01 Disease Reservoirs and Transmission Flashcards
Disease transmission is a result of
interaction between the host, agent, and environment
John Snow
1841 published evidence that cholera is transmitted by the fecal-oral route and by the water supply
Robert Koch
1876 first isolated the bacterium –and used experimental infection of naïve animals to prove that B. anthraciscauses anthrax
Pasteur
1881 developed and tested an early vaccine in sheep, goats, and cattle
Typhoid Mary
Asymptomatic Carrier, Caused several outbreaks of typhoid fever (SalmonellaTyphi = anthroponotic) between 1900-1915
Ronald Ross
1897 malaria is transmitted by mosquitoes; some credit the discovery to the Italian scientist, Grassi
Walter Reed
1900 yellow fever is transmitted by mosquitoes
In disease prevention, knowing the _____ is generally more important than ______
mode of transmission, identifying the specific agent
“Chain” of Infection
host susceptability-pathogenic microorganism-reservior-means of escape-mode of transmission-means of entry
Reservoir definition
habitat in which an infectious agent normally lives, grows, and multiplies (humans, animals, or the environment)
Reservoirs do this
maintain pathogens over time, from year to year or generation to generation
3 questions to define a reservior
- Is it naturally infected with the pathogen?
- Can that species of animal (etc.) maintain the pathogen over time?
- Can this source transmit the disease to a new, susceptible host?
Two questions concerning reservoirs in practical disease control
1) Can an acceptable level of control be accomplished without consideration of a reservoir?
2) If not, what populations constitute the reservoir?
Clinically ill animals that are reservoir competent are probably infectious (T/F)
True
Asymptomatic animals can be infectious = carrier (T/F)
True
All sick animals are reservoirs (T/F)
False
Verticle transmission includes
- Congenital: some pathogens can cross the placenta, infect eggs, etc.
- Perinatal: during parturition, via colostrum
Horizontal transmission includes
- Direct: directly from the reservoir to a susceptible host
- Indirect: via any sort of intermediary, animate or inanimate
Direct contact
Skin-skin contact, mucous membrane contact (including sexual transmission), direct contact with a soil reservoir, bite, scratch, etc
Direct projection
-aka droplet spread
–Wet, large, and short range aerosols (sneezing, coughing or talking)
Airborne*
Considered to be a form of direct transmission because disease agents do not generally survive for extended periods within aerosolized particles
Vehicle
An inanimate object which serves to communicate disease.
Vector
A living organism that serves to communicate disease.
Common vehicles
–Food, water
–Contaminated IV drugs
Fomites
Object that can be contaminated and transmit disease on a limited scale
Mechanical vector
the agent DOES NOT multiply or undergo part of its life cycle while in/on the arthropod
Biological vector
the agent undergoes changes or multiples while in the vector; these activities are required for transmission
