Title: Can we improve vaccines and there use for preventing and controlling avian influenza? Author
Submitted to: World Veterinary Poultry Association
Publication Type: Abstract Only
Publication Acceptance Date: August 10, 2013
Publication Date: August 19, 2013
Citation: Swayne, D.E. 2013. Can we improve vaccines and there use for preventing and controlling avian influenza? [abstract]. Can We Improve Vaccines and their Use for Prevention and Control of Avian Influenza?. Book of Abstracts for 18th Congress for World Veterinary Poultry Association, Nantes, France, August 19-23,2013. p.69. Technical Abstract: There have been 32 epizootics of high pathogenicity avian influenza (HPAI) in birds since 1959. The largest has been the H5N1 HPAI panzootic that emerged in China during 1996 and has spread to infect poultry and/or wild birds in 62 countries during the past 17 years. The majority of the outbreaks occurred in Indonesia, Egypt, Vietnam, and Bangladesh, in decreasing order. Most recently (2011-2012), 19 countries reported outbreaks of HPAI in domestic poultry, wild birds or both with the majority of the cases being H5N1 HPAI, but HPAI outbreaks of H5N2 subtype occurred in Chinese Taipei (chickens) and South Africa (ostriches), H7N3 subtype in Mexico (egg-type chickens) and H7N7 subtype in Australia (egg-type chickens). Twenty-seven HPAI epizootics have been eradicated using traditional stamping-out programs, but beginning in 1995, five epizootics have added vaccination as an additional, interim control tool. Vaccination prevents clinical disease and mortality in poultry from HPAI, and rural livelihoods and food security were maintained. Fewer outbreaks of H5/H7 low pathogenicity avian influenza (LPAI) have been reported than HPAI. A comprehensive review of AI control methods, especially vaccines and vaccination, was completed in 2011. From 2002-2010, >113 billion doses of AI vaccine were used in poultry in 15 countries to protect from HPAI; 95.5% as oil-emulsified, inactivated whole AIV vaccines and 4.5% as live vectored vaccines. The majority of vaccine has been used in the four H5N1 HPAI enzootic countries (China [91%], Egypt [4.7%], Indonesia [2.3%], and Vietnam [1.4%]) where vaccination programs are directed to all poultry. 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 11 other countries/regions have used less than 1% of the vaccine, administered in a focused, risk-based approach. In contrast to HPAI, only six countries used vaccine in control programs for H5/H7 LPAI which accounted for 8.1% of the total H5/H7 AI vaccine usage. Field outbreaks of HPAI and H5/H7 LPAI have occurred in vaccinated flocks from both failure of the vaccines and failure in administration or immune response of the target species. 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 AI viruses. To overcome or prevent such failures, an effective AI vaccination program will require: 1) vaccine must be used in the correct type of vaccination program; 2) vaccines must contain antigenically relevant seed strain and vaccine seed strains must be changed as field virus drifts; 3) vaccine must have sufficient antigen content in each dose; 4) a minimum of two vaccinations must be administered and they should be boosted every six months of life; 5) vaccinated populations must be monitored for protective titers with a goal of greater than 80% of birds in a population being immune; and 6) vaccinated populations must have surveillance to find infections, and infected premised should have birds culled.