Canine, Equine, Avian Influenza Flashcards
1
Q
What is the structure of influenza viruses?
A
- (-)ssRNA
- enveloped
- 8 segments - ~14kb
- Classified based on hemagglutinin (16+2) and neuraminidase (9+2): spike-like proteins that project from the surface; important for cell entry and targets for neutralizing Abs
2
Q
What are the 4 genera of Influenza viruses?
A
- A - humans birds mammals
- B - humans seals
- C - humans, pigs, dogs
- D - cattle pigs
3
Q
What is Hemagglutinin?
A
- Binds to sialic acid receptors on hos cells
- Allows virus entry into cells
- 18 subtypes (H1-H18)
- high rate of mutation
- Target of neutralizing Abs (vaccines
- dominant Ag recognized by the immune system
4
Q
What is Neuraminidase?
A
- Cleaves sialic acid on host cells
- Allows virus release from host cells and penetration of mucus
- 11 subtypes
- Oseltamivir (Taiflu): neuraminidase inhibitor
5
Q
How are influenza viruses named?
A
Type/creature/origin/StrainID/year isolated (H#N#)
6
Q
How does the Influenza virus evolve?
A
- Antigenic drift:
- subtle point mutations & small changes that occur gradually over time
- driven by RNA polymerase and hose immune system
- Affects antigenic sits in HA and NA
- Ab no longer fully protective
- Reason for seasonal flue changes
- does NOT usually result in pandemics
- Genetic Reassortment:
- Allows rapid major changes in the genetic make-up of influenza viruses (antigenic shift)
- Exchange of gene segments
- Results in subtype change
- Can cause pandemics
7
Q
What is Avian Influenza (AI)?
A
- Caused by influenza type A viruses (IAVs)
- Natural reservoir is aquatic birds
- Classified by 2 proteins;
- Hemagglutinin
- Neuraminidase
- differnt combos creat different subtypes
- Classified by pathogenicity based on the ability of a particular strain to produce disease in domestic poultry
- Low pathogenic avian influenza viruse (LPAIV)
- Highly pathogenic avian influenza virus (HPAIV; “fowl plague”)
8
Q
What is the Avian-human species barrier?
A
- Avian influenza viruses prefer a2-3 sialic acid receptors
- respiratory and GI tract of birds
- Human influenza viruses prefers a26 sialic acid receptors
- upper respiratory
- a2-3 in lower respiratory
9
Q
What are Low Pathogenic Avian Influenza viruses
A
- Worldwide distribution
- Subclinical, respiratory signs, reduced egg production
- frequently recovered from clinically normal shorebirds and migrating waterfowl
- found in backyard flocks, live-poulty markets
- Most commercial poulty are free
10
Q
What are highly pathogenic avian influenza viruses?
A
- Arise from mutations in the cleavage sit fo the H5 and H7 hemagglutinins of LPAI viruses
- Sever systemic disease, epidemics, high mortality, sudden death
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11
Q
How are AIs transmitted?
A
- Direct or indirect contact with feces or respiratory secretions
- Inhalation or ingestion
- between farms;
- breaches in biosecurity practices
12
Q
What is the incubation period for AIs?
A
- variable
- Few days to 2 weeks
- Usually 1-7 days
13
Q
What are the results of a LPAI infection?
A
- Subclinical
- respiratory signs: sneezing, coughing, ocular and nasal discharge, swollen infraorbital sinuses
- Lesions: sinusitis, congestion and inflammation of the trachea and lungs
- Layers/breeders: 5-30% decrease in egg production, reduced fertility, ova rupture or involution, mucosal edema and exudate in oviduct lumen
- Low morbidity and low mortality
14
Q
What are the results of a HPAI infection?
A
- severe systemic disease with high mortality
- morality can approach 100% within days
- Peracute form: sudden death with no premonitory signs
- Acute:
- Cyanosis and edema of the head, comb, wattle
- Edema and red discoloration of the lower limbs and feet due to subcutaneous ecchymosis
- Petechia in visceral organs and muscles
- Blood-tinged oral and nasal discharge
- Green colored diarrhea
- CNS signs: torticollis, opisthotonos, incoordination, paralysis, drooping wings
- Gross lesions: variable - edema, hemorrhage and necrosis in visceral organs, skin and CNS
15
Q
How is AI diagnosed?
A
- Virus detection:
- oropharyngeal/cloacal swabs
- pooled organs or feces
- virus isolation, RT-PCR
- Antibody:
- HI, AGID, or ELISA
