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VET YEAR ONE > DISEASE E&E (Transmission 2) > Flashcards

DISEASE E&E (Transmission 2) Flashcards

1
Q

Indirect horizontal transmission:

A

-occurs whenever horizontal transmission of the pathogen between two hosts of the same species requires another organism

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2
Q

Vector-borne life cycles:

A

-require an arthropod vector and a vertebrate host

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3
Q

Complex life cycles of helminth parasites:

A

-require an intermediate host and final host

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4
Q

Vector-borne diseases:

A

-caused by vector-borne pathogens that are transmitted among vertebrate hosts by hematophagous (blood-feeding) arthropod vectors

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5
Q

Examples of important arthropod vectors:

A

-mosquitoes
-ticks
-sandflies
-assassin bugs

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6
Q

When do arthropod vectors transmit the vector-borne pathogens?

A

-during the blood meal

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7
Q

Vector-borne pathogen (VBP) examples:

A

-viruses
-bacteria
-protozoan parasites
-nematode worms

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8
Q

Vector-born pathogens lifecycle 2 critical steps:

A
  1. Uninfected vectors must acquire VBP from an infected vertebrate host
  2. Infected vectors must transmit the VBP to other uninfected hosts
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9
Q

Condition of vector-borne transmission:

A

-vector must take at least 2 blood meals on different vertebrate hosts

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10
Q

Dengue virus life cycle example:

A

-mosquitos=vector
-humans=host
1. Human-to-mosquito transmission: uninfected mosquito feeds on infected human and acquires Dengue
2. Mosquito-to-human transmission: infectious mosquitos bites an uninfected human and human becomes infected

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11
Q

Vector becomes infectious:

A

*vector is not immediately infected after feeding on an infected host
-need to migrate the pathogen from the midgut to the salivary glands (can take days or weeks)
-in salivary glands=infectious

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12
Q

EIP:

A

-time for a vector to become infectious after feeding on infected host

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13
Q

Temperature and EIP:

A

-influences the rate at which vectors become infectious

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14
Q

High temperature on EIP:

A

-increase pathogen replication and migration
-higher abundance of infectious vectors
*shorter EIP

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15
Q

Pros of VB life cycle:

A

-motivated vector: hematophagous arthropods are motivated to seek out new hosts
-dispersal: winged arthropods can travel distances and contact new hosts
-one infected host can produce many infected arthropod vectors

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16
Q

Cons of VB life cycle:

A

-evolve ability to live in both arthropod vector and vertebrate host
-infected vector may feed on ‘wrong’ vertebrate host

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17
Q

West Nile fever:

A

-mosquito-borne disease
-an RNA virus
-birds: reservoir hosts
-mammals: dead-end hosts

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18
Q

Reservoir hosts:

A

-competent hosts
Ex. birds with high viremia (WNV) have high host-to-mosquito transmission

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19
Q

Dead-end hosts:

A

-incompetent hosts
Ex. mammals have low levels of WNV in their blood (ex. low viremia)
>WN doesn’t want to be in a mammal

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20
Q

Low vs. high viremia when mosquitoes feed on infected birds:

A

-low: fewer mosquitoes acquire WNV
-high: most mosquitoes acquire WNV
*high viremia in birds, increases chance of WNV transmission to feeding mosquitoes

21
Q

Infection with WNV mortality:

A

*can kill both reservoir and dead-end hosts and also be asymptomatic
-high in birds
-outbreaks recognized in crows
-40% mortality in horses
-humans are asymptomatic
*mortality and morbidity are not good predictors of host competence

22
Q

“bridge” vector:

A

-connects reservoir host (birds) and the dead-end hosts of interest (humans and humans)
Ex. have 2 species that prefer bird blood but will do 20% of their blood from mammals

23
Q

Vector competence:

A

-the ability of a vector to transmit a disease
-occurs because VBP have evolved to become adapted to certain species of arthropod vectors

24
Q

Vector competence comprises of:

A
  1. Capacity of vector to be infected
  2. Maintain and transmit an infectious agent
25
Q

Vector competence ticks:

A

-few spirochetes: unable to transmit Lyme disease (D. variabillis, A. Americanum)
-I. scapularis: high

26
Q

Complex life cycle (macroparasites):

A

-carried by one or more intermediate hosts (invertebrate or vertebrate) and one final vertebrate host
-sexual reproduction often takes place in final vertebrate host
-results in shedding of an infectious stage into the environment
-eggs hatch and resultant life stages infect the intermediate host

27
Q

Food chains (complex life cycle):

A

-facilitate tropic transmission of parasites form intermediate hosts to predators

28
Q

Type of hosts (complex life cycle):

A

-final or definitive host
-intermediate host

29
Q

Final or definitive host:

A

-organism in which parasite reaches maturity and reproduces sexually

30
Q

Intermediate host:

A

-organism that harbors the immature stages of the parasite
-required by the parasite to undergo development and compete its life cycle

31
Q

Types of helminths (parasitic worms):

A

-roundworms
-flukes
-tapeworms
-thorny-headed worms

32
Q

Parasitic roundworms and direct life cycles:

A

-infective L3 larvae eaten by vertebrate host: develop into adult worms
-adult worms produce fertilized eggs expelled into fecal matter
-eggs hatch in dung
-L3 move onto pasture and cycle continues
*direct=one-species
*roundworm larvae spend lots of time in the environment

33
Q

Fasciolosis in livestock:

A

-common liver fluke
-complex lifecycle: final vertebrate host and intermediate snail host
-adult worms in liver produce eggs
-miracidia and cercariae

34
Q

Miracidia (fasciolosis):

A

-infect snails and develop into free-swimming cercariae

35
Q

Cercariae (fasciolosis):

A

-encyst on water plants and are ingested by vertebrate hosts

36
Q

Is FMDB a complex life cycle?

A

-no
-it is NOT REQUIRED to have a second host

37
Q

Life cycle of tapeworm: Echinococcus multilocularis

A

-complex
-final and intermediate hosts are canids and rodents
-adult host lives in small intestine of the definitive host and produces eggs
-intermediate host (rodent) ingests eggs
-eggs hatch in small intestine and release oncosphere that targets liver

38
Q

Oncosphere (echinococcus)

A

-develops into cyst, which grows over time and produces protoscolices
-dog eats mouse and protoscolices develop into adult worms

39
Q

Cysts replace tissues in liver (echinococcus):

A

-organ will lose it’s function

40
Q

If dog or human ingests tapeworm egg (echinococcus):

A

-it will treat the dog or human as an intermediate host

41
Q

Alveolar echinococcosis:

A

-if dog or humans consumes eggs, tapeworm will treat them as intermediate host
-eggs hatch into oncosphere that develops cysts in liver
-growing cysts in liver will kill patient because organ stops functioning
*tapeworm cannot skip steps in its complex cycle

42
Q

How could cysts in dog complete life cycle (echinococcus);

A

-dog would need to die and be consumed

43
Q

Cons of a complex life cycle:

A

-evolve ability to make a living in many different hosts
-expect probability of completing a life cycle to decrease with number of hosts

44
Q

Host size and trophic level vs. helminth life-cycle length:

A

-host mass increased along the links of the parasite life cycle
-host tropic level increased along the links of the parasite life cycle

45
Q

Size of final host and adult parasite vs. life-cycle length:

A

-final host was larger in helminth life cycles with more hosts
-adult parasites were larger in helminth lifecycle with more hosts

46
Q

Advantages of a helminth life cycle with more hosts:

A
  1. First hosts are small and numerous and easy to find
  2. Final hosts are larger, longer-lived endotherms that allow bigger adult body size
    >Bigger female worms produce more offspring
47
Q

Advantages of adding a predator to the lifecycle:

A

-bigger host=more resources
-longer-lived=more time to reproduce
-parasite can grow larger=produce more offspring
*adding the predator offsets losses due to predation

48
Q

Advantages of adding a prey host to the lifecycle:

A

-predators are unlikely to ingest immature stages (ex. eggs) in the environment
-prey more common=easier to encounter
-prey more likely to feed on immature stages
-high predation rates concentrate parasite into original predator host

49
Q

Trophic transmission:

A

-highly efficient because food webs are ubiquitous in nature
-predators encounter prey frequently
-infecting prey is a great way to meet a predator
-delay sexual maturation until you reach your final host: have space and a long life

VET YEAR ONE (108 decks)

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