Disease Reservoirs & Transmission Flashcards
Disease transmission is a result of the interaction between _______,_______, and ______.
Host, agent, and environment
Note: The presence of these alone is NOT enough to cause disease
Who used the “shoe-leather epidemiology” technique, by going door to door mapping the cases of cholera transmitted by the fecal-oral route and by the water supply in London?
A. Richard Dawkins
B. Louis Pasteur
C. Robert Koch
D. John Snow
D. John Snow
Robert Koch first isolated this bacterium _________ and used experimental infection of naive animals to prove the the bacteria caused anthrax. Therefore supporting the “germ theory”.
B. Anthracis
Who was an asymptomatic carrier that caused several outbreaks of typhoid fever (Salmonella Typhi = anthroponotic) between 1900-1915.
Typhoid Mary
- outbreak followed wherever she worked (she was a cook) and had to be quarantined for the rest of her life.
________ discovered that malaria is transmitted by mosquitoes.
A. Laveran
B. Walter Reed
C. Ronald Ross
D. Louis Pasteur
C. Ronald Ross
Note: some credit the discovery to Grassi (Italian scientist)
________ discovered that yellow fever is transmitted by mosquitoes. (1900)
A. Laveran
B. Walter Reed
C. Ronald Ross
D. Louis Pasteur
B. Walter Reed
_______ (the French physician) discovered the agent plasmodium in 1880.
A. Laveran
B. Walter Reed
C. Ronald Ross
D. Louis Pasteur
A. Laveran
True or False ?
In disease prevention, knowing the mode of transmission is generally more important than identifying the specific agent.
True
Note: This is where you make your interventions. The mode of transmission is very important, since you will not know the etiology right away.
What are the 6 factors of the “chain” of infection ?
- Host susceptibility
- Pathogenic microorganism (bacteria, virus, parasite, fungus, prion)
- Reservoir
- Means of escape ( “Portal of exit”: cough, sneeze, feces, urine etc.)
- Mode of transmission
- Means of entry (Exposure)
Define reservoir:
Habitat in which an infectious agent normally lives, grows, and multiplies (humans, animals, or the environment). Could be a living thing; the environment (soil, water)
- maintain pathogens over time, from year to year or generation to generation
What is balanced pathogenicity ?
When the reservoir doesn’t get sick from the pathogens they carry
What questions should you ask yourself when recognizing a reservoir ?
- Is it naturally infected with the pathogen ?
- Can that species of animal (etc.) maintain the pathogen over time ? (Typically years to generations)
- Can this source transmit the disease to a new, susceptible host ?
If you answered YES to all three of these the animal, soil, or water is a reservoir. Has to satisfy ALL three questions.
If an animal has a disease it means it is a competent reservoir
True or False ?
False
Why are reservoirs easy to miss ?
- Elusive - can go years without being discovered
- — Balanced pathogenicity (they don’t look sick)
- — Persistence of infection
- — Transmission may be sporadic - Role is often incompletely understood (lack of understanding)
True or False
To eliminate diseases completely (eradication) control measures must be directed towards the reservoir ?
True
True or False
Infection = Disease = Infectivity
False
They do not mean the same thing
True or False
Clinically ill or asymptomatic animals that are reservoir competent are probably infectious.
True
Vertical transmission
From a reservoir host to its offspring.
Congenital - pathogens crossing the placenta; infect eggs); (Perinatal - during parturition, via colostrum
Horizontal transmission
From the reservoir to a new host
(Direct- directly form the reservoir to a susceptible host);
(Indirect - via any sort of intermediary, animate or inanimate object)
Name some types of horizontal direct transmission:
- Direct contact - skin-skin contact, bite, scratch
- Direct projection (droplet spread) - sneezing, coughing or talking
- Airborne - form of direct transmission; acts like a droplet. Disease agents do not generally survive for extended periods within aerosolized particles.
What are the two types of horizontal indirect transmission ?
- Vehicle - an inanimate object which serves to communicate disease. (Ex. Boots, medical supplies)
- Vector - a living organism that serves to communicate disease (Ex. Tick, flea, mosquitos)
Name some types of vehicles involved in the process of indirect transmission
- Common vehicle -> food, water, contaminated IV drugs
- Fomites -> objects that can be contaminated and transmit disease on a limited scale…knife, door knob, gloves. (Most nosocomial and iatrogenic infections are transmitted by fomites).
Name and describe the two type of vectors
- Mechanical = the agent DOES NOT multiply or undergo part of its life cycle while in/on the arthropod
- Biological = the agent undergoes changes or multiplies while in the vector; these activities are required for transmission
The first one to bring attention to the authorities is called an ______ ________.
Index patient
What causes tularemia ?
Francisella tularensis ( Gram negative)
Note: not passed person to person
Transmission: Inhalation, ingestion, direct contact, mucous membranes, broken skin, vectors (Arthropoda;ticks)
