What is the pathogen responsible for the black death?
Yersinia pestis
For which two conditions is Yersinia pestis responsible?
Bubonic plague and Pneumonic Plague
What 3 pathogens are part of the Yersenia genus?
Y. pestis
Y. pseudotuberculosis
Y. enterocolitica
Each line of the following children's rhyme depicts a characteristic of an infection with Y. pestis, identify: Ring-a-ring of roses, A pocketful of posies, Atishoo, Atishoo, We all fall down.
Ring-a-ring of roses : round, red rash
A pocketful of posies : used to mitigate smell
Atishoo, Atishoo : sneezing early symptom
We all fall down : death
Y. pseudotuberculosis and Y. enterocolitica both affect:
GI tract and cause abscesses that can lead to peritonitis and death.
How do humans become infected with Y. enterocolitica?
Y. enterocolitica is a cow/deer pathogen, and it reaches humans via contaminated water.
Describe the Y. pestis pathogen
- small coccobacilli
- Gram -
- bipolar staining
- rat pathogen, reaches humans through fleas
- can survive in soil
Describe the stepwise mechanism by which Y. pestis reaches humans hosts.
- Active in wild rodents populations
- Wild Rodents come in contact with city rodent and fleas transmit the pathogen.
- Y. pestis infects and kills the city/domestic rodent population.
- Infected fleas seek new hosts = humans.
Describe the effects on a flea after it bites a host infected with Y. pestis.
- Y. pestis multiplies and forms a biofilm in the pro-ventriculus
- Biofilm blocks the passage of the blood meal into the midgut. (this prevents digestion/destruction of pathogen by flea’s GI system, not expelled in feces)
- Flea becomes more voracious and bites a new host regurgitating Y. pestis into their bloodstream.
How does the flea infected with Y. pestis appear when compared to a flea that is not infected?
The infected flea will appear contracted/constipated, with coagulated, blocked, blood meal in the foregut.
A normal flea with look uniform with its fresh blood meal passing through the midgut.
What is the pro-ventriculus?
The pro-ventriculus is a valve that connects the esophagus of the flea to the midgut.
Describe the progression of Y. pestis infection in a human host.
- reproduce intracellularly in the macrophages (only 10 will cause an infection reaching lethal #’s 2-3 days after infection)
- 1 week: reaches lymph nodes, inguinal most commonly
Why is it called bubonic plague?
The most common affected lymph nodes are the ones near the groin (inguinal = boubon [greek]).
What are black buboes?
Lymph nodes become hot, swollen, hemorrhagic and tender.
How quickly does Y. pestis reach lungs, spleen and liver?
within hours
What is the pneumonic plague?
Y. pestis reaches the lungs and causes a severe bacterial pneumonia, allowing for human to human transmission via droplets.
Death rate of Y. pestis.
90% of untreated victims will die. Near 100% for Pneumonic.
What are the symptoms of Y. pestis infection?
high fever, Low BP, chills, fatigue.
Pneumonic: cough, chest pain, shortness of breath, bloody sputum.
Where can Y. pestis be found in-between outbreaks?
In the wild rat population
In the US 25% of cases infected with Y. pestis did not present with:
Lymph node involvement
What is the human body louse? How does it relate to Y. pestis?
Human Lice, can serve as a vector for Y. pestis.
Human-Human Transmission.
