History and Causation Flashcards
Plagues in medieval Europe
Life expectancy at birth in the middle ages was 33 yrs because Babies, children, teens died from infectious diseases
- Common diseases include dysentery, malaria, diphtheria, flu, typhoid, smallpox, leprosy, bubonic plague
- Causes of disease were unknown and people were mostly helpless. Plagues were punishment by god
Edward Jenner and smallpox vaccine
English doctor and scientist who developed the smallpox vaccine (world’s first vaccine)
Known as the father of immunology
“Saved more lives than the work of any other human”
Smallpox
- Two virus variants: Variola major and Variola minor
- Characteristic fluid-filled blisters
- Transmission between people via contaminated objects
- High mortality rate of 30%, killed hundreds of millions of people
- Eradicated in 1980 by vaccination (only exists now within labs in US and Russia)
Smallpox within Whistlebury (1796)
Jenner observed that milkmaids were less likely to acquire the smallpox infection. He assumed that all professionals were equally likely to be exposed.
Milkmaids spent time with cows who could be carrying cowpox. Cowpox and smallpox similar, so milkmaids close contact gave them immunity because Cowpox is not dangerous to humans and is cleared by immune system… led to the development of the smallpox vaccine
Experimentation: James Phipps (8 year old boy given cowpox, and then exposed to smallpox later but he had immunity). Very Unethical but led to vaccine!
Miasma theory
Idea that disease caused my miasma (bad air) from rotting organic matter or environment (contaminated water, foul air, poor hygienic conditions)
Major obstacle of scientific understanding of infectious disease as they did not know where microorganisms came from. Believed there was no transmission between people, no microscopic agent, and disease prevention was all about avoidance.
What theory replaced miasma theory?
Germ theory of disease
Louis Pasteur and Robert Koch
Two biggest contributors to the germ theory of infectious disease
Pasteurization of Milk
Diseases of wine, beer, and milk lead to economic losses so Pasteur heated liquids that killed the bacteria and fungi (called pasteurization).
Determined that diseases caused by microorganisms in both beverages and believed in humans as well
How did Pasteur disprove spontaneous generation?
Pasteur disproved this by using broth, heat, and open vs swan necks on containers. Boiled broth to ensure nothing within liquid. Open neck=spoiled by microbes. Swan neck= unspoiled. Proved that microbes came from outside
Pasteur’s contributions
- pasteurization of milk
- disproved spontaneous generation
- discovered bacteria that caused anthrax = spores
- discovered bacteria causing cholera
- discovered bacteria causing TB
Koch’s postulates
- Diseased animals have microbes. Healthy Animals do not have microbes
- Microbes must be isolated from a diseased individual and grown in culture
- Cultured organism/disease should cause the disease when introduced to a healthy animal
- Microbes must be re-isolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent
Exceptions to Koch’s postulates
- Asymptomatic Carriers
- Not all pathogens can be cultured
- Not all organisms exposed to the infectious agent will acquire the infection (ie. Immunity)
Discovery of viruses
- Caused issues with Koch’s postulates and germ theory since viruses could not be seen under a light microscope.
- Discovered by working on Tobacco Mosaic Disease (TMD)
Research on TMD
- Blended TMD leaves, passed through filter still caused disease which means it is a very small bacterium or toxin
- Diluted blended leaves still resulted in infectious agent that could replicate and was not a toxin
*** Infectious Agent that was extremely small and could replicate = “VIRUS”
How were viruses able to be seen?
Electron microscope in 1931, critical step for virology
Showed that TMV was made from proteins and nucleic acids and that it was a particle
