11 Disease Flashcards
what is the definition of health?
being free from disease
having physical, social and mental wellbeing
having good nutrition
being suitably housed
what is the definition of disease?
a malfunction of the body and/or mind that adversely affects the health of an individual and leads to impairment of normal functioning
what is a communicable disease?
a disease or infection capable of being transmitted or communicated to another living organism
what is required for a disease to be communicated successfully?
the pathogen must:
- enter the host (i.e. pass the first line of defence)
- colonise affected tissue
- leading to development of symptoms
what is virulence?
a measure of the ability of a pathogen to cause disease
how do bacteria cause harm? give an example
production of toxin –> symptoms
e.g. streptococcus produces a pyrogenic toxin, causing a rash and high temperatures
how do viruses cause harm?
enter host cell and inhibit normal DNA/RNA/protein synthesis
then use these mechanisms to produce new viral particles
once sufficient have been formed, the cell ruptures and the virus spreads
how do fungi cause harm?
secretion of enzymes that causes an allergic reaction and allows the spread of pathogens through tissues
what is the difference between a pathogen and a parasite?
a pathogen always causes disease, whereas a parasite doesn’t always
a parasite gains energy from the host, whereas a pathogen does not
how does TB cause disease?
inhibits the action of lysosomes in phagocytic leucocytes
what happens during the 1° infection of TB?
bacteria multiply inside lung tissue and destroy it
a healthy immune system should be able to deal with it
what happens during the 2° infection of TB?
phagocytic cells accumulate round infected cells, causing a tubercule (granuloma)
lung tissue is damaged and sputum becomes blood-stained
can spread to immune system, bones, gut and kidneys
how is TB communicated?
inhalation of inhaled droplets (T)
long term contact (T)
contaminated meat/unpasteurised milk (B)
how is TB diagnosed?
microscopical analysis of sputum and chest xrays
how can TB be prevented?
reduce over-crowding
improve ventilation
testing of cattle
pasteurising milk
improve general health
give four symptoms of TB
fever
night sweats
coughing up blood
tiredness
what is latent TB?
no symptoms ∴ treatment not required but must be monitored
how is TB treated?
isolation during infectious period
intensive care and antibiotics
how are antibiotics used to treat TB?
2 antibiotics daily for 6 months
2 antibiotics daily for 2 months
n.b. if infection spreads outside lungs, used for 12 months
what are the consequences of developing MDR-TB or XDR-TB?
require 18 months’ treatment with up to 4 antibiotics and a treatment team
what is a retrovirus?
a virus that contains RNA and reverse transcriptase
which types of cell does HIV infect?
T helper cells, macrophages and brain cells
how does HIV cause disease?
reverse transcriptase creates a DNA copy of viral genome
becomes part of the cell (a provirus)
provirus activates viral DNA –> synthesis of viral RNA and viral proteins
T helper cell ruptures to prevent immune system resistance
how is HIV transmitted?
direct contact of contaminated body fluids, e.g.:
- blood
- semen
- mother’s milk/across placenta
what are the symptoms of HIV infection?
presence of other opportunistic diseases (e.g. TB; pneumonia)
weakened immunity
weight loss
how can HIV transmission be prevented?
testing ‘at risk’ groups
contraceptives
blood screening
monogamy
education
what is the function of a capsid in a virus/bacteria?
surrounds and protects enzymes and RNA
what is the function of reverse transcriptase?
creates double-stranded DNA copy of viral RNA
what are features of an acellular particle?
cannot:
- grow
- reproduce/divide (on its own)
- transform energy
- synthesise proteins
what are the features of aseptic technique?
washing hands
bunsen flame
flaming the inoculating loop
flaming the neck
streaking the plate
incubating at 25.C
outline the procedure of Gram staining
stained with crystal violet for 30s
washed briefly with deionised water
flooded with iodine (mordent)
rinsed with water again
alternating 95% alcohol and water until no further colour change is observed
counterstain (safranin) applied
explain the results of Gram staining
Gram +ve: thick peptidoglycan wall takes up crystal violet and binds to it ∴ it is purple
Gram -ve: thin peptidoglycan wall takes up crystal violet, but the alcohol washes it away ∴ counterstain taken up ∴ pink
give two strengths and two weaknesses of Gram staining
+ distinct colour difference
+ quick + relatively straightforward
- easy to make method error
- does not identify individual species
what are the four aspects of colony morphology?
shape
colour
edges
surface features
give two strengths and two weaknesses of colony morphology as a means of identifying bacterial species
+ many clear features
+ easy to see contamination
- many different types have similar colony morphology ∴ it is not a reliable means of identification
what are the three shapes of bacterial morphology?
cocci = spherical
bacilli = rod-shaped
spirilla = corkscrew
what is meant by the ‘incidence rate’?
the number of new cases in a population each year
what is the definition of an endemic?
an infectious disease being constantly present in a population
what is the definition of an epidemic?
a sudden increase in the incidence of an infectious disease in a confined area
what is the definition of a pandemic?
an increase in the incidence of an infectious in several countries
what is the definition of morbidity?
the number of people who have a certain disease
what is the definition of mortality?
the number of people who have died from a certain disease within a population
what are the control measures implemented to reduce the spread of disease?
control of population movement
improving hygiene standards
vaccination programmes
improving housing
isolation
provision of drugs
improving nutrition
education of population on prevention methods and symptoms
what is a notifiable disease?
a disease that, upon diagnosis by a doctor, must be reported to the local authorities and Public Health England
give an example of a notifiable disease
MMR
whooping cough
viral hepatitis
TB
anthrax
malaria
cholera
food poisoning
