Epi Curves and Determinants of Disease Flashcards
What is a latent period?
Microbes are replicating, but not yet enough for the host to be INFECTIOUS.
What is the incubation period?
Microbes are replicating, but not yet SYMPTOMATIC. NOTE: Doesn’t always correlate with the latent period.
Define infection.
Invasion and multiplication in/on a host.
Define infestation.
Invasion, but NOT multiplication in/on a host.
Define contagious.
Disease transmissible via direct or airborne routes.
Define communicable.
Disease transmissible by direct, airborne or indirect routes.
What do epi curves represent?
The number of new cases of disease over time.
What information can an epi curve provide (4 things)?
Most probable source of outbreak If pathogen is contagious If outbreak is ending or not Incubation period Outliers
What is the incubation period in this epi curve?
3 days
Describe the propagated source pattern.
Exposure followed by waves of cases.
What diseases have a propagated source?
Contagious diseases
What epi curve pattern is this?
Propagated source.
Describe the common source single point exposure pattern.
All animals are exposed at once from the same source, has a bell-curve shape.
What diseases show a common source single point exposure pattern?
Non-contagious diseases.
What type of incubation time can be determined from a common source single point exposure pattern.
The minimum, average and maximum incubation time can be determined.
What epi curve pattern is this?
Common source single point exposure
Describe the common source with intermittent exposure curve.
No pattern. Animals are exposed at different times.
What type of incubation time can you determine from a common source with intermittent exposure curve?
Incubation period is not clearly shown.
What epi curve pattern is this?
Common source with intermittent exposure.
What main 3 factors does the epi curve depend on?
Host, agent an environment.
What factors fall under the “host” umbrella?
Host immunity or resistance, direct transmission.
What factors fall under the “agent” umbrella?
Infectiousness of agent, latent and incubation periods, duration of infectivity.
What factors fall under the “environment” umbrella?
Fomites, etc.
Describe endemic vs. epidemic.
Endemic is always present at a steady state in a given population, epidemic is a big spike.
What is a determinant of disease?
Factors that help determine the probability, distribution or severity in a population.
Why are determinants of disease important to know?
Helps identify animals at risk, helps prevent disease, helps with differential diagnoses.
What is a primary determinant?
A MAJOR contributing factor, usually necessary.
What is a secondary determinant?
Factors that make the disease more or less likely (predisposing or enabling factors).
What is an intrinsic determinant?
Factors that are internal to the animal (age, breed, sex).
What is an extrinsic determinant?
Factors that are external to the animal (housing, medical treatment, etc.)
T/F: Primary determinants must always be present.
True.
What are the two agent determinants?
Mutations
Resistance
What are the 6 environmental determinants?
Demographics
Macroclimate
Microclimate
Housing and crowding
Diet
Stress
What are the 6 host determinants?
Age
Sex and behaviour
Genotype
Breed
Nutrition
Immunity
T/F: Genetic diseases are entirely determined by genotype.
True
T/F: Genetic susceptibilities are entirely determined by genotype.
False. Genetic susceptibilities are only partially determined by genotype.
T/F: Breeds cannot be used as a visual cue to other, less haritable traits.
False. Breed CAN be used as a visual cue.
T/F: Diet is intrinsic, Nutrition is extrinsic.
False. Diet is extrinsic because it’s a management issue. Nutrition is intrinsic because it directly pertains to the animal.
T/F: Immunity is intrinsic, vaccines are extrinsic.
True.
Define “herd immunity”.
Infectious disease can be contained if the population’s resistance to infection is high enough. Doesn’t protect individuals, but many others will be protected indirectly.
