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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
indirect contact - premises/spaces
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
indirect contact - means of transport, vehicles
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
indirect contact with inanimate fomites
1 - water 2 - food 3 - soil 4- air 5 - objects 6 - spaces 7 - means of transport
28
indirect contact with live intermediaries
passive and mechanical transmission vertebrate animals arthropods humans - iatrogenic spread
29
indirect contact - vertebrates
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
indirect contact - arthropods
= 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
indirect contact - humans
iatrogenic spread = through veterinary work clothes etc can be contaminated with pathogen and then mechanically transmitted by contact
32
human activities - animal, animal product and by product trade
disease spread by trade of sick or carrier animals possibility of disease to be spread over long distance and transcontinentally
33
human activities - intensive farming and animal shelters
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
human activities - migratory and extensive animal husbandry
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
human activities - exhibitions, fairs and competitions
direct contact of lots of animals from different epizootiological units transport reduces resistance and stress during shows etc help the spread
36
human activities - war and natural disasters
resources channelled elsewhere so animal health and disease control not a priority also during economic crises
37
human actives and modes of transmission
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
vogralink chain
virulence and infectious dose source of infection modes of transmission portal of entry host susceptibility
39
portal of entry definition
a site through which microorganisms enter the susceptible host often enter though same route they exited the reservoir
40
portals of entry
epithelial surfaces to the environment 1. skin 2. mucous membranes 3. placenta
41
skin as a portal of entry
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
mucous membrane examples
resp tract alimentary tract genital tract conjunctiva
43
non specific defence mechanisms of mm
- 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
placenta as a portal of entry
vertical transmission from mother to foetus diseases = BVD, equine herpes, Lepto
45
diseases with unknown portals of entry
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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