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Flashcards in Lecture 5: Transmission of Diseases Deck (29)
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1

Modes of infectious disease transmission

-Direct contact with pathogen (vector borne diseases)
-Ingestion of pathogen
-Inhalations of pathogen from air

2

Vector

Invertebrate serves as a mechanism to transport the pathogen to a host

3

Transmission efficiency

The rate at which pathogens are transmitted from invertebrate host
-Influenced by: environmental factors, weather, infection rates, insect life history

4

Mechanical transmission

Pathogen does not biologically interact with the arthropod
("hitching a ride" often on the mouth)

5

Biological transmission

-Pathogens depend on arthropod as part of life cycle and for transmission
-Propagative, cyclo-developmental, cyclo-propagative

6

Propagative transmission

When the pathogen simply propagates (reproduces) within the arthropod

7

Cyclo-developmental transmission

Seen only in parasites, where the parasite must be in the arthropod host to complete part of its life cycle

8

Cyclo-propagative transmission

Pathogen both completes a developmental stage and can propagate within the arthropod

9

Trans-ovarial transmission

-Vertical transmission occurs when pathogens are passed from a parent arthropod to offspring (TOT)
-Females infect eggs during any part of egg development
-Males infect offspring with infected sperm

10

Trans-stadial transmission

-Transmission of a disease within the same organism from one developmental stage to the next
-Molting, Metamorphosis, Pupation

11

Horizontal transmission

Disease travels from one arthropod to another via a vertebrate host
(ex: cofeeding)

12

Pathogen in the vector

-Often ingested by vector, multiplies in midgut, infects salivary glands

13

Barriers

-Limit transmission
-Physical: lining of midgut, body cavity
-Chemical: chemical or immune responses that may limit or prevent virus from disseminating

14

How do diseases enter the host

-Passive transfer
-Active transfer

15

Passive transfer

Pathogen is transmitted from the vector to the host via some mechanism involving the vector
-commonly through saliva, sometimes feces or regurgitation

16

Active transfer

Some pathogens rely on the host destroying/crushing the body of the vector, releasing the pathogen

17

Incubation period

Time from when an organism ingests the pathogen to when it is capable of transmitting it

18

Intrinsic incubation period

From when the host becomes infected to when it can transmit the pathogen

19

Extrinsic incubation period

From when the vector ingests the pathogen to when it can transmit

20

Primary transmission cycle

Transmission that occurs under natural settings which is essential to the survival and continued transmission of the pathogen

21

Enzootic transmission

-The vertebrate host in primary transmission is an animal
-May serve as "reservoir" for long term survival of the pathogen

22

Dead end hosts

Transmission cycle will stop

23

Epidemic transmission

Can refer to any transmission that involves a human host

24

Disease amplification

Rapid increase in prevalence of a pathogen over a short period of time under specific conditions

25

Arboviruses

-Febrile, hemorrhagic, or neuropathic effects (many share common "flu-like" symptoms)
-Mild infection to severe encephalitis to death

26

Rickettsiae

-Genus of ancient bacteria
-Almost always involves hematophagous arthropods
-Frequently transmitted via TOT
-Often lethal; all (except typhus) involved in enzootic transmission cycle

27

Bacteria

-Only a few involved in arthropod transmission cycles (mostly mechanical)
-Biologically by hematophagous arthopods
-Antibiotics

28

Protozoa

-Sporozoans and flagellates may utilize arthropods for transmission
-Produce serious, widespread epidemics
-Complex life cycles and transmission patterns
-Most transmitted in the salivary glands
-Most cycles are enzootic, but some use humans

29

Helminths

-Develop in arthropod, but do not reproduce there
-Usually not fatal