Diseases + populations Flashcards
Describe the relevance of molecular biology to studies in wild animal health/wild animal biology
Detection of pathogens
Microsatellites for looking at relatedness
Understand the difference between DNA, RNA and protein and their roles in the cell.
DNA is transcribed into mRNA which is translated into a protein for cellular processes
Describe the principles behind PCR and microsatellites, and how these can be applied to studies in WAB.
Polymerase chain reaction (PCR) is a technology used for quick and easy amplifying DNA sequences, which is based on the principle of enzymatic replication of the nucleic acids
A microsatellite is a strand of repetitive DNA in which certain DNA motifs are repeated and they are used as genetic markers to follow the inheritance of genes in families
Design oligonucleotide primers that will work in PCR if given a DNA sequence.
Your primers should have a nucleotide content of approximately 50% G:C and 50% A:T base pairs, they should have a minimum length of 17 bp. Second primer needs to be the matching sequence and reversed, because extension is at the 3’ end.
Understand the mechanisms of the host immune response to different pathogen groups and some of the immune evasion strategies employed by some pathogens.
Innate response – produces interferon for defence and makes cells more resistant to infection
Adaptive response – B cells produce virus-neutralising antibody, CD8 and killer T cells destruct infected cells
Evasion strategies - e.g. mimicking host cells, hiding within host cells
Describe the different types of immunoassays that can be used for diagnostic purposes.
ELISA – using antibody and protein to have an antigen bind if it is present
Immunofluorescence – using a sample and introducing antibodies so that if they bind we know antigens are present
Appreciate how the formulation and delivery of vaccines can influence protective immunity and give some reasons for vaccine failure.
Passive immunisation lasts approx. 3 months vs active which lasts longer
It may be a different strain of antigen that the host is exposed to, incorrect storage and administration will also reduce effectiveness
Discuss the evolutionary and ecological drivers for development of the immune system in different species.
The host may be too young/old, be immunocompromised, or be genetically pre-programmed with a poor response
Environment may not be suitable for the reproduction of some pathogens
Understanding infectious disease - transmission dynamics
Depends on birth, immigration, death, and emigration and also on the level of immunity
Introduction to compartment models
Susceptibility, exposure, number of infectious individuals, and those that are removed (immune/dead)
Disease modelling: understanding the importance of demographics
Allows for the prediction of an epidemic’s properties, e.g. how the populations within compartments changes over time
What is R0
The average number of secondary cases generated from a primary case introduced into a susceptible population
Understanding the importance of critical community size
The minimum size of a closed population which a pathogen can persist indefinitely. When the CCS falls below this, the low density of hosts causes extinction of the pathogen.
Impact on wild populations; edge factors
Structures of populations change at boundaries, and fragmentation causes an increased exposure to a range of pathogens
Impact on vegetation dynamics
Vaccinations developed can increase populations of host, which can impact the landscape, e.g. grazers
Impact on livestock and livelihoods
Outbreaks, e.g. foot and mouth disease, can require culling which loses money for farmers
Impact on human health
Zoonoses are causing more outbreaks due to spill over and increased contact with infected wildlife
Approaches to wildlife disease management
Direct efforts within target population
Direct efforts to blocking transmission between reservoir and target
Reduce infection prevalence in the reservoir population
Age-linked serology to understand the temporal relationships
Look for mutations and genetic based changes to look at relationships between cases and the direction of spread
Intervention studies: eg vaccination campaigns, culling hosts to remove a population from the epidemiological equation
Monitoring population dynamics to see if the intervention has positive effects
describe the underlying factors behind disease spread in natural populations
Transmission rate, virulence, birth and death rate
describe the components required to design and implement models
Infected (infectious and latent) and non-infected (susceptible an immune)
discuss the advantages and limitations of computer-based modelling in wildlife medicine
Can give some predictions which can be used for interventions and control or adapting these methods, but relying on assumptions means they may not be accurate
provide definitions of veterinary epidemiology
The study of disease, productivity and welfare in animal populations
provide examples of multi-factorial webs of causation
Age, health status, genetics, environment etc. > infection > tissue invasion and reaction > disease
define components of epidemiological triad
Agent, environment, host
describe different temporal patterns of disease occurrence
Continuously increasing rate, fluctuating rate etc.
describe the difference between counts, proportions, rates and ratios
ratios – relative size of two quantities expressed by dividing a numerator by a denominator
counts – number of individuals infected, diseased, or dead
proportions – a ratio whose numerator is included in the denominator
rates – a ratio representing the magnitude of change in occurrence of an event
define prevalence, cumulative incidence and incidence density
prevalence – total number of individuals who have a disease at a particular time divided by the population at risk
cumulative incidence – proportion of disease-free individuals developing a disease over a specified time
incidence density – instantaneous potential for change in disease status per unit of time, relative to the size of disease free population at time
discuss the differences between non-observational and observational studies
non-observational – recording the outcome of a planned intervention
observational – recording what happened
describe the design and discuss the advantages/disadvantages of intervention studies, clinical trials
Often randomised control trials with comparisons between a placebo group and those receiving the intervention
Control over confounding variables, control over selection bias, assessed intervention effectiveness
Expensive, may need a large sample size, may need a large follow-up, only possible if there’s a suitable intervention
describe the design and discuss the advantages/disadvantages of cross-sectional, case-control and cohort studies
cross-sectional – data on a factor and outcomes at the same time, inexpensive and easy but information on changes over time is limited
case-control – 2 or more groups e.g. exposed and not exposed and checked later to see if they have the disease, good for rare outcomes but not for rare exposures
cohort studies – disease and non-diseased group comparison looking retrospectively at whether they were exposed to a factor, good for rare exposures but not for rare diseases
define measures of strength of association – relative risk, odds ratio
relative risk – probability of getting disease if exposed / probability if not exposed, OR probability of outcome if on drug / probability if not on drug
odds ratio – odds that the diseased were exposed / odds the controls were exposed
describe measures of potential impact – attributable risk, attributable fraction
attributable risk – disease in exposed / disease in not exposed
attributable fraction – AR / risk of disease in exposed group
to identify in an example, define and differentiate the terms related to sampling methodology
probability based: convenience and haphazard sampling – biased samples and errors in conclusions
non-probability based: simple random and systematic sampling – equal likelihood of selection but each have their downfalls e.g. is it truly random?
to give advantages/disadvantages of each sampling method
convenience – easy and quick but biased to what’s available
judgement sample – what you think is representative but it’s biased
simple random – easy but the individuals may not all be easily available
systematic – high validity but is it true randomness (takes away equal opportunity of being chosen)
Describe contemporary issues in major diseases affecting wild artiodactyls and in the context of livestock
There is often an association between wild artiodactyls and livestock, especially when vector borne
Critically evaluate the importance of disease in the conservation of wild artiodactyls
Artiodactyl loss will continue as each population shrinks and fragments
