MODULE 7. INFECTIOUS DISEASE Flashcards
what is an infectious disease
INFECTIOUS DISEASE = Disease which can be transmitted from one organism to another, and are caused by pathogens.
what is a pathogen
PATHOGEN = Any organism which is capable of causing disease
list the types of different pathogens from smallest to largest
bacteria fungi protozoa virsuses prions parasites
how is bacteria characterised
prokaryotic unicellular organisms which don’t have membrane bound organelles and are made of one cell
how can bacteria cause disease
by releasing toxins or damaging host tissues
e.g. of bacteria
tuberculosis
- caused by mycobacterium tuberculosis that enters the lungs when a person inhales infectious droplets
how is fungi characterised
- Eukaryotic, non-photosynthetic, heterotrophic organisms with a cell wall. Can be either unicellular or multicellular
how does fungi cause disease
- The damage caused by fungi mostly arises from the enzymes they produce.
e.g. fungal disease
tinea
Mode of transmission = direct contact, skin to skin contact, surfaces e.g. shower floor
- The fungi lives in the outside layer of human skin, where they produce chemicals which break down keratin
- Symptoms include itchiness, inflammation and flaky skin
how is protozoans characterised
- Unicellular microorganisms with internal membranes. Eukaryotic with a complex lifestyle.
e.g. protozoans
• E.G. MALARIA
- Caused by plasmodium
- Plasmodium floats freely in the blood of an infected person
- It feeds on haemoglobin in the red blood cells causing them to pop
- Symptoms include fever, nausea, muscle pain and headaches
how are viruses characterised
- Non-cellular entities (not living), consisting of a single type of nucleic acid (DNA or RNA) encased in a protein coat.
how does viruses cause disease
- Needs a host cell to reproduce The virus attaches to a host cell, which it then penetrates. It hijacks the hots enzymes and nutrients to make its own viral proteins and nucleic acid
- The viral materials assemble into new viruses which are released from the host cell and infects other cells
e.g. virus
influenza
covid19
how are prions characterised
- Protein that has been altered from its normal structure and can then alter other proteins to develop more prions, so that the change spread like a chain reaction.
e.g. prions
SPONGIFORM ENCEPHALOPATHY IN CATTLE (MAD COW DISEASE)
- Progressive, degenerative and fatal disease affecting the central nervous system in cattle
- The human form is called Creutzfeldt-Jakob disease (vCJD)
- Symptoms include loss of intellect and memory, changes in personality, loss of co-ordination, slurred speech, vision problems and blindness.
define outbreak
where the disease pops up temporialiy in an isolated area
define endemic level
people affected by the disease at any given time
define pandemic
an increase in the number of cases throughout a continent or across the world
what are the two levels that contribute to epidemics
pathogen level
human level
what are factors that contribute to epidemics at a pathogen level
virulence antibiotic resistance toxins genetic shift herd immunity
how does virulence contribute to epidemics @ a pathogen level
Pathogens ability to infect or damage a host
- The greater the virulence the greater effect it will have on the health of the host
- Mutations increase a pathogens virulence, allowing it to evade detection in hosts
how does antibiotic resistance contribute to epidemics @ a pathogen level
Antibiotic resistant pathogens can’t be treated and are spread more easily.
how does toxins contribute to epidemics @ a pathogen level
- Make host more susceptible to infection
- Deter other pathogens
how does genetic shift contribute to epidemics @ a pathogen level
- Can occur if there is a loss of genetic variation or selection pressures that cause the population to lose genetic resistance
how does herd immunity contribute to epidemics @ a pathogen level
- In populations where a significant proportion of individuals are immune, the group becomes immune
how does migration contribute to epidemics @ a human level
- People can be disease vectors, so movement between different groups increases the chances of disease being transmitted between them
how does infrastructure contribute to epidemics @ a human level
- When populations are densely packed together, increased exposure to pathogens is likely
- Lack of amenities like clean running water, effective sewage systems and adequate health services promote disease survival
how does health care contribute to epidemics @ a human level
- Disease spread is increased where people do not have access to drugs and vaccines
1. Instructure is lacking, so clinics are not accessible
2. High cost of medicine
what are the three ways to control an epidemic
- identifying the pathogen
- environmental management
- quarantine
how does identifying the pathogen contribute to controlling an epidemic
Health workers help identify disease through:
a. Clinical observation
b. Laboratory confirmation
c. Data is collected on the number of cases presented and fed into larger surveillance systems
how does environmental management contribute to controlling an epidemic
- Cleansing water supplies of disease
- e.g. boiling, chlorinating, sealing - Reducing the risk of food contamination
- e.g. limiting food preparation, disposing of old food. - Creating sanitary conditions
- e.g. removing waste from public areas, providing sealed sewage systems
how does quarantine contribute to controlling an epidemic
A period of restricted movement and separation of people, animals and materials which may spread infectious disease
LARGE scale = travel bans, border regulation
SMALL scale = protective clothing, isolation
what is direct contact
- DIRECT CONTACT = physical contact between an infected organism and a susceptible organism allows the transfer of infected bodily fluids.
what is indirect contact
- INDIRECT CONTACT = Infectious diseases can also be spread indirectly through the air and other mechanisms.
what are the two ways direct contact can cause disease
person to person contact
droplet spread
disease e.g.s from person to person contact
STDs
ring worm
needle injections
how does person to person contact occur
shaking hands
touching
sex
how does droplet spread occur
when a person breathes talks coughs or sneezes
e.g. of direct contact
tuberculosis
what ways can indirect contact occur
airborne transmission
contaminated object (fomites)
contaminated food and water (vehicular)
how does airborne transmission occur
Some infectious agents can travel long distances and remain suspended in the air for an extended period of time.
how does fomites occur
Some organisms can live on objects for a short time. If you touch an object, such as a door knob, soon after an infected person, you might be exposed to infection. Transmission occurs when you touch your mouth, nose, or eyes before thoroughly washing your hands.
how can vehicular transmission occur
Infectious diseases can be transmitted via contaminated food and water,
E.G. E. coli is often transmitted through improperly handled produce or undercooked meat
how does vector borne disease occur
- VECTOR BORNE DISEASE (INSECT BITES) = Infectious diseases can also be spread indirectly through the air and other mechanisms.
e.g. of vector borne diseases
E.G. malaria Caused by a protist called plasmodium. The plasmodium pathogen floats in the blood of an infected person and feeds on haemoglobin causing red blood cells to pop.
Symptoms: Fever, muscle pain, nausea, headaches, weakness
When the female mosquito bites an infected person the pathogen is taken up with the blood
how did koch build on germ theory
koch isolated and grew the bacteria responsible for causing anthrax
what did koch discover
kochs postulates
what are kochs postulates
KOCH’s POSTULATES = list of criteria which must be met to prove that a particular organism causes a particular disease.
list kochs postulates
- The suspected pathogen must be present in every diseased individual, and absent in healthy individuals.
- The suspected pathogen must be able to be isolated from the host and grown in pure culture.
- A healthy potential host must develop the same symptoms as the original host, when inoculated with the suspected pathogen (essentially the disease must be able to reproduced)
- The suspected pathogen must be re-isolated from the second host and grown in pure culture, appearing identical to the original culture (essentially, the organism must be re-isolated)
how did louis pasteur build on the microbial fermentation theory
- In 1857, Pasteur discovered that sour wine contained two types of microorganisms. One of was yeast which he discovered was responsible for fermenting sugars to make alcohol. This resulted in the idea that fermentation is caused by microbes, known as the microbial fermentation theory.
what is pasteurisation
Pasteurisation was on the principle that heating liquids to 60-100oC would kill most microbes, and was so effective that Pasteur recommended the process for the sterilisation of objects as well as liquids e.g. beer, wine, milk…
what is louis pasteurs proof on germ theory
Pasteur proved the germ theory of disease (which states that many diseases are caused by the presence and actions of specific microorganisms within the body) using his swan-neck flask experiment. • Swan neck flask - Broth placed in swan neck flask, boiled to get rid of micro-organisms, one flask was broken, and one was normal. Broken one had spoiled (proves that bacteria don’t just generate randomly, they come from exposure to the air)
In doing so, he disproved the theory of spontaneous generation.
what are the causes of plant diseases
infectious agents
abiotic factors
what are the effects of plant diseases
o Infectious diseases impede a plants ability to function normally and therefore has a significant impact on the yield and quality
o Plant diseases cost millions each year and impacts our ability to trade (locally and internationally)
o It is estimated that pathogens cause 12.5% crop loss globally
o Significant social impacts (potato famine of 1845-1849)
o Adverse effect on biodiversity in natural ecosystems.
what are causes of disease in animals
infectious agents
effects of animal diseases
economic - food security…
health risks - potenial risk to infect humans
prevention control and treatment: what does local factors refer to
usually related to a neighbourhood, town or city
what are hygiene practices used for
prevention
what does hygiene practices entail
personal level
government regulations
safe food practices
hygiene pracitces at a personal level
cleaning:
- yourself
- clothing
- surroundings
- using contraceptives
hygiene: gov regulations
- collection and disposal of waste
- the provision of access to clean water (filtered, chlorinated, tested)
hygiene practices: safe food practices
- wearing gloves
- properly cleaning surfaces when preparing food
what is quarantine
a period of isolation used to control the spread of infectious disease
what scales does quarantine involve
small scale
large scale
quarantine: small scale
confining patients
- to their homes
- to their hospital beds
quarantine: large scale
o Confining whole communities
- Schools and work places closed
- Borders cut off and patrolled with strict exit/entry criteria based on health
o Goods and transport
- Banning the movement of fruits across borders to protect against fruit flies
what does vaccines provide individuals with
artificial active immunity
why are vaccines used
prevent
why is quarantine used
to control
why are public health campaigns used
prevention and control
what are pesticides
substances which control pest
what is the human benefit of using pesticides
o Protecting against: - Vector-borne diseases - Crop - Livestock o Defends the health of communities by sustain their food source
dangers of using pesticides
Biomagnification: Pesticide accumulates in the body tissues of organisms in the food chain in increasing amounts of higher trophic levels.
Resistance: Overuse of pesticides promotes the selection of naturally resistant strains
why is genetic engineering used
to modify the genetic structure of an organism
why is genetic engineering used to prevent disease
Used to produce plants and animals which are resistant to pests and disease
- To disable vectors from spreading disease
- To modify animals to produce biomedical products.
what are antivirals
drugs that treat viral infections
how are antivirals used
- Prevent viruses entering host cells by binding to receptors
- Inhibiting enzymes which catalyse the reproduction of the viral genome(preventing viral replication)
- Blocking transcription and translation of viral proteins – since they don’t have ribosomes, viruses need to use the ribosomes of a host cell to make their protein coat
- Preventing a virus from leaving the cell
- Grabbing the virus whilst outside the cell by targeting capsid proteins
what are antibiotics
drugs that treat bacterial infections
what are ways antibiotics work
killing bacteria causing the disease
slowing of the growth bacteria, giving the immune system a greater change of being able to remvoe it
e.g. of antibiotics
penicillin
how does penicillin work
o Causes the bacterial cell walls to weaken, resulting in the death of the cell
how does antibiotic resitance happen
through mutation
what is dengue fever
mosquito borne tropical disease caused by dengue virus
incidence of dengue fever
390 mil/year - globally
mortality of dengue fever
22mil/year - globally
define bush medicine
• A term used to describe the skills and practices used to maintain health, based on indigenous beliefs and practices.
e.g. of bush medicine
tea tree oil
eucalptus oil
