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H7N9 Avian Influenza: What You Need to Know, Not Fear

H7N9 Avian Influenza: What You Need to Know, Not Fear. Nathaniel L. Tablante , DVM, MPVM, MS, DACPV Associate Professor and Extension Poultry Veterinarian VA-MD Regional College of Veterinary Medicine University of Maryland College Park 8075 Greenmead Drive College Park, MD 20742

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H7N9 Avian Influenza: What You Need to Know, Not Fear

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  1. H7N9 Avian Influenza: What You Need to Know, Not Fear Nathaniel L. Tablante, DVM, MPVM, MS, DACPV Associate Professor and Extension Poultry Veterinarian VA-MD Regional College of Veterinary Medicine University of Maryland College Park 8075 Greenmead Drive College Park, MD 20742 Tel 301-314-6810 Fax 301-314-6855 nlt@umd.edu www.who.int

  2. Outline • Introduction • Avian influenza (AI): definition and classification • Sources of AI virus • Types of AI in domestic poultry • Incubation and survival of AI virus • Modes of transmission • Mutation and Reassortment • Antigenic Drift/Shift • Avian Influenza Infections in Humans • Flu Pandemics • Prevention of AI in Humans

  3. What is Avian Influenza (AI)? • Avian influenza (AI) is an infectious, viral disease of birds caused by several subtypes of the type A strain of the influenza virus • Avian influenza viruses usually do not infect humans but several cases of human infection have been reported since 1997

  4. Influenza A virus host range is polygenic a2-6Gal a2-3Gal a2-3Gal a2-6Gal a2-3Gal a2-6Gal (Perez, 2006)

  5. Classification • Influenza viruses are subtyped according to surface glycoproteins: hemagglutinin(HA) and neuraminidase (NA) • Currently, there are 16 hemagglutinins (H1 to H16) and 9neuraminidases (N1 to N9) • 144 possible sub-types • Hemagglutininattaches the virus to the surface of the host cell so the virus can replicate • Neuraminidase lets the newly replicated viruses out of the cell to infect more cells http://micro.magnet.fsu.edu/cells/viruses/influenzavirus.html

  6. Where does AI virus come from? • All known subtypes of influenza A viruses circulate among wild birds, especially migratory waterfowl (e.g. ducks and geese) which are considered natural reservoirs for influenza A viruses • Domestic poultry like chickens and turkeys are not natural reservoirs for AI virus and usually develop clinical disease when infected with AI virus

  7. What are the types of Avian Influenza in domestic poultry? • Low pathogenic avian influenza (LPAI) • mild or no clinical signs • low to moderate mortality • However, the low pathogenicH5 and H7strains are capable of mutating under field conditions into highly pathogenic strains • Highly pathogenic avian influenza (HPAI) • sudden onset • severe clinical signs • high mortality

  8. Low Pathogenic AI Highly Pathogenic AI

  9. What is the incubation period? • Usually 3 to 7 days • Depends on: • strain of virus • dose of inoculum • age and immune status of bird • management and environmental factors

  10. How long can AI virus survive? • AI virus is shed in feces for 7 to 14 days after infection • AI virus can survive in manure for up to 105 days especially with high moisture and low temperature • 1 gram of contaminated manure can infect 1 million birds • 1 gram of manure will cover the surface of a dime

  11. How does AI virus spread? • Exposure of poultry to migratory waterfowl

  12. How does AI virus spread? • Exposure of commercial poultry to AI-infected backyard, gamebird, or hobby flocks

  13. How does AI virus spread? • Contact with AI-infected live bird markets Dr. S. Trock Dr. S. Trock

  14. How does AI virus spread? • Bird to bird contact (through feces) • Aerosol droplets

  15. How does AI virus spread? • Manure, equipment, vehicles, egg flats, crates, contaminated shoes and clothing

  16. How does AI virus spread? • Wildlife vectors/scavengers Photos courtesy of G. Malone University of Delaware

  17. How do humans get infected with H7N9? • Mainly through direct contact with infected poultry • When people sell or slaughter and consume infected birds • Exposure during slaughter, defeathering, butchering, and preparation of poultry for cooking • So far, evidence suggests that the source of H7N9 virus is poultry and live bird markets and the most likely route of transmission from poultry to humans www.cnn.com www.terradaily.com

  18. Why should we be concerned about H7N9? • H7N9 has not been previously reported in humans • No background or pre-existing immunity • H7N9 is more easily transmissible from poultry to humans than H5N1 • However, unlike H5N1 infections, poultry infected with H7N9 appear healthy

  19. How do AI viruses change or mutate? • Antigenic Drift • Occurs through small changes in the virus that happen continually over time • Produces new virus strains that may not be recognized by antibodies to earlier influenza strains • Antigenic Shift • An abrupt, major change in influenza A viruses, resulting in a new influenza virus that can infect humans (one that has not been seen in humans for many years)

  20. Mutation and Reassortment 1 1. Mutation AVIAN virus HUMAN virus 2. Reassortment Reassortant HUMAN- AVIAN virus Dr. R. Schieber, CDC

  21. Mutation and Reassortment 2 1. Mutation AVIAN virus HUMAN virus 2. Reassortment Reassortant HUMAN- AVIANvirus Dr. R. Schieber, CDC

  22. Can H7N9 spread from person to person? Avian flu Human flu • The spread of infection in birds increases the opportunities for direct infection of humans • Humans concurrently infected with human and avian influenza strains could serve as a “mixing vessel” for the emergence of a novel subtype with sufficient humans genes that can be transmitted from person to person • However, the virus has not yet developed the ability to pass easily from human to human Novel flu subtype

  23. Avian Influenza Infections in Humans • 1997: Hong Kong (HPAI H5N1) • Infected chickens and humans • 18 sick (6 died) • Spread primarily from birds to humans • Person-to-person infection noted but rare • 1.5 million chickens destroyed yaleglobal online

  24. Avian Influenza Infections in Humans • 2003: China andHong Kong (HPAI H5N1) • Occurred among members of a Hong Kong family that had traveled to China • 1 person recovered, another died • Another family member in China died • Origin unknown

  25. Avian Influenza Infections in Humans • 2003: Netherlands (HPAI H7N7) • Occurred among poultry workers and their families during an AI outbreak in poultry • 89 cases reported (mostly conjunctivitis and some respiratory signs) • 1 veterinarian died from acute respiratory infection • Most cases occurred due to direct contact with infected poultry

  26. Avian Influenza Infections in Humans • 2013: China (H7N9) • 126 cases (24 deaths) as of 29 April 2013 ecdc.europa.eu

  27. 1918-19 Spanish Flu (H1N1) • 20-50 million infected worldwide • >500,000 deaths U.S. • 1957-58 Asian Flu (H2N2) • 70,000 deaths U.S. • 1968-69 Hong Kong Flu (H3N2) • 50,000 deaths U.S. • 2009-2010 Swine Flu (H1N1) • 60 million infected worldwide • 18,000 deaths Pandemics are rare but deadly

  28. Can another pandemic happen again? • Only when three conditions have been met: • a new influenza virus subtype emerges • it infects humans, causing serious illness • it spreads easily and sustainably among humans* *has not yet occurred with H7N9 or H5N1 http://en.wikipedia.org/wiki/File:Spanish_flu_victims_burial_North_River_Labrador_1918.JPG

  29. What can we do to prevent AI in humans? • Practice normal hygienic precautions • Wash hands with soap and water for 15-20 seconds • Cover your mouth when you cough or sneeze • Get vaccinated for seasonal flu • Stay home and rest if you have the flu • Practice “social distancing” if there is a flu outbreak • Avoid live bird markets

  30. Questions?

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