Final Flashcards
(105 cards)
How much of the european population did the black death kill?
50%
What was responsible for the plaque??
Yersinia
A gram-negative, rod-shaped, non-motile facultative anaerobe. There are 3 human pathogens among 11 species. Causes zoonotic disease.
What are the three types of yersinia that affect humans? Name and compare.
Y. enterocolitica: enteric pathogen acquired by the consumption of contaminated food or water, causing inflammation of the intestinal tract
Y. pseudotuberculosis: enteric pathogen but causes less severe inflammation of the intestines
Y. pestis: more virulent of the three but not enteric.
Describe Y. pestis.
It is a nonmotile, coccobacillus, facultative anaerobe, non-enteric pathogen. It is one of the most virulent bacteria known with an infectious dose of 1-10 cells. Disease progresses very quickly, within a few days, and has caused more than 75 million deaths.
What are the different diseases caused by Y. pestis?
Bubonic plague (50-70% fatal) Septicaemic plague (~95% fatal) Pneumonic plague (100% fatal)
How is Y. pestis transmitted?
Rodents are hosts for the natural endemic cycle with fleas as the vector for spread. The bacteria in the fleas blocks the esophagus, causing them to starve and feed more aggressively, jumping from host to host. Humans can get it through both rodent sand fleas as well as through airborne transmission in the case of pneumonic.
Describe the bubonic plague (transmission, signs, symptoms).
Most common form of the plague (80% of cases)
Transmitted through bites of infected fleas or direct contact with an infected host. It incubates for 2-6 days then causes fever, chills, headache, and very swollen, painful lymph nodes called bubo.
Describe the pneumonic plague (transmission, signs, symptoms).
A rare, highly contagious version with aerosol transmission. It is the most rapidly developing and life threatening form of the plague, with an incubation period of 1-4 days. Symptoms include fever, cough, headache, bleeding in the lungs, etc., and difficulty breathing that can develop into respiratory failure.
What are the two types of pneumonic plague?
Primary: direct inhalation
Secondary: spread of bacteria from the bubo to the lungs, more common
Describe the septicaemia plague (transmission, signs, symptoms).
Occurs when Y. pestis enters the bloodstream and causes septicaemia. Results in fever, chills, extreme weakness, abdominal shock, and possibly bleeding into the skin and other organs. Although it can occur as the first symptom of the plague, this is relatively rare and more often develops from untreated bubonic. Known as the black death due to appearance of dead infected tissue.
Describe the virulence factors of Y. pestis.
The bacteria has 3 plasmids with important virulence factors. pPCP is a pla protease causing organ destruction. pMT1 codes for Ymt causing flea toxicity and envelope F1 antigen causing antiphagocytic properties. pCD1 codes for a type III secretion system.
Describe the pCD1 plasmid in Y. pestis.
It codes for T3SS and is essential for virulence in the species. It allows for the injection of Yersinia outer proteins (Yops) into target host cells. These have antiphagocytic and/or anti-inflammatory effects.
Describe the evolution of Yersinia species.
Non-pathogenic environmental yersiniae split into Y. enterocolitica and y.pseudotuberculosis when it picked up the pCD1 plasmid. After this, the y. pseudoteberculosis gained the pPCP and pMT1 plasmids developing into ancestral Y. pestis. A series of gene mutations, genome rearrangements, gene inactivation, and gene gains resulted in the modern Y. pestis.
Discuss the diagnosis and treatment of Y. pestis.
The diagnosis and treatment must be rapid due to the progression and deadliness of the plague, usually looking for the characteristic symptoms (bubo). Treatment includes antibacterial drugs such as gentamicin, ciprofloxacin, doxycycline, and streptomycin.
How has the distribution of the plague changed since 1954?
See somewhat regular spikes int he number of cases, mainly among Asian and African countries.
What were the three major plague pandemics?
Plague of justinian (541-750) Black plague (1347-1352) Third Pandemic (1855-1896)
What are the three main causes of the increased rate of the plague in the 21st century?
Increased international trade
Rising urban population
Lack of medical knowledge
Describe the measles virus (MeV).
It is a non-segments, -ssRNA virus with an envelop and a helical capsid. It is in the genus morbillivirus and family paramyxoviridiae. The natural host is humans and can cause measles as well as subacute sclerosing pan encephalitis. (SSPE).
Describe the transmission of MeV.
It is highly infectious and airborne, spread through respiratory droplets and contact with infected secretions. It can exist for hours outside outside the body as aerosols.
Describe the genome of MeV.
Contains 6 genes: fusion protein, large protein, hemagglutinin protein, phosphoprotein, metric protein, and nucleocapsid protein.
Describe the state of measles prior to the introduction of the vaccine.
It was estimated that prior to 1963, there were 30 million cases per year with more than 2 million deaths. Overall, it has resulted in around 200 million deaths.
How and why has the rate of measles changed?
After the introduction of the vaccine, case numbers began to drop but they dropped more sharply in 2001 after the global measles and rubella initiative, with a 79% decrease and 17.1 million deaths prevented from 2001 to 2014.
Describe the state of measles globally today.
In 2017, 110 000 people died from measles, mostly children under the age of 5. It has a fatality ration of less than 0.01% in industrialized countries and greater than 5% in developing countries.
What caused the decrease in measles mortality seen in industrialized countries in the early 1900s?
Economic development combined with improved nutrition statue and better supportive care, in particular antibiotic therapy for measles associated bacterial pneumonia, helped improve the survival rate of measles prior to the vaccine.
