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

Question 1

What is infectious disease:

Answer 1

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

Question 1

What is infectious disease:

Answer 1

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

Question 2

Importance of infectious diseases

Answer 2

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)

Question 3

Sources of infection

Answer 3

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

Question 4

Transmission of diseases: 2 types

Answer 4

Vertical and horizontal

Question 5

Vertical transmission

Answer 5

Parent to offspring
Germinative
Intrauterine
Galactogen

Question 6

Horizontal transmission

Answer 6

Spread in the same group, infecting each other

Question 7

Types of zoonoses:

Answer 7

1. Orthozoonoses
2. Cyclozoonoses
3. Metazoonoses
4. Sapronoses

Question 8

Orthozoonoses, explanation and example

Answer 8

Animal to host (direct and indirect)

e.g. rabies

Question 9

Cyclozoonoses, explanation and example

Answer 9

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.

Question 10

Metazoonoses, explanation and example

Answer 10

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

Question 11

Sapronoses

Answer 11

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

Question 12

Way of infection

Answer 12

Place of entry
Natural orifices
Percutaneous

Question 13

Forms of infection

Answer 13

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

Question 14

Outcome of the infection depends on:

Answer 14

Agent - host - environment

Question 15

1. Agent subcategories

Answer 15

1. 1 Host-parasite relationship
2. 2 Pathogenicity
3. 3 Virulence
4. 4 Invasiveness
5. 5 Amount of agent
6. 6 Way of infection

Question 15

1. Agent subcategories

Answer 15

1. 1 Host-parasite relationship
2. 2 Pathogenicity
3. 3 Virulence
4. 4 Invasiveness
5. 5 Amount of agent
6. 6 Way of infection

Question 16

1.1 Host-parasite relationship

Answer 16

Symbiosis, mutualism, commensalism, parasitism

“normal” microflora

Question 17

1.2 Pathogenicity

Answer 17

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

Question 18

1.3 Virulence

Answer 18

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

Question 19

1.4 Invasiveness

Answer 19

Intracellular - protected from body

Extracellular

Question 20

1.5 Amount of agent

Answer 20

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

Question 21

1.6 Way of infection

Answer 21

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

Question 22

2. Host

Answer 22

2. 1 Species, age
3. 2 Race, individual resistance
4. 3 Production
5. 4 Non-specific resistance
6. 5 Specific resistance
7. 6 Effect of immune suppression
8. 7 Fetal immune reaction
9. 8 Immune reaction of newborns
10. 9 Cellular immune reaction

Question 23

2.1 Species, age

Answer 23

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

Question 24

2.2 Race, individual resistance

Answer 24

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

Question 25

2.3 Production

Answer 25

Feeding, laying - intensively fattening animals predisposed to certain diseases

Question 26

2.4 Non-specific resistance

Answer 26

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

Question 27

2.5 Specific resistance

Answer 27

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

Question 28

2.6 Effect of immune suppression

Answer 28

Decreases resistance of animal | Toxicosis, medicine, mycotoxins, parturition etc

Question 29

2.7 Fetal immune reaction

Answer 29

In ovo vaccination - immune after hatching

Question 30

2.8 Immune reaction of newborns

Answer 30

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

Question 31

2.9 Cellular immune reaction

Answer 31

0-2 weeks long, limited at beginnning then faster

Question 32

3. Environment

Answer 32

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

Question 33

3.1. Nutrition, management

Answer 33

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

Question 34

3.3 Environmental effects on animals

Answer 34

Weather, temp, humidity