Anthrax: diagnosis, treatment, prevention

Anthrax is a zoonotic disease caused by Bacillus anthracis. Herbivores are the natural host. Humans acquire the disease incidentally by contact with infected animals or animal products. The incidence of disease has decreased dramatically in developed countries as a result of animal vaccination programs and improved industrial hygiene. Clinical disease in humans presents in three distinct forms: cutaneous, gastrointestinal, and inhalational. More than 90% of naturally occurring cases of anthrax in the United States are of the cutaneous form. Eschar formation and edema at the site of inoculation characterize cutaneous anthrax. Gastrointestinal anthrax has never been reported in this country. Inhalational anthrax results from inhalation of B. anthracis endospores. The spores germinate in mediastinal lymph nodes before hematogenous dissemination. Disease progresses rapidly from nonspecific symptoms to death in the majority of cases. Diagnosis can be made by Gram stain or by culture of body fluids or lesions. Serologic tests including enzyme-linked immunosorbent assay and polymerase chain reaction are available in specialized laboratories. Marked widening of the mediastinum on chest radiograph is the most characteristic clinical finding. Penicillin is the drug of choice for the treatment of anthrax infections. Other acceptable alternatives include ciprofloxacin and doxycycline. Supportive care in an intensive care unit is a critical part of treatment for all but uncomplicated cutaneous infections. A vaccine is available for anthrax. Persons with high-risk occupations, such as laboratory workers and military forces, should receive the vaccine. In the case of suspected bioterrorism, ciprofloxacin or doxycycline should be given as chemoprophylaxis. The vaccine should be given concurrently, if available.