Epidemic Curves & Determinants of Disease Flashcards
What is happening during the incubation period?
The microbe is replicating but not symptomatic yet.
What is happening during the latent period?
The microbe is replicating but not yet enough for the host to become infectious.
Does the incubation period always correlate with the latent period?
No
What does infectious mean?
Disease caused by the invasion and multiplication of a living agent in/on a host.
What does infestation mean?
Invasion, but not multiplication of an organism in/on a host (fleas, ticks, some parasites).
What does contagious mean?
Disease transmissible from one human/animal to another via direct or airborne routes.
What does communicable mean?
Disease caused by an agent capable of transmission by direct, airborne or indirect routes from an infected person, animal, plant or a contaminated inanimate reservoir.
What do epidemic curves represent?
The number of new cases of disease over time.
T/F: Epidemic curves are simple to make and interpret.
True
What are 5 things epidemic curves can tell you?
- Most probable source of the outbreak.
- If the pathogen is contagious.
- If the outbreak is ending, or if it will continue.
- Incubation period of the pathogen (sometimes).
- About outliers.
A propagated source epidemic curve indicates what?
What is this type of curve seen with?
- Exposure followed by “waves” of secondary and tertiary cases.
- Contagious diseases
What are 3 things a common source single point exposure epidemic curve show you?
- All animals are exposed at once.
- All are exposed to the same source of infection.
- Not contagious.
What can a common source single point exposure epidemic curve determine?
The minimum, average and maximum incubation time.
What does a common source with intermittent exposure epidemic curve show you?
- Animals are exposed at different times.
- Exposed to the same source.
- Incubation period is not clearly shown.
- Not contagious.
The shape of the epidemiological curve depends on what 3 factors?
- Host: immunity or other resistance to disease, direct transmission
- Agent: infectiousness of agent, latent and incubation periods, duration of infectivity
- Environment: especially important for indirect routes of transmission
What is endemic stability?
A situation in which all factors influencing disease are relatively stable, resulting in little fluctuation in disease incidence over time.
What are 3 factors of endemic stability?
- New cases occur at a regular, usually low level.
- Young individuals may enter the population.
- Old individuals die or are removed.
T/F: Babesiosis generally causes severe symptoms in calves and mild symptoms in adults.
False - symptoms are generally mild in calves and severe in adults.
What is a determinant?
Factors that help determine the probability, distribution or severity of a disease in an animal or population of animals.
What is an example of a determinant?
Host susceptibility
Why is it important to know what determinants are?
- Identifies animals at particular risk.
- Disease prevention.
- Aid to differential diagnosis.
What is a primary determinant?
A major contributing factor, usually a necessary one.
What is a secondary determinant?
Factors that make the disease more or less likely; predisposing or enabling factors.
What is an intrinsic determinant?
Determinants that are internal to the animal (age, breed, sex, etc.).
What is an extrinsic determinant?
Determinants that are external to the animal (housing, medical treatment, etc.).
T/F: Primary determinants must always be there in order for disease to occur.
True
Name 6 extrinsic factors that can be associated with the agent.
- Infectivity
- Pathogenicity
- Virulence
- Immunogenicity
- Mutation rate
- Resistance
Name 6 extrinsic factors associated with the environment.
- Demographics
- Climate
- Housing
- Crowding/density
- Diet
- Stress
What are 4 things mutations can include?
- Increased infectivity within typical hosts.
- Ability to infect new species/populations of hosts.
- Acquisition of new toxins.
- Immune system evasion.
What are 3 ways anti-microbial resistance can be obtained?
- De novo
- Through mutation
- Lateral transfer from another organism
What are 6 examples of intrinsic host factors?
- Age
- Sex & behavior
- Genotype
- Breed
- Nutrition
- Immunity
What is a genotype?
A term describing the DNA sequence, or “type,” of an individual.
T/F: Genetic diseases are entirely determined by genotype.
True
T/F: Genetic susceptibilities are entirely determined by genotype.
False - They are partially determined by genotype and partially by other factors.
Is breed a primary or secondary determinant?
Secondary
Does overall health status alter susceptibility to diseases?
Yes
Nutrition has a strong effect on what?
Immune system
Is diet an intrinsic or extrinsic determinant?
Extrinsic
Is the body condition score of an animal an extrinsic or intrinsic determinant?
Intrinsic
Is the nutritional status of an animal an extrinsic or intrinsic determinant?
Intrinsic
Is a vaccine an intrinsic or extrinsic determinant?
Extrinsic
Is the status of the body being immune an intrinsic or extrinsic determinant?
Intrinsic
What is herd immunity?
The idea that infectious diseases can be contained if the population’s resistance to infection is high enough.
Does herd immunity protect individuals?
No
