22. Disease Control Strategies I

Question 1

Disease eradication usually refers to:

Answer 1

-regional elimination of an infectious disease
Ex. brucellosis, hog cholera, FMD
*time limited campaign

Question 2

Global eradication of disease:

Answer 2

-very few can be or have been
>human smallpox
>rinderpest

Question 3

Disease eradication consists of reduced prevalence to level that:

Answer 3

-the transmission does not occur
-disease is no longer a major health problem

Question 4

3 things necessary to be able to potentially eradicate an infectious disease:

Answer 4

1. Effective intervention available to interrupt transmission of agent
2. Practical diagnostic tools with sufficient sensitivity and specificity to detect levels of infection that lead to transmission
3. No other vertebrate reservoirs and the disease does NOT amplify in environment

Question 5

Economic considerations of disease eradication:

Answer 5

-can we justify the use of limit resources?
>alternative health interventions
>other non-health societal needs
*cost-benefit analyses can be difficult

Question 6

Disease eradication initiative is largely depend on:

Answer 6

-level of societal and political commitment
>beginning to end

Question 7

Social and political criteria:

Answer 7

-recognized public health importance
-broad national/international appeal
-worthy goal for all levels of society
-specific reasons for eradication

Question 8

All disease eradication decisions involve:

Answer 8

-risk
-uncertainty
*we deal with risk every day in a variety of ways

Question 9

If we know the answer (risk analysis):

Answer 9

-do NOT need to do risk analysis

Question 10

If we know the exact probability (risk analysis):

Answer 10

-we need to decide if we are COMFORTABLE with the level of risk

Question 11

Clinicians assess and communicate risk on a daily basis for:

Answer 11

-surgery or treatment
-vaccines
-contracting various infectious disease
-warning clients of zoonotic pathogens
-disease outbreaks

Question 12

Most of us are risk averse:

Answer 12

-we don’t like risk
*precautionary principle
>get fire insurance on our house even though many wont need it

Question 13

2 components of risk:

Answer 13

1. Probability of harm
2. Severity of impact of hazard

Question 14

Risk for rabies example:

Answer 14

-probability: low (higher than public)
-impact: HIGH
*better get vaccinated

Question 15

Risk for influenza example:

Answer 15

-probability: high
-impact: low if you are young and healthy

Question 16

Risk perception and communication:

Answer 16

-difficult
-how does the public perceive risk?

Question 17

Consumers and risk perception:

Answer 17

-less aware of probabilities and size of risk
*more aware of broader qualitative attributes

Question 18

Broader qualitative attributes of risk:

Answer 18

1. What do we know about it? (vertical)
2. How much control do we have? (horizontal)

Question 19

Nuclear weapons (war) example:

Answer 19

-know enough about it
-we have little control

Question 20

Risk communication principles:

Answer 20

-foster partnerships with public (positive relationships)
-collaborate and coordinate with credible sources
-meet needs for media and remain accessible
-listen to public’s concerns and understand your audience

Question 21

Risk communication: communicate with

Answer 21

-compassion, concern, and empathy
-demonstrate honesty, candour and openness

Question 22

Risk communication accept:

Answer 22

-uncertainty and ambiguity

Question 23

Risk communication provide messages that:

Answer 23

-foster self-efficacy
>give people meaningful actions to do
>help to restore sense of control

Question 24

Disease control:

Answer 24

-reduction of morbidity and mortality
*embraces all measures
-ongoing process
-infers population level control

Question 25

Biosecurity: any practice or system that

Answer 25

1. Prevents spread of infectious agents
2. Prevents introduction of infected animals to herd, region or country where the infection has not occurred

Question 26

Factors affecting control:

Answer 26

-mode of transmission
-host specificity
-ease of spread

Question 27

Important factors in vet disease control programs:

Answer 27

-knowledge of cause, maintenance, and transmission of disease
-veterinary infrastructure
-diagnostic feasibility
-availability of replacement stock
-producer’s opinion and cooperation
-public opinion

Question 28

Important factors in disease control programs:

Answer 28

-public health considerations
-requirement for legislation and compensation
-ecological consequences
-financial support
Ex. badgers in UK

Question 29

Diagnostic tactics:

Answer 29

-not always necessary to have a diagnosis
-need to identify elements in the ‘web of causation’ that can be manipulated
Ex. routes of transmission, indirect causes
*early detection is important
*screening tests

Question 30

Calf scours diagnostic tactics:

Answer 30

-don’t need to know the exact virus, can still get a control system set up

Question 31

Pathognomonic tests:

Answer 31

-absolute predictor of disease or disease agent
-can have false negatives
Ex. culture bacteria (Brucella abortus from milk, T. foetus)

Question 32

Surrogate tests:

Answer 32

-detect SECONDARY changes that will hopefully predict the presence or absence of disease or disease agent
-can have false negatives AND false positives
Ex. serology, antigen tests, viral isolation, etc.

Question 33

Diagnostic test should be:

Answer 33

-backed by data comparing its accuracy to an appropriate standard

Question 34

“gold standard”:

Answer 34

-standard of validity
-one can determine if the disease is truly present of absent
-some cases there may not be a gold standard

Question 35

What is often regarded as the ultimate conformational test?

Answer 35

-post mortem (PM) exam

Question 36

Titre test possibilities:

Answer 36

-true positive
-true negative
-false positive
-false negative
*come up with a cutoff point
*use a 2x2 table

Question 37

True prevalence equation:

Answer 37

-true positive + false negative (disease is present)
-divide that by total in population (N)
=(those with disease present)/(N)

Question 38

Apparent prevalence equation:

Answer 38

-true positive + false positives (just got a positive test)
-divide that by N
=(those that tested positive)/(N)

Question 39

Sensitivity equation:

Answer 39

-true positive
-divided by true positive and false negatives (disease is present)
=true positive/(true positive and false negatives)

Question 40

Sensitivity:

Answer 40

-proportion of diseased animals that tested positive
-ability of a diagnostic test to DETECT disease
=(1-false negative rate)
*SnNOUT

Question 41

High sensitivity:

Answer 41

-will find more animals in the population that have the disease
*very few false negatives

Question 42

Specificity equation:

Answer 42

-true negatives
-divided by true and false positives (disease is not present)
=true negatives/(true and false positives)

Question 43

Specificity:

Answer 43

-proportion of non-diseased animals that test negative
-ability of diagnostic test to detect NON-diseased animals
=(1-false positive rate)
*SpPIN

Question 44

What is better, high sensitivity or high specificity?

Answer 44

-depends on what you are trying to rule out

Question 45

Trying to rule out a disease:

Answer 45

-SnNOUT
-test with high SENSITIVITY and high negative predictive value
>works best when prevalence of disease is low

Question 46

Trying to rule in a disease or confirm a diagnostic:

Answer 46

-SpPIN
-use a test with high SPECIFICITY and a high PPV (positive predictive value)
>works best when prevalence of a disease is high

Question 47

What is cost of a false negative test? Ex. FMD

Answer 47

-consequences are DISASTROUS
>need a highly SENSITIVE tests even at the cost of specificity
>*avoid false negatives at all costs

Question 48

What is the costs of a false positive test?

Answer 48

-high treatment costs
-treatments that are potentially dangerous
-euthanasia of valuable animal might be possible
-use highly SPECIFIC tests