Diseases + populations

Question 1

Describe the relevance of molecular biology to studies in wild animal health/wild animal biology

Answer 1

Detection of pathogens

Microsatellites for looking at relatedness

Question 2

Understand the difference between DNA, RNA and protein and their roles in the cell.

Answer 2

DNA is transcribed into mRNA which is translated into a protein for cellular processes

Question 3

Describe the principles behind PCR and microsatellites, and how these can be applied to studies in WAB.

Answer 3

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

Question 4

Design oligonucleotide primers that will work in PCR if given a DNA sequence.

Answer 4

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.

Question 5

Understand the mechanisms of the host immune response to different pathogen groups and some of the immune evasion strategies employed by some pathogens.

Answer 5

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

Question 6

Describe the different types of immunoassays that can be used for diagnostic purposes.

Answer 6

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

Question 7

Appreciate how the formulation and delivery of vaccines can influence protective immunity and give some reasons for vaccine failure.

Answer 7

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

Question 8

Discuss the evolutionary and ecological drivers for development of the immune system in different species.

Answer 8

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

Question 9

Understanding infectious disease - transmission dynamics

Answer 9

Depends on birth, immigration, death, and emigration and also on the level of immunity

Question 10

Introduction to compartment models

Answer 10

Susceptibility, exposure, number of infectious individuals, and those that are removed (immune/dead)

Question 11

Disease modelling: understanding the importance of demographics

Answer 11

Allows for the prediction of an epidemic’s properties, e.g. how the populations within compartments changes over time

Question 12

What is R0

Answer 12

The average number of secondary cases generated from a primary case introduced into a susceptible population

Question 13

Understanding the importance of critical community size

Answer 13

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.

Question 14

Impact on wild populations; edge factors

Answer 14

Structures of populations change at boundaries, and fragmentation causes an increased exposure to a range of pathogens

Question 15

Impact on vegetation dynamics

Answer 15

Vaccinations developed can increase populations of host, which can impact the landscape, e.g. grazers

Question 16

Impact on livestock and livelihoods

Answer 16

Outbreaks, e.g. foot and mouth disease, can require culling which loses money for farmers

Question 17

Impact on human health

Answer 17

Zoonoses are causing more outbreaks due to spill over and increased contact with infected wildlife

Question 18

Approaches to wildlife disease management

Answer 18

Direct efforts within target population
Direct efforts to blocking transmission between reservoir and target
Reduce infection prevalence in the reservoir population

Question 19

Age-linked serology to understand the temporal relationships

Answer 19

Look for mutations and genetic based changes to look at relationships between cases and the direction of spread

Question 20

Intervention studies: eg vaccination campaigns, culling hosts to remove a population from the epidemiological equation

Answer 20

Monitoring population dynamics to see if the intervention has positive effects

Question 21

describe the underlying factors behind disease spread in natural populations

Answer 21

Transmission rate, virulence, birth and death rate

Question 22

describe the components required to design and implement models

Answer 22

Infected (infectious and latent) and non-infected (susceptible an immune)

Question 23

discuss the advantages and limitations of computer-based modelling in wildlife medicine

Answer 23

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

Question 24

provide definitions of veterinary epidemiology

Answer 24

The study of disease, productivity and welfare in animal populations

Question 25

provide examples of multi-factorial webs of causation

Answer 25

Age, health status, genetics, environment etc. > infection > tissue invasion and reaction > disease

Question 26

define components of epidemiological triad

Answer 26

Agent, environment, host

Question 27

describe different temporal patterns of disease occurrence

Answer 27

Continuously increasing rate, fluctuating rate etc.

Question 28

describe the difference between counts, proportions, rates and ratios

Answer 28

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

Question 29

define prevalence, cumulative incidence and incidence density

Answer 29

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

Question 30

discuss the differences between non-observational and observational studies

Answer 30

non-observational – recording the outcome of a planned intervention
observational – recording what happened

Question 31

describe the design and discuss the advantages/disadvantages of intervention studies, clinical trials

Answer 31

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

Question 32

describe the design and discuss the advantages/disadvantages of cross-sectional, case-control and cohort studies

Answer 32

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

Question 33

define measures of strength of association – relative risk, odds ratio

Answer 33

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

Question 34

describe measures of potential impact – attributable risk, attributable fraction

Answer 34

attributable risk – disease in exposed / disease in not exposed
attributable fraction – AR / risk of disease in exposed group

Question 35

to identify in an example, define and differentiate the terms related to sampling methodology

Answer 35

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?

Question 36

to give advantages/disadvantages of each sampling method

Answer 36

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)

Question 37

Describe contemporary issues in major diseases affecting wild artiodactyls and in the context of livestock

Answer 37

There is often an association between wild artiodactyls and livestock, especially when vector borne

Question 38

Critically evaluate the importance of disease in the conservation of wild artiodactyls

Answer 38

Artiodactyl loss will continue as each population shrinks and fragments