Bacillus anthracis

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This bacterium infects multiple types of hosts including herbivorous mammals such as livestock and is considered zoonotic however humans are a dead end host and do not become infectious.

Cutaneous: skin contact with spores from infected animals (95% of Cases; Most in Africa, Asia, and eastern Europe).
Gastrointestinal: eating poorly cooked meat/dairy from infected animal.
Inhalation: Inhalation of spores
Injectional: soft tissue infection associated with injection drug use
[1]
Anthrax is not contagious and cannot be transmitted from person-to-person. [2]

Case fatality ratios
Case Fatality Ratio Pathway/conditions Population References
1% Cutaneous with treatment General US Population [3]
20% Cutaneous without treatment General US population [3]
75% Inhalation despite treatment Not Reported [3]
89% Inhalation Occupationally Acquired: 20th century untreated [1]
45% 2001 US Attack Adult US [4]
14% (5 of 37) Cutaneous Children 1900-2005 [5]
60% Inhalation Children 1900-2005 [5]
65% (13 of 20) Gastrointestinal Children 1900-2005 [5]
100% Gastrointestinal Unreported [1]
100% (6 of 6) primary meningoencephalitis Children 1900-2005 [5]
100% (6 of 6) primary meningoencephalitis Children 1900-2005 [5]
1.5% (of 132) Not reported Hospitalized adults and children, Turkey 1986 to 2000 [6]
30% (3 of 10) Injectional Adults aged 23-53, UK [1]

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Incubation Times
Days Pathway Population Reference
0-1 Cutaneous Not Reported [3]
1-7 days Inhalation

Ingestion

Not Reported [3]
60 (max) Inhalation

Ingestion

Not Reported [3]
10 Days (SD: 8.67) Inhalation Sverdlovsk 1979 outbreak (70 cases) [2]

Duration of infectiousness and disease

Gastrointestinal: 10-14 days[1]

Symptomology

Cutaneous:

  • Primary skin lesion 3-5 days after infection is painless puriritic papule.
  • Lesion forms a necrotic vesicle leaving a black eschar surrounded by edma.
  • Eschar dries and sloughs in next 1-2 weeks.


Gastrointestinal:

  • Oral-pharyngeal form: oral or esophageal ulcer with regional lymphadenopathy edema and sepsis
  • Lower GI form: primary intestinal lesions predominantly in terminal ileum or cecum. Nausea, vomiting, malaise, bloody diarrhea, acute abdomen, and sepsis are common symptoms of the Lower GI form.


Inhalational:
Two-stages

  • 1: Flu-like symptoms including cough fever, fatigue that last from hours to a few days
  • 2: Rising fever, dyspnea, diaphoresis, shock. In advanced form, cyanosis and hypotension progress rapidly and death can occur within hours


Injectional:

  • Tissue swelling around the injection site
  • Abdominal symptoms[1]


Excretion Rates (see Exposure)

Spores are cleared from the lung at a rate between 8-14% per day. [2]

Immunity

Anthrax vaccination consists of 5 total intramuscular injections, followed by recommended annual boosters to maintain immunity. [3]

Gram +, aerobic, encapsulated, nonmotile. Exists in a dormant spore or an actively replicating vegetative rod form Extremely hardy spores can persist for years, even decades.[1]


References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Int Care Med
  2. 2.0 2.1 2.2 Brookmeyer, R., Johnson, E., & Barry, S. (2005). Modelling the incubation period of anthrax. Statistics in Medicine, 24(4), 531–542. doi:10.1002/sim. Full Text
  3. 3.0 3.1 3.2 3.3 3.4 3.5 3.6 CDC
  4. Holty J, Bravata D, Liu H, Olshen R, Mcdonald K, and Owens D. (2006) Systematic Review: A Century of Inhalational Anthrax Cases from 1900 to 2005. Annals of Internal Medicine. 144, 4. 270-280. Full Text
  5. 5.0 5.1 5.2 5.3 5.4 Bravata D, Holty J, Wang E, Lewis R, Wise P, McDonald K, and Owen D. (2007) Inhalational, Gastrointestinal, and Cutaneous Anthrax in Children. Arch Pediatr Adolesc Med. 161 (9): 896-905. Full Text
  6. Kaya A, Tasyaran M, Erol S, Ozkurt Z, and Ozkan B. (2002) Anthrax in Adults and Children: A Review of 132 Cases in Turkey. Eur J Clin Microbiol Infect Dis. 21: 258-261. Full Text