Anthrax

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Anthrax

• Major disease threat to herbivores (cattle,
  sheep, horses, hogs, goats)
• Humans infected by direct contact with diseased
  animal, hides, wool, brushes, or bone meal
• Inhalation of infected dust (Wool sorter's
  disease)
• Basis for Kochs postulate

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Historical

• It will become fine dust over the whole land of
  Egypt, and festering boils will break out on men
  and animals throughout the land.
• Exodus (99)

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• Germany sponsored covert use of Bacillus
  anthracis against the allies

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Morphology Physiology

• Gram-positive, aerobic, spore-forming bacilli
• Spores formed in culture, soil, and dead animal
  tissues but not in live animals
• Spores remain viable in soil for decades

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Characteristic long Gram positive B. anthracis
rods
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Gram positive B. anthracis in the CSF
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Forms of Anthrax

• Cutaneous
• Pulmonary
• Gastrointestinal

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Cutaneous anthrax

• Accounts for more than 95 of human cases
• Spores enter the broken skin, germinate and
  rapidly proliferate at the site of entry

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Cutaneous anthrax

• Vesicular Papule at the site of infection

• Blue black edema

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Cutaneous anthrax

• Rupture of papule will reveal a black eschar
  (malignant pustule)

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Cutaneous anthrax
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Pulmonary Anthrax

• Spore inhalation and phagocytosis
• Germination, replicate and infection of hilar
  lymph nodes
• Hemorrhagic necrosis of lymph nodes
• Fever, malaise, myalgia, and non-productive cough
• Systemic spread and in death within 24 hours

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Gastrointestinal Anthrax(Not seen in the US)

• Ingestion of infected meat
• Proliferation within the GI tract
• Epithelial invasion and ulceration
• Spreads to mesenteric lymph nodes
• Septicemia and shock

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• Hemorrhagic infiltration of brain

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Pathogenesis (virulence factors)

• Capsule (plasmid coded)
• Exotoxins (plasmid coded)
• edema factor (EF)
• lethal factor (LF)
• protective antigen (PA)

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B. anthracis capsule

• Polypeptide of D-glutamic acid
• Antiphagocytic
• Plasmid encoded
• Not a good immunogen
• Antibodies to the capsule are not protective
  against the disease

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Pathogenesis (edema factor EF)
PA
Calm
Adenylate cyclase
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Pathogenesis (lethal factor LF)
PA
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Pathogenesis
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Treatment

• Penicillin is the antibiotic of choice

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Prevention

• Antibody to the toxin complex is neutralizing and
  protective
• Two vaccines
• 1. Immunize cattle and other herbivores
• 2. Immunize humans at risk