|DEJESUS, ERIC - Orise Fellow|
|COSTA-HURTADO, MAR - Orise Fellow|
|DAUPHIN, GWENAELLE - Food & Agriculture Organization (FAO)|
|TRIPODI, ASTRID - Food & Agriculture Organization (FAO)|
Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/16/2015
Publication Date: 3/15/2016
Publication URL: http://handle.nal.usda.gov/10113/62194
Citation: Pantin Jackwood, M.J., Kapczynski, D.R., Dejesus, E., Costa-Hurtado, M., Dauphin, G., Tripodi, A., Dunn, J.R., Swayne, D.E. 2016. Efficacy of a recombinant turkey herpesvirus H5 vaccine against challenge with H5N1 clades 1.1.2 and 184.108.40.206 highly pathogenic avian influenza viruses in domestic ducks (Anas platyrhynchos domesticus). Avian Diseases. 60:22-23.
Interpretive Summary: Domestic ducks play an important role in the spread of H5N1 highly pathogenic avian influenza (HPAI). In this study, the efficacy in ducks of a live recombinant vector vaccine based on a turkey herpesvirus (HVT) expressing the H5 gene from an H5N1 HPAIV (rHVT-H5) was examined. The vaccine was given alone or in combination with an inactivated H5N1 vaccine. After vaccination, all ducks were challenged with one of two H5N1 HPAI viruses. These viruses produced 100% mortality in non-vaccinated control ducks. The rHVT-H5 vaccine alone conferred 30% protection against mortality after challenge with either H5N1 HPAI virus, and surviving ducks from these groups shed virus for longer than the ducks vaccinated only with the inactivated vaccine. A booster effect was found on reduction of virus shedding when using both vaccines. However, presence of HVT and rHVT-H5/2.2 vaccine in several duck tissues was not detected, indicating minimal levels of viral replication. In conclusion, these studies demonstrate the suboptimal protection with the rHVT-H5/2.2 vaccine given alone in ducks against H5N1 HPAI viruses, but additive effect on virus shedding reduction when used with an inactivated vaccine.
Technical Abstract: The Goose/Guangdong (Gs/GD)-lineage H5N1 highly pathogenic avian influenza (HPAI) viruses continue to circulate and cause great economic losses in poultry in Asia, the Middle East, and Africa. Recently, the Gs/GD-lineage H5N8 HPAI virus belonging to clade 220.127.116.11 and its reassortants have caused outbreaks in poultry in Europe and North America (7,24). These viruses, similar to the H5N1 HPAI viruses, can be spread by wild waterfowl. In Asia, free-range and nomadic domestic duck flocks play a major role in perpetuating the H5N1 HPAI virus in agricultural systems and have been associated with disseminating viruses between premises (4,5,6,20). Domestic ducks are also common backyard poultry in many countries and thus frequently in contact with wild waterfowl. Given the widespread infection of waterfowl with H5N1 HPAI viruses in certain parts of the world, reducing the risk of virus infection in domestic ducks is considered crucial for controlling the spread of H5N1 HPAI virus (16). Vaccination can decrease infection rates and reduce viral shedding among infected animals, especially when enforcement of enhanced biocontainment measures is impractical (21). Present vaccination schemes are not suitable for current extensive production duck practices prevailing in South East Asia, thus the need for more effective H5N1 vaccines and alternate vaccination strategies, such as hatchery-based vaccination. However, there is insufficient information on the effectiveness of H5N1 HPAI vaccination in domestic duck species to guide disease control programs. The objective of this study was to examine the efficacy of a commercial live recombinant vector vaccine based on a turkey herpesvirus (HVT) expressing the H5 gene from a hemagglutinin (HA) clade 2.2 H5N1 HPAI virus, an inactivated H5N1 reverse genetic (rg) vaccine based on the HA clade 18.104.22.168 Chinese seed strain (similar to the Chinese Re-6 vaccine), or both, in protecting Pekin ducks (Anas platyrhynchos domesticus) from challenge with recent HA clades 1.1.2 and 22.214.171.124 H5N1 HPAI viruses.