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Title: Efficacy of commercial vaccines in protecting chickens and ducks against H5N1 highly pathogenic avian influenza viruses from Vietnam

Author
item Pfeiffer, Jennifer
item Suarez, David
item Sarmento, Luciana
item TO, THANH LONG - NATL CTR VET DIAG VIETNAM
item NGUYEN, TUNG - NATL CTR VET DIAG VIETNAM
item Pantin Jackwood, Mary

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2009
Publication Date: 3/1/2010
Citation: Pfeiffer, J., Suarez, D.L., Sarmento, L., To, T., Nguyen, T., Pantin Jackwood, M.J. 2010. Efficacy of commercial vaccines in protecting chickens and ducks against H5N1 highly pathogenic avian influenza viruses from Vietnam. Avian Diseases. 54:262-271.

Interpretive Summary: Highly pathogenic avian influenza is a severe disease of poultry, including ducks and chickens. One approach to control the disease is with vaccination. A good vaccination program will provide protection from clinical disease as well as reduce the amount of virus that infected birds shed into the environment. A good vaccine must produce high levels of antibody that are specific to the virus the birds are infected with. This study examined how protective several commercially available vaccines in Vietnam are to challenge with recent viruses from Vietnam. The three commercial vaccines provided protection from clinical disease and death for most birds, but birds with one vaccine had more disease and infected birds shed more virus. This vaccine would not be recommended for use. The other two vaccines appeared to provide a better response and can still be recommended. However, avian influenza viruses continue to change in the field, and further studies are needed to assure that the available vaccines are still providing adequate protection.

Technical Abstract: Highly pathogenic (HP) H5N1 avian influenza (AI) viruses continue to circulate in Asia and have spread to other regions of the world. Though attempts at eradication of the viruses during various outbreaks have been successful for short periods of time, new strains of H5N1 viruses continue to emerge and have become endemic in parts of Asia and Africa. Vaccination has been employed in Vietnam as part of AI control programs. Domestic ducks, which make up a large part of poultry in Vietnam, have been recognized as one of the primary factors in the spread of AI in this country. As a result, ducks have been included in the vaccination programs. Despite the effort to control AI in Vietnam, eradication of the disease has not been possible due in part to the emergence and spread of new viruses. Here, we tested the abilities of avian influenza oil emulsion vaccines of different genetic origin to protect against disease and viral shedding in both two-week old white leghorn chickens and one-week-old Pekin ducks. Seventy-five to 100% of vaccinated chickens were protected from mortality, but viral shedding occurred for at least two days post challenge. All but one vaccinated duck were protected from mortality, however, all shed virus up through at least five days post challenge, depending on the vaccine and challenge virus used. Differences in levels of hemagglutination inhibition (HI) antibody titers induced by the vaccines were observed in both chickens and ducks. While the vaccines tested were effective in protecting against disease and mortality, updated and more efficacious vaccines are likely needed to maintain optimal protection.