AI: type of virus
Orthomyxoviridae
- enveloped, segmented, ssRNA virus
- 2 surface glycoproteins: H and N
- HA is the major viral antigen
Antigenic drift
Result of point mutations accumulated during AIV replication
-requires incorporation of emerging strains in current vaccines
Antigenic SHIFT
Reassorted AIV emerges when 2 different sub-types infect the same host
-new reassortants may allow for the infection of different host species
Distr. of AI
Worldwide
Recently: netherlands, Australia, SE Asia, Eurasia, Nigeria, Egypt, Germany, Mexico, US
Pathology of AI
(Similar to NCD)
Transmission of AI
- migratory waterfowl are main reservoirs
- once in poultry flocks, virus spreads by mvmt of infected poultry, secretions, excretion, contaminated equipment, airborne, or garbage flies
- juvenile Mallard ducks have the highest isolation rate (60% in late summer)
CS of LPAI
(Varies by age, species, and virus virulence)
- resp. Signs: cough, sneeze, wheeze, tears, sinus swelling
- dec. egg production, wt. loss
- depression, anorexia
Major site of HPAI virus replication
Nasal cavity
Pathogenesis of HPAI
1) Infection via inhalation/ingestion
2) virus replicates in nasal cavity
3) enzymes cleave virus HA
4) virus invades sub-mucosa and damages vascular endothelium
5) virus replicates systemically
6) multiple organ failure and death
CS of HPAI
- sudden death (>90%) 2-12 days after first signs
- head edema, comb/wattle cyanosis, hemorrhage
Post-mortem lesions of HPAI
- sometimes none if death was sudden
- severe congestion of muscles
- SC edema of head/neck
- extensive hemorrhage and/or plugs in trachea
- multifocal hemorrhages
Is LPAI reportable to OIE?
Yes (used not to be)
There is also mandatory pre-slaughter testing in breeding birds, commercial turkeys, broilers, and flocks with respiratory signs
Most costly animal diease in the US ever
avian influenza ($3 billion est. cost for 2014-2015 outbreak, with >48 million turkeys and hen layers destroyed)
Top ddx for AI**
Velogenic exotic newcastle disease (clinically indistinguishable)
Others:
Avian infectious laryngotracheitis
Avian infectious bronchitis
Acute bacterial diseases (Fowl cholera, E. Coli infection)
Dx of AI
- virus isolation (ie. in allantoic cavity of embryonated hen’s eggs)
- all infections are reportable and of zoonotic potential
Vax for AI
None licensed in the US!
Pathophys. Of duck viral enteritis
- acute infectious and highly contagious dz of ducks, geese, swans
- caused by Alphaherpesvirus
- induces vascular damage and hemorrhages
- can be immunosuppressive –> secondary infections
2ary infections common with duck viral enteritis
- Pasteurella
- Riemerella anapestifer
- E. Coli (esp. In ducklings)
Trans. Of duck viral enteritis
- direct contact with infected wild ducks
- contaminated env.
- contaminated water**
Incubation period of duck viral enteritis
3-7 days
CS of duck viral enteritis
Outstretched drooped wings, difficulty standing up, ducks die 1-5 days later
-morbidity and mortality persists: dropped egg production, prolapsed phalluses in mature males, inappetence, ataxia, thirst, nasal dc, half-closed eyelids, soiled vents, watery diarrhea
Gross path of duck viral enteritis
- evidence of DIC
- necrotic GIT, lymphoid tissue
- hemorrhages throughout body (esp. Liver, heart, pancreas, mesentery) with free blood in cavities
- annular bands of hemorrhage correspond to areas of necrosis and hemorrhage of GALT
Dx of duck viral enteritis
- Presumptive based on Hx, lesions
- Definitive dx requires virus isolation with IFA or duck embryo liver cell cultures, or virus ID with PCR
Best tissues for virus isolation or ID of duck viral enteritis
Liver, spleen, esophagus, small intestines
Ddx for duck viral enteritis
Duck viral hepatitis
Pasteurellosis
Necrotic/hemorrhagic enteritis
Tx of duck viral enteritis
- None
- avoid contact with wild birds
- annual vaccine in use for small flocks (not used commercially)
- no tx approved for wild ducks
