Anthrax is an acute infectious disease caused by the gram-positive, encapsulated, nonmotile, spore-forming rod Bacillus anthracis. The incubation period is 1 to 7 days (may be longer in the inhalation form). Person-to-person transmission from cutaneous lesions rarely occurs.
PATHOGENESIS AND EPIDEMIOLOGY
An antiphagocytic capsule and 2 exotoxins (lethal toxin, edema toxin) are responsible for the clinical illness cause by B anthracis. The toxins are responsible for the clinical manifestations (eg, hemorrhage, edema, necrosis) of the various clinical presentations as well as the morbidity and mortality associated with illness due to anthrax. Therefore, treatment not only requires antimicrobial therapy to kill the organism, but antitoxin therapy may also be indicated.
B anthracis affects domestic and wild animals throughout the world. Human infections are a result of contact with infected animals or contaminated animal products (eg, meat, skin, hair). In the United States, the most common form has been cutaneous infections among animal handlers, but more invasive cases (eg, inhalation) have been described in drum makers working with contaminated animal hides or in people participating in drumming events where spore-contaminated drum heads were being used. In 2001 in the United States, 22 cases of anthrax occurred due to purposeful contamination of the mail. Because of the potential of biological terrorism with this organism, every suspected case should be reported to the local or state health department.
Cutaneous anthrax occurs when B anthracis spores enter through an abrasion. A small, erythematous papule vesiculates to form a painless, black eschar with marked edema. Lymphadenopathy or lymphangitis may occur. Untreated, mortality is up to 20%, but with appropriate treatment, it is less than 1%.
Inhalation anthrax occurs after respiratory exposure to B anthracis spores. Initial symptoms are nonspecific, mimicking influenza. Symptoms become fulminant over a few days, often leading to death. Mediastinal widening and pleural effusions on chest radiograph are common. Hemorrhagic meningitis and bacteremia are often present. Even with treatment, mortality rates are 40%.
Gastrointestinal anthrax follows ingestion of contaminated, undercooked meat. It may present in 2 forms. In the intestinal form, patients present with nausea, vomiting, and malaise, progressing to bloody diarrhea, gross ascites, hemorrhagic lymphadenitis, and sepsis. The oropharyngeal form of anthrax may present with dysphagia and oropharyngeal necrotic ulcers, profound submental swelling, regional adenopathy, and sepsis. Like inhalation, mortality rates are 40%.
Injection anthrax is a rare clinical manifestation of disease and has not been reported in children but has been described primarily in heroin-injecting populations.
Gram stain and culture of vesicular fluid, necrotic tissue, tissue biopsy specimens, blood, cerebrospinal fluid, respiratory specimens, or rectal swabs or stool may confirm the diagnosis of anthrax. B anthracis grows in ordinary nutrient broth and on blood agar, appearing as large, gram-positive, sporulating bacilli ...