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39 Cards in this Set
- Front
- Back
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What is the symmetry of Orthomyxoviridae?
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Helical
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Does Orthomyxoviridae have an envelope?
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Yes
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What special features does Orthomyxoviridae have?
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segmented RNA (8)
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What is the important Genus of Orthomyxoviridae?
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Influenzavirus A
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What are the subtypes of the influenza A virus?
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H7N7 - Horse
H3N8 - Horse, Dog H1N1, H3N2 - Pig, Human H5N1 - Cat |
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In Influenza, what does the H stand for?
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Hemagglutinin
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In Influenza, What does the N stand for?
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Neuraminidase
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What is the reservoir for Influenzavirus A and what type of infection does it cause?
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migratory waterfowl like ducks and geese shed the virus in their feces, causing GI tract infections
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How does Hemagglutinin (HA) work?
(Activation of virus) |
Binds sialic acid residues --> receptor-mediated endocytosis
membrane fuses with endosome, influx of protons activates virus RNA replicates in the nucleus |
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Nomenclature of Influenza
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Virus type (A/B/C)
Origin Strain # Year isolated Virus subtype |
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Structure of Influenza A
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Medium size
Spherical/filamentous Enveloped with spikes Matrix protein with trimers and tetramers gives it its shape |
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What are 3 methods of capping viral RNA?
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1. Use of cellular capping machinery
2. Viral coding capping machinary 3. Cap snatching |
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Function of 5* cap
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Protect mRNA from degradation by ribonucleases
Pre-mRNA splicing; direct mRNA export from nucleus Recognition of mRNA for translation An uncapped mRNA is detected as "non-self" and an immune response is triggered |
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How does cap snatching occur? How do antivirals target this?
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Cleavage of cellular capped mRNA; capped fragment serves as primer for mRNA synthesis
Drugs are developed that block the polymerase, thus blocking cap snatching |
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What are the 3 mechanisms of genetic variation of influenza virus?
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1. point mutations
2. genetic reassortment 3. genetic recombination |
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What is a point mutation? Why do they occur?
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A random change in single nuclueotide
They occur due to a lack of proofreading of RNA polymerase Multiple point mutations needed for a new strain, and passage through multiple hosts necessary |
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What is genetic recombination?
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Swapping of small regions of gene segments
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What is genetic reassortment?
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Swapping of entire gene segments
Mixed infection is necessary |
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What horses does Equine influenze virus infect?
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Affects young horses 2-6 months
Causes mild respiratory disease with high morbidity |
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How is Equine influenza diagnosed?
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history
HI ELISA virus isolation human influenza A test kits |
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How is Equine Influenza virus controlled?
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isolation of new horses
quarantine of infected horses vaccination (H3N8 and H1N7) for short term immunity |
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What subtype is canine influenza and where did it come from?
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H3N8 (equine influenza)
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What dogs are susceptible to Canine Influenza?
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All dogs. High morbidity (80%) but low mortality (1-5%)
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What are the clinical signs of Canine Influenza?
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Fever, nasal discharge
mild - severe resp disease can be mistaken for kennel cough |
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How is Canine Influenza diagnosed?
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HI
PCR virus isolation (often negative) Flu antigen ELISA kit |
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How is canine influenze controlled?
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cleaning/disinfection
quarantine inactivated vaccine will decrease duration, severity and viral shedding |
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What illnesses are associated with Feline Influenza virus?
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Fatal H5N1 infections in domestic cats and zoo felids fed virus-infected chickens
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What are the symptoms of feline influenza virus?
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diffuse alveolar damage
death |
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How is feline influenza virus transmitted?
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horizontal transmission
human to cat transmission high mortality rate but no human-human transmission |
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What illness does Swine influenza cause?
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acute, contagious respiratory disease of pigs
*transmissible to people!* |
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What are the clinical signs of Swine influenza in pigs?
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fever, nasal discharge, coughing, dyspnea
high morbidity Rapid recovery (5-7 days) May see bronchopneumonia or interstitial pneumonia |
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How is Swine influenza diagnosed?
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history
H1N1/H3N2 ELISA virus isolation HI |
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How is Swine influenza controlled?
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management
reduce stress vaccination |
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What illness is caused by avian influenza?
*REPORTABLE!* |
contagious respiratory and systemic disease
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What species are mainly infected by avian influenza?
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chickens and turkeys
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What are the signs of the low pathogenic strain of avian influenza?
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sneezing, coughing, sinusitus
may be subclinical decreased egg production low morbidity/mortality |
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What are the signs of the high pathogenic strain of avian influenze (fowl plague)?
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severe systemic disease
high mortality (90-100%) mutation from LPAI hemorrhage and edema cyanosis of combs and wattles involves respiratory, digestive, and urogenital systems +/- CNS signs sudden death |
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How is avian influenza diagnosed?
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clinical signs
AGID basic screening test ELISA HI virus isolation PCR Reportable disease |
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How is avian influenza prevented/controlled?
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Vaccination
Routine disease surveillance Quarantine Depopulation Disinfection |
