Increased resistance of vaccinated turkeys to experimental infection with an H7N3 low-pathogenicity avian influenza virus

Authors: Capua, Ilaria1; Terregino, Calogero1; Cattoli, Giovanni1; Toffan, Anna1

Source: Avian Pathology, Volume 33, Number 2, Number 2/April 2004 , pp. 158-163(6)

Publisher: Taylor and Francis Ltd

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Abstract:

A trial was performed to establish whether turkeys vaccinated against avian influenza with a vaccine containing a strain with a heterologous neuraminidase to the challenge virus required a higher infectious dose to develop infection than naïve birds. Birds were vaccinated with a commercially available, inactivated oil emulsion product containing the strain A/ty/Italy/99/(H7N1) and challenged with different dilutions of a LPAI isolate A/ty/Italy/8000/02(H7N3) obtained during the 2002 to 2003 Italian epidemic. Groups of 10 vaccinated and 10 unvaccinated birds were infected experimentally with a virus suspension containing 10 2 , 10 4 and 10 6 median embryo infective dose (EID50)/0.1 ml. Infected birds were observed daily with tracheal and cloacal swabs collected at regular intervals for antigen detection, virus isolation and real-time reverse transcription-polymerase chain reaction. Pre-infection and post-infection serology was also performed. The results of the experiment indicate that infection is achieved in naïve birds with 10 4 EID50, while vaccinated birds are resistant at this challenge dose. Vaccinated and unvaccinated birds were susceptible to infection with 10 6 EID50, although the duration and/or the number of birds shedding was reduced in the vaccinated group. The data presented indicate that heterologous vaccination in the framework of a ‘Differentiating Infected from Vaccinated Animals' strategy can be a valid tool to support eradication measures in areas with high densities of susceptible animals.

Document Type: Research article

DOI: 10.1080/03079450310001652077

Affiliations: 1: OIE and National Reference Laboratory for Newcastle Disease and Avian Influenza, Istituto Zooprofilattico Sperimentale delle Venezie, Viale dell'Università 10, 35020, Legnaro, PD, Italy

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