Molecular characterization of an Avian Metapneumovirus strain isolated in guinea fowls (Numida meleagridis) experiencing respiratory disease

Avian Metapneumovirus (AMPV) subtype A and B affect mainly turkeys and chickens. However, also pheasants and guinea fowls are susceptible to natural and experimental infection. In this report an outbreak of respiratory disease, which occurred in February 2012 in a flock of guinea fowls located in an highly populated poultry area of Northern Italy, is described. An AMPV of subtype B, named aMPV/B/IT/GuineaFowl/1818/12, was isolated from oro-pharingeal swabs in chicken embryo tracheal organ cultures, and typed by a subtype specific qRT-PCR. In order to characterize the strain, the F and G genes were sequenced. Nucleotide sequences were edited and assembled using Bioedit software then aligned against analogous gene sequences of AMPV subtype B isolated in Italy or deposited/published on Genbank using Clustal W. Phylogenetic analysis was carried out under distance criterion, with neighbourjoining as algorithm, using MEGA4 software. Bootstrap values were obtained with 1.000 replicates. Branches with bootstrapping values >70 were considered significant. The trees constructed on alignments of sequence data sets of F and G genes showed that the isolate clustered with other AMPVs of subtype B isolated in Italy from turkeys and chickens after 2000. These findings do not support genetic differences correlated to the host tropism and suggest that circulation of closely related AMPV strains occurs among different avian species in densely poultry populated areas. Managerial and environmental factors involved in determining the disease outbreak are discussed.