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Title: Avian influenza: worldwide situation and effectiveness of current vaccines

item Swayne, David

Submitted to: International Seminar of Avian Pathology
Publication Type: Proceedings
Publication Acceptance Date: 3/10/2014
Publication Date: 3/24/2014
Citation: Swayne, D.E. 2014. Avian influenza: worldwide situation and effectiveness of current vaccines. In: Proceedings of the XIII International Seminar of Avian Pathology and Production, March 24-28, 2014, Athens, Georgia. 2014 CDROM.

Interpretive Summary:

Technical Abstract: The H5N1 high pathogenicity avian influenza (HPAI) virus emerged in China during 1996 and has spread to infect poultry and/or wild birds in 63 countries during the past 18 years. The majority of the recent outbreaks of H5N2 HPAI have occurred in Indonesia, Egypt, Vietnam, and Bangladesh, in decreasing order. The majority of the cases were H5N1 HPAI but outbreaks of H5N2 occurred in Chinese Taipei (chickens) and South Africa (ostriches), an outbreak of H7N3 HPAI in Mexico (egg-type chickens), an outbreak of H7N7 HPAI in Australia (free range layers), an outbreak of H7N2 HPAI in Australia (free range chickens and layers) and an outbreak of H5N8 HPAI in South Korea (breeder and meat ducks). Field outbreaks of H5N1 HPAI have occurred in vaccinated flocks from both failure of the vaccines (i.e. vaccine efficacy) and failure in administration or immune response of the target species (i.e. vaccination effectiveness). Antigenic drift in field viruses has resulted in failure of protection by classic H5 vaccines strains in Mexico, China, Egypt, Indonesia, Hong Kong and Vietnam. This challenge has been met by developing new vaccine strains that provide protection against ever changing HPAI viruses. A comprehensive review of AI control methods by World Organization for Animal Health has been completed. From 2002-2010, >113 billion doses of AI vaccine were used in poultry in 15 countries. The majority of vaccine (>91%) was used in China while significant amounts were used in Egypt, Indonesia, and Vietnam. Implementation of vaccination in these four countries occurred after H5N1 HPAI became endemic in domestic poultry and vaccination did not result in the endemic infections. The other 11 countries used less than 1% of the vaccine. Inactivated AI vaccines accounted for 95.5% and live recombinant virus vaccines for 4.5% of vaccine used. Clinical disease and mortality were prevented in chickens, and rural livelihoods and food security were maintained by using vaccines during HPAI outbreaks. Fewer outbreaks of Low pathogenicity notifiable avian influenza (LPNAI) have been reported than HPAI and only six countries used vaccine in control programs which accounted for 8.1% of the total H5/H7 AI vaccine usage. Stamping-out without vaccination has been the preferred method for HPAI control and eradication used successfully in 27 HPAI epizootics.