Bacillus anthracis

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Bacillus anthracis - Anthrax

Hosts

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.

Transmission/Exposure Routes

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
(Int Care Med)
Anthrax is not contagious and cannot be transmitted from person-to-person. [1]

Case fatality ratio

Case fatality ratios
Case Fatality Ratio Pathway/conditions Population References
1% Cutaneous with treatment General US Population [2]
20% Cutaneous without treatment General US population [2]
75% Inhalation despite treatment Not Reported [2]
45% 2001 US Attack Adult US [3]
14% (5 of 37) Cutaneous Children 1900-2005 [4]
60% Inhalation Children 1900-2005 [4]
65% (13 of 20) Gastrointestinal Children 1900-2005 [4]
100% (6 of 6) primary meningoencephalitis Children 1900-2005 [4]
1.5% (of 132) Not reported Hospitalized adults and children, Turkey 1986 to 2000 [5]

Incubation Times

Incubation Times
Days Pathway Population Reference
0-1 Cutaneous Not Reported [2]
1-7 days Inhalation

Ingestion

Not Reported [2]
60 (max) Inhalation

Ingestion

Not Reported [2]
10 Days (SD: 8.67) Inhalation Sverdlovsk 1979 outbreak (70 cases) [1]

Burden of Disease

Duration of infectiousness and disease

Symptomology

Cutaneous:

  • 3-5 days after infection = primary skin lesion 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

Flu-like symptoms including: Fever (temperature greater than 100 degrees F). The fever may be accompanied by chills or night sweats. Cough, usually a non-productive cough, chest discomfort, shortness of breath, fatigue, muscle aches Sore throat, followed by difficulty swallowing, enlarged lymph nodes, headache, nausea, loss of appetite, abdominal distress, vomiting, or diarrhea

Excretion Rates (see Exposure)

Spores are cleared from the lung at a rate between 8-14% per day. [1]

Immunity

Anthrax vaccination consists of 5 total intramuscular injections, followed by recommended annual boosters to maintain immunity. [2]

Microbiology

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. (Int Care Med)

Envrionmental Survival

Recommended Dose Response model

Dose response models for Bacillus anthracis

Exponential model: optimal value of k is 1.65E-05
Exponential model.png



References

  1. 1.0 1.1 1.2 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
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 CDC
  3. 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
  4. 4.0 4.1 4.2 4.3 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
  5. 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

http://en.wikipedia.org/wiki/Anthrax
Int Care Med