02 Epidemic Curves & Determinants of Disease Flashcards
Latent period
microbe is replicating but not yet enough for the host to become infectious
Incubation period
microbe is replicating but not symptomatic yet. Does not always correlate with the latent period
Infectious disease
disease caused by the invasion and multiplication of a living agent in/on a host
Infestation
invasion, but not multiplication of an organism in/on a host (fleas/ticks, sometimes parasites)
Contagious
disease transmissible from one human/animal to another via direct or airborne routes
Communicable
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
Epidemic Curves
- Represent the number of new cases of disease, over time
- Are simple to make and interpret
- Can tell you:
- —Most probable source of the outbreak
- —If the pathogen is contagious
- —If the outbreak is ending – or will continue
- —Incubation period of the pathogen (sometimes)
- —About outliers
Shape of Epidemiological Curve depends on
Host --Immunity or other resistance to disease --Direct transmission Agent --Infectiousness of agent --Latent and incubation periods --Duration of infectivity Environment
Endemic Stability
A situation in which all factors influencing disease are relatively stable, resulting in little fluctuation in disease incidence over time
What Is A Determinant?
Factors that help DETERMINE the probability, distribution, or severity of a disease in an animal or population of animals
-Host susceptibility, social, economic, physical characteristics, etc.
Determinant are important to know because
Identifies animals at particular risk
Disease prevention
Aid to differential diagnosis
Shape of Epidemiological Curve Depends On
Host --Immunity or other resistance to disease --Direct transmission Agent --Infectiousness of agent --Latent and incubation periods --Duration of infectivity Environment
Endemic Stability
A situation in which all factors influencing disease are relatively stable, resulting in little fluctuation in disease incidence over time.
- -New cases occur at a regular, usually low, level
- -Young individuals may enter the population
- -Old individuals die or are removed
Primary determinants
- a MAJOR contributing factor
- MUST ALWAYS be there in order for disease to occur
Secondary determinants
factors that make the disease more or less LIKELY; predisposing or enabling factors
Intrinsic determinants
determinants that are internal to the animal (age, breed, sex, etc.)
Extrinsic determinants
determinants that are external to the animal (housing, medical treatment, etc.)
Agent determinant mutations can include
- Increased infectivity within typical hosts
- Ability to infect new species / populations of hosts
- Acquisition of new toxins
- Immune system evasion
Environmental determinants include
“Demographics” Macroclimate Microclimate Housing and crowding Diet Stress
Genetic diseases are entirely determined by genotype
T/F
True
Genetic susceptibilities are entirely determined by genotype and partially by other factors (T/F)
False- they’re partially determined by them
Diet is extrinsic, a management issue, but that the body condition score of the animal and nutritional status are intrinsic. (T/F)
True
Immunity to the pathogen may be due to inherited or acquired factors. Example of each intrinsic and extrinsic.
Giving a vaccine = extrinsic.
The status of the body being immune = intrinsic
Herd Immunity
The idea that infectious diseases can be contained if the population’s resistance to infection is high enough
–Does NOT protect individuals
–Some non-immune individuals will probably become infected…
–Many others will be protected, indirectly, by the immunity of their herd-mates
Can be applied to populations of people as well as populations of animals!
