CHAPTER 6: DISEASE CHALLENGES AND STRATEGIES Flashcards
what are infectious diseases
transmitted from person to person through the transfer of a pathogen such as bacteria, viruses, fungi or parasites
what are emerging diseases
a disease caused by a newly identified or previously unknown agent
what are re-emerging diseases
- a disease that reappears after a significant decline in its incidence
- re-emerging diseases were once controlled but have increased to a level that causes significant health issues
epidemic
- the widespread of an infectious disease in an area at a particular time
- cholera in Haiti (2010-present)
- ebola in west Africa (2013-2016)
pandemic
- the global outbreak of a disease
- widespread outbreak of a disease over a large geographical area
- an epidemic has become a pandemic once there are community-level outbreaks in at least two WHO regions
- eg COVID-19 6.28 million deaths → 0.08% of population
why living in a ‘globally connected world’ increases the likelihood of pandemics
- transport (planes)
- interact with more people from different communities
impact of European arrival on Indigenous Australians
- Australia is geographically isolated
- prior to European arrival, there was little interaction between Indigenous peoples and Europeans
- after settlement, they brought various new diseases and pathogens
- Major epidemic diseases were introduced
- smallpox, chicken pox, syphilis, tuberculosis, influenza
- indigenous populations had no immunity against them
- large numbers of susceptible individuals and low herd immunity
- the rapid spread of new infectious diseases and significant fatalities
what is in a vaccine
- vaccines are substances that cause an immune response without inducing the disease
- active, artificial immunity
- they can be pathogens that are:
- live attenuated - strain of pathogen that doesn’t cause the disease
- inactivated
- toxoid
- subunits
- they work because your body makes antibodies and memory cells
3 vaccines that are on the Australian vaccination schedule and the age at which they are given
- meningococcal ACWY - 12 months and 14-16yrs
- measles - 12 and 18 months
- HPV - 12-13 years
how vaccines provide long-term immunity
- Stimulate the immune system to produce memory cells
- These memory cells remain in lymphatic system and can initiate a stronger and more rapid immune response upon reinfection with the same specific antigen
why are boosters needed for some vaccines
- to retain a memory of the pathogen and maintain the concentration of antibodies
- killed/inactivated vaccines produce a weaker immune response than live attenuated vaccines so immunity lasts for a shorter period
- need booster for killed/inactivated vaccines to maintain immunity
- BOOSTER SHOTS HELP CREATE LONG TERM MEMORY BECAUSE IT INCREASES THE NUMBER OF MEMORY B CELLS
- This is because memory cells are short lived
why diseases such as Influenza need new vaccines each year
- the virus changes each year
- to keep up with the different strains of the virus
- target the antigens of the specific strain
- any previous vaccinations wouldn’t be effective against the new strains of virus because antigens are different
herd immunity
- indirect protection of populations from infection
- protection is created by the presence of immune individuals
- protection is received by unvaccinated individuals
- those who cannot be vaccinated (old, young, sick and immunocompromised)
- no vaccination - contagious disease spreads
- high vaccination - contagious disease contained (reducing the number of hosts that continue to transmit the pathogen) decreases the spread
- vaccines protect those who can’t be vaccinated
- reduces the number of incidences
95%
the percentage of a population that must be exposed to a disease or a vaccine to achieve herd immunity varies widely for different diseases.
reasons that prevent some people from being vaccinated
- they are immunocompromised
- access to hospitals/medical facitilities
- lack of education
- lack of accessibility to vaccines due to cost
- lack of medical staff who can deliver and administer vaccines
- lack of mandatory vaccination laws
identifying bacteria
- phenotypic methods:
- cell size/shape
- gram -/+
- aerobic/anaerobic
- immunological methods
- MAB
- ELISA
- immunofluorescence
- genotypic/molecular method
- sequence
- probes
identifying viruses
- physical methods
- X-ray crystallography
- electron microscopy
- immunological
- ELISA
- molecular
- probes
- fingerprinting
what is ELISA
- enzyme-linked immunosorbent assay
- wells are coated with an antigen specific to the disease being tested
- antibodies present in the sample bind to the antigen in the well
- the wells are then washed to remove any unbound antibodies
- new different conjugated antibodies are added to each well → the antibody also has an associated enzyme indicator
- the substrate for the enzyme is added leading to colour change if an antigen-antibody complex is formed → indicates a positive test
identify the host and mode of transmission
- the reservoir of a pathogen is the habitat in which it lives, grows and multiplies
- host - an organism that can get the disease
- zoonotic diseases are infectious diseases that are transmitted from animals to humans
- pathogens can spread via
- direct contact - touch, air, droplets, swapping fluids
- indirect contact - aerosol, surfaces, food/water, host animals
- vectors
control measures to prevent spread of disease
- prevention: clean water, wash hands, safe sex
- vaccination: reduce the number of hosts, long-term immunity
- medication: treat people to reduce transmission
- surveillance: monitor outbreaks
- modification of environment: drain ponds, mosquito nets (vector control)
- improving infection control standards: sterilisation of surfaces/objects, mask, quarantine
antibiotics
- antibiotics treat bacterial infection
- role: inhibit the growth of or kill bacteria
- action
- penicillin inhibits cell wall synthesis in bacteria and so targets actively reproducing bacteria. Since human cells do not have cell walls, penicillin does not attack human cells and so has low toxicity
- chloramphenicol, erythromycin, tetracyclines and streptomycin inhibit protein synthesis by acting on the ribosomes of prokaryotic cells.
- sulfanilamide acts as an antimetabolite by competitively inhibiting enzyme activity in bacteria.
- rifampin and quinolones inhibit nucleic acid synthesis.
- injury to plasma membrane
action of viruses
viruses need to be able to :
- find and attach to host cells
- get through plasma membrane
- take over host DNA and replicate by getting into nucleus, insert their DNA
- get out
antivirals
- act only on viruses actively replicating
- mode of action
- block entry of the virus into host cells
- block fusion of the virus with host cell
- block uncoating
- prevent replication of the viral genome
- prevent the release of new viruses
- stimulate the host immune system
sensitivity test
carried out to determine the antibiotic that would be most effective to treat a bacterial infection
why are antibiotics not effective in treating viral infections
antibiotics are a useful treatment against bacterial diseases because:
- antibiotics inhibit the reproduction of bacteria/cell wall synthesis/protein synthesis
- but viruses do not have cellular structures as they are not cellular
- and viruses are reproduced by a host cell