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United States Department of Agriculture

Agricultural Research Service

Research Project: Intervention Strategies to Control and Prevent Disease Outbreaks Caused by Avian Influenza and Other Emerging Poultry Pathogens

Location: Exotic and Emerging Avian Viral Diseases Research Unit

Title: Suboptimal protection against highly pathogenic avian influenza (H5N1) viruses from Vietnam in ducks vaccinated with commercial poultry vaccines

Authors
item Cha, Ra Mi
item Smith, Diane
item Shepherd, Eric
item Donis, Ruben -
item Nguyen, Tung -
item Suarez, David
item Pantin-Jackwood, Mary
item Nguyen, Hoang -
item Do, Hoa -
item Inui, Ken -
item Swayne, David

Submitted to: Virology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 13, 2013
Publication Date: N/A

Interpretive Summary: Domestic ducks have been recognized as one of the primary factors in the spread of highly pathogenic (HP) H5N1 avian influenza (AI) viruses. These viruses continue to be a threat to poultry around the world. In this study, we examined the efficacy of two vaccines used in Vietnam to H5N1 HPAI in ducks. Three experiments were conducted using the commercial inactivated Re-1 and Re-5 vaccines to vaccinate ducks. Ducks were then challenged with H5N1 HPAI viruses isolated in Vietnam in 2008, 2010 and 2011. Ducks vaccinated with the Re-1 vaccines were protected after infection with the two H5N1 HPAI viruses isolated in 2008 showing no mortality and limited virus shedding. The Re-1 and Re-5 vaccines conferred 90-100% protection against mortality after challenge with the 2010 H5N1 HPAI viruses; however, the vaccinated ducks shed viruses for more than 7 days after challenge. Similarly, the Re-1 and Re-5 vaccines did not protect well against the 2011 H5N1 HPAI viruses. High number of ducks shed virus for more than 10 days and 50% mortality was observed in ducks vaccinated with Re-1 and challenged with one of these viruses. These studies demonstrate the poor protection conferred by the Re-1 and Re-5 commercial vaccines against H5N1 HPAI viruses isolated from 2010-2011 in Vietnam, underlining the importance of routine examination of vaccine efficacy in the control of H5N1 HPAI in ducks.

Technical Abstract: Highly pathogenic (HP) H5N1 avian influenza (AI) viruses continue to circulate in Asia and other regions of the world. Vaccination is used as part of H5N1 HPAI control programs in many countries; however, eradication of the disease has not been possible due to the emergence and spread of new viruses. Domestic ducks, which constitute an important part of poultry in many Asian countries including Vietnam, have been recognized as one of the primary factors in the spread of H5N1 HPAI. In this study, we examined the efficacy of two vaccines used in Vietnam to protect ducks against H5N1 HPAI. Three experiments were conducted using the commercial inactivated Re-1 and Re-5 vaccines to vaccinate ducks twice before one month of age followed by challenge with H5N1 HPAI viruses isolated in Vietnam in 2008, 2010 and 2011. These viruses belonged to the hemagglutinin (HA) clades; 1, 2.3.4, and 2.3.2. Ducks vaccinated with the Re-1 vaccines were protected after infection with the two H5N1 HPAI viruses isolated in 2008 (HA clades 1 and 2.3.4) showing no mortality and limited virus shedding. The Re-1 and Re-5 vaccines conferred 90-100% protection against mortality after challenge with the 2010 H5N1 HPAI viruses (HA clade 2.3.2); however, the vaccinated ducks shed viruses for more than 7 days after challenge. Similarly, the Re-1 and Re-5 vaccines did not protect well against the 2011 H5N1 HPAI viruses (HA clade 2.3.2). High number of ducks shed virus for more than 10 days. Furthermore, 50% mortality was observed in ducks vaccinated with Re-1 and challenged with one of these viruses. Comparison between the HA gene sequences of the vaccines and the challenge viruses showed less similarity between the vaccines and the viruses from 2011, which correlates with the lack of protection observed with these viruses. These studies demonstrate the poor protection conferred by the Re-1 and Re-5 commercial vaccines against H5N1 HPAI viruses isolated from 2010-2011 in Vietnam, underlining the importance of routine examination of vaccine efficacy in the control of H5N1 HPAI in ducks.

Last Modified: 7/23/2014
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