Brazilian avian metapneumovirus subtypes A and B: experimental infection of broilers and evaluation of vaccine efficacy

• Main Authors: Márcia B. dos Santos, Matheus C. Martini, Helena L. Ferreira, Luciana H.A. da Silva, Paulo A. Fellipe, Fernando R. Spilki, Clarice W. Arns
• Format: Article
• Language: English
• Published: Colégio Brasileiro de Patologia Animal (CBPA) 2012-12-01
• Series: Pesquisa Veterinária Brasileira
• Subjects: Metapneumovirus aviário; replicação in vivo; proteção vacinal
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-736X2012001200008&lng=en&tlng=en

Avian metapneumovirus (aMPV) is a respiratory pathogen associated with the swollen head syndrome (SHS) in chickens. In Brazil, live aMPV vaccines are currently used, but subtypes A and, mainly subtype B (aMPV/A and aMPV/B) are still circulating. This study was conducted to characterize two Brazilian aMPV isolates (A and B subtypes) of chicken origin. A challenge trial to explore the replication ability of the Brazilian subtypes A and B in chickens was performed. Subsequently, virological protection provided from an aMPV/B vaccine against the same isolates was analyzed. Upon challenge experiment, it was shown by virus isolation and real time PCR that aMPV/B could be detected longer and in higher amounts than aMPV/A. For the protection study, 18 one-day-old chicks were vaccinated and challenged at 21 days of age. Using virus isolation and real time PCR, no aMPV/A was detected in the vaccinated chickens, whereas one vaccinated chicken challenged with the aMPV/B isolate was positive. The results showed that aMPV/B vaccine provided a complete heterologous virological protection, although homologous protection was not complete in one chicken. Although only one aMPV/B positive chicken was detected after homologous vaccination, replication in vaccinated animals might allow the emergence of escape mutants.