Bubonic Plague

Question 1

What is the pathogen responsible for the black death?

Answer 1

Yersinia pestis

Question 2

For which two conditions is Yersinia pestis responsible?

Answer 2

Bubonic plague and Pneumonic Plague

Question 3

What 3 pathogens are part of the Yersenia genus?

Answer 3

Y. pestis
Y. pseudotuberculosis
Y. enterocolitica

Question 4

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.

Answer 4

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

Question 5

Y. pseudotuberculosis and Y. enterocolitica both affect:

Answer 5

GI tract and cause abscesses that can lead to peritonitis and death.

Question 6

How do humans become infected with Y. enterocolitica?

Answer 6

Y. enterocolitica is a cow/deer pathogen, and it reaches humans via contaminated water.

Question 7

Describe the Y. pestis pathogen

Answer 7

• small coccobacilli
• Gram -
• bipolar staining
• rat pathogen, reaches humans through fleas
• can survive in soil

Question 8

Describe the stepwise mechanism by which Y. pestis reaches humans hosts.

Answer 8

1. Active in wild rodents populations
2. Wild Rodents come in contact with city rodent and fleas transmit the pathogen.
3. Y. pestis infects and kills the city/domestic rodent population.
4. Infected fleas seek new hosts = humans.

Question 9

Describe the effects on a flea after it bites a host infected with Y. pestis.

Answer 9

1. Y. pestis multiplies and forms a biofilm in the pro-ventriculus
2. 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)
3. Flea becomes more voracious and bites a new host regurgitating Y. pestis into their bloodstream.

Question 10

How does the flea infected with Y. pestis appear when compared to a flea that is not infected?

Answer 10

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.

Question 11

What is the pro-ventriculus?

Answer 11

The pro-ventriculus is a valve that connects the esophagus of the flea to the midgut.

Question 12

Describe the progression of Y. pestis infection in a human host.

Answer 12

• 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

Question 13

Why is it called bubonic plague?

Answer 13

The most common affected lymph nodes are the ones near the groin (inguinal = boubon [greek]).

Question 14

What are black buboes?

Answer 14

Lymph nodes become hot, swollen, hemorrhagic and tender.

Question 15

How quickly does Y. pestis reach lungs, spleen and liver?

Answer 15

within hours

Question 16

What is the pneumonic plague?

Answer 16

Y. pestis reaches the lungs and causes a severe bacterial pneumonia, allowing for human to human transmission via droplets.

Question 17

Death rate of Y. pestis.

Answer 17

90% of untreated victims will die. Near 100% for Pneumonic.

Question 18

What are the symptoms of Y. pestis infection?

Answer 18

high fever, Low BP, chills, fatigue.

Pneumonic: cough, chest pain, shortness of breath, bloody sputum.

Question 19

Where can Y. pestis be found in-between outbreaks?

Answer 19

In the wild rat population

Question 20

In the US 25% of cases infected with Y. pestis did not present with:

Answer 20

Lymph node involvement

Question 21

What is the human body louse? How does it relate to Y. pestis?

Answer 21

Human Lice, can serve as a vector for Y. pestis.

Human-Human Transmission.