Lecture 13: Disease Reservoirs and Transmission Flashcards

1
Q

Disease transmission is a result of interaction between

A

host, agent, and environment

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2
Q

Infectious disease

A

disease caused by the invasion and multiplication of a living agent in/on a host

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3
Q

Infestation

A

Invasion, but not multiplication of an organism in/on a host (fleas/ticks, some parasites)

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4
Q

Contagious

A

disease transmissible from one human/animal to another via direct or airborne routes

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5
Q

Communicable

A

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

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6
Q

Zoonotic disease

A

disease that is transmitted from animals to humans

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7
Q

Latent period

A

microbe is replicating but not yet enough for the host to become infectious

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8
Q

Incubation period

A

microbe is replicating but not symptomatic yet.

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9
Q

Does the incubation period always correlate with the latent period?

A

Nope

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10
Q

Reservoir

A
  • Habitat in which an infectious agent normally lives, grows, and mulitplies
  • Maintain pathogens over time, from year to year or generation to generation
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11
Q

How do pathogens make it so that animals become susceptible again and again

A

They mutate

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12
Q

How do pathogens allow infections to occur after a short time period?

A

They evade immunity

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13
Q

Balanced pathogenicity

A

Chronic infections with minimal symptoms

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14
Q

Are all sick animals reservoirs?

A

Nope

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15
Q

Three questions that you must answer yes to in order for soemthing to be a reservoir

A
  1. Is it naturally infected with the pathogen?
  2. Can the species of animal maintain the pathogen over time?
  3. Can this source transmit disease to a new, susceptible host?
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16
Q

Two main types of transmission

A
  1. Vertical

2. Horizontal

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17
Q

Two types of horizontal transmission

A
  • Direct

- Indirect

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18
Q

Vertical transmission

A

From a reservoir host to its offspring

19
Q

Congenital transmission

A
  • Vertical

- Some pathogens can cross the placenta, infect eggs, ect

20
Q

Perinatal transmission

A
  • Vertical

- During parturition, via colostrum

21
Q

Horizontal transmission

A

from reservoir to new host

22
Q

Direct horizontal transmission

A

Directly from the reservoir to a susceptible host

23
Q

Indirect horizontal transmission

A

Via any sort of intermediary, animate or inanimate

24
Q

Three types of horizontal/direct transmission

A
  1. Direct transmission - contact
  2. Direct projection - droplet spread
  3. Airborne - Considered to be a form of direct
25
Q

Vehicle

A

Inanimate object which communicates the disease

26
Q

Vector

A

Living organism that communicates the disease

27
Q

Two types of vehicles

A
  1. Common - food, water, contaminated IV drugs

2. Fomites - object that can be contaminated and transmit disease on a limited scale (ex. door knob)

28
Q

Most vectors are

A

arthropods (mosquitoes, flies, fleas, ants, ticks)

29
Q

Mechanical vector

A

Agent does not multiply or undergo part of its life cycle while in/on arthropod

30
Q

Biological vector

A

Agent undergoes changes or multiplies while in the vector and these changes are required for transmission

31
Q

Emerging disease

A
  • Previously unknown disease that suddenly appears

- Known disease that suddenly appears in a new population

32
Q

Re-emerging disease

A

-Known disease, previously on the decline, that is becoming more common and will likely continue to do so

33
Q

Exposure

A
  • Introduction of a new agent into a susceptible population

- Exposure is caused by movement of infectious agents

34
Q

New pathogens originate from

A

old pathogens

35
Q

Transmission

A
  • Adoption, establishment, and dissemination in the susceptible population
  • Requires a pathogen that can adapt to, and transmit between, these hosts
36
Q

7 determinants of emergence

A
  1. Type of agent (pathogen)
  2. Mutation/change (pathogen)
  3. Phylogenetic distance (reservoir)
  4. Reservoir size (transmission)
  5. Pathogen prevalence (transmission)
  6. Contact frequency (transmission)
  7. Susceptibility (host)
37
Q

What percentage of human pathogens are zoonotic

A

61%

38
Q

What percentage of emerging diseases are zoonotic

A

75

39
Q

How likely are zoonotic diseases to be associated with emerging diseases?

A

Twice as likely

40
Q

What do mutations do for pathogens

A
  • Increased antibiotic resistance
  • Increased virulence (transmissibility within or between species)
  • Evasion of host immunity
41
Q

Phylogenetic distance between reservoir and new host

A
  • Best transmission is within species

- More likely to be crossed to closely related species

42
Q

Pathogens that cross very different species often cause

A

Very different, often more severe, disease

43
Q

Two reasons for new host susceptibility

A
  • Intensive agriculture

- More populations with weakened immune systems

44
Q

Three factors that increase transmission

A
  • Increasing abundance of reservoir
  • Increasing pathogen prevalence in reservoir
  • Increasing contact between the reservoir and new host