Disease Control

Question 1

Three things are necessary to be able to

potentially eradicate an infectious disease

Answer 1

– Effective intervention is available to interrupt
transmission of the agent
– Practical diagnostic tools with sufficient
sensitivity and specificity are available to
detect levels of infection that lead to
transmission
– There are no other vertebrate reservoirs and
the disease does not amplify in the
environment

Question 2

A disease eradication initiative is largely

dependent on

Answer 2

the level of societal and

political commitment

Question 3

Two components of RISK

Answer 3

(1) Probability of Harm
(2) Severity of Impact of a
Hazard

Question 4

8 Factors affecting Risk

Perception

Answer 4

• Catastrophic potential
• Familiarity
• Understanding
• Scientific certainty
• Controllability
• Is exposure voluntary?
• Impact on children
• Dread results

Question 5

In broad terms what is Disease Control

Answer 5

Reduction of morbidity and mortality

Question 6

What is Biosecurity

Answer 6

Any practice or system that prevents the spread
of infectious agents from infected animals to susceptible animals.

Any practice that prevents the introduction of
infected animals into a herd, region or country
in which the infection has not occurred.

Question 7

Factors affecting Control

Answer 7

• Mode of transmission
• Host specificity
• Ease of spread

Question 8

6 Important Factors in Veterinary

Disease Control Programs

Answer 8

• Knowledge of the cause, maintenance and
transmission of the disease
• Veterinary infrastructure
• Diagnostic feasibility
• Availability of replacement stock
• Producer’s opinions and cooperation
• Public opinion

Question 9

4 Important Factors in Disease

Control Programs

Answer 9

• Public health considerations
• Requirement for legislation and
compensation
• Ecological consequences
• Financial support

Question 10

Pathognomonic tests

Answer 10

• Absolute predictor of disease or disease agent

* Can have false negatives

Question 11

Surrogate Tests

Answer 11

• Detect secondary changes that will hopefully predict the presence or absence of disease or the disease agent
• Can have false negatives and false positives

Question 12

True Prevalence =

Answer 12

True Prevalence = (A+C)/N

Question 13

Apparent Prevalence =

Answer 13

Apparent Prevalence = (A+B)/N

Question 14

Sensitivity =

Answer 14

Sensitivity = A/(A+C)

Question 15

SnNout

Answer 15

If highly sensitive test has a negative result you can rule out false negative

Question 16

Specificity =

Answer 16

Specificity = D/(B+D)

Question 17

SpPin

Answer 17

Positive result with specificity test you can rule in.

Question 18

What does sensitivity test for?

Answer 18

Proportion of diseased animals that test
positive

Ability of diagnostic test to detect disease

Question 19

What does specificity test for?

Answer 19

Proportion of non-diseased animals that
test negative

Ability of diagnostic test to detect nondiseased
animals

Question 20

What type of test do you want to run if you are trying to rule out a disease?

Answer 20

Use a test with high sensitivity and a high
negative predictive value.

SnNout

Question 21

What type of test do you run if you are trying to rule in a disease or
confirm a diagnosis?

Answer 21

Use a test with high specificity and a high
PPV.

SpPin

Question 22

What is the cost of a false positive test?

Answer 22

– High treatment costs
– Treatments that are potentially dangerous
– Euthanasia of valuable animal might be
possible
– Use highly specific tests
– Multiple tests should be interpreted in series

Question 23

Strategies for Directed Action
against Disease at the
Population Level

Answer 23

1. Selective Slaughter
2. Depopulation
3. Quarantine
4. Reduction of Contact
5. Mass treatment
6. Mass Immunization
7. Education
8. Environmental Control
9. Applied Ecology
10. Genetic Improvement

Question 24

Selective Slaughter

Answer 24

Test and slaughter

Slowly Spreading disease

More expensive as disease becomes rarer

Example = Brucilosis

Question 25

Depopulation

Answer 25

Whole pop including non-infected

Rapidly Spreading disease

Example = Foot and Mouth

Question 26

Quarantine

Answer 26

Physical separation of sick animals from healthy

Difficult with large size areas like wood bison national park

Question 27

Reduction of Contact

Answer 27

Separate physically

Separate in time - dont milk staph cows b4 clean cows

Example = Staph mastitis

Question 28

Mass Treatment

Answer 28

Treat all animals (sick and well)

Diseases occurring at very high prevalence

Example: Deworming

Problems: Disease resistance

Question 29

2 problems with mass immunization?

Answer 29

1. Panacea - ppl thin that if vaccinated that they dont have to worry about other preventative measures
2. Can interfere with screening (cant tell vaccinated from infected)

Question 30

Example of Education

Answer 30

Somatic cell count penalty programs