Disease Reservoirs And Transmission Flashcards
What is the “chain of infection”?
Exposure - host susceptibility - pathogenic organism - reservoir - portal of exit (means of escape) - mode of transmission.
What is disease transmission?
Result of interaction between host, agent and environment.
What is a reservoir?
Habitat where an agent normally lives, grows and multiplies and maintains pathogens over time.
How do you recognize a reservoir?
Is it naturally infected? Does it maintain the pathogen over time? Can it transmit the disease to others?
If yes to all, it is a reservoir.
Name 3 ways pathogens can persist.
They can mutate, they can evade immune system, they can cause chronic infections with minimal symptoms.
Are all sick animals reservoirs?
No. Some animals can carry without showing signs.
What is vertical transmission?
From host to offspring.
What are the types of vertical transmission?
Congenital (crosses placenta) and Perinatal (during parturition or via colostrum).
What is horizontal transmission?
From the reservoir to a new host.
What are the two ways of horizontal transmission?
Direct and indirect transmission.
What is direct transmission?
From reservoir directly to new host.
What is indirect transmission?
From the reservoir, to an intermediary (fomite, insect, etc) to the new host.
Name three ways for direct transmission.
Direct contact, direct projection (droplets, short range), airborne.
Do airborne agents survive long?
Generally no, exception is FMD.
Name two modes of indirect tranmission.
Vehicles (fomites), and vectors.
What are common vehicles?
Food, water, contaminated IV drugs.
What is a fomite?
An object that can transmit a disease on a limited scale.
What is a vector?
A live organism, mostly arthropods.
What constitutes mechanical transmission?
Agent does NOT undergo part of its life cycle in the vector.
What constitutes a biological vector?
Agent undergoes part of its life cycle in the vector.
What are we more concerned with, mechanical or biological vectors?
Biological vectors because agent can persist in a biological organism.
