Submitted to: American Veterinary Medical Association Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 2002
Publication Date: July 13, 2002
Citation: Swayne, D.E., Spackman, E., Suarez, D.L., Beck, J.R., Schultz Cherry, S.L., Tumpey, T. 2002. Development And Evaluation Of A Challenge Model For Measuring Efficacy Of Vaccines Against Mildly Pathogenic Avian Influenza Viruses. American Veterinary Medical Association Abstract. Technical Abstract: Evaluation of vaccine efficacy for mildly pathogenic (MP) avian influenza viruses (AIV) is difficult since such viruses usually do not cause illness or death in experimentally infected poultry. In a series of experimental trials, vaccinated chickens were evaluated for morbidity rates, mortality rates, and serologic response. AIV isolated from the oropharynx and cloaca was quantified by RT-PCR and virus isolation/titration. In the first trial, 3 week-old white Leghorn chickens were immunized with inactivated A/chicken/NY/13142-5/94 (H7N2) MP AIV or sterile allantoic fluid in an oil emulsion base. At 5 weeks of age half of the birds received a second immunization and at 6 weeks of age all chickens were challenged with A/chicken/13142-5/94 (H7N2). Serologically, all 1x (5 weeks of age) and 2x (6 weeks of age) AIV vaccinated birds and all challenged birds (8 weeks of age) were positive for antibodies in the agar gel precipitin test. The mean hemagglutination inhibition (HI) titer for 1x vaccinated birds at 5 weeks of age) was 1:13 while at 6 weeks of age the mean HI titers were 1:84 and 1:208 for 1x verses 2x vaccinate groups. Following challenge, the 3 of 10 1x vaccinated birds and 2 of 10 2X vaccinated birds had amnestic responses. No clinical signs or mortality occurred in any of the challenged birds either in sham or inactivated vaccine groups. Correlation between reduction in virus and serologic parameters will be presented.