5: Why do you look for disease patterns? Flashcards
Survival/success of pathogen depends on a continuous chain of effective _______ from host to host
Transmission
Successful transmission requires (at least) 3 steps:
1)__________
2) Find a new host
3) Start infection in new host
1) Get out of host
2) Find a new host
3) Start infection in new host
Successful transmission requires (at least) 3 steps:
1) Get out of host
2) _____________
3) Start infection in new host
1) Get out of host
2) Find a new host
3) Start infection in new host
Successful transmission requires (at least) 3 steps:
1) Get out of host
2) Find a new host
3) ____________________
1) Get out of host
2) Find a new host
3) Start infection in new host
What are the 3 steps of successful transmission?
Successful transmission requires (at least) 3 steps:
1) Get out of host
2) Find a new host
3) Start infection in new host
Incubation period
The interval time between time of infection and the time when an individual shows clinical signs.
I.E. The discrepancy between the time of observing clinical sign and the animal starting to become infectious
Latent period
Interval between time of infection and the time when an individual becomes infectious
What is another word for latent period when describing macro-parasites?
Pre-patent period
Infectious period
Interval between start and end of excreting infectious agents
Virulence
Degree to which an infectious agent causes clinical disease in a particular host; expresses the severity.
Host infectiousness
Relative amount and duration of agent release
What are two main categories of transmission routes?
Horizontal and Vertical
What are the two categories under horizontal transmission?
Direct and Indirect
Describe vertical transmission
Hereditary or Congenital
Infections transmission from parent to offspring by infection of the embryo or fetus while in uteri or in ovo or through milk
Describe horizontal transmission
Infections transmitted from one host to another either from host to host by close contact or through an intermediate vehicle.
Contact structure influenced by:
-___________
-movements
-habitat
-behaviour
Contact structure influenced by:
-density
-movements
-habitat
-behaviour
Contact structure influenced by:
-density
-____________
-habitat
-behaviour
Contact structure influenced by:
-density
-movements
-habitat
-behaviour
Contact structure influenced by:
-density
-movements
-________
-behaviour
Contact structure influenced by:
-density
-movements
-habitat
-behaviour
Contact structure influenced by:
-density
-movements
-habitat
-____________
Contact structure influenced by:
-density
-movements
-habitat
-behaviour
Contact structure influenced by:
-density
-movements
-habitat
-behaviour
Susceptibility
Capacity of host of getting infected by a particular pathogen
Infectivity
Amount of an organism that is required to initiate infection —> minimum infectious dose
What factors might influence the minimum infectious dose of a pathogen?
Species, age, sex, genotype, general condition
What factors might influence susceptibility/infectivity?
Vaccination
Prophylactic treatments (e.g antibiotics)
Genetic Makeup
Other Determinants of Health
Transmission rate (B)
The number of susceptible animals that will get infected by one infectious animal per unit of time
Average duration of infectiousness (d)
How long an animal is expected to remain infectious
Basic reproduction number - R naught
R naught = Bd
Average number of secondary infections when an infectious individual is introduced to a fully susceptible population
R naught =
Bd
What can we assume about transmission if R naught >1?
Each infected spreads the infection to more than one other person/animal
What can we assume about transmission if R naught <1?
On average an infected does not replace itself in the infected population. Infection cannot grow.
Epidemic curve
A visual representation in the form of a graph of the progression of an outbreak of a disease in a population
Epidemic
An occurrence of disease in excess of its anticipated frequency
What is the point of studying epidemic curves?
To understand the time trends of outbreaks, to find outliers, to get a general sense of the magnitude of an outbreak, to make predictions, and to determine the most likely time of exposure.
