Efficacy of a commercially available coryza vaccine against challenge with recent South African NAD-independent isolates of Haemophilus paragallinarum in chickens.

In South Africa the incidence of NAD-independent Haemnophilus paragallinarum isolation from clinical cases is increasing. This study was carried out to test whether a commercially available coryza vaccine (Nobilis Coryza, Intervet International BV) could protect chickens against challenge with recent NAD-independent isolates. SPF chickens were vaccinated twice at 3 and 7 weeks of age and were challenged at 9 weeks of age with 5 different NAD-independent isolates of serotype A or C-3. The results after challenge show that the coryza vaccine induces good protection against challenge with the different South African NAD-independent isolates of H. paragallinarum, including serotype C-3.