Canine, Equine, Avian Influenza

Question 1

What is the structure of influenza viruses?

Answer 1

• (-)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

Question 2

What are the 4 genera of Influenza viruses?

Answer 2

• A - humans birds mammals
• B - humans seals
• C - humans, pigs, dogs
• D - cattle pigs

Question 3

What is Hemagglutinin?

Answer 3

• 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

Question 4

What is Neuraminidase?

Answer 4

• Cleaves sialic acid on host cells
• Allows virus release from host cells and penetration of mucus
• 11 subtypes
• Oseltamivir (Taiflu): neuraminidase inhibitor

Question 5

How are influenza viruses named?

Answer 5

Type/creature/origin/StrainID/year isolated (H#N#)

Question 6

How does the Influenza virus evolve?

Answer 6

• 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

Question 7

What is Avian Influenza (AI)?

Answer 7

• 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”)

Question 8

What is the Avian-human species barrier?

Answer 8

• 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

Question 9

What are Low Pathogenic Avian Influenza viruses

Answer 9

• 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

Question 10

What are highly pathogenic avian influenza viruses?

Answer 10

• Arise from mutations in the cleavage sit fo the H5 and H7 hemagglutinins of LPAI viruses
• Sever systemic disease, epidemics, high mortality, sudden death
  *

Question 11

How are AIs transmitted?

Answer 11

• Direct or indirect contact with feces or respiratory secretions
  
  • Inhalation or ingestion
• between farms;
  
  • breaches in biosecurity practices

Question 12

What is the incubation period for AIs?

Answer 12

• variable
• Few days to 2 weeks
• Usually 1-7 days

Question 13

What are the results of a LPAI infection?

Answer 13

• 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

Question 14

What are the results of a HPAI infection?

Answer 14

• 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

Question 15

How is AI diagnosed?

Answer 15

• Virus detection:
  
  • oropharyngeal/cloacal swabs
  • pooled organs or feces
  • virus isolation, RT-PCR
• Antibody:
  
  • HI, AGID, or ELISA

Question 16

Is there a vaccine for AIs?

Answer 16

• requires the approval of state veterinarian
• prevents clinical signs and death
• reduces viral replication and shedding

Question 17

What is Equine Influenza Virus (EIV)?

Answer 17

• Highly contagious
• Widespread
• Caused by H3N8 equine influenza A - and H7N7 (extinct?)
• Clinical disease varies widely

Question 18

What are the clinical signs of EIV?

Answer 18

• high fever 106F
• serous nasal discharge
• submandibular lymphadenopathy
• nonproductive cough
• depression
• decreased appetite
• weakness

Question 19

What is the pathogenesis fo EIV?

Answer 19

• Virus replicates in respiratory epithelial cells:
  
  • destruction of tracheal and bronchial epithelium and cilia
  • Inflammation, hyperemia, edema, desquamation
• 3 weeks for respiratory tract epithelium to regenerate
  
  • risk for secondary bacterial infections:
    
    • mucopurulent nasal dischange, pneumonia, pleuropneumonia, chronic bronchitis

Question 20

What lesions are seen with EIV?

Answer 20

• early: Rhinitis and tracheitis with epithelial degeneration and loss of ciliated epithelium
• Late: epithelial hyperplasia and suppurative bronchopneumonia, proliferation of type II pneumocytes

Question 21

How is EIV diagnosed?

Answer 21

• Nasopharyngeal swabs:
  
  • collect soon after clinical onset
  • virus isolation, RT-PCR or ELISA
  • commercial rapid antigen detection kit
• Paired serum samples

Question 22

How is EIV treated?

Answer 22

• Non-specific: rest and supportive care
  
  • NSAIDS fever >104
  • Antibiotics if fever longer than 3-4 days, purulent nasal discharge or signs of pneumonia
• Minimize complications:
  
  • restriction of strenuous activity
    
    • min 3 weeks
  • avoid stress
  • control dust
  • provide superior ventilation
  • Environmental hygiene

Question 23

Is there a EIV vaccine?

Answer 23

• AAEP: Risk-based vaccinations
• 2 types:
  
  • Intranasal modified live virus vaccine
  • Intramuscular inactivated, adjuvanted vaccine
• duration limited - may need boosters every 6 months if high risk

Question 24

What causes Canine influenza?

Answer 24

• Influenza A H3N8 or H3N2

Question 25

How is CIV transmitted?

Answer 25

• Spread via aerosolized respiratory secretions (coughing, barking, sneezing) or contaminated fomites
  
  • virus infectious for up to 48hrs on surfaces

Question 26

What are the clinical signs of CIV?

Answer 26

• Mild form:
  
  • cough (dry/moist, 10-21 days) fever, oculonasal discharge, sneezing, lethargy, decreased appetite
• Severe form:
  
  • high fever 104-106, tachypnea, dyspnea
  • Radiographs may show evidence of pneumonia

Question 27

How is CIV diagnosed?

Answer 27

• Virus detection:
  
  • Nasal or pharyngeal swabs
  • lung and trachea if post-mortem
  • RT_PCR, Virus Isolation
• Ab detection
  
  • paired serum samples - 4x increase in titer
  • hemagglutination inhibition

Question 28

What is the treatment for CIV?

Answer 28

• most dogs recover uneventfully within 2-3 weeks
• If sever disease:
  
  • NSAIDS, fluids, antibiotics, oxygen

Question 29

What is the prognosis for CIV?

Answer 29

• Morbidity 80%
• Mortality < 10 %

Question 30

Is there CIV vaccinations?

Answer 30

• AAHA risk-based for dogs:
  
  • H3N8 - inactivated virus
  • H3N2 - inactivated virus
  • bivalent available
  • none approved for use in cats