Lecture 2- Bacteriology - The Black Death

Microbiology and Immunology 2500

• Course Title: Microbiology and Immunology 2500

• Lecture: The Black Death

• Instructor: Dr. Idowu Olawoye (iolawoye@uwo.ca)

• Institution: Western University Canada

Learning Objectives

• Recognize the impact of microbes on societies

• Understand the historical context of plague

• Comprehend the pathogenic mechanisms of Yersinia pestis and its various forms of plague

Yersinia Overview

• Type of Bacteria: Gram-negative, rod-shaped

• Pathogenic Species:

  • Y. enterocolitica: Causes yersiniosis (rare diarrhea and abdominal pain)

  • Y. pseudotuberculosis: Primarily an animal pathogen; can cause tuberculosis-like symptoms in animals and enteritis in humans

  • Y. pestis: Causative agent of the plague

Yersinia pestis Details

• Discovery: Identified by Alexandre Yersin and Kitasato Shibasaburo in the late 1800s

• Virulence: Highly virulent; can lead to death in 2-4 days due to sepsis or pneumonia

• Colonization: Not an efficient colonizer of humans

Signs and Symptoms of Plague

• Incubation Period: 3-7 days

• Acute Symptoms:

  • Sudden onset of fever, chills, headaches, muscle pain, and weakness

  • Painful lymph node swellings (buboes) in armpits, legs, neck, or groin

  • Severe health issues: high fever, delirium, mental dete

• How we know Y. pestis caused black death?

  • took teeth of people infected by the plague and were able to sequence the genome from the bodies

  • strain that caused black death and plague of Justinian are different. However, both strains share a common ancestor, which provides insight into the evolution of Yersinia pestis and its various pathogenic forms.

• Timeframe: 6th century (541-542 AD)

• Impact: Spread throughout Europe, resulting in ~50% population death rate

• Duration: Cycled for ~200 years until 750 AD, killing an estimated 100 million people

2. The Black Death

• Origin: Linked to Yersinia pestis, spread from Asia to Europe in late 1340s

• Impact: Global population reduced from ~450 million to ~350 million; ~25 million Europeans (1/3) died

• Response: Widespread panic, beliefs in divine retribution, persecution of minorities, collapse of social structures

3. Mid-19th Century Pandemic

• Origin: Started in China (1850s), spread worldwide until 1959

• Casualties: Over 12 million deaths in China and India; reached San Francisco in 1900

• Current Status: Y. pestis remains established in Southwestern U.S.

Pathogenesis of Yersinia pestis

• Transmission: Primarily from rodents via fleas; classified as a zoonotic pathogen

  • blocks hunger of flea which causes flea to infect more people trying to satisfy hunger

• Mechanism: Causes blocking in fleas, biofilm formation leads to regurgitation of bacteria during feeding

• Infective Dose: As few as 10 cells can cause infection; Y. pestis grows in innate immune cells and lymphoid organs

• Consequences: Swelling lymph nodes (buboes); can multiply in the bloodstream, elevating mortality risk

Virulence Factors of Yersinia pestis

• Immune Evasion: Can evade the innate immune response allowing for unchecked proliferation

• Key Factors:

  • Type III secretion system for injecting virulence factors

  • Phospholipase to aid survival in fleas

  • Plasminogen activator (clot buster for dissemination)

  • Yersiniabactin (iron-binding siderophore)

  • Mutated LPS structure for immune evasion

Forms of Plague

1. Bubonic Plague

• Description: Most common form; transmitted via flea bites

• Symptoms: Painfully swollen lymph nodes (