Animal Health 2
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- When were viruses first detected and what were they thought to be?
- 1890's, proposed as "poisons"
- When were viruses first seen and how?
- First seen in the 1930's via an electron microscope.
- What is the definition of a virus?
- Subcellular agent, consisting of a core of nucleic acid, surrounded by a protein coat that must use the metabolic machinery of a living host to replicate and produce more viral particles.
- Viruses are obligate intracellular parasites, true or false?
- True
- What size range are viruses? Are they larger or smaller than bacteria?
- 20-300nm (20-3000*10^-9) in diameter. Smaller
- What is the only type of microscope that is powerful enough to see a virus?
- electron microscope
- What is the central core made of?
- DNA or RNA, can be single or double stranded
- What is the name for the protective coat around a virus? What's it made of? What are the subuits also known as?
- Capsid; made of protein subunits called capsomeres.
- What is the core + capsid called?
- nucleocapsid
- Do all viruses have enelopes?
- No
- What does the outter covering (envelope) consist of?
- proteins, lipids, carbohydrates, and in some viruses, "spikes
- What is a virion?
- The complete, infective viral structure
- What are 6 ways of categorizing viruses?
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1. Nucleai Acid
2. Enveloped vs. Non-enveloped
3. Capsid Architecture
4. Symptoms
5. Mechanism of transmission
6 Organ system affected - What are three types of capsid architecture and an example for each?
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Helical: rabies, ebola
Polyhedral: polio, adenovirus
Complex: bacteriophage - List 6 routes of infection
- Gastrointestinal Tract, Respiratory Tract, Injection (insects, vaccines), Skin Breaks, Urogenital Tract, Conjunctiva
- Are viruses specific (ie, will only attack certein cells depending on what virus they are)?
- Yes, they are specific
- What is tissue tropism?
- Viral specificity towards its host cell type
- Give an example of tissue tropism?
- Influenza virus affects respiratory cells.
- List the steps in viral infection.
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1. Adsorption/attachment
2. Penetration and uncoating
3. Synthesis of viral proteins
4. Maturation and assembly
5. Release - Describe adsorption/attachment.
- It's the interaction b/w receptors on the surface of the host cell and the virus. It's the basis for tissue tropism. Interaction results in binding of the virus to the host cell surface.
- List the different kinds of penetration and uncoating
- Endocytosis, Fusion, Direct penetration
- Describe Endocytosis
- receptor/virus complexes are invaginated on cell surface, combine w/lysozymes that digest the viral layers & release the nucleocapsid into the cell
- Describe Fusion
- fusion of viral envelope w/cell membrane, releasing nucleocapsid into cell
- Describe direct penetration
- Direct passage of small, non-enveloped virus through cell membrane.
- What happens once the virus is inside the cell?
- It's uncoated, the capsid and envelope are removed and the viral nucleic acid is released.
- Describe the synthesis of viral proteins.
- The viral genome is transcribed by the host cell machinery, producing viral proteins
- What are two types of release (of the virus from the host cell) and describe them.
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1. Budding: enveloped viruses are released through exocytosis...the host cell survives.
2. Cell lysis: rupture of cell and release of formed virions. Cell host dies. - List 4 viral effects on the host cells.
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1. Cell lysis
2. Alteration in cell function
3. Persistent infection
4. Cell transformation - Give an example of a virus and its effect on the host cell
- Poliovirus lyses motor neurons, leading to loss of function of corresponding muscles.
- What causes the alteration in cell function?
- The viral genome incorporation into the host cell's genome causes an alteration in host cell protein synthesis.
- Give an example of how influenza virus alters it host cell
- it alters respiratory epithelium and thereby decreasesciliary activity.
- What are the three types of persistent infection?
- Latent, chronic, and slow virus infection
- Describe the qualities of a latent infection
- Virus is in equilibrium w/host. Infectious virus is not produced but its genome is present in its host cell
- Describe the qualities of a chronice infection
- Virus does cause cell death, but symptoms are subclinical
- Describe the qualities of a slow virus infection
- Long incubation period (yrs). Virus continues to multiply slowly and causes protracted tissue damage.
- Give 1 or more examples of latent infection, chronic infection, and slow virus infection
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latent= herpes, cold sores
chronic= hepatites B in human
slow= HIV & scrapie - Which persistant infection type may be affected by stress and immunosuppression and what is the result of the stress or immunosuppression?
- Latent infection; acute, intermittent flare-ups of clinical disease and virus is released and detectable during these episodes
- What happens in cell transformation by a virus?
- Viral transformation of normal cells into cancerous cells (oncogenic virus). Loss of the property of contact inhibition
- Give some examples of cell transformation
- Human carriers of hepatitis B vius are 100x more likely to develop liver cancer. Also, FeLV in cats.
- List 3 ways to diagnose a viral disease
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1. Complete history and physical exam
2. Procedures that demonstrate the presence of infectious virus
3. Serology - What must be done in getting a Complete History and Physical Exam?
- Must secure appropriate tissue samples
- What types of ways/machines are used to demonstrate the presence of infectious viruses?
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1. Electron microscopy
2. Virus isolation/culture
3. PCR (polymerase chain reaction-identifies viral DNA) - Describe virus isolation/culturing
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1. Introduction of suspected virus sample into appropriate living cell culture
2. If present, the virus will damage the culture cells, giving a visible cytopathic effect(s) (CPE)
3. CPE's will be characteristic for different viruses and culture cell - What are two things to look for during serology? (the wording may not be getting at what the answer is, but this last section was hard to do)
- Detect the presence of either viral antigen in the sample or presence of host serum antibody
- What reaction must be made visible during serology? What type of reaction is this typically?
- The reaction b/w viral Ag and host Ab: it usually is an agglutination reaction.
- What are 3 types of methods/tags used to carry out serology?
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1. Fluorescent antibody(FA)2. ELISA test (enzyme linked immunosorbent assay, "snap test")
3. HAI (haemagglutination inhibition) - What is titre?
- The concentration of serum antibody compared to a particular organism
- Give an example of titre
- Serial dilution
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Explain titre dilution results/logic??
Umm...yeah, no clue; Bree, can u think of a way to word this question better? - The greatest dilution at which a positive reaction is seen. The greater (higher) the titre, the greater (stronger) the immunity to the disease
- Is a single titre generally enough to make a diagnostic of the disease?
- No. Previous exposure, Vaccination, and exposure to similar organisms (i'm not sure what these are supposed to be, maybe other things that need to be taken into account? What do u think?)
- What is the diagnosis of the disease based on in regard to titre?
- A significant rise in titre from an initial (acute) sample to a second (convalescent) titre taken later (usually about 2 weeks)