the black death Flashcards
what’s the hidden meaning behind the song “ring around the rosy”?
the black death
ring around the rosy = lesions
pocket fully of posy = stench (tho it was transmitted by smell)
ashes, ashes = bodies were burned
we fall down = death
describe the yersinia bacterial genus (characteristics)
gram-
rod-shaped
what are the 3 pathogenic species of the yersinia genus? what do they cause?
y. entercolitica = yersinionsis, a rare cause of diarrhea and abdominal pain
y. pestis = plague
y. pseudotuberculosis = tuberculosis-like symptoms in animals AND enteritis in humans
who discovered yersinia pestis
discovered by Alexandre Yersin and Kitasato Shibasaburo in the late 1800s
did yersinia pestis really cause black death
if one’s infected, there would be bacteria in the blood which would get lodged in teeth (it’s hard & can protect
DNA)
sequence (nearly) the entire genome of Y. pestis using victim’s teeth –
this is the closest form of proof that Y. pestis caused the Black Death
how long is incubation of the plague? when may death occur from the plague?
3-7 days
2-4 days following incubation
— MAY occur
what are the symptoms of the plague?
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
name the 3 historical plague events in order?
plague of justinian
the black death
3rd plague pandemic
describe the 1st plague event
plague of justinian
- named after the Eastern Roman Emperor justinian
started in the 6th (541 AD) century
spread to Mediterranean, Italy, and throughout Europe
around 50% of the population is believed to have died
– estimated to have killed 100 million people
continued in cycles for another 200 years until about 750 AD then disappeared for approximately 800 years
describe the 2nd plague event
the black death
– a medieval pandemic
originated in Asia and reached Europe in the late 1340s
reduced global population from ~450 million to ~350 million
—- killed approximately 25 million Europeans (1/3 the total population)
what are plague doctors?
during the black death
normal people who assumed physician’s role
put flowers and herbs in their beak to protect themselves as they thought the cause was “bad air”
— didn’t actually protected them from the plague (but did protect from pneumonic)
— but their clothes that fully covered them did
how did the plague destroy the European feudal system during the black death?
plague killed the rich/powerful, creating vacancies for positions of
authority to be filled (e.g. physicians, clergy, gravediggers)
provided new opportunities for peasants
what was believed to have caused the black death?
God’s anger or Satan’s influence – led to the persecution of strangers, minorities, and witches
describe the 3rd plague event
started in China in 1850s → spread to ALL continents, where it remained active until 1959
> 12 million deaths in China & India alone
reached San Francisco in 1900 → infected rats on ships exchanged w/ fleas and local wildlife
currently endemic in Southwestern U.S. (carried by animals)
describe the infection phase of pathogenesis of yersinia pestis (in rodents and fleas)
a zoonotic pathogen
— organisms live in rodents and are transmitted by fleas
causes “blocking” in the flea, a biofilm formation in the proventriculus “starving fleas”, makes them regurgitate
rodents = reservoir
fleas = vectors
describe the growth phase of pathogenesis of yersinia pestis
very low infective dose (only around 10 cells)
it initially survies and grows in innate immune cells and replicates in lymphoid organs (spleen, bone marrow, lymph nodes, liver)
– can evade the mammalian innate immune response, allowing for infection prior to an immune response
lymph nodes swell, becoming buboes
y pestis kills phagocytes and continues to grow extracellularly
– they have a remarkable ability to overcome immune
defense mechanisms resulting in massive growth in vivo
at the terminal stage of the disease, the blood contains high concentrations of the bacterial cells
— essential for the transmission cycle because fleas take a blood meal
what are the major virulence factors of yersinia pestis?
lipopolysaccharides (it’s gram-) which are “mutated” – septicemia (enter the bloodstream and spread)
phospholipase - important for survival in the flea
plasminogen activator (host protein) - breaks down clots and spreads bacteria
yersiniabactin - attracts iron, nutrients for bacteria
type III secretion system
—- typical for gram- intracellular pathogens
—- secretes virulence factors (“effectors”) directly into host cells across the cell membrane
—- effectors ‘poison’ host cell by targeting host cell signaling pathways
what is nutritional immunity?
when body isolates or sequesters nutrients from infectious agents
e.g. iron
describe the evolution of yersinia pestis
evolved from yersinia pseudotuberculosis
acquires new virulence plasmid that encodes the type III secretion system
—- yersinia is now pathogenic
acquires plasmid
—- yersinia pseudotuberculosis is now primarily an intestinal animal pathogen (widespread)
acquires another plasmid
—- yersinia pestis can infect the flea & is hypervirulent in humans; but does not survive well in animal intestine
—- now have pandemic yersinia
essentially: bacteria moving around, taking up plasmids (that encode things) and acquiring pathogenic traits
what the 3 major forms of plague?
bubonic
septicemic
pneumonic
describe the bubonic plague
most common form
transmitted by flea bites
symptoms: painfully swollen lymph nodes (“buboes”) in groin, armpits and
neck
can develop into both septicemic and pneumonic plague
what’s the mortality of the bubonic plague?
40-60% mortality if untreated
describe the septicemic plague
presence of Y. pestis is systemic (in the blood)
an overwhelming and
progressive bacteremia
fleas can now pick up Y. pestis
to transmit to a new host
symptoms: gangrene (decomposition of tissue)
and disseminated intravascular
coagulation (clotting disorder that’s LPS mediated)
can develop into pneumonic plague
what’s the mortality of the septicemic plague?
50-90% mortality if untreated
what’s the mortality of the pneumonic plague?
95-100% if untreated – treatment should be within first 24 hours
describe the pneumonic plague
most dangerous
transmission via aerosols
directly into the lung, or spread to lungs from septicemic plague (allows person to person transmission - no flea necessary)
disease can pass directly from person to perso thru coughing up blood
– short incubation
what are the 4 routes of transmission for human disease of yersinia pestis
fleabite (most common)
inhalation from humans (pneumonic) or animals
handling infected animals (e.g. skin contact, scratch, bite)
ingesting infected meat
historically, rat-borne urban
epidemics
now mostly wildlife associated plague with sporadic outbreaks
describe diagnosis, treatment, and prevention for yersinia pestis
rapid diagnosis and treatment is essential
– culture and identification from bubo aspirate, sputum, blood (postmortem) may take 4 days
in endemic regions, there are stains and rapid antigen tests
– non-endemic regions may not recognize it as quickly
must isolation pneumonic plague patients
outbreaks
- insecticides are used to kill fleas, human cases treated with appropriate antibiotics including prophylaxis to exposed individuals (just in case)
what level of bioterrorism was the plague categorized as?
category A (highest level)
bc it’s easily disseminated or transmitted from person-to-person
high mortality rates; potential for major public health impact
may cause panic
what are known incidents where the plague was used as a bioterrorism agent?
used by Mongol armies in 1300s → catapulted infected bodies into city of Caffa, Ukraine
in WWII, Unit 731 (Japanese) released infected fleas into China
in the world, where is the plague not found?
all continents except Australia
why can’t the plague be eradicated in modern times?
since Y. pestis is widespread in wildlife rodent reservoirs
describe the plague outbreak in madagascar
large outbreak starting in Aug 2017
approximately 2400 probable/confirmed cases, most were pneumonic
greater than 200 deaths
