Emergency Diseases / Highly Pathogenic Avian Influenza (HPAI)

1. Emergency Diseases / Highly Pathogenic Avian Influenza (HPAI) Andre F. Ziegler, DVM, MPVM, Dip. ACPV CVM 6880, Spring 2003

2. Reportable Avian Diseases in Minnesota • Highly Pathogenic Avian Influenza • Velogenic / Exotic Newcastle Disease • Other paramyxoviruses other than ND • Infectious Laryngotracheitis • Mycoplasma infection in breeders (MG,MS and MM) • Chlamydia psittaci infection

3. Reportable Avian Diseases in Minnesota (cont.) • Avian Encephalomyelitis • Salmonella pullorum or S. gallinarum infection • S. typhimurium infection in breeders • S. enteritidis in layers • Avian tuberculosis

4. Avian Influenza • Caused by Orthomyxoviridae, type A (multiple stranded RNA virus) • Multiple spike glycoproteins— Hemagglutinin (15) Neuraminidase (9) • Viruses classified on combination of H and N types (eg. H5N2) • Recombination occurs very commonly by “shift and drift”

5. Subdivisions of virus types on basis of pathogenicity: • Nonpathogenic • Low pathogenicity • High pathogenicity • Pathogenicity determined by live bird inoculations or viral genomic sequencing analysis • Establishing viral H&N / pathotype very important in outbreak response • Birds can get all 15 H and 9 N types of type A Influenza

6. Reservoir primarily waterfowl • Co-mingling with waterfowl considered primary risk factor for introduction of viruses to domestic poultry • Range rearing • Improper “bird proofing” of houses • Waterfowl typically subclinical infections • Live bird markets where co-mingling occurs also major source of virus • Multiple species present in LBMs • Limited to non-existent full C&D of facilities • Multiple sources of birds supplying LBM system

7. LPAI vs. HPAI • Critical distinction! • LPAI = mild or no disease, not uncommon • HPAI = severe disease, rare in US • Can have high mortality with LPAI due to complicating factors, such as coliform pneumonia • LPAI can become HPAI in some cases • Occurs only with H5 and H7 types of influenza • Result of genetic changes in Hemagglutinin genetic sequence

8. LPAI vs. HPAI • LPAI conversion to HPAI has occurred several times in recent past • Pennsylvania, 1983 • Mexico, 1995 • Italy, 2001 • Pakistan, ongoing • Multiple others, undocumented / untested in numerous countries in world • Because of possible conversion of H5 and H7 LPAI to HPAI, special attention is paid to these two Hemagglutinin types

9. Avian Influenza transmission • Can persist in affected birds and flocks for months • Transmitted by most means • Easily transmitted on contaminated clothing, shoes, equipment, cages, etc.

10. HPAI-clinical signs • Clinical signs • Disease in most species of birds--in US, most in chickens and turkeys • Repiratory disease—snicking, sneezing, lacrimation, sinusitis, etc. • High mortality • Neurologic disease (in some cases) • May be sudden mortality without significant clinical signs • Change in eggshell pigmentation, shell-less eggs produced

13. HPAI-Gross Lesions • Cyanosis of face, comb, wattles • Subcutaneous hemorrhage of shanks • Periorbital / facial edema • Vesicles on comb / wattles • Sinusitis / nasal discharge • Caseous to hemorrhagic tracheitis • Hemorrhage at ventricular / proventricular junction • Vascular damage / edema & hemorrhage at numerous sites

18. Diagnosis • Serology • Many good tests available: • AGID most commonly used in US • ELISA (multiple different kits available) • HI (common in other countries) • Done at most diagnostic laboratories that do bird work in US • Antigen capture ELISA tests (several) • PCR

19. Diagnosis (cont.) • Virus isolation • Gold standard • Done in SPF chicken embryos • Needed for significant workups on samples • Good samples for VI include trachea, lung and / or cloacal swab (from affected sick or dead birds best) • Genetic sequencing / relationships may be established after virus isolation

20. Control of HPAI • Prevention of exposure to likely carriers of AIV (waterfowl, exotic pets, LBM, etc.) • Regional monitoring • Quarantine zone implementation / official notification systems in place for positive areas • If in area, depopulation within region of affected or at risk flocks

21. HPAI Control (vaccination) • Effective at limiting disease, reducing viral shed • Used successfully as adjunct to quarantine and depopulation • Special restrictions imposed on use of H5 or H7 types of antigen • Vaccines efficacy based on hemagglutinin antigen (no cross-protection)

22. Low Path AI Control • Controversial • More and more H5 and H7 LPAI depopulation programs • May depopulate entire regions and bury carcasses, rather than permit movement to slaughter • Different “rules” for turkeys vs. chickens • Different “rules” for states • Different “rules” for different industries?

23. Low Path AI Control (cont.) • New national system being developed for mandatory testing • Actions driven largely by: • Trade restrictions imposed by foreign trading partners • OIE considers vaccination for H5/H7 evidence of HPAI infection in country unless special conditions apply • Move underway for OIE to consider ANY H5/H7 tantamount to HPAI

24. Current HPAI Outbreak in EU • Began in the Netherlands on February 28, 2003 • Classified as H7N7 HPAI • Immediate culling response • Subsequent spread over Belgian border (4/15/03) • Most recently, spread from NE to Germany (5/13/03 confirmation)

25. HPAI outbreak in EU • Mid-April: multiple cases of conjunctivitis reported from workers associated with infected flocks. • Mid-April: One of company veterinarians dies following bout with pneumonia. Avian Influenza isolated from lungs, no other demonstrable causes of death

27. HPAI in EU • Approximately 250 outbreaks confirmed infected in NE, 21 million poultry destroyed • 8+ confirmed outbreaks in BE. 1.4 million poultry destroyed • Vaccination being discussed in Germany around site of infection

28. HPAI in EU • Possible infection of swine in region? • Antibody positive with serology (HI) test • No virus isolated from any of “infected” farms • False positives? Specificity limitations? • Depopulation of swine in region carried out “just in case” • Possible spread from a worker to family (secondary exposure) • Vaccination of all livestock workers in region for H7 type A influenza, antiviral therapy (Tamiflu)

29. 1] Swine in mixed herds with infected poultry are at risk for introduction of the avian influenza, subtype H7N7. 2] Swine in mixed herds with no infected poultry or swine in herds with no poultry at all are at no significant risk for introduction of the avian influenza, subtype H7N7. 3] No evidence was found for (ongoing) transmission between pigs. Most of the infections seem to be transmitted from poultry to swine, either directly or indirectly. 4] No evidence was found that the virus is able to remain for a long period in the swine herds after the removal of the source of infection, namely the infected poultry. 5] It seems most likely that no residual avian influenza virus was present in any of the swine herds tested.

30. Previous zoonotic concerns with HPAI • 1998: H5N1 HPAI circulating in Hong Kong LBM system • Mainland China widely suspected of having endemic H5 HPAI circulating • 18 associated cases of H5N1 avian influenza in humans, 6 associated deaths • First time virus recognized to move directly from fowl to humans

31. HPAI in Hong Kong (cont.) • Depopulation of Hong Kong LBM started & then reported cases ceased • End of problem? • Endemic mainland China disease? • Forthright reporting system? • Did depopulation stop worldwide pandemic?

32. Conclusions • HPAI a devastating disease, may emerge independently or from H5 or H7 LPAI • Other LPAI outbreaks may also be significant • Significant barriers to trade from affected regions • Possible zoonotic concern • Possible direct concern to other species