Intro to Epidemiology

Question 1

Of the >1400 species of pathogens that can infect humans, roughly what percentage of those are zoonotic?

Answer 1

Over 60 % of pathogens that infect humans are zoonotic.

Question 2

Zoonotic pathogens account for what percentage of emerging diseases?

Answer 2

75% of emerging diseases

Question 3

Define Epizootiology.

Answer 3

The study of the distribution and determinants of disease and other health outcomes in animal populations.

Question 4

What is the difference between contagious and communicable?

Answer 4

Contagious diseases are transmissible via direct or airborne routes.

Communicable diseases are transmissible via direct, airborne OR indirect routes (i.e. an inanimate reservoir)

Question 5

What to “Endemic Curves” represent?

Answer 5

The number of New cases of disease over time.

Question 6

What can “Endemic Curves” tell you about a disease?

Answer 6

1. The most probable source
2. If it is contagious
3. If the outbreak is ending or likely to continue
4. Incubation period of the pathogen
5. Information about outliers

Question 7

What is “Endemic Stability”

Answer 7

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

Question 8

Why are determinants important to know?

Answer 8

Determinants are factors that help determine the probability, distribution or severity of a disease in a population (ex. Host susceptibility).

Determinants can help:

• Identify animals at particular risk
• Aid in disease prevention
• Aid in coming up with DDx

Question 9

What is a Primary vs. Secondary Determinant?

Answer 9

Primary Determinants are major contributing factors. Usually necessary for disease to occur.

Secondary Determinants are factors that make the disease more or less likely. Predisposing or enabling factors.

Question 10

What is an Intrinsic vs. Extrinsic Determinant?

Answer 10

Intrinsic Determinants are internal to the animal. Age, Breed, Sex, etc

Extrinsic Determinants are external to the animal. Housing, Medical treatment, etc

Question 11

What three factors or “sectors” determine the ultimate outcome of a disease?

Answer 11

Host (intrinsic), Agent (extrinsic) and Environment (extrinsic).

Question 12

What are 5 things that can occur from antigenic mutation?

Answer 12

1. Increased infectivity in typical hosts
2. Ability to infect new species
3. Acquisition of new toxins
4. Immune system evasion
5. Antimicrobial resistance

Question 13

List the environmental determinants.

Answer 13

1. Demographics
2. Microclimate
3. Macroclimate
4. Housing and Crowding
5. Diet
6. Stress

Question 14

What two host characteristics are determined by the intrinsic determinant, Genotype?

Answer 14

Genetic diseases are ENTIRELY determined by Genotype.
and
Genetic susceptibilities are PARTIALLY determined by Genotype and partially by secondary factors.

Question 15

Why can Breed be used as a cue to less obvious, heritable traits?

Answer 15

Certain Genotypes are more likely in certain Breeds.

Question 16

How does Nutrition affect Immunity?

Answer 16

Health status alters susceptibility to disease. Nutrition has a strong effect on immune function

Question 17

What is “Herd Immunity”?

Answer 17

The idea that infectious diseases can be contained if a population’s resistance to infection is high enough.

Can be applied to people and to animals.

Question 18

What are some of the effects of Herd Immunity?

Answer 18

• Some non-immune individuals will likely become infected
• Does NOT protect individuals
• Many other will be protected, indirectly, by the immunity of their herd-mates. The infection will never reach them