Military/Bacterial Warfare: may produce either cutaneous or inahlational anthrax
Goat Hair:
Wool: inhalational anthrax is also known as “woolsorter’s disease”
Animal Hide Exposure:
Etiology
Bacillus anthracis Infection
Large spore-forming gram-positive rod
CDC Category A Agent: potential to be easily disseminated, have higher contagiousness, have high morbidity and mortality, and require increased public health preparedness
Physiology
Transmission and Mechanism: inhalation of 3-5 µ Bacillus anthracis spores into alveoli
Spore engulfment by macrophages -> carried to hilar (regional) nodes -> multiplication of organism in its vegetative state in hilar and mediastinal nodes (where anthrax toxin is produced)
High-Grade Bacteremia may result with production of 3 toxins (protective antigen, edema factor, lethal factor)
Protective factor binds to cell surface and facilitates endocytosis of edema and lethal factors
Toxin released into circulation causes septic shock
Anti-Phagocytic Capsule: enhances lethality
Estimated LD50: 2500-55k inhaled spores (although as few as 1-3 spores may cause disease in some reported cases in 2001)
Incubation Period: 6 days (may vary with level of exposure)
Accidental release in Sverdlovsk: incubation period was as long as 100 days
Diagnosis
Sputum GS/Cult+Sens:
CXR/Chest CT patterns:
Mediastinal Widening (due to mediastinal adenopathy and/or hemorrhagic mediastinitis):
Patchy, Non-Segmental Infiltrates:
Unilateral or Bilateral Pleural Effusion:
Blood c/s: frequently positive in <12 hrs, if antibiotics have not been given
Level A hospital labs: can isolate the organism from routine cultures and provide presumptive identification
Level B hospital labs: can confirm
PCR and Specific Antigen Staining Assays: available from CDC
Clinical Presentations
Cutaneous Anthrax
Epidemiology: most common presentation
Clinical
Pruritic Vesicles/Papules: ultimately develop into ulcers -> eschars
Regional Lymphadenopathy: accompanies rash
Inhalational Anthrax (Woolsorter’s Disease)
Epidemiology: rare presentation (only 18 cases reported in US in the 20th century)
Clinical
Flu-Like Symptoms (fever, headache, malaise, dry cough, abdominal discomfort): occur for first few days
Typical flu symptoms like rhinorrhea and sore throat are uncommon
Absence of severe bronchospasm
Biphasic Presentation (makes diagnosis difficult): patient may transiently improve without therapy, but will usually deteriorate after that with respiratory symptoms
CNS Infection (50% of cases): hemorrhagic meningitis/SAH
Prognosis
Historical Case-Fatality Rate: 80-100%
Recent Case-Fatality Rate: 45% (presumably better due to rapid diagnosis and treatment)
GI Anthrax
Epidemiology: very rare (has never been diagnosed in US)
Treatment
Cipro + Clinda: notably, clinda inhibits toxin production
Alternative: doxy + clinda
Vanco or Rifampin: may be added to cover CNS infection
Need to check antibiotic sensitivities, as weaponized anthrax may have altered sensitivities
All anthrax strains are resistant to Cephalosporins and some have an inducible penicillinase
Infection Control: standard precautions (no human-to-human transmission, regardless of type of anthrax)
Prophylaxis: prophylaxis of close contacts is not required
Anthrax Vaccine: available
Acellular, contains protective antigen
SE: mild in 63% of recipients, severe in <1% of recipients
Pre-Exposure Regimen: 6 injections over 18 mo period with annual boosters
Post-Exposure Prophylaxis: 3 doses of vaccine + antibiotics (cipro or doxy) x 30 days
Alternative: cipro
Alternative: doxy x 60-100 days
Alternative: amox x 60-100 days (for pregnant women and children
References
Shafazand S, Doyle R, Ruoss S. Inhalational anthrax: epidemiology, diagnosis, and management. Chest 1999; 116:1369-1376
Franz D, Jahrling P, Friedlander A, et al. Clinical recognition and management of patients exposed to biological warfare agents. JAMA 1997; 278:399-411
Pile J, Malone J, Eitzen E, et al. Anthrax as a potential biological warfare agent. Arch Int Med 1998; 158:429-434
Inglesby T, Henderson T, Bartlett J, et al. Anthrax as a biologic weapon: medical and public health management. JAMA 1999; 281:1735-1745
Dixon T, Meselson M, Guillemin J, et al. Medical progress: anthrax. N Engl J Med 1999; 341:815-826
