Causes of Infectious Disease Flashcards
def health
According to WHO “a state of complete mental physical and social wellbeing, and not merely the absence of disease or infirmity”
diff path types
- prion
- virus
- bac
- protozoa
- fungi
- macroparasite
path types nonliving
- prion
- virus
path types living
- bac
- prot
- fungi
- macroparasite
prion def + e.g.
- Defective form of protein molecule not containing 🧬 or RNA
- e.g. CJD (Creutzfeldt-Jakob disease) - caused by BSE prion
eat nerve tissue, prion proteins are not digested in the gut & can enter the 🩸stream, eventually reaching the 🧠
prion sz
10 nm
vir def + e.g.
- Microscopic non-cellular infectious agents containing DNA, RNA, protective coating of protein
- e.g. Polio caused by Human Polio Virus (HPV)
contagious via faecal-oral route - virus present in faeces of infected -> poor personal hygiene -> contaminated 💧 + 🍽️
vir sz
< 500 nm
bac def + e.g.
- Unicellular, prokaryotic, microscopic pathogens with a nucleus containing DNA
- e.g. TB - caused by Mycobacterium tuberculosis
spread from 🧑🏻 to 👧🏻 through the air
bac sz
1 μm
prot def + e.g.
- Eukaryotic unicellular organisms
- e.g. Malaria - caused by Plasmodium sp.
parasite first travels to a human’s liver to grow and multiply
then travels into the 🩸stream and infects and destroys RBCs
prot sz
50-150 um
fungi def + e.g.
- Single or multi-celled organisms that can survive outside a host, has nucleus + cell wall
- e.g. Tinea (Athlete’s 🦶) - caused by Tinea pedis (a mould-like fungus)
Highly contagious disease which feeds on skin, causing itchy, smelling, flaking skin (usually from wet areas)
macrop def + e.g.
- Eukaryotic multicellular organisms visible with naked 👀 (ecto = external, endo = internal)
- e.g. Tapeworm disease - caused by Taenia saginata which causes malnutrition, diarrhoea & weight loss
fungi sz
4 μm (uni
cellular)
(check)
macrop sz
> 1mm
epidem disease case study
Ebola Virus Disease (EVD)
West Africa
2013-2016
origin of ebola
- Handling wild animals (e.g. in the ⚫ market), e.g. fruit 🦇
- In Dec 2013, in a small village in Guinea, the Ebola virus left its traditional host—probably a 🦇—and infected a young 👦🏻
ebola pathology
-> responsible path
caused by viruses in the Ebolavirus and Filoviridae families
- Zaire ebolavirus species is 1 of the 5 species in the genus Ebolavirus & is the most fatal (contains 7 distinct proteins of large molecules arranged in a long, braided strand of negative RNA)
ebola key sympt
- Incubation period 2-21 days
- Initial: Fever, fatigue, muscle pain, headache, sore throat
- Severe: vomiting, rash, diarrhoea, impaired kidney + liver function, internal/external bleeding
ebola transmission
Initially transmitted to human from an infected animal (vector), and continues to spread through a population by direct human-to-human contact (through broken skin or mucous membranes) - come in contact with bodily fluids
adaptations of ebola
In early 2014, Ebola virus picked up a mutation called A82V, which made it worse at infecting 🦇 cells, but better at infecting 👨🦱 ones
A82V doubles the Ebola virus’s ability to infiltrate 👨🦱 cells
environmental or societal factors that contributed to the spread of ebola
- Population density (esp high density slum areas, markets, etc)
- Highly mobile communities
- Lack of Public Health infrastructure
- Cultural beliefs and behavioural practices (e.g. burial ceremonies where mourners come into direct contact with the infected body, which can further spread the virus)
ebola treatment? effectiveness?
- Currently no cure
- Patients supported with oral and intravenous fluids + treatment of specific symptoms
- 2016 successful highly protective rVSV-ZEBOV vaccine but pricing/distribution is a problem
ebola # affected and died
&
fatality rate
Killed 11,300 out of 28,600 infections
Severe, often fatal disease with average fatality rate 50%
econ, health, edu impacts of ebola 2013-2016
- According to 2014 projections from the WB, an estimated $2.2 bil was lost in 2015 in the GDP of Guinea, Liberia and Sierra Leone
- 881 doctors, nurses, and midwives were infected with Ebola in West Africa (513 died)
- Students who want to study abroad are being denied the opportunity to do so due to living in a country with the Ebola virus outbreak & all schools in Libera were closed (to prevent spread) but they don’t have the luxury of online learning = affect learning
ebola control methods
- In Sierra Leone, hospitals were shut down & quarantined & army soldiers sent house to house to find Ebola victims to then quarantine them, whole neighbourhoods roped off
- To prevent cross-border transmission, travellers leaving West Africa were screened at airports
aim of your microbial practical experiment?
To investigate the effectiveness of various 💧 treatment options on the growth of bac in 💧 samples
components of your microbial prac exp?
take water sample containing the bacteria E. coli
💧 purification methods:
* chlorine
* charcoal
* antibiotic discs
* boiling ♨
* tea tree (🍵🌲)
ind, dep, contr variables in your microbial prac exp?
ind - Method of filtration used
dep - Microbes present in sample
contr - Water source, agar jelly, incubation period/temp
✍🏻 out the method of your microbial prac exp
most effective 💧 filt technique?
chlorine (no bacteria dots)
vert trans. of path
btwn mother and offspring during birth
horiz trans. of path
btwn members of same generation
non cellular path types
- viruses
- prions
cellular path types divided into…
prokaryotic - bacteria
eukaryotic - protozoa, fungi
modes of trans. of path
- direct: host-to-host
- indirect: e.g. infectious droplets suspended in air for long time
- vehicle: inanimate object becomes contaminated
- vector: living organism that carries a disease causing agent from one host to another in the life cycle of a pathogen
vector
mechanical vs biological transmission
- mech: an animal that carries a pathogen from one host to another without being infected itself
- bio: when the pathogen reproduces within a biological vector that transmits the pathogen from one host to another
koch’s 📮ulates
- The microbe must be found in abundance in all those suffering from the disease, and not be found in healthy individuals
- The microbe must be isolated from a diseased individual and grown in pure laboratory culture
- The cultured microbe must be recorded to cause the disease if introduced into a healthy individual
- The microbe must be re-isolated from this experimental host & shown to be identical to the originally isolated microbe
limitations of koch’s 📮ulates
- It was soon found that pathogens could be present in abundance in perfectly healthy people, which violates postulate 1 (e.g. Typhoid Mary - asymptomatic carrier of bacterium Salmonella Typhi that causes typhoid fever)
- At that time, many pathogens either could not be found (viruses too small for scopes at that time) and/or could not be grown in pure culture. This made postulate No.2 useless.
- Carrying out postulate No.3, even on willing volunteers, raised many ethical and moral questions about the entire process.
status of koch’s 📮ulates 🕑day
- Postulates no longer used in their literal sense (bc of limitations + development of modern technology offers new ways of identifying the pathogen of a new disease/strain)
- However, this does not diminish their importance in history when modern microbiology, pathology + medicine were kick-startin
prior to pasteur…
what did pasteur aim to prove?
‘spontaneous generation’ - living things came from non-living things
to demonstrate that microbes were air-borne and did not spontaneously generate
Contributions of Louis Pasteur
- Disproved spontaneous generation
- Developed world’s first attenuated vaccine for anthrax, chicken cholera and rabies → revolutionised work in prevention of infectious diseases
- Demonstrated fermentation was caused by living organisms - 1858: Pasteur demonstrated fermentation was caused by living yeast
- Invented PASTEURisation
Pasteur studied harmful effects of microorganisms on food + beverage → invented pasteurisation in 1862
Involves heating liquid to high temperatures (60 and 100 degrees Celscius to kill microorganisms that cause spoilage or disease)
adaptation =
a characteristic that enable an organism to be successful in a particular environment
virulence =
the degree to which a pathogen causes disease
