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Anthrax

Anthrax. March 23 rd , 2010. Bacterial pathogens in soil. Many bacteria are natural residents of the soil Some are pathogens Some are zoonoses For the most important ones, humans are incidental or dead-end hosts This is the case with anthrax. The genus Bacillus.

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Anthrax

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  1. Anthrax March 23rd, 2010

  2. Bacterial pathogens in soil • Many bacteria are natural residents of the soil • Some are pathogens • Some are zoonoses • For the most important ones, humans are incidental or dead-end hosts • This is the case with anthrax

  3. The genus Bacillus • Naturally occurring soil bacteria; large diverse genus • Ubiquitous in the environment • Some useful for pest control • Major human pathogens • Bacillus cereus (food) • B. anthracis

  4. Bacillus anthracis • Gram + • Spore former • 1st bacterium to be proven as a cause of disease

  5. Life cycle • soil-animal-soil • Spores in the soil • Vegetative bacteria in the host • Domestic and wild animals • Herbivores • Goats, sheep, horses, cattle • Infection causes hemorrhage; dying and dead animals release organisms back into the soil

  6. Occurrence • Endemic in many areas of the world • Sub-Saharan Africa • Asia • Central and South America • Central and southern Europe

  7. Anthrax • Three distinct forms of the disease, depending on the route of exposure • Cutaneous • Treatable, rarely fatal • Gastrointestinal • Treatable, but dangerous; can be fatal • Inhalational • Almost universally fatal before modern intensive care

  8. Pathogenesis • An exotoxin mediated disease • Bacteria release the toxin into the tissue • Toxin is carried on a plasmid (X01); bacteria must have the plasmid to cause anthrax • Toxin has three components • Edema factor • Lethal factor • Protective antigen

  9. Pathogenesis • These components must assemble into the exotoxin to cause disease • Increase in CO2 levels triggers toxin production • Toxin affects cyclic AMP within the cell • Similarity to cholera • Edema

  10. Cutaneous anthrax • Skin infection • Spores get into skin and become vegetative bacteria • Release toxin • Forms an eschar • Untreated fatality rate up to 20% • Rarely fatal with treatment

  11. Gastrointestinal anthrax • Ingested spores • Usually from consuming meat of an animal that died of anthrax • become vegetative bacteria in the GI tract • Release toxin • Large explosive outbreaks • Treatable, but can be fatal

  12. Inhalational anthrax

  13. Inhalational anthrax • Inhalation of spores directly into the lungs • Spores are ingested by macrophages • Undergo transition to vegetative bacteria • Release toxin • Massive edema • Progress to septicemia • High fatality rate

  14. Inhalational anthrax • Treatable in the prodomal period • Ciprofloxacin, other fluoroquinolones • Survival decreases sharply once symptoms appear • Intensive supportive care • Survival of inhalational anthrax is a recent medical phenomenon

  15. Exposures • Organism is ubiquitous in soil • Contact with infected animal products • Hides • Wool • Bones • Meat

  16. Control • Avoidance of products from animals that have died of anthrax • Education about the risks of eating livestock that have died suddenly of unknown cause • Incineration or very deep burial of carcasses

  17. Control • Occupational exposure control • Hides and bones • Vets and animal handlers • Control at herd level • Vaccination

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