Highly pathogenic avian influenza (HPAI) in Hunter Valley (NSW): UPDATE

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Saturday, 17 November, 2012

H7 avian Influenza virus has been confirmed in a flock of 50,000 layer hens in the lower Hunter Valley, near Maitland, New South Wales, Australia. The property has been quarantined and the birds are being culled. DPI and the Livestock Health and Pest Authority are continuing surveillance and tracing to confirm the virus has not spread.

Additional information on this outbreak is available at the NSW Department of Primary Industries website: http://www.dpi.nsw.gov.au/aboutus/news/all/2012/avian-influenza-hunter. Control of avian influenza in commercial poultry is directed by AusVet Plan. The current guidelines (Version 3.4, 2011) are available here.

Update 24 November 2012
Additional details supplied to World Organisation for Animal Health (OIE) on 22/11/2012 - Reference OIE 12612.

Agent is influenza A H7N7.
Outbreak is at Maitland (-32.7225 151.4914) in free-range layer hens.
Outbreak commenced 9/11/2012. When notified on 15/11/2012, 5000 birds had died of a flock of 50,000. No further cases have occurred.

Control measures applied: Quarantine, stamping out (remaining 45,000 hens were destroyed), movement control (restricted area of 1 km surrounded by a control area of 9 km has been established).
Control measures to be applied: Disinfection of infected premises.

NSW DPI updated their website on 21/11/2012 to report that poultry on 12 surrounding farms have tested negative (no details given).

Comment: Good news that no further cases had been detected by 22/11/2012. H7 is endemic at low prevalence in wild birds in Australia, but as low pathogenic avian influenza (LPAI) (Haynes et al 2009). LPAI viruses are less virulent and cause a range of clinical signs in susceptible poultry, including depression, respiratory disease, a decrease in egg production and low mortality (Hamilton et al 2009). Only H5 and H7 HA subtype viruses are known to cause HPAI, but most H5 and H7 viruses are not highly virulent (Hamilton et al 2009). LPAI can mutate to HPAI (Banks et al 2001). The origin of this outbreak is suspected to be from wild ducks attracted by dams on the property.

Comment on H7N7
H7N7 is one of the types of highly pathogenic avian influenza. The current global pandemic of HPAI caused by H5N1 has not yet reached Australia. A large H7N7 outbreak in poultry started in Netherlands in 2003 and spread to Germany. It inflected many species of birds, as well as pigs and humans (Jong et al 2009). In the past Australian H7N7 has been genetically different from the European and Asian H7N7 influenza viruses (Banks et al 2000).

H7N7 is pathogenic to humans; it is a zoonosis. In the 2003 European outbreak due to H7N7 a Dutch veterinarian died and 89 laboratory confirmed cases were identified in poultry workers and their families (Koopmans et al 2004). Of the confirmed cases 26% developed conjunctivitis only, 5% had influenza-like illness (ILI) only and 9% had both.

This year conjunctivitis with no systemic or respiratory signs due to a HPAI H7N3 virus was diagnosed in poultry workers in Mexico (CDC 2012). A LPAI H7N2 virus was also identified as the cause of fever and pneumonia in an man immunocompromised by HIV/AIDS in New York (Ostrowsky et al 2012). The patient reported an initial conjunctivitis.

Message for clinicians: Think of avian influenza in a patient who presents with conjunctivitis or ILI and works or has contact with poultry (particularly if ill).

Literature cited:
Banks J, Speidel EC, McCauley JW, Alexander D. Phylogenetic analysis of H7 haemagglutinin subtype influenza A viruses. Archives of Virology 2000;145:1047–1058.
Banks J, Speidel ES, Moore E, Plowright L, et al. Changes in the haemagglutinin and the neuraminidase genes prior to the emergence of highly pathogenic H7N1 avian influenza viruses in Italy. Archives of Virology 2001;146(5):963-973.
Centers for Disease Control and Prevention (CDC). Notes from the field: Highly pathogenic avian influenza A (H7N3) virus infection in two poultry workers--Jalisco, Mexico, July 2012. MMWR Morbidity and Mortality Weekly Report 2012;61(36):726-727.
de Jong MC, Stegeman A, van der Goot J, Koch G. Intra- and interspecies transmission of H7N7 highly pathogenic avian influenza virus during the avian influenza epidemic in The Netherlands in 2003. Rev Sci Tech 2009;28(1):333-340.
Hamilton S, East I, Toribio JA, Garner M. Are the Australian poultry industries vulnerable to large outbreaks of highly pathogenic avian influenza? Australian Veterinary Journal 2009;87(5):165-174.
Haynes L, Arzey E, Bell C et al. Australian surveillance for avian influenza viruses in wild birds (July 2005 to June 2007). Australian Veterinary Journal 2009;87(7):266–272.
Koopmans M, Wilbrink B, Conyn M, Natrop G, van der Nat H, Vennema H, Meijer A, van Steenbergen J, Fouchier R, Osterhaus A, Bosman A. Transmission of H7N7 avian influenza A virus to human beings during a large outbreak in commercial poultry farms in the Netherlands. Lancet 2004;363(9409):587-593.
Ostrowsky B, Huang A, Terry W, Anton D, et al. Low pathogenic avian influenza A (H7N2) virus infection in immunocompromised adult, New York, USA, 2003. Emerging Infectious Diseases 2012;18(7):1128-1131.

Posted by Rick Speare