Intro to Infectious Diseases & Epidemiology

Question 1

Principles of Infectious Diseases

Answer 1

Interconnected:
Susceptible Host
Pathogen
Environment
Infectious Disease

Question 2

Susceptible Host

Answer 2

breed, age, sex, genotype
physiology & susceptibility
immune response

Question 3

Environment

Answer 3

abiotic & biotic factors
housing management
population density
sanitation
nutrition
prevention

Question 4

Pathogen

Answer 4

pathogenicity
dispersal efficacy
survival efficacy
inoculation dose

Question 5

infection

Answer 5

the invasion & multiplication of pathogens in an individual or population

Question 6

disease

Answer 6

a disorder of structure or function in the host that adversely impacts the host and is not simply a result of physical injury

Question 7

infectious diseases

Answer 7

diseases caused by pathogenic microorganisms (e.g. bacteria, viruses, parasites, fungi, or prions); communicable & non-communicable

Question 8

communicable disease

Answer 8

diseases that can spread directly or indirectly, from one animal to another

Question 9

etiology

Answer 9

study of the cause of disease / cause of origin of disease

Question 10

microorganism/microbe

Answer 10

any organism that is invisible to the naked eye
(Antoine van Leeuwenhoek); there are more on one person’s hand than there are people on the planet

Question 11

microbes in order of size (smallest to largest)

Answer 11

prions-viruses-bacteria-fungi-protozoa-multicellular parasites

Question 12

commensal microbe-host relationship

Answer 12

• microorganism is a normal inhabitant of the body
• either microbe or host (or both) benefits
• neither is harmed under normal circumstances

Question 13

pathogen

Answer 13

• microorganism capable of causing disease
• include commensals AND noncommensals

Question 14

opportunistic pathogen

Answer 14

microorganism which does not ordinarily cause disease, but under certain conditions (e.g. impaired immunity), becomes pathogenic

Question 15

obligate pathogen

Answer 15

• microorganism that must produce disease to transmit and thereby survive evolutionarily
• NOT commensals, but can produce asymptomatic infection

Question 16

commensal pathogen

Answer 16

a microorganism that is commonly found within the indigenous microbiota that can cause disease in normal hosts with some regularity

Question 17

environmental pathogen

Answer 17

a microorganism capable of causing disease that is transmitted to the host from an environmental source such as water or soil

Question 18

Outcomes of Exposure to Infectious Agents

Answer 18

Exposure –> no infection

Exposure –> infection –> sub-clinical –> carrier

Exposure –> infection –> sub-clinical –> pathogen elimination –> immunity OR non-immunity

Exposure –> infection –> clinical –> death

Exposure –> infection –> clinical –> carrier

Exposure –> infection –> clinical –> pathogen elimination –> immunity OR non-immunity

Exposure does NOT = infection does NOT = disease

Question 19

Koch’s Postulates

Answer 19

1. The suspected pathogen must be found in every case of disease (all diseased individuals) and not be found in healthy individuals.
2. The suspected pathogen (aka causative agent) can be isolated and grown in pure culture.
3. A healthy test subject infected with the
   suspected pathogen (cultured agent) must develop the same signs and symptoms of disease.
4. The pathogen (same causative agent) must be re-isolated from the new host.

Question 20

Limitations of Koch’s Postulates

Answer 20

• Inability to isolate the organism in pure culture
• Inability to isolate the organism in cell-free culture
• Organisms for which a single species acts as host
• Subclinical infection
• Organisms that cause ‘distant’ infection
• Disease caused by toxins
• Diseases that require co-infection
• Organisms associated with tumors

Question 21

Stage 1 of an Infectious Disease

Answer 21

Incubation - pathogen multiplies without clinical signs

Question 22

Stage 2 of an Infectious Disease

Answer 22

Prodromal - general and unspecific signs

Question 23

Stage 3 of an Infectious Disease

Answer 23

Illness - signs and symptoms are more severe and specific

Question 24

Stage 4 of an Infectious Disease

Answer 24

Decline - number of pathogens and clinical signs begin to decline

(# of microbes peaks in between period of illness and decline)

Question 25

Stage 5 of an Infectious Disease

Answer 25

Convalescence - return to normalcy

Question 26

One Health

Answer 26

A collaborative, multisectoral, and transdisciplinary approach

working at the local, regional, national, and global levels

with the goal of achieving optimal health outcomes recognizing the interconnection between people, animals, plants, and their shared environment.

Question 27

Epidemiology

Answer 27

science of study and analysis of the DISTRIBUTION (who, where, when) and DETERMINANTS of health and disease conditions in defined populations

Question 28

veterinary epidemiologist

Answer 28

have advanced training in monitoring, controlling, and preventing disease in animal populations

Question 29

epidemiology purposes

Answer 29

1. discover
2. determine
3. identify
4. evaluate

DDIE

Question 30

Discover (epidemiology purpose)

Answer 30

agent, host and factors that affect health

Question 31

Determine (epidemiology purpose)

Answer 31

relative importance of causes of illness, disability, and death

Question 32

identify (epidemiology purpose)

Answer 32

population at risk from specific causes