproductive cough and mild chest discomfort. These symptoms, persisting for 2 or 3 days, are followed by sudden onset of increasing respiratory distress. The onset of respiratory distress is followed by rapid onset of shock and death within 24 to 36 hours. Mortality has been essentially 100 percent despite appropriate treatment. Oropharyngeal and gastrointestinal anthrax result from the ingestion of infected meat that has not been sufficiently cooked. Patients with oropharyngeal disease present with severe sore throat or a local oral or tonsillar ulcer, usually associated with fever, toxicity, and swelling of the neck. Gastrointestinal anthrax begins with nonspecific symptoms of nausea, vomiting, and fever, followed by severe abdominal pain. Mortality in both forms may be as high as 50 percent, especially in the gastrointestinal form. The most critical aspect in making a diagnosis of anthrax is a high index of suspicion associated with a compatible history of exposure. Penicillin is the drug of choice for anthrax. Tetracycline, erythromycin, and chloramphenicol have also been used successfully. Treatment with antibiotics beginning 1 day after exposure to a lethal aerosol challenge with anthrax spores can provide significant protection against death. A licensed nonliving vaccine is available for human use. 69 references