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Title: EFFICACY OF TWO H5N9 INACTIVATED VACCINES AGAINST CHALLENGE WITH A RECENT H5N1 HIGHLY PATHOGENIC AVIAN INFLUENZA ISOLATED FROM A CHICKEN IN THAILAND

Author
item BUBLOT, MICHEL - MERIAL SAS,R&D, FRANCE
item LE GROS, FRANCOIS-XAVIER - MERIAL SAS,R&D, FRANCE
item NIEDDU, DANIELA - MERIAL ITALIA,SPA, ITALY
item PRITCHARD, NIKKI - MERIAL SEL-GAINESVILLE,GA
item MICKLE, THOMAS - MERIAL SEL-GAINESVILLE,GA
item Swayne, David

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/19/2006
Publication Date: 3/1/2007
Citation: Bublot, M., Le Gros, F., Nieddu, D., Pritchard, N., Mickle, T.R., Swayne, D.E. 2007. Efficacy of two H5N9 inactivated vaccines against challenge with a recent H5N1 highly pathogenic avian influenza isolated from a chicken in Thailand. Avian Diseases. 51(Supplement):332-337.

Interpretive Summary: Several avian influenza (AI) vaccines are available for use in poultry to protect against both low pathogenic and highly pathogenic avian influenza. This study examined how well two killed AI vaccines performed in protecting chickens against the H5N1 highly pathogenic AI (HPAI) virus. All unvaccinated challenged birds died within 2 days, whereas 90% and 100% of chickens vaccinated with USA and Italian vaccine strains were protected from disease and death. Both vaccines prevented fecal shedding of HPAI virus and greatly reduced oral shedding of the HPAI virus. Both vaccines reduced contact transmission of the HPAI virus. These vaccines could be useful in an AI control program.

Technical Abstract: The objective of the study was to compare the efficacy of two avian influenza (AI) H5 inactivated vaccines containing either an American (A/turkey/Wisconsin/68 H5N9, H5N9-WI) or a Eurasian isolate (A/chicken/Italy/22A/98 H5N9 or H5N9-It). Three-week-old SPF chickens were vaccinated once and challenged three weeks later with a H5N1 highly pathogenic (HP) AI virus isolated from a chicken in Thailand during 2004. All unvaccinated challenged birds died within 2 days, whereas 90% and 100% of chickens vaccinated with H5N9-WI and H5N9-It were protected against mortality and morbidity. Both vaccines prevented cloacal shedding and reduced significantly oral shedding of the challenge HPAI virus. Additional chickens (vaccinated or unvaccinated) were placed in contact with the directly challenged birds 18 hours after challenge. All unvaccinated chickens in contact with unvaccinated-challenged birds died within 3 days after contact, whereas unvaccinated chickens in contact with vaccinated-challenged birds did not become infected or show a significantly delayed mortality. All vaccinated-contacts were protected against clinical signs and most did not shed a detectable amount of HPAI virus. Altogether these data indicate that both vaccines protected very well against mortality and morbidity, and reduced or prevented shedding induced by direct or contact exposure to Asian H5N1 HPAI virus.