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EPI FINAL > 1. Definition of infectious diseases, sources of infection, factors influencing infectious diseases (pathogen-host relationship, protection of the host, environmental factors) > Flashcards

1. Definition of infectious diseases, sources of infection, factors influencing infectious diseases (pathogen-host relationship, protection of the host, environmental factors) Flashcards

1
Q

What is infectious disease:

A

Agent - lower ranked (taxonomically)
Host - higher ranked
Exposition: agent infects host
Disposition: host has to be able to be infected

Phases of infection: entry, colonization, replication, damage of the host, transmission

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1
Q

What is infectious disease:

A

Agent - lower ranked (taxonomically)
Host - higher ranked
Exposition: agent infects host
Disposition: host has to be able to be infected

Phases of infection: entry, colonization, replication, damage of the host, transmission

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2
Q

Importance of infectious diseases

A

All areas of vet med, economic impact, trade of animals and animal products, zoonoses, food hygiene and safety (25% of human death is due to infective agents)

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3
Q

Sources of infection

A

Generally from infected animals/humans
Direct: tissue of infected animal in contact with tissue of susceptible host, e.g. rabies bite

Indirect:

  • excretions, secretions
  • products of animal origin
  • drinking water, feed, soil, environment
  • aerogenic
  • arthropods: true vectors, mechanical vectors
  • nosocomial infections
  • iatrogenic infections
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4
Q

Transmission of diseases: 2 types

A

Vertical and horizontal

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5
Q

Vertical transmission

A

Parent to offspring
Germinative
Intrauterine
Galactogen

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6
Q

Horizontal transmission

A

Spread in the same group, infecting each other

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7
Q

Types of zoonoses:

A
  1. Orthozoonoses
  2. Cyclozoonoses
  3. Metazoonoses
  4. Sapronoses
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8
Q

Orthozoonoses, explanation and example

A

Animal to host (direct and indirect)

e.g. rabies

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9
Q

Cyclozoonoses, explanation and example

A

Spread by arthropods, circulated infection between arthropod and maintaining host - humans can accidentally enter this cycle
- Requires more than one vertebrate

e.g. Lyme disease, tick borne incephalitis, taenia sp.

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10
Q

Metazoonoses, explanation and example

A

Requires both a vertebrate and invertebrate host to complete life cycle
All arboviruses + Rickettsia, Leishmania
Black plague –> fleas

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11
Q

Sapronoses

A

From a source like soil, water, decaying plants etc. Replicate in non-living matter
Like some protozoa etc

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12
Q

Way of infection

A

Place of entry
Natural orifices
Percutaneous

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13
Q

Forms of infection

A

Simple infection - ONE AGENT

Repeated infection - ALSO ONE AGENT

  • Reinfection: after the infection has cleared up
  • Exacerbation: the agent is isolated in nodule/abscess then break out causing secondary infection
  • Superinfection: infected animal is infected again with the same infection e.g. TB

Infection of multiple agents:
Secondary infection (complication)
Mixed infection - e.g. kennel cough

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14
Q

Outcome of the infection depends on:

A

Agent - host - environment

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15
Q
  1. Agent subcategories
A
  1. 1 Host-parasite relationship
  2. 2 Pathogenicity
  3. 3 Virulence
  4. 4 Invasiveness
  5. 5 Amount of agent
  6. 6 Way of infection
15
Q
  1. Agent subcategories
A
  1. 1 Host-parasite relationship
  2. 2 Pathogenicity
  3. 3 Virulence
  4. 4 Invasiveness
  5. 5 Amount of agent
  6. 6 Way of infection
16
Q

1.1 Host-parasite relationship

A

Symbiosis, mutualism, commensalism, parasitism

“normal” microflora

17
Q

1.2 Pathogenicity

A

Euryxen: wide host range (rabies, anthrax)
Stenoxen: narrow host range (ASF, EIA)
Obligate pathogen: no predisp needed
Facultative pathogen: predisp needed

18
Q

1.3 Virulence

A

Virulence factors, MLD, LD, change of virulence
How able is the agent to cause disease in amount
Avirulent and low virulent strains can be used for vaccination

19
Q

1.4 Invasiveness

A

Intracellular - protected from body

Extracellular

20
Q

1.5 Amount of agent

A

A minimum amount is required. If it is more virulent, less pathogens are needed

21
Q

1.6 Way of infection

A

Has to be optimal
Henle Koch postulates: detect agent, isolate in pure culture, should provoke the same clinical signs/PM lesions:

The microbe is present in all cases of the disease
The microbe does not occur in other diseases
The agent can be isolated in pure culture
The same disease can be caused with the isolated agent and it can be re-isolated

22
Q
  1. Host
A
  1. 1 Species, age
  2. 2 Race, individual resistance
  3. 3 Production
  4. 4 Non-specific resistance
  5. 5 Specific resistance
  6. 6 Effect of immune suppression
  7. 7 Fetal immune reaction
  8. 8 Immune reaction of newborns
  9. 9 Cellular immune reaction
23
Q

2.1 Species, age

A

Has to have the appropriate receptors to the agent - stenoxen/euryxen

24
Q

2.2 Race, individual resistance

A

Lines, e.g. certain poultry hybrids susceptible to Mareks

25
Q

2.3 Production

A

Feeding, laying - intensively fattening animals predisposed to certain diseases

26
Q

2.4 Non-specific resistance

A

Skin, mm, cilia, excretions
MPS
Complement, properdin, opsonin systems
IL, IF, TNF

27
Q

2.5 Specific resistance

A

Targeting certain agents
Passive immunity: natural (maternal), induced (hyperimmune serum)
Active immunity: natural, induced (vaccine)
Humoral resistance: IgA - local protection, IgG - circulation etc.
Cellular resistance: intracellular bacteria, viruses

28
Q

2.6 Effect of immune suppression

A

Decreases resistance of animal

Toxicosis, medicine, mycotoxins, parturition etc

29
Q

2.7 Fetal immune reaction

A

In ovo vaccination - immune after hatching

30
Q

2.8 Immune reaction of newborns

A

More susceptible
Calf: Ig 4-32 days - immune reaction improves with time
Calf, piglet: local immune reaction occurs immediately after birth, disappears

31
Q

2.9 Cellular immune reaction

A

0-2 weeks long, limited at beginnning then faster

32
Q
  1. Environment
A
    1. Nutrition, management
  2. 2 Survival of the agent in the environment
  3. 3 Environmental effects on animals
  4. 4 Predisposing factors to facultative pathogens
33
Q

3.1. Nutrition, management

A

Poor nutrition (deficiencies, mycotoxins) and management (overcrowding, ventilation, humidity)
Technology: weaning, grouping, treatment, castration, sheering, transport
Physiological effects: laying, pregnant, fattening, use of animal

34
Q

3.3 Environmental effects on animals

A

Weather, temp, humidity

EPI FINAL (5 decks)

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