Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2003
Publication Date: 3/1/2004
Citation: Tumpey, T., Kapczynski, D.R., Swayne, D.E. 2004. Evaluation Of A Commercial Avian Influenza (H7N2) Vaccine For Protection In Turkeys Against An Avian Influenza Virus (H7N2) Isolated From Turkeys In Virginia During 2002.. Avian Diseases 48(1):167-176, 2004. Interpretive Summary: In 2002, a low pathogenic avian influenza (LPAI) virus, type H7N2, was isolated in the Shenandoah Valley of Virginia and adjacent states. This outbreak started in and was largely confined to turkey breeder flocks and before the last positive farm was detected in July of 2002, Virginia's State Veterinarian quarantined 197 Shenandoah Valley poultry farms and ordered the depopulation of 4.7 million turkeys and chickens. This outbreak of H7N2 virus raised questions about the potential of available vaccines to provide protection in poultry. A study was undertaken to determine if an existing commercial H7N2 LPAI vaccine manufactured by Lohmann Animal Health could provide protection against a recent H7N2 2002 isolate. In vaccine trials, neither control nor H7N2-vaccinated turkeys developed clinical signs or death following challenge with A/turkey/Virginia/158512/02 (H7N2) LPAI virus. The inactivated vaccine groups (1x and 2x vaccinated) had a significant reduction in titers of challenge virus shed from the oropharynx when compared to sham-vaccinated groups for days 1-7 after challenge. These studies suggest that a currently available commercial vaccine can provide protection to a recent H7N2 avian influenza isolate.
Technical Abstract: During the spring of 2002, a low pathogenic avian influenza (LPAI) A (H7N2) virus caused a major outbreak in commercial poultry in Virginia and adjacent states. The virus primarily affected turkey flocks causing respiratory distress and decreased egg production. Experimentally, turkeys were more susceptible than chickens to H7N2 virus infection and higher titers of infectious virus could be recovered from the oropharynx in comparison to the cloaca. The outbreak of H7N2 virus raised concerns regarding the availability of vaccines that could be used for the prevention and control of this virus in poultry. We sought to determine if an existing commercial AI vaccine prepared from a 1997 seed stock virus could provide protection against a 2002 LPAI H7N2 virus isolated from a turkey (A/Turkey/Virgina/158512/02 [TV/02]) in Virginia that was from the same lineage as the vaccine virus. The inactivated AI vaccine, prepared from A/Chicken/Pennslyvania/21342/97 (CP/97) virus, significantly reduced viral shedding from vaccinated turkeys in comparison to sham controls, but did not prevent infection. The protective effect of vaccination correlated with the level of virus-specific antibody as a second dose of vaccine increased antiviral serum IgG and hemagglutination inhibition (HI) reactivity titers in two different turkey age groups. Serum from CP/97-vaccinated turkeys reacted equally well to CP/97 and TV/02 antigens by HI and ELISA. These results demonstrate the potential benefit of using an antigenically related 1997 H7N2 virus as a vaccine candidate for protection in poultry against a H7N2 virus isolate from 2002.