Midterm 2 Lecture 7 Flashcards
What is an infectious disease?
any disease caused by invasion by a pathogen which grows and multiplies in the body
Why are infectious diseases of major importance in agricultural animals?
- have an impact on the individual animal, the producer, and effect regional, national and international governing and trade policies
Examples of infectious agents
viruses, bacteria, fungi, parasites, protozoa, prions
What does it mean if an agent is contagious?
Capable of being spread from one individual to another
What are viruses?
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
Where are viruses found?
- in collections on nucleic acid, protein and some lipid
Virion
complete virus particle
What is the goal of a virus?
- 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
What is happening to viral infections that were once considered eradicated?
- they are re-emerging and are considered more virulent
How are viruses controlled and prevented?
- vaccination; but all the easy viral vaccines have been produced
- antimicrobials are not practical in livestock
- quarantine is a problem
- test and slaughter (potentially the optimal method)
- induce trade restrictions
Bacteria
- prokaryote
- doesn’t need the host cells components to survive, it can survive outside the cell
- invades host by cells or intercellular spaces
How does bacteria cause injury?
- releases exotoxins or endotoxins resulting in cell death/organ failure/ host death
How is bacteria controlled and prevented?
- vaccination but all the easy bacterial vaccines are produced
- antimicrobials are safe
- quarantine is a problem for non-reporter vaccine
- test and slaughter (seropositive animals euthanized)
- enforce trade restrictions
Fungi/Molds
- eukaryotic
- uptake nutrients from environment; a primary decomposer of dead material
- reproduces asexually and sexually
Hyphae and mycelium
Hyphae = long tubes
Mycelium = mat of hyphae
What is the primary fungi pathogen?
Cryptococcus neoformans
- affects lungs, CNS, and skin
- disseminates systemically in immune compromised ppl and other species
How can fungi/molds be prevented/controlled?
- no vaccinations
- antimicrobials can be unsafe
- not able to quarantine
- cannot test and slaughter
- trade restrictions are not really put in place
Parasites
- eukaryotes, multicellular
- endo (gut, lungs), ecto (skin) and epi (live off another parasite) parasites
- complex life cycle
Screwworm (parasite)
- 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
Life cycle of Cystic Hydatid Disease (Echinococcus sp.)
- 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
How can parasites be prevented/controlled?
- can vaccinate against some small numbers
- anthelminthics
- can’t quarantine
- can’t test and slaughter
- trade restrictions for some specific cases (ectoparasites)
