Viro - Midterm 2

drraythe's version from 2015-08-30 21:41

Viral Families, Retroviridae

Question Answer
Enveloped or not?ENVELOPED. (Usually need direct or vertical xmission) Distinct 3 layers are visible by EM.
Explain replicationReverse transcription of virion RNA into double‐stranded DNA by reverse transcriptase w/ integration into the host chromosomal DNA (Provirus state). Retroviruses behave as a DNA virus in the sense that is quite species-specific
Diagnostics?PCR (to detect the provirus) or antibody ELISA
Vx?W/ the exception of Feline Leukemia, most Retroviral dzs do not have vaccines. Control of these cases are based on detection & removal, avoid transmission, etc
Unique things about this familySS+ diploid. Has a proviral state. Is often species-specific. Some produce TUMORS (some have v-oncogenes, others do it diff ways), others make IMMUNODEFICIENCY syndromes. All Retroviral infxns are for life either chronic or latent

Viral Families, Reoviridae

Question Answer
DNA or RNA?DS RNA, SEGMENTED → Genetic reassortment between viruses w/in genus or serogroup
Enveloped or not?NAKED
Clinical signs?Orbivirus cause serious systemic dz. Rotavirus causes diarrhea
Diagnostic tests?RT-PCR, EM, Antigen ELISA , IF & viral isolation
Vx?Vaccination is done for Orbiviruses & vaccination of the dams is done for Rotaviruses to transfer maternal antibodies that are locally protective (IgA)
Unique things?SEGMENTED!!! Orbiviruses are Arboviruses therefore their distribution is limited to the vector’s distribution. Not zoonotic, although in the same family as human stuff.

Viral Families, Paramyxoviridae

Question Answer
Enveloped or not?ENVELOPED. Characteristic herring bone nucleocapsid. Most require direct contact but indirect contact is also possible
Diagnostics?Vary by dz
Vx?Yes, for all
Unique things?Form syncytiums & intracytoplasmic & intranuclear inclusion bodies, "herring bone nucleocapsid"

Viral Families, Orthomyxoviridae

Question Answer
DNA or RNA?RNA ss- SEGMENTED! → Reassortment
Enveloped or not?ENVELOPED → large peplomers of 2 kinds:
Rod-shaped HA (hemagglutinin) which is the viral receptor
Mushroom shape NA (neuraminidase). Both HA & NA molecules are important for typing, diagnostics (antigenic or agglutinate RBCs in HA) & target of flu medications
Transmission?Transmitted by direct contact (aerosols) except for avian Influenza which is also shed in feces into the water where it survives & infects other birds
Clinical signs?In mammals Influenza virus cause respiratory dz & may cause Abortion indirectly (w/o infecting the fetus). In avian species it involves both the respiratory & GI system & in some strains cause systemic dz
Diagnostics?Laboratory tests include serology (paired samples), HI, RT-PCR, viral isolation & in most cases virulence need to be determined
Vx?Vaccines are available but need to be constantly modified as these viruses quickly evolve. Vaccines are not always used
Unique things?Avian & swine Influenza viruses are Zoonotic & notifiable. Segmented → REASSORTMENT. 2 kinds of peplomers → RODS (hemagglutination) MUSHROOM (neuraminidase). Had to make vx for segmented constantly evolving things

Viral Families, Picornaviridae

Question Answer
Enveloped or not?NAKED → resistant
Clinical signs?Different genus behave differently. Some will affect the mucosas while others will affect the myocardium, the liver or the CNS
Diagnostics?Antigen ELISA & RT-PCR are mostly used followed by viral isolation & antibody ELISA which require more time & may not be useful in urgent diagnosis situations
Vx?Vaccines are available but the high mutation rates of these viruses require constant vaccine development
Unique things?NOTIFIABLE & ZOONOTIC! High mutation rate makes vx's difficult

Viral Families, Rhabdoviridae

Question Answer
DNA or RNARNA SS- Replicates in the cytoplasm & has ****intracytoplasmic inclusion bodies (Negri bodies)***
Enveloped or not?Enveloped, spiky projections.
Diagnosis?Diagnosis also depend on the genus. DFA, RT-PCR & culture for Rabies, serology can also be used for other genus
Unique things?THIS. IS. RABIEESSSS! ****intracytoplasmic inclusion bodies (Negri bodies)***, EXTREMELY wide host range for Rabies. Vesicular stomatitis & Rabies are notifiable dzs

Viral Families, Caliciviridae/ Arteriviridae

Question Answer
Calici- DNA or RNA?RNA, SS+
Calici- enveloped or not?Naked.
Calici- vx?Yes
Art- enveloped or not?Enveloped, BUT although enveloped, can be transmitted both directly & indirectly. There is sexual & vertical transmission
Art- clinical signs?Cause respiratory dz & Abortions


Question Answer
What are Prions?INFECTIOUS PROTEINS, not viruses
What are the diffs between Prions & normal proteins? What is their interaction?Difference in conformational changes (folded different). If a normal protein touches a Prion, its folding gets messed up too & it also becomes pathogenic
How can you tell the diff between a norm protein & a Prion, when they share the same amino acid sequence?There is a monoclonal antibody that can distinguish the two (conformational epitope).
How come Prions accumulate? What is this called? What is the result of all of this?They are resistant to endogenous proteases! This leads to accumulation into aggregates called Scrapie associated fibrils (SAF) that form plaques which cause spongiform damage & neuronal dysfunction
How would you disinfect a Prion? Is it easy?Prions are also very resistant to heat, UV radiation & chemicals. Autoclaving at 132ºC for 90 min, 1 M NaOH & phenol extraction are the most effective methods of reducing its infectivity
What are the clinical signs of Prions?Prions have a long incubation period & clinical signs vary from behavior, pruritus, emaciation, tremors, paralysis, etc.... NO INFLAMMATION, NO IMMUNE RESPONSE!
Important thing to know about a Prion infxn (in terms of host response)NO INFLAMMATION, NO IMMUNE RESPONSE
How do you diagnose Prions?Diagnosis is based on histopathology, IHC & WB of the brain & cannot be confirmed until postmortem

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