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Infectious Colloquium > Modes of transmission > Flashcards

Modes of transmission Flashcards

1
Q

3rd epizootiological factor

A

modes of transmission

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2
Q

what is mode of transmission

A

ways of spreading the pathogenic microorganism from source of infection to a suitable portal of entry of the susceptible host

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3
Q

a successful mode of transmission

A

involves transmission of pathogenic microorganism in at least 1 minimum infective dose

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4
Q

why do we need to know modes of transmission

A

for the most effective prophylaxis

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5
Q

factors affecting possibility of transmission

A

the pathogen environmental tenacity
environmental conditions
minimum infective dose
time duration of spread of pathogenic microorganism from source to susceptible host

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6
Q

environmental tenacity

A

the resistance of microorganisms to environmental conditions

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7
Q

most important environmental conditions

A

temperature and exposure to UV light

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8
Q

minimum infective dose

A

the lowest amount of pathogenic microorganism sufficient to cause infection

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9
Q

3 main modes of transmission

A

direct contact
indirect contact - inanimate fomites or live intermediates
human activities

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10
Q

source of infection v mode of spread

A

source = in a certain place in one moment, where a large amount of microorganisms are located just before the outbreak in susceptible group of animals
spread = implies an action, which usually lasts and allows pathogenic microorganism transmission

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11
Q

transmission by direct contact

A

is spread of a pathogen by direct contact between a sick or a carrier animal as a source of infection and the suitable portal of entry of a susceptible host

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12
Q

types of direct contact

A

direct body contact
fecal-oral and droplet transmission
transplacental transmission
cohabitation

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13
Q

direct body contact

A

possible for almost all infectious diseases
very effective as spreading occurs instantaneously so environmental conditions down affect infectivity
prophylaxis = prevent contact between sick animals and susceptible
example of disease spread this way = rabies

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14
Q

fecal-oral and droplets

A

involves excretion of pathogen in to faeces that contaminates body of animal
contamination of anterior part of GI tract of susceptible animal can occur - profuse diarrhoea (example - Rotavirus)
also indirect contact
droplets = excretion of at least 1 infective dose in droplets that come directly to the portal of entry of susceptible host (example = TB, covid)
prophylaxis = separation of sick and healthy

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15
Q

transplacental transmission

A

intergenerational transmission so is vertical transmission
transmission from mother to offspring via milk is also direct contact
prophylaxis = immunoprophylaxis of female

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16
Q

transovarial transmission

A

in birds and arthropods vertical transmission to eggs

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17
Q

cohabitation

A

living together in close co existence
can be considered a consequence of human activity
prophylaxis = separation of animals and immunoprophylaxis

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18
Q

indirect contact in general

A

requires an intermediary that will allow a pathogen to remain infective, in at least 1 infectious dose, during transmission from diseased/carrier animal to suitable portal of entry of susceptible host
allows transmission over long distances
can occur through inanimate and live intermediaries

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19
Q

indirect contact with fomites

A

involves transmission of a pathogen by mechanical transport from source to portal of entry
efficiency of this spreading is influenced by tenacity and minimum infectious dose, environmental conditions and duration of transmission

20
Q

indirect contact - water

A

running water most important due to expansion of space
running water = often not found in minimum infective dose
standing water = easier to have a larger amount of pathogen
when microorganism transmitted through water = hydric infections or waterborne diseases
water also indirect source - when water spreads spores over an area or rain washes spores away eg Anthrax
prophylaxis = give animals clean, fresh water and control disinfection of water

21
Q

indirect contact - food

A

GI tract = portal of entry = alimentary infections
can be transmitted over long distances and time via food eg BSE
2 ways of transmission:
-food originates from infected animal
- food contaminated during preparation and feeding of animals
prophylaxis = supervisor and control of microbiological safety of foo and storage etc

22
Q

indirect contact - soil

A

soil diseases - anthrax, tetanus, blackleg and malignant edema
soil is a passive vehicle of the causative agent of spores - soil to wound
prophylaxis = remediation of soil containing spores (anthrax)
clostridium tetani - injury prevention, immunoprophylaxis, hyperimmune sera

23
Q

indirect contact - air

A

airborne transmission = spread of an infectious agent caused by the dissemination of droplet producing aerosols that remain infectious when diseased animal is no longer present
possible for pathogens that are resistant to environmental conditions
when pathogen remains infectious in dust eg hantavirus
risk increased indoors - air conditioning
favoured at lower temps and more frequent in winter
prophylaxis = ventilation and staying outside

24
Q

indirect contact - object

A

most common fomites
animal care equipment, drinking and feeding equipment
main mode of transmission for - dermatophytosis, parvovirosis, equine rhinopneumonitis, foot and mouth
prophylaxis = dont share equipment between different animals

25
Q

indirect contact - premises/spaces

A

contaminated premises = source
bringing susceptible animal to premises = MOT
prophylaxis = disinfection of surfaces and objects in all areas
in vet clinics, organise admission of patients so contagious diseases ones avoid crossing paths with other patients

26
Q

indirect contact - means of transport, vehicles

A

when it isn’t disinfected after carrying a sick/carrier animal
foot and mouth is highly resistant and can be mechanically transmitted on tyres or vehicle surfaces
prophylaxis = disinfect horse boxes etc and have drive through disinfection

27
Q

indirect contact with inanimate fomites

A

1 - water
2 - food
3 - soil
4- air
5 - objects
6 - spaces
7 - means of transport

28
Q

indirect contact with live intermediaries

A

passive and mechanical transmission
vertebrate animals
arthropods
humans - iatrogenic spread

29
Q

indirect contact - vertebrates

A

same species - when intermediate animal is resistant to infection due to previous illness or immunprophylaxis
different species - dog or cat can be contaminated with foot and mouth and spread it to susceptible ungulate host
wild animals
birds
prophylaxis = prevent entry of animals of other species in to farms with susceptible animals and prevent contact with animals for which we do not know epizootiological data

30
Q

indirect contact - arthropods

A

= transmissible infectious diseases/vector borne diseases
biological transmission = transmission of a pathogenic microorganism that multiplies in the arthropod
mechanical transmission = pathogen transmitted from contaminated surface or hematophagous transmission (proboscis contaminated with blood from sick animal and then feed on a susceptible one and pathogen is transmitted)
prophylaxis = insect repellents, nets, keep indoors at night

31
Q

indirect contact - humans

A

iatrogenic spread = through veterinary work
clothes etc can be contaminated with pathogen and then mechanically transmitted by contact

32
Q

human activities - animal, animal product and by product trade

A

disease spread by trade of sick or carrier animals
possibility of disease to be spread over long distance and transcontinentally

33
Q

human activities - intensive farming and animal shelters

A

direct and indirect contact with living or inanimate objects constant
shelters = animals of unknown health and immune status, from different age groups and geographical areas mixed daily.

34
Q

human activities - migratory and extensive animal husbandry

A

eg sheep herd moving from one pasture to another
extensively farmed animals more exposed to wildlife, rodents and arthropods which can be reservoirs for infectious diseases

35
Q

human activities - exhibitions, fairs and competitions

A

direct contact of lots of animals from different epizootiological units
transport reduces resistance and stress during shows etc help the spread

36
Q

human activities - war and natural disasters

A

resources channelled elsewhere so animal health and disease control not a priority
also during economic crises

37
Q

human actives and modes of transmission

A
  1. trade of animals and products etc
  2. intensive farming and shelters
  3. extensive farming
  4. exhibitions, fairs and comps
  5. wars and natural disasters
38
Q

vogralink chain

A

virulence and infectious dose
source of infection
modes of transmission
portal of entry
host susceptibility

39
Q

portal of entry definition

A

a site through which microorganisms enter the susceptible host
often enter though same route they exited the reservoir

40
Q

portals of entry

A

epithelial surfaces to the environment
1. skin
2. mucous membranes
3. placenta

41
Q

skin as a portal of entry

A

intact skin = cornfield cells (keratin) and other non specific defence mechanisms eg acidity of skin secretions
protects body but can be broken by trauma or inoculation (arthropods)
diseases = Rabies, Bluetongue, Tetanus, Lepto

42
Q

mucous membrane examples

A

resp tract
alimentary tract
genital tract
conjunctiva

43
Q

non specific defence mechanisms of mm

A
  • sticky mucous
  • stomach = HCl and protein digesting emzymes
  • saliva and lacrimal fluids = bacteria destroying enzymes
  • nasal hairs
  • cilia
  • acidity of the vagina
  • acidity of urine
44
Q

placenta as a portal of entry

A

vertical transmission from mother to foetus
diseases = BVD, equine herpes, Lepto

45
Q

diseases with unknown portals of entry

A

Lumpy skin disease
maybe arthropod vector?
infected bulls can excrete virus in semen but transmission through semen is not possible
unknown if transmission can occur via fomites
can be infected experimentally by inoculation with material from cutaneous nodules or blood

Infectious Colloquium (17 decks)

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