Infection

Question 1

What is the difference between infection and disease?

Answer 1

Infection = colonisation of an individual (host) by an infectious agent

Disease = Normal body functions are impaired to reduce performance leading to clinical signs.

Question 2

What is aetiology?

Answer 2

The cause(s) of a disease or condition. (Some diseases of single or multiple aetiologies)

Question 3

What is an incubation period for infection?

Answer 3

The time between infection and clinical signs showing. Can be short (a day) or long (a month).
Very important when isolating newly bought animals.

Question 4

What is the difference between microorganisms and macroparasites?

Answer 4

Microorganisms can only be seen through a microscope (e.g., bacteria, viruses, prions, protozoa).
Macroparasites are parasitic organisms you can see by eye as they are multicellular (e.g., fleas, ticks).

Question 5

Can all parasites cause disease by themselves?

Answer 5

Some can infect healthy individuals alone, but many require a host to reproduce.

Question 6

What is an opportunistic infection?

Answer 6

Infection caused by an infectious agent due to an opportunity that occurred.

Question 7

Give 4 examples of how an opportunistic infection may occur.

Answer 7

1. Weakened immune system
2. Removal of microbiome (e.g., antibiotics can remove healthy bacteria in the gut).
3. Breached barrier (e.g., trauma via cut, abcess, ticks)
4. Current infection

Question 8

What is a commensalism/ mutualism?

Answer 8

A relationship where one or both party benefit, without detriment effect to either.
(e.g., Wolbachia and D.immitis)

Similar to symbiosis which is a close and long-term relationship between two or more different species

Question 8

What is a saphrophyte?

Answer 8

Microorganism that lives on dead or decaying organic matter.
Can impact post mortems by colonising and removing evidence of cause of death.

Question 8

How can location be used to categorise infectious agents?

Answer 8

Extra or intracellular?
Localised or disseminated?
Lymphatic or bloodstream spread?

Question 8

Compare the differences between prokaryotes and eukaryotes:

Answer 8

Prokaryote;
- Circular chromosomes
- < 5μm
- Reproduce via binary fission
- No endoplasmic reticulum

Eukaryote
- Nucleus containing genetic info
- Linear chromosomes
- > 5μm
- Reproduction via mitosis
- RER, SER, Golgi app

Question 8

Why are viruses not classified as a eukaryote or prokaryote?

Answer 8

Viruses are not classified as an organism because they cannot replicate independently.

Question 9

What are prions and why don’t they fit into prokaryote or eukaryote categories?

Answer 9

Prions are transmissable/ infectious proteins that can misfold host proteins.

Question 9

What is the difference between endoparasites and ectoparasites?

Answer 9

Endoparasites = inside host (e.g., tapeworm)
Ectoparasites = outside host (e.g., fleas, lice)

Question 10

What are Toll-like receptors? (TLRs)

Answer 10

TLRs are cell surface and intracellular proteins that detect and respond to microbial antigens.

Question 11

Name 7 methods of disease transmission

Answer 11

1) Ingestion (grooming can ingest worms)
2) Aerial
3) Direct contact (e.g., skin, coitus)
4) Indirect contact (e.g., via fomites)
5) Inoculation (vector borne-mosquito bites)
6) Iatrogenic transmission (doctor created)
7) Across placenta

Question 12

What is the difference between horizontal and vertical transmission?

Answer 12

Horizontal - transmitted from any individual to another of the same generation
Vertical - transmission from one generation to the next by infection of the embryo/ newborn from the parent

Question 13

What is a zoonosis?

Answer 13

Any disease or infection that is naturally transmissable from vertebrate animals to humans.

Question 14

What are the 3 types of zoonoses? (explain each)

Answer 14

1) Endemic zoonoses = present in many places and affects many people/ animals
2) Epidemic zoonoses = sporadic in temporal and spatial distribution
3) Emerging/ re-emerging zoonoses = newly appearing or have existed previously but are rapidly increasing.

Question 15

What is the difference between endemic and pandemic?

Answer 15

A pandemic cuts across international boundaries, as opposed to regional epidemics

Question 16

What are notifiable diseases?

Answer 16

Diseases you must immediately notify the government if suspected/ found.

Question 17

How can you prevent entry of a pathogen into a country?

Answer 17

Border controls, quarantine of infected, vector (insect) controls, traceability and identification.

Question 18

What is self-declaration?

Answer 18

Document statement regarding the absence of one or several diseases in a country/ zone.

Question 19

What are the benefits of self-declaration?

Answer 19

Visibility of disease freedom (safe trade), transparency, evidence successful precautions.

Question 20

Compare eradication against control.

Answer 20

Eradication: Elimination of pathogen or reduction to negligible levels. Inc., test & slaughter or cull entire herd.

Control: Reduction to prevalence below a certain level. Inc., vaccination.

Question 21

What are 7 obstacles to disease control?

Answer 21

1. Deficient measures (funding, political)
2. Global transport (World = small place)
3. Reservoir hosts (unaffected but spread)
4. Nature of the organism (incubation periods)
5. Pathogen mutation (viruses may mutate and vaccination then useless)
6. Vaccine failure (can’t work against all strains, lack of herd immunity, improper storage, wrong administration).

Question 22

What does sporadic mean?

Answer 22

Refers to a disease that occurs infrequently and irregularly.

Question 23

What is a cluster?

Answer 23

Refers to an aggregation of cases grouped in place that are greater than expected.

Question 24

What is a neglected zoonotic disease?

Answer 24

Zoonotic disease with sub-optimal control -> usually in poor countries with low resources.