Epidemic Curves and Determinants of Disease

Question 1

What is a latent animal?

Answer 1

Microbe is replicating but not yet enough for the host to become infectious.

Question 2

What is the incubation period?

Answer 2

Microbe is replicating but not symptomatic yet. It does not always correlate with the latent period.

Question 3

What is infectious disease?

Answer 3

A disease caused by the invasion and multiplication of a living agent in/on a host.

Question 4

What is infestation?

Answer 4

Invasion, but not multiplicatio of an organism in/on a host (fleas/ticks, sometimes parasites.)

Question 5

What is a contagious disease?

Answer 5

A disease transmissable from one human/animal to another via direct or airborne routes.

Question 6

What is a communicable disease?

Answer 6

A disease caused by an agent capable of transmission by direct, airborne or indirect routes from an infected person, animal, plant or contaminated inanimate reservoir.

Question 7

Why are these distinctions important to public health and epidemiology?

Answer 7

If something is communicable we are worried about water source, soil, vector and also direct contact spread.

Question 8

What is an epidemic curve?

Answer 8

Represents the number of new cases of disease over time.

Can tell you:

• Most probable source of the outbreak.*
• If the pathogen is contagious.*
• If the outbreak is ending–or will continue.*
• Incubation period of the pathogen (sometimes.)*
• About outliers. (With epidemiology you do look at outliers.)*

Question 9

What does one of these bars stand for?

Answer 9

A wave.

Question 10

What does each higher “peak” represent?

Answer 10

An incubation period which you will notice on this graph is separated by 3 days of incubation.

Question 11

What does the Y axis represent on this graph?

Answer 11

The # of new cases seen.

Question 12

What does X axis represent here?

Answer 12

Here it represents days that have passed but could also be weeks or months depending on graphs (and disease that is being referenced.)

Question 13

Would a disease like this recover without interference?

Answer 13

No, something needs to be done.

Question 14

What kind of graph is this?

Answer 14

Common Source Single Point Exposure.

• All animals are exposed at once.*
• All are exposed to the same source of infection.*
• Not contagious–get sick and then get over it.*

Question 15

Would you need to do something about this type of disease?

Answer 15

No, occuring within one incubation period.

Question 16

What kind of graph is this?

Answer 16

Common Source with Intermittent Exposure.

• Animals are exposed at different times.*
• Exposed to the same source.*
• Incubation period is NOT clear represented–lack of a pattern.*
• ex: Farmers putting cows out onto pasture and there is a pond that is infected with Leptospirosis. Brought to a different pasture and then reintroduced to pasture and pond again.*

Question 17

Should someone intervene with a case like this?

Answer 17

Yes

Question 18

The shape of the epidemiological curve depends on what things?

Answer 18

1. Host: Immunity or other resistance to disease or direct transmission.
2. Agent: Infectiousness of agent, or latent and and incubation periods, or duration of infectivity.
3. Environment: Especially important for indirect routes of transmission.

Question 19

What is endemic stability?

Answer 19

A situation in which all factors influencing disease are relatively stable, resulting in little fluctuation in disease incidence over time.

• New cases occur at a regular, usually low level.*
• Young individuals may enter the population.*
• Old individuals die or are removed.*

Question 20

What is the animal term for endemic?

Answer 20

Enzootic

Question 21

T/F: Most cases that we deal with on a daily basis are epidemic.

Answer 21

False, they are endemic.

Question 22

What is a determinants?

Answer 22

Factors that help determine the probability, distribution, or severity of a disease in an animal or population of animals.

Determinants can be a determinant for health or a determinant for disease.

ex: Host susceptibility is one kind of derminant –but certainly not the only one.

Question 23

Why is it important to recognize determinants?

Answer 23

1. Identifies animals at particular risk.
2. Disease prevention.
3. Aids in a differential diagnosis.

Question 24

What is a primary determinant?

Answer 24

A major contributing factor, usually a necessary one.

Question 25

What is a secondary determinant?

Answer 25

Factors that make the disease more or less likely; predisposing or enabling factors.

Question 26

What are intrinsic determinants?

Answer 26

Determinants that are internal to the animal. (age, breed, sex, etc…)

Question 27

What are extrinsic determinants?

Answer 27

Determinants that are external to the animal. (housing, medical treatment, etc…)

Question 28

_______ determinants must always be present in order for the disease to occur.

Answer 28

Primary

Aka: necessary causes.

Question 29

Primary determinants satisfy the _____ ____ ____ test.

Answer 29

Gotta have it.

Everything else is just secondary or just a component cause.

Question 30

For Bovine Shipping Fever what is the:

Primary intrinsic: ______

Primary extrinsic: ______

Secondary intrinsic: ________

Secondary extrinsic: ______

determinants.

Answer 30

Primary intrinsic: Immunologically naive animals (genetic.)

Primary extrinsic: exposure to shipping.

Secondary intrinsic: they are young (calves.)

Secondary extrinsic: mixing the cows.

Question 31

Complex interactions between all 3 sectors [host, agent and environment] determine what?

Answer 31

The ultimate outcome (a disease.)

Question 32

What are the 3 sectors for Flea Bite Hypersensitivity?

Answer 32

Host: Dog or cat

Agent: Fleas

Environment: Humid like the state of FL.