Midterm 2 Lecture 7

Question 1

What is an infectious disease?

Answer 1

any disease caused by invasion by a pathogen which grows and multiplies in the body

Question 2

Why are infectious diseases of major importance in agricultural animals?

Answer 2

• have an impact on the individual animal, the producer, and effect regional, national and international governing and trade policies

Question 3

Examples of infectious agents

Answer 3

viruses, bacteria, fungi, parasites, protozoa, prions

Question 4

What does it mean if an agent is contagious?

Answer 4

Capable of being spread from one individual to another

Question 5

What are viruses?

Answer 5

replicating microorganisms among the smallest life form; this simplicity has led to obligate requirements for intracellular growth and heavy dependence on host-cell structure and metabolic components

Question 6

Where are viruses found?

Answer 6

• in collections on nucleic acid, protein and some lipid

Question 7

Virion

Answer 7

complete virus particle

Question 8

What is the goal of a virus?

Answer 8

• to transfer nucleic acids (DNA/RNA) from on cell to another; each has individual methods to enter then exit the cell; it can rupture the cell on exit or ‘bud’ from cell and potentially have latent infections

Question 9

What is happening to viral infections that were once considered eradicated?

Answer 9

• they are re-emerging and are considered more virulent

Question 10

How are viruses controlled and prevented?

Answer 10

1. vaccination; but all the easy viral vaccines have been produced
2. antimicrobials are not practical in livestock
3. quarantine is a problem
4. test and slaughter (potentially the optimal method)
5. induce trade restrictions

Question 11

Bacteria

Answer 11

• prokaryote
• doesn’t need the host cells components to survive, it can survive outside the cell
• invades host by cells or intercellular spaces

Question 12

How does bacteria cause injury?

Answer 12

• releases exotoxins or endotoxins resulting in cell death/organ failure/ host death

Question 13

How is bacteria controlled and prevented?

Answer 13

1. vaccination but all the easy bacterial vaccines are produced
2. antimicrobials are safe
3. quarantine is a problem for non-reporter vaccine
4. test and slaughter (seropositive animals euthanized)
5. enforce trade restrictions

Question 14

Fungi/Molds

Answer 14

• eukaryotic
• uptake nutrients from environment; a primary decomposer of dead material
• reproduces asexually and sexually

Question 15

Hyphae and mycelium

Answer 15

Hyphae = long tubes
Mycelium = mat of hyphae

Question 16

What is the primary fungi pathogen?

Answer 16

Cryptococcus neoformans
- affects lungs, CNS, and skin
- disseminates systemically in immune compromised ppl and other species

Question 17

How can fungi/molds be prevented/controlled?

Answer 17

1. no vaccinations
2. antimicrobials can be unsafe
3. not able to quarantine
4. cannot test and slaughter
5. trade restrictions are not really put in place

Question 18

Parasites

Answer 18

• eukaryotes, multicellular
• endo (gut, lungs), ecto (skin) and epi (live off another parasite) parasites
• complex life cycle

Question 19

Screwworm (parasite)

Answer 19

• larvae emerges 8-12 hrs after eggs deposited into wound; little movement, hard to see
• 3 days: bloody foul discharge
• animal is depressed off feed and isolated, stands in water to alleviate discomfort
• eats healthy flesh
• death due to secondary infection
• if left untreated more female flies attracted to wound and lay

Question 20

Life cycle of Cystic Hydatid Disease (Echinococcus sp.)

Answer 20

• definitive host: carnivore releases eggs into enviro
• intermediate host: ruminant ingests eggs; eggs hatch and larvae migrate to different body organs; forms hydated cysts and protoscolices
• carnivore eats intermediate host and protoscolies from eggs
• man: dead-end intermediate host, top of food chain

Question 21

How can parasites be prevented/controlled?

Answer 21

1. can vaccinate against some small numbers
2. anthelminthics
3. can’t quarantine
4. can’t test and slaughter
5. trade restrictions for some specific cases (ectoparasites)