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39 Cards in this Set

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What is the symmetry of Orthomyxoviridae?
Helical
Does Orthomyxoviridae have an envelope?
Yes
What special features does Orthomyxoviridae have?
segmented RNA (8)
What is the important Genus of Orthomyxoviridae?
Influenzavirus A
What are the subtypes of the influenza A virus?
H7N7 - Horse
H3N8 - Horse, Dog
H1N1, H3N2 - Pig, Human
H5N1 - Cat
In Influenza, what does the H stand for?
Hemagglutinin
In Influenza, What does the N stand for?
Neuraminidase
What is the reservoir for Influenzavirus A and what type of infection does it cause?
migratory waterfowl like ducks and geese shed the virus in their feces, causing GI tract infections
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
Nomenclature of Influenza
Virus type (A/B/C)
Origin
Strain #
Year isolated
Virus subtype
Structure of Influenza A
Medium size
Spherical/filamentous
Enveloped with spikes
Matrix protein with trimers and tetramers gives it its shape
What are 3 methods of capping viral RNA?
1. Use of cellular capping machinery
2. Viral coding capping machinary
3. Cap snatching
Function of 5* cap
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
How does cap snatching occur? How do antivirals target this?
Cleavage of cellular capped mRNA; capped fragment serves as primer for mRNA synthesis

Drugs are developed that block the polymerase, thus blocking cap snatching
What are the 3 mechanisms of genetic variation of influenza virus?
1. point mutations
2. genetic reassortment
3. genetic recombination
What is a point mutation? Why do they occur?
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
What is genetic recombination?
Swapping of small regions of gene segments
What is genetic reassortment?
Swapping of entire gene segments
Mixed infection is necessary
What horses does Equine influenze virus infect?
Affects young horses 2-6 months
Causes mild respiratory disease with high morbidity
How is Equine influenza diagnosed?
history
HI
ELISA
virus isolation
human influenza A test kits
How is Equine Influenza virus controlled?
isolation of new horses
quarantine of infected horses
vaccination (H3N8 and H1N7) for short term immunity
What subtype is canine influenza and where did it come from?
H3N8 (equine influenza)
What dogs are susceptible to Canine Influenza?
All dogs. High morbidity (80%) but low mortality (1-5%)
What are the clinical signs of Canine Influenza?
Fever, nasal discharge
mild - severe resp disease
can be mistaken for kennel cough
How is Canine Influenza diagnosed?
HI
PCR
virus isolation (often negative)
Flu antigen ELISA kit
How is canine influenze controlled?
cleaning/disinfection
quarantine
inactivated vaccine will decrease duration, severity and viral shedding
What illnesses are associated with Feline Influenza virus?
Fatal H5N1 infections in domestic cats and zoo felids fed virus-infected chickens
What are the symptoms of feline influenza virus?
diffuse alveolar damage
death
How is feline influenza virus transmitted?
horizontal transmission
human to cat transmission
high mortality rate but no human-human transmission
What illness does Swine influenza cause?
acute, contagious respiratory disease of pigs

*transmissible to people!*
What are the clinical signs of Swine influenza in pigs?
fever, nasal discharge, coughing, dyspnea
high morbidity
Rapid recovery (5-7 days)
May see bronchopneumonia or interstitial pneumonia
How is Swine influenza diagnosed?
history
H1N1/H3N2 ELISA
virus isolation
HI
How is Swine influenza controlled?
management
reduce stress
vaccination
What illness is caused by avian influenza?

*REPORTABLE!*
contagious respiratory and systemic disease
What species are mainly infected by avian influenza?
chickens and turkeys
What are the signs of the low pathogenic strain of avian influenza?
sneezing, coughing, sinusitus
may be subclinical
decreased egg production
low morbidity/mortality
What are the signs of the high pathogenic strain of avian influenze (fowl plague)?
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
How is avian influenza diagnosed?
clinical signs
AGID basic screening test
ELISA
HI
virus isolation
PCR
Reportable disease
How is avian influenza prevented/controlled?
Vaccination
Routine disease surveillance
Quarantine
Depopulation
Disinfection