Wednesday, July 23, 2014
     

Anthrax

Epidemiology:

  • Anthrax can be transmitted by inhalation, ingestion, or inoculation (inhalation) is the most likely during a bioterrorist attack)
  • The spore form of ANTHRAX is highly resistant to physical and chemical agents: spores can persist in the environment for years.
  • Anthrax is not transmitted from person to person

Clinical:

  • Incubation period is 1-5 days (ranges up to 43 days)
  • Inhalation anthrax presents as acute hemorrhagic mediastinitis
  • Biphasic illness, with initial phase characterized by nonspecific flu-like illness followed by acute phase characterized by acute respiratory distress and toxemia (sepsis)
  • Chest x-ray findings: Mediastinal widening in previously healthy patient in the absence of trauma is pathognomonic for anthrax
  • Mortality rate for inhalation anthrax approaches 90%, even with treatment. Shock and death within 24-36 hours

Laboratory Diagnosis:

  • Laboratory specimens should be handled in a Bio-safety Level 2 facility (e.g. California state Microbial Diseases Laboratory)
  • Gram stain shows gram positive bacilli, occurring singly or in short chains, often with squared off ends (safety pin appearance). In advanced disease, a gram stain of unspun blood may be positive
  • Distinguishing characteristics on culture included: non-hemolytic, non-motile, capsulated bacteria that are susceptible to gamma phage lysis
  • ELISA and PCR test are available at national reference laboratories

Patient Isolation:

  • Standard barrier isolation precautions. Patients do not require isolation rooms
  • Anthrax is not transmitted person to person

Treatment:

  • Prompt initiation of antibiotic therapy is essential
  • Antibiotic susceptibility testing is KEY to guiding treatment * Ciprofloxician (400 mg IV q 12 hr) is the antibiotic of choice for penicillin-resistant anthrax or for empiric therapy while awaiting susceptibility results
  • All patients should be treated with anthrax vaccine if available; antibiotic treatment should be continued until 3 doses of vaccine have been administered (day 0, 14 and 28). If vaccine is unavailable, antibiotic treatment should be continued for 60 days.

Prophylaxis:

  • If vaccine is available, all exposed persons (as determined by local and state health deparmemt) should be vaccinated with 3 doses of anthrax vaccine (days 0, 14 and 28)
  • Start antibiotic prophylaxis immediately after exposure with ciprofloxicin (500 mg po q 12 hrs) or doxycycline (100 mg po q 12 hrs). (If strain is penicillin -susceptible, therapy can be modified to penicillin or amoxicillin.)
  • Antibiotic prophylaxis should be continued until 3 doses of vaccine have been administered; if vaccine is unavailable, antibiotics should be continue for 60 days.