The Plague/ The Black Death Flashcards
Plague - Symptoms
- incubation of 2-6 days, death in ~2-4 days
- patients experience sudden onset of fever, chills, headaches, muscle pain, weakness
- painful swellings (buboes) of the lymph nodes in the armpits, legs, neck, or groin
- high fever, delirium and mental deterioration, large blackish pustules that burst, vomiting of blood, bleeding in the lungs
Plague Pandemic - The Plague of Justinian
- the first pandemic
- named after the Eastern Roman Emperor Justinian
- started in the 6th century (541-542 AD)
- caused by Yersinia pestis
- spread to the Mediterranian, Italy and throughout Europe
- ~50% of the population is estimated to have died
- continued in cycles for another 200 years until about 750 AD then disappears for ~800 years
- estimated to have killed 100 million people
Yersinia - bacteria type and shape
- gram negative, rod shaped
Yersinia - Name three species that are pathogenic for humans
Y. enterocolitica
Y. pseudotuberculosis
Y. pestis
Y. enterocolitica
causes “yersiniosis” – a rare cause of diarrhea and abdominal pain
Y. pseudotuberculosis
primarily an animal pathogen that can cause tuberculosis-like symptoms in animals, enteritis in humans
Y. pestis
- cause of the plague
- discovered by Alexandre Yersin in 1894
- pestis –> pestilence (contagious or infectious epidemic disease)
- an extraordinarily virulent pathogen
- may causes death in 2-4 days by sepsis and/or overwhelming pneumonia with respiratory failure
- NOT an efficient colonizer of humans
What nursery rhyme is based on the Black death?
Ring-a-round-a-rosie
Plague Pandemics - The Black Death
- the second pandemic
- a medieval pandemic caused by Yersinia pestis
- originated in Asia and reached Europe in the late 1340s
- reduced the global population from ~450 million to ~350 million
- killed ~25 million Europeans (1/3 of the total population)
- European social order, family structure, agriculture, military and feudal system were destroyed
When did the Black death occur?
1348, a time when there was no real treatment and the feat turned to panic
What did people believe was the cause of the pandemic?
- God’s anger or Satan’s influence
What is the Feudal System
- Political and Social structure prevalent in Europe
- little opportunity for advancement
- a few people had everything, most had little
- Plague created vacant towns and farms, positions of authority need to be filled
- demand for physicians, clergy, gravediggers
- provided new opportunities for the peasants
Did Y. pestis really cause the Black Death? What is the evidence?
Re-sequenced the bacteria of teeth of the people that have died in that time (from cemetery)
It did cause it
The one of Justinian was a different strain, eventually bacteria killed all of its hosts and it ended up dying off
Where do Yersinia pestis live and how are they transmitted?
- organisms live in rodents and are transmitted by fleas
- a “zoonotic” pathogen
- Y. pestis causes “blocking” in the flea
- biofilm formation in the proventriculus
- “starving fleas”
- causes regurgitation of organisms
Where do Yersinia pestis live and how are they transmitted?
- organisms live in rodents and are transmitted by fleas
- a “zoonotic” pathogen
- Y. pestis causes “blocking” in the flea
- biofilm formation in the proventriculus organ
- “starving fleas” because fleas cannot take the blood meal to its stomach
- causes regurgitation of organisms as they continue to bit other organisms
Virulence Factors of Yersinia pestis
- Y. pestis has a remarkable ability to overcome immune defense mechanisms resulting in massive growth in vivo
Major virulence factors include:
- LPS (septicemia)
- Phospholipase (survival in the flea)
- Plasminogen activator –> clot buster (dissemination)
- Yersiniabactin – iron binding siderophore
- Type III secretion (typical for Gram negative intracellular pathogens)
Virulence Factors of Yersinia pestis
- Y. pestis has a remarkable ability to overcome immune defense mechanisms resulting in massive growth in vivo
Major virulence factors include:
- LPS (septicemia)
- Phospholipase (important for survival in the flea)
- Plasminogen activator –> clot buster (dissemination; allows bacteria to spread)
- Yersiniabactin – iron binding siderophore
- Type III secretion (typical for Gram negative intracellular pathogens)
Evolution of Y. pestis
- Y. pestis evolved from Y. pseudotuberculosis
- Y. pestis acquired new virulence plasmids
- all pathogenic Yersinia contain pYV which encodes the type III secretion system
- primary an intestinal pathogen of animals and is found widely in the environment
- can infect the flea and is hypervirulent in humans, but does not survive well in the animal intestine
What are the three major forms of the Plague disease?
- bubonic plague
- septicemic plague
- pneumonic plague
Bubonic plague
- most common form, transmitted by flea bites
- painfully swollen lymph nodes (“buboes”) in groin, armpits and neck
- can develop into both septicemic and pneumonic plague
- 40-60% mortality if untreated
Septicemic Plague
- presence of Y. pestis is systemic (in the blood)
- an overwhelming and progressive bacteremia
- fleas bites can now pick up Y. pestis to transmit to a new host
- patients experience gangrene and disseminated intravascular coagulation (LPS mediated)
- 50-90% mortality if untreated
Pneumonic Plaque
- most dangerous
- transmission via aerosols directly into the lung, or spread to lungs from septicemic plague
- short incubation
- disease can pass directly from person-to-person through coughing (coughing up blood)
- 95%-100% mortality if untreated, but treatment should be within first 24h of symptoms
What is a pandemic?
An epidemic that becomes widespread over several regions, countries or continents.
What are the four routes of transmission for the human disease?
- Flea-bite (most common)
- Inhalation from humans (pneumonic) or animals
- Handling infected animals (skin contact, scratch, bite)
- Ingesting infected meat
Historically, what is transmission of the plague related to?
- rat-borne urban epidemics
What is transmission of the plaque now mostly associated with/
wild-life associated with sporadic outbreaks
Diagnosis, Treatment and prevention of the Plague
- rapid diagnosis and treatment is essential
- culture and identification from bubo aspirate, sputum, blood (post-mortem) may take 4 days
- isolation of pneumonic plague patients
- insecticides to kill fleas, treat human cases with antibiotics, prophylaxis to exposed individuals
Plague as a bioterrorism agent
- The Centers for Disease Control and Prevention identify Plague as a “Category A” organism
- can be easily disseminated or transmitted from person to person
- result in high mortality rates and have the potential for major public health impact
- might cause public panic and social disruption
- Y. pestis is easy to grow (2 days)
Known incidents
- in 1347 the Mongol armies catapulted plague-ridden bodies over the city walls in Caffa, Ukraine
- In WWII, Unit 731 of the Japanese Imperial Army infected fleas and released them in China
- Larry Wayne Harris, an American “microbiologist”, with suspect motives obtained Y. pestis through the mail (American Type Culture Collection)
WHO worst - case scenario
Aerosol release of 50 kg Y. pestis over city of 5 million people (150,000 infected; 36,000 deaths)
