ARS | Publication request: RESEARCH UPDATE ON H7N2 AVIAN INFLUENZA VIRUS IN TURKEYS AND CHICKENS

Submitted to: United States Animal Health Association Proceedings
Publication Type: Proceedings
Publication Acceptance Date: October 23, 2002
Publication Date: January 1, 2003
Citation: Swayne, D.E., Tumpey, T., Suarez, D.L. 2003. Research Update on H7N2 Avian Influenza Virus in Turkeys and Chickens. United States Animal Health Association Proceedings, p585, 2003.

Technical Abstract: The outbreak of H7N2 low pathogenicity avian influenza (LPAI) in Virginia during 2002 raised questions about the susceptibility of turkeys verses chickens to the virus and the potential of vaccines to provide protection. The virus A/turkey/Virginia/158512/02 (H7N2) replicated from day 2 through 7 post-intranasal inoculation (PI) in 4 week-old White Plymouth Rock chickens with peak recovery of virus from the oropharynx at day 3 PI (104.5 EID50/ml of swab media). Virus recovery from the cloaca was inconsistent and of low titer (101.5 EID50/ml). In contrast, turkeys shed virus from the respiratory tract at higher mean peak titer (106.0 EID50/ml), but the length of shed was similar. In comparing infectivity, turkeys were at least 20-50x more susceptible to H7N2 LPAI virus infection than chickens. In vaccine trials, neither sham-vaccinated nor inactivated H7N2 vaccinated turkeys developed clinical signs or death following challenge with H7N2 LPAI virus. The inactivated vaccine groups (1x and 2x vaccinated) had reduction in titers of challenge virus shed from the oropharynx when compared to sham-vaccinated groups for days 1-7 PI. This mean reduction ranged from 101.2-4.1 EID50/ml. These studies suggest that turkeys were more susceptible to infection with the H7N2 LPAI virus and shed more virus from the respiratory tract when infected. However, current vaccines can provide protection.