Anthrax

Anthrax-Microbiology

  • Bacillus anthracis-gram +, spore-forming, bacillus
  • Spores may remain infectious in environment for as long as 50 years
  • Endemic infection in animals
  • Spores enter host, germinate in a macrophage and are transported to regional lymph nodes where local toxins cause edema and death of tissue
  • Humans develop infection naturally from handling contaminated fluids or hides ("Woolsorters Disease") or eating contaminated raw or undercooked meat

Anthrax: Inhalational, N=10

  • Incubation (known for 6 cases)
  • Range: 4-6 days
  • Median: 4 days
  • Age
  • Range: 43-73
  • Median: 56 years
  • 7 of 10: male

Symptom Number
  • Myalgias 6
  • Headache 5
  • Confusion 4
  • Abdominal pain 3
  • Sore throat 2
  • Rhinorrhea 1

Anthrax: Inhalational, N=10

  • WBC: Median 9.8 (7.5 - 13.3)
    • Differential - neutrophilia (>70%) in 7 of 10
  • Elevated transaminases (9 of 10)
  • Hypoxemia 6 of 10
  • CXR: abnormal in all
  • 2-initial reading WNL
  • 8-pleural effusions
    • Often large, hemorrhagic, reaccumulated
  • 7-mediastinal widening
  • 7-infiltrates (some multilobar)
  • CT (N=8): Mediastinal changes present in all

Anthrax: Inhalational, N=10

  • Confirmation of Bacillus anthracis
  • 7-positive blood cultures
    • Blood cultures positive in all who had not received antimicrobials
  • Negative cultures
    • Bronchial or pleural biopsy-specific immunohistochemical staining
    • PCR
    • 4x rise in IgG to protective antigen (with confirmatory inhibition test)

Anthrax: Patient requests for testing

  • There are no screening tests for anthrax
  • Nasal swabs are
  • A research tool
  • ONLY used as part of an epidemiological investigation of KNOWN anthrax exposure
  • Are NOT used to determine who should be treated or prophylaxed
  • Should only be done at the request of Public Health

Anthrax: Patient requests for testing, cont.

  • Asymptomatic patient WITHOUT known exposure:
  • Reassurance
  • No lab tests
  • Asymptomatic patient WITH suspected (as determined by law enforcement/FBI) or known exposure:
  • Consult with Public Health for recommendations
  • Patient with non-specific symptoms
  • Reports having had an exposure to unknown substance-not evaluated by law enforcement
  • Does not fit any known risk profile (occupation, previously identified exposures)
  • Reassurance about rarity of infection and frequency of viral URIs
  • Evaluate for symptoms
  • If afebrile, instruct patient to monitor for fever and other symptoms

Anthrax: Cutaneous

  • Incubation 1-12 days
  • Skin lesion: Macule or papule è vesicles è ulcer è depressed black eschar
  • Initially often have pruritis
  • Usually painless
  • Vesicles may surround ulcer
  • Edema usually develops, may be severe
  • May have fever, malaise, headache, regional lymphangitis, painful lymphadenopathy

Anthrax: Cutaneous, cont.

  • Dx:
  • Vesicular fluid/exudate/inflammed area of eschar
    • Gram stain (may be falsely negative)
    • Culture
  • Biopsy-
    • Immunohistochemical staining, PCR, silver stain
  • Consider blood culture

Cutaneous Anthrax: D/dx

  • Ecthyma
  • Folliculitis
  • Brown recluse spider bite
  • Ecthyma gangrenosum
  • Orf
  • Pyoderma gangrenosum
  • Sweet's syndrome

(http://www.acponline.org/-American College of Physicians)

Cutaneous Anthrax: Clues to the diagnosis

  • Usually solitary lesion
  • Initial pruritis
  • Painless
  • Most often on upper extremities
  • Evolution to eschar formation
  • Non-pitting edema
  • Regional adenopathy
  • May be associated with constitutional sx

Anthrax Treatment

  • Inhalational
  • Doxycyline or ciprofloxacin, IV
  • Plus: 1 or 2 other drugs
    • Rifampin, clindamycin, chloramphenicol, vancomycin, clindamycin
  • Not cephalosporins or trimethopirm-sulfamethoxazole

Anthrax Epi Investigation
CDC, as of December 5

  • 22 cases
  • 11 inhalational-5 deaths
  • 11 cutaneous (7 confirmed, 4 suspected)
  • All but 2 cases: postal employees or media-related
  • NJ and Washington DC mail sorting facilities
  • Widespread environmental contamination
  • ~85 million pieces of mail processed after implicated letters passed through until shutdown
  • Mail from these facilities distributed to metropolitan areas with 10.5 million people

Anthrax Epi Investigation
CDC, as of December 5, cont.

  • Risk for additional inhalational cases due to exposure to cross-contamination is very low
  • Persons remaining concerned about their risk may want to
  • Not open suspicious mail
  • Keep mail away from face when opening
  • Don't sniff mail or contents
  • Wash hands after handling mail
  • However, efficacy of these measures unknown