microbio 2125 unit 5 (part 20) plague

etiological agent

Yersinia pestis

Distinguishing characteristics of etiological agent:

• Gram-negative rod

• Unusual bipolar staining

• Capsules

Virulence Factor(s):

• Capsular and envelope proteins (protect against phagocytosis, foster intracellular growth)

• Coagulase

• Endotoxin

• Murine toxin

Predisposing Factors:

• Contact with wild or domestic animals

• Flea bites

• Exposure to infected humans

Transmission:

• Flea vectors (blocked esophagus from coagulase, ravenous biting causing fleas to eat more even if full)

• Wild animals (sylvatic plague)

• Domestic animals (urban plague)

• Human-to-human (pneumonic form)

Syndrome (signs + symptoms): Bubonic plague

necrosis, swelling of lymph nodes (bubo) in groin or axilla (armpit), Incubation period lasts 2 – 8 days ends in fever, chills, headache, nausea, weakness

Syndrome (signs + symptoms):Septicemic plague

intravascular coagulation, subcutaneous hemorrhage, purpura (black plague)

Syndrome (signs + symptoms): Pneumonic plague

lung infection, highly contagious, fatal if untreated

Affected body region/system:

• Lymphatic system (bubonic)

• Bloodstream (septicemic)

• Lungs (pneumonic)

Treatment:

• Streptomycin, tetracycline, or chloramphenicol

• Treated plague has 90–95% survival rate

Prevention:

• Killed or attenuated vaccine for at-risk individuals

• Quarantine infected individuals

• Control rodent and flea populations near human habitats

Other notes:

• ID = 3–50 bacilli

• Death can occur 2–4 days after symptom appearance if untreated

• Bacteria spread to amplifying hosts through flea vectors

• Diagnosis:

• Imperative as death may occur 2 – 4 days after appearance of symptoms

• Depends on travel & exposure history, symptoms, and lab findings from aspiration of buboes