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VET 401 Basic Foundations > Exam 4 > Flashcards

Exam 4 Flashcards

1
Q

Pathogen

A

Organism that causes pathology, damage, disease or disrupts normal host function or fitness

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2
Q

Frank pathogen

A

Organism that causes disease in some/most of the animals
Needs sufficient dose, no other factors
NOT part of host’s normal flora

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3
Q

Opportunistic pathogen

A

Causes disease only if other factors are present that compromise host defenses
Ex: skin wounds, catheter, URI, etc.
Frank can be opportunistic in some species and vice versa

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4
Q

Virulence

A

Measure of pathogenicity (capacity of a microbe to cause disease in a host
How much damage

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5
Q

Virulence traits

A

Essential for virulence - directly result in host damage
Virulence-associated - control expression of virulence genes, help with secretion or processing of virulence proteins
Virulence lifestyle - allow colonization, evasion of host defenses

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6
Q

Examples of virulence traits

A

Anthrax virulence genes - Anthrax toxin: protective antigen, lethal toxin, edema toxin
Virulence-associated genes
Virulence lifestyle genes - spore formation, capsule

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7
Q

Gram negative

A

Thin peptidoglycan layer
Contain LPS
Stain red/pink

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8
Q

Gram positive

A

Thick peptidoglycan layer
Stain purple

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9
Q

Exotoxins

A

Protein secreted from bacterial cell (Gram + and -)
Cause host-cell damage or disruption of function, often antigenic
Ex: Anthrax lethal toxin/edema toxin, Tetanus tetanospasmin, Botulism botulinum toxin

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10
Q

Endotoxins

A

Potent stimulator of inflammation
Ex: Lipid A causes endotoxic shock, important virulence factor

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11
Q

Molds

A

Multicellular filamentous fungi
Hyphae are filaments
Fruiting structures
Spores or conidia - basic reproductive unit
Ex: Aspergillus or Penicillium

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12
Q

Yeast

A

Single celled fungi
Reproduce by budding
Ex: Malassezia - ear/skin infections, Candida - opportunistic infections, Cryptococcus - nasal and systemic infections (cats primarily)

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13
Q

Viral components

A

Nucleic acid - DNA or RNA (not both)
Capsid - protein core, holds nucleic acid
Envelope - lipid bilayer surrounding some viruses (enveloped viruses tend to be less resistant to the environment than non-enveloped viruses)

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14
Q

Viral cycle

A

Attachment
Entry
Uncoating
Replication
Release

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15
Q

Pasteurella multocida is frequently found as part of the upper respiratory flora of healthy dogs, cats, pigs, and cattle. When it causes pneumonia in its host species it is considered which of the following?
a. Frank
b. Opportunistic

A

Opportunistic pathogen

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16
Q

The mature virus particle (virion) always contains which of the following?
a. ribosomes
b. DNA or RNA
c. envelope
d. peptidoglycan

A

DNA or RNA

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17
Q

Which of the following components or structures are commonly found in yeast?
a. hyphae
b. cell wall
c. fruiting structures
d. peptidoglycan

A

Cell wall

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18
Q

Epidemiologic triad

A

Set of complex relationships and interactions b/w host. disease agent, and the environment
More realistic scenario for causal relationships underlying development of disease in a host

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19
Q

Examples of determinants for infectious diseases

A

Survival outside host, virulence, infectiousness, dose, duration of contact, reproductive status, susceptibility, behavior, movement, housing, other species nearby, climate, water availability

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20
Q

Examples of determinants for non-infectious diseases

A

Potency, degranulation, biomagnification, dose, duration of exposure, genetics, stress, immune response, weather, wind

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21
Q

Arthropods

A

Ectoparasite
Multicellular
Both micro-/macroscopic

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22
Q

Protozoa

A

Endoparasite
Unicellular
Microscopic
Both direct/indirect life cycle

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23
Q

Nematodes

A

Endoparasite
Multicellular
Both micro-/macroscopic
Both direct/indirect life cycle

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24
Q

Trematodes

A

Endoparasite
Multicellular
Both micro-/macroscopic
Only indirect life cycle

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25
Q

Cestodes

A

Endoparasite
Multicellular
Both micro-/macroscopic
Only indirect life cycle

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26
Q

Direct life cycle

A

Life cycle completed on one host

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27
Q

Indirect life cycle

A

Life cycle completed on more than one host

28
Q

Definitive host

A

Where parasite reaches adult stage (sexual maturity)

29
Q

Intermediate host (IH)

A

Some parasites must undergo development in IH to reach adult stage in definitive host
Ex: heartworm uses mosquito as vector & IH

30
Q

Infective stage

A

Where parasite is in form that can infect/invade host cycle

31
Q

Diagnostic stage

A

Where parasite can be detected with naked eye or lab methods

32
Q

Pathogenic stage

A

Where parasite causes disease in host

33
Q

Key features of Toxocara canis life cycle

A

Larvae mature to adults in small intestine of young dogs only (tracheal or liver-lung migration)
In older dogs, larvae encyst in tissue until pregnancy - transplacental/transmammary transmission ensures pups born infected
High zoonotic potential

34
Q

Which of the following best defines the definitive host for a parasite?

A

The host where adult (sexually mature) parasites are found

35
Q

Parasites are generally most pathogenic when they are in their diagnostic stage
True/false

A

False

36
Q

The pathogenic stage(s) of Toxocara canis is/are which of the following?
a. embryonated (contains larvae) egg
b. unembryonated egg
c. adult worms in the intestine
d. larvae migrating through liver and lung

A

Adult worms in the intestine
Larvae migrating through liver and lung

37
Q

Outbreak

A

Synonymous with epidemic
Occurrence in a community or region of cases of an illness, specific health related behavior, or other health related events clearly in excess of normal expectancy

38
Q

John Snow

A

Original contact tracer
Went house to house in London counting deaths from cholera and compared death rates among households getting their water from different supplies
Determined disease-causing agent was transmitted by contaminated water and the point source was a public water pump

39
Q

Associations vs. risk factors vs. causes

A

Associations go together
Risk factors increase susceptibility
Causes are essential components related to progression of disease, may be related to agent/host/environment

40
Q

Causal framework - 1964 guidelines (9 criteria)

A

Temporality - exposure to causal agent must have occurred before disease developed
Strength of Association
Dose Response
Experiment
Consistency (replication)
Biological Plausibility
Alternate explanations
Specificity
Coherence

41
Q

Causal framework - 1986 guidelines

A

Temporality
Biological plausibility
Consistency
Lack of confounding

42
Q

Necessary causes

A

Must precede disease, but presence does not guarantee disease (ex: bacteria, viruses, etc.)

43
Q

Sufficient causes

A

Diseases can have multiple component causes, which in various combinations can produce sufficient causes - complete causal mechanisms/pathways (pies) that inevitably produce disease

44
Q

Observational study types

A

Case-control
Cohort
Cross-sectional

45
Q

Experimental study types

A

Randomized controlled trials (RCTs)
Gold standard for assessing causation
If you can manipulate the exposure (i.e. treatment) before an outcome is measured, causal order is guaranteed

46
Q

Sample size

A

Small sample sizes make it hard to detect an association if there is one, and findings may not be generalizable to a larger population

47
Q

Over-testing hypotheses

A

Increases likelihood of finding an association just by chance (“p-hacking”)

48
Q

Confounding

A

Inadequate accounting for important factors associated with exposure and outcome

49
Q

Information bias

A

Accidental misclassification of risk factor status or disease status
Correct classification depends on accurate diagnostic tests and accurate patient history

50
Q

Selection bias

A

If random sampling is not used, sample groups selected may not be reflective of the population of interest

51
Q

Case definition

A

Cases of disease (and controls) can be defined in many ways:
Mortality (caused by the disease)
Clinical symptoms
Clinical treatment
Diagnostic test results
Combinations of the above

52
Q

Ratios (odds)

A

a:b
a/b
Not as useful as probability statistics
Can be converted to a proportion (a/(a+b))

53
Q

Proportions

A

Fraction in which numerator (frequency of disease or condition) is also included in the denominator
a/a+b
Can be used as probabilities or risks (%)

54
Q

Rates

A

Relationship between an event and defined population-at-risk evaluated over a specified time period

55
Q

Crude mortality

A

Death from all causes / population at risk for death

56
Q

Cause-specific mortality

A

Deaths from disease X / population at risk for death

57
Q

Case fatality for disease X

A

Deaths from disease X / cases of disease X

58
Q

Proportionate mortality for disease X

A

Deaths from disease X / deaths from all causes

59
Q

Dr. Johnson found that 38% of sea otter deaths were due to parasitic diseases. What measure of risk was used?
a. case-fatality
b. proportionate mortality
c. crude mortality
d. cause-specific mortality

A

Proportionate mortality

60
Q

In one year 30 sea otters die, with 3 of the deaths due to shark bite, out of the total sea otter population of 3000. What is the crude mortality?
a. <1%
b. 1%
c. 10%
d. 100%

A

1%
30/3000

61
Q

Prevalent cases

A

All cases at a given point in time (mix of new cases and existing cases)

62
Q

Incident cases

A

New cases occurring during a given time interval

63
Q

Prevalence

A

Number of cases observed at time / total number of individuals at risk at time
Like a photograph of all disease present at a given point in time (old & new cases)
Static measure of disease
Proportion or percentage
For an individual, measures risk of being a case rather than becoming a case

64
Q

Incidence

A

Measures risk or rate of becoming a new (incident) case
Proportion or percentage per time interval, or case/time at risk
Important in predicting future impact of disease
Usually harder to measure than prevalence
2 main types: cumulative incidence (CI) and incidence density rate (IDR)

65
Q

Risk ratio

A

risk of disease in exposed group / risk of disease in unexposed group
a = # affected in exposed group
c = # affected in unexposed group
a + b = total # in exposed group
c + d = total # in unexposed group
RR = [a / (a+b)] / [c / (c+d)]

VET 401 Basic Foundations (4 decks)

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