Where is Y. pestis (the plague) found?
All continents except Australia
Why can the plague not be eradicated?
Because it is widespread in wildlife rodent reservoirs
Where is the plague endemic?
Madagascar
How man cases in US, Canada and globally
US: 10-15 cases/year
Canada: none since 1939
Globally: 1500 cases/year since 1965
How long does the plague take to infect someone?
Incubation: 2-6 days
Death: 2-4 days
What are the symptoms?
- Fevers, chills, headaches, muscle pain, weakness
- painful swellings (buboes) of the lymph nodes in armpits, legs neck or groin
- High fever, delirium, mental deterioration, large blackish pustules that burst, vomiting of blood, bleeding in lungs
When was the first pandemic?
Plague of Justinian, started 541-542 AD, caused by Y. pestis
~ 50% of pop. died
Continued in clucles for 200 years and disappeared for ~800 years
- killed 100 million people by the end
What are the 3 species of Yersinia?
Gram-, rods, facultative anaerobes
- Y. enterocolitica - causes yersiniosis - rare cause of diarrhea and abdominal pain
- Y. pseudotuberculosis - animal pathogen, causes tuberculosis-esque sympotoms in animals, enteritis in humans
Y. pestis - causes plague
Who discovered Y. pestis?
Alexandre Yersin and Shibasaburo Kitasato in 1894
Is Y. pestis an efficient colonizer of humans?
No, it is extremely virulent, causes death within 2-4 days by sepsis and overwhelming pneumonia
When was the second pandemic?
“Black Death”, medieval apndemic caused by Y. pestis
Started in Asia and reached Europe in 1340
Reduced the global pop. from 450 million to 350 million
Killed 25 milion europeans, destroyed the feudal system (many jobs needed to be filled)
When was the 3rd pandemic?
Started in China in 1850s and spread to all continents (active til 1959)
- 12 million deaths in China and Indea alone
- Reached sanfranscisco in 1900 - infected rats exchanged fleas with local wildlife (Y. pestis is now established in SW US)
How is Y. pestis transmitted?
- Live in rodents, transmitted by fleas (bites)
- zoonotic pathogen
- Y. pestis causes “blocking” in the flea (Biofilm formation in proventriculus)
- Handling infected animals (sin contact, scratch, bite)
- inhalation from humans (pneumonic) or animals
- Ingested infected meat
What is the infective dose?
~ 10 cells
Where does Y. pestis survive and grow?
Initially it survives and grows in macrophages
- then is transported to lymph nodes causing major swelling
- Y. pestis continues to grow extracellularly
When does host blood contains high [bacterial cells]?
At the terminal stage, this is essential for transmission as fleas take a blood meal
What did Y. pestis evolve from? What is different about it?
Y. pseudotuberculosis within the last 20,000 years
- has new virulence plasmids
- does not survive well in animal intestines, but can infect flea and is hypervirulen in humans
Virulence factors of Y. pestis include:
Type 3 secretion (intracellular pathogen)
Phospholipase (survival in flea)
LPS (septicemia)
Plasminogen activator -> clot buster (dissemination)
- CAN OVERCOME MANY IMMUNE DEFENSE MECHANISMS RESULTING IN MASSIVE GROWTH
What is Bubonic plague?
- Transmitted by flea bites
- Can develop into the other types, 40-60% mortality if untreated
- Painfully swollen lymph nodes
What is Septicemic plague?
- Presence of Y. pestis is systemic (in blood) an overwhelming and progressive bacteremia
- Can be transmitted to new host
- Gangrene and disseminated intravascular coagulation (no blood clots)
- 50-90% mortality if untreated
What is Pneumonic plague?
- Most dangerous
- Transmission via aerosols directly into the lung, or spread from septicemic plague
- Short incubation
- Can be transmitted directly from person-person by coughing
- 95-100% mortality if untreated, but only treatable within 1st 24 hours
Diagnosis, treatment and prevention
Rapid = essential
Endemic regions - stains, antigen tests
Isolation of pneumonic plague patients
Outbreaks - insecticides for fleas, treat humans with antibiotics, prophylaxis to exposed individuals
What Bioterrorism potential is there?
Category A organism (easily disseminated/transmitted from person to person)
- potential for major public health impact
- easy to grow (2 days)
Worst case scenario:
50kg Y. pestis over city of 5 million people (150,000 infected, 36,000 deaths)
