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Epi Final > Topic 1: Definitions, sources of infection, influencing factors > Flashcards

Topic 1: Definitions, sources of infection, influencing factors Flashcards

1
Q

What is an infectious disease

A

disorders caused by an agent (lower ranked, bacteria, virus etc), which acts on a host (higher ranked)

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2
Q

Agent

Exposition

A

Lower ranked
Virus, bacteria, Protozoa fungi etc

exposition: needed from the agent, must be able to cause the disease - host must eb exposed to the agent

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3
Q

Host

A

Higher ranked organism

  • from host, we need a disposition
  • must be infected by the agent, and therefore will cause the disease
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4
Q

5 phases of infection

A
  1. Entry (agent enters host)
  2. Colonisation (agent must find the optimal place to colonies host)
  3. replication (agent must propagate in the host)
  4. Damage (with the help of the agents metabolites . toxins etc, must damage the host
  5. transmission (to other susceptible animals
    - host will excrete agent
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5
Q

Direct transmission

A
  • Not so common
  • infected hosts tissue contacts susceptible host
  • bite, sexual transmission
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6
Q

Indirect

A
  • more common
  • involvement of excretions and secretions
  • drinking water, feed
  • products of animal involvement
  • soil, environment
  • aerogenic
  • arthropods
  • iatrogenic
  • nosocomial
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7
Q

Aerogenic transmisson

A
  • coughing, sneezing
  • excretion in particle form
  • indirect, as air is involved in transmisson
  • less than 5 micrometers; can get into the alveoli
  • 5 - 10 micrometres ; can get into the bronchiole
  • over 10 micrometres ; better situation fr the host, can only get into the nasal cavity
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8
Q

Arthopod transmission

A
  • important for agents that would not survive in the environment
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9
Q

Iatrogenic infefctions

A

contaminated surgical tools, gloves, equipment

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10
Q

Nosocomial

A

hospital infections, eg salmonella in Equine clinics

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11
Q

Vertical Transmisson

A
  • from one age group to another, usually parent to offspring
  • germinative, Intrauterine and galactogenic
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12
Q

Germinative transmission

A
  • vertical
  • rare in mammals, as infected embryos are often not viable
  • infected eggs in birds can be hatched
    eg. avian leucosis
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13
Q

Intrauterine transmission

A
  • if it is generalised int he mother, it will reach uterus and the embryo, replication, death or birth
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14
Q

Galactogenic transmission

A

Nb infected through mothers milk

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15
Q

Horizontal Transmisson

A

animal to animal, where they are kept together

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16
Q

Type of Zoonoses

A

Orthozoonoses
Cyclozoonoses
Metazoonoses
Sapronoses

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17
Q

Orthozoonoses

A

from animal to humans, and humans to animals

eg rabies

18
Q

Cyclozoonoses

A
  • Focal infection, maintained by a host and arthpod is involved
  • infection circulating btw them
  • Lyme borrelisos
    Maintaining host: small rodent
    ticks= arthopod
    humans can enter the cycle through a tick bite
19
Q

Metazoonoses

A

From animals to humans via wound infections

  • Erysipelas, usually occurring in pigs
20
Q

Sapronoses

A

not a zoonoses
- same disease occurring in animals and humans
source of the infection is the same

Tetanus, CL. tetani
- spores present in soil, both humans and animals can eb infected

21
Q

Routes of infections

A

Natural orifices; PO, intranasal(aerogenic), Sexual transmisson, udder

Conjuvtical, Per cutan (arbo), wounds

22
Q

Optimal entrance

A

which requires the least amount of agent to cause the infection

APP in swine; aerogenic is optimal, (PO possible, but a larger amount of agent required to cause disease)

23
Q

Types of infection

A

Simple: agent enters, host is infected
Reinfection:
Exacerbation: when agent is isolated in a lesion (tubercle) in aerogenic infections
Superinfection; infection occurs after initial infection

24
Q

Secondary Infection

A

primary than secondary infection

primary infection causing immunosupression, secondary can colonise and cause disease

25
Q

Mixed infection

A

infections happen at the same time, eg kennel cough, parainfluenza 2 and bordetella bronchiseptica

26
Q

Agent relationship with host

A

Symbiotic: live in the the presence of each other, on skin or MM

Mutualism: both parties benefit, eg enteric gut flora

Commensalism: bacteria benefits from host, but is neither beneficial or harmful to host

Parasitism: when the agent can cause a disease

*Normal microflora are not necessary for the host to live, can live fine without it

27
Q

Pathogenicity

A

the ability of an agent to cause a disease

Obligate; do not need PDFs to cause disease, if the animal is infected and not immune, disease will occur. eg bacillus antracis, anthrax will be the result

Faculative; need PDF, eg bad management, nutrition or primary infection with a virus

28
Q

Host spectrum

A

Stenoxenous agents: narrow host range, ASF only infects swine

Euryxenous: wide host range, eg B anthracis

29
Q

Virulence

A

the different strengths of pathogenicity found with a bacterium or viral species

virulence isn’t stable and usually decreases because they lose their virulence factors

Highly virulent; cause severe disease
Mildily; do not cause severe disease, or need a high amount of agent to do so
Avirulent; pathogenic by species, but not able to cause disease –> used for vaccines

30
Q

Virulence factors

A

Capsule; protects bacteria
Toxins, endo or exotoxins
extracaelluar enzymes
surface proteins

the more virulence factors, the more virulent an agent

31
Q

Measuring virulence

A

LD50, amount of agent that will kill 50% of animals

MLD, minimal lethal dose: less reliable

32
Q

Invasiveness

A

Genrealised infection, eg herpes, anthrax spread in host

Local; eg papillomatosis, local lesions in the skin

IC/ extracellular; IC much more protected from the immune system response, so increase pathogenicity

33
Q

Amount of agent

A

has. different effect on different species

one spore of bacillus anthracis can kill a sheep but several needed to kill a pig

34
Q

Henle - Koch postulates

A

When can we say an agent is responsible for a disease?

  1. agent can always be detected in infected animals
  2. it can always be isolated from the animals
  3. it can then be replicated with a culture and will cause the same clinical signs
35
Q

Species specific resistance

A

ASF cannot infect horses

36
Q

age

A

regarded a PDF

37
Q

race, individual resistance

A

Canine ehrlichiosis is frequent in GSD, other breeds more resistant

38
Q

Non specific resistance

A

Skin, mm, excretions, macrophage, complement system,, properdin, opsonin, IL, IF, TNF

(Cannot target specific cells, can only recognise non self)

39
Q

Passive immunity

A

natural; maternal protection t birth door new born animals

Artificial; Its in the hyper immune set protects young animals

40
Q

Active immunity

A

natural; if the animal survives an infectious disease, in the immune system creates AB against it

induced; vaccine

Humoral (IgA,G etc)

41
Q

Immune rxn of Nb

A

Calf Ig 4-32 days

Calf/ piglet, local immune rxn immdieatelt, but no immune memory

cellular immune rxn, after 2 weeks

colostrum contains lymphocytes and iG

42
Q

Management, Technology, Physiological factors

A

overcrowding, important pdf

weaning, grouping, treatment, castration, all stress factors

farrowing increases cortisol, host resistance decreases

Epi Final (11 decks)

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