Intro to Agents of Disease

Question 1

What is Disease?

Answer 1

CHange in state of health of host - resulting in inability to carry out normal function due to the actions of an agent

Question 2

What is clinical disease?

Answer 2

Obvious change with readily detectable signs of disfunction or illness

Question 3

What is subclinical disease?

Answer 3

no readily detectible signs of dysfunction or illness –> subtle changes in productivity, growth and fitness

Question 4

What factors affects HPEI?

Answer 4

agent of disease (pathogen)
Effect on host (pathology)
ost repomse (immunity/inflam and repair)
Enviro (external world reltes to host and pathogen

Question 5

What is parasitism

Answer 5

Symbiotic relationship between organism and host causes harm to host (disease)

Question 6

Mutualism

Answer 6

symbiotic relationship that benefits both organism and host

Question 7

Commensalism

Answer 7

Symbiotic relationship where organism does no obvious harm to host

Question 8

opportunistic pathogens

Answer 8

organisms that become pathogenic after alternation to hosts health

Question 9

What % of human infectious diseases have an animal origin?

Answer 9

75%

Question 10

What causes infectious diseases

Answer 10

The action of infectious agents in the host

Question 11

What factors influence disease?

Answer 11

Parasitic (pathogen)
host
Environment

Question 12

What are parasitic factors?

Answer 12

strains
virulence
properties (e.g adaptability)
toxins
dose
method and duration of exposure

Question 13

What are host factors?

Answer 13

animal species
genotype
age
nutritional status
repro status
past exposure/immunity
concurrent disease/ injuries
immune competence
behaviours

Question 14

What are environmental factors?

Answer 14

Climate
Altitude/topography
other species
population density
food, water, soil and air
season

Question 15

What is DNA-DNA Hybridisation?

Answer 15

2 complimentary ss DNA/RNA molecules bind together to form a double stranded molecule
Complementary base pairing

Question 16

How do we do Viral nomenclature

Answer 16

grouped into families
subdivision by host species affected and clinical disease

Question 17

What is a strain?

Answer 17

an organism within a species which is a clonal descendent from a single isolate

Question 18

Gram positive cell wall

Answer 18

long chain polymers
bound to cell membrane and or peptidoglycan
antigenic specificy

Question 19

Gram neg cell wall

Answer 19

lipopolyssacharide
protect cell against enzymatic attack
endotoxins
aids survival in small intestine
o antigen used in serotype identification

Question 20

What are the nutrient requirements of bacteria?

Answer 20

water
carbon and energy source
nitrogen and sulphur
phosphorus
other elements

Question 21

What is the difference between aerobic and anaerobic metabolism?

Answer 21

Aerobic metabolism = respiration
Anaerobic metabolism = fermentation

Question 22

What is a virion?

Answer 22

The complete infectious virus particle
helical or cubical/icosahedral

Question 23

Enveloped virus properties:

Answer 23

host phospholipids
glycoproteins of viral origin
lipid rich
sensitive to lipid solvents
more fragile

Question 24

Non enveloped virus properties:

Answer 24

More resilient
capsid cell surface proteins
- similar functions to the glycoproteins

Question 25

DNA virus properties:

Answer 25

Double stranded
replicate in nucleus (except poxvirus)
stable and less prone to mutation
persistent infection
temporal regulation of gene transcription

Question 26

RNA virus properties:

Answer 26

single stranded
linear (can be segmented)
pos or neg sense
pos sense go straight into protein synth
most replicate in cytoplasm
labile (easily changed) and prone to mutation
antigenic drift

Question 27

Athropod examples

Answer 27

Insects (flies, mozzies, lice)
Acarines (ticks and mites)

Question 28

Helminths examples:

Answer 28

Nematodes (roundworms)
Cestodes (tapeworms)
Trematodes (flukes)

Question 29

Arthropod properties:

Answer 29

Ectoparasites
- live on host surface
- vectors

Life cycle
- pupation
- larva and pupa (complete)
- nymph (incomplete)

Question 30

Nematodes properties:

Answer 30

endoparasites
cylindrical multi-cellular eukaryotes
mouth pieces
repro structures & external features

Direct & indirect life cycles:
Direct = single host animal species
Indirect = no difinitive host (intermediate host)

Question 31

Cestodes properties:

Answer 31

endoparasitic segmented flatworms

3 parts: neck, strobila, scolex
nutrition absorbed through cuticle
disease associated with attachment and occupation

Question 32

Trematode properties:

Answer 32

endoparasitic non segmented flatworms
FLUKES
in direct life cycle
Lymnaeid snail
Young migrate through liver
adult develop in bile duct

Question 33

Protozoa properties

Answer 33

single cell eukaryotes
enveloped
tropism (blood cells)
various modes of motility
inter or intracellular in host
repro asexually and sexually

Question 34

What is pathogenicity

Answer 34

the quality or state of being pathogenic, the potential ability to produce disease

Question 35

What is virulence?

Answer 35

The ability of a microorganism to cause damage to its host.

Question 36

What 3 characteristics of a pathogen determine virulence?

Answer 36

Invasiveness (ability to spread to adjacent tissues)
Infectivity (ability to establish infection)
Pathogenicity (ability of pathogen to cause disease

Question 37

What are the 3 categories of factors influencing pattern of disease?

Answer 37

Environment (Saprophytes)
Other animals (obligate parasites)
The animal itself (opportunistic pathogens)

Question 38

What are the 2 forms of transmission?

Answer 38

Vertical (parent to offspring)
Horizontal (between individuals by a physical means)

Question 39

Modes of horizontal transmission

Answer 39

Direct (suseptible animal in physical contact with infected animal or their infectious secretions)
Indirect (no direct physical contact/ carried from source to suseptible animal/ living (vectors) or non-living (fomites))

Question 40

Types of vectors

Answer 40

Mechanical (salmonella from animal faeces)
Biological (arboviruses) - mozzies, flies and ticks

Question 41

Fomites

Answer 41

inanimate objects that transmit agent
e.g. furniture, posts, blankets, milking machienes