Abstract
Avian Metapneumovirus (aMPV) has been recognized as a respiratory pathogen of turkey and chickens for a long time. Recently, a crescent awareness of aMPV, especially subtype B, clinical and economic impact has risen among European researchers and veterinarians. Nevertheless, the knowledge of its epidemiology and evolution is still limited. In the present study, the broadest available collection of partial G gene sequences obtained from European aMPV-B strains was analyzed using different phylodynamic and biostatistical approaches to reconstruct the viral spreading over time and the role of different hosts on its evolution. After aMPV-B introduction, approximatively in 1985 in France, the infection spread was relatively quick, involving the Western and Mediterranean Europe until the end of the 1990s, and then spreading westwards at the beginning of the new millennium, in parallel with an increase of viral population size. In the following period, a wider mixing among aMPV-B strains detected in eastern and western countries could be observed. Most of the within-country genetic heterogeneity was ascribable to single or few introduction events, followed by local circulation. This, combined with the high evolutionary rate herein demonstrated, led to the establishment of genetically and phenotypically different clusters among countries, which could affect the efficacy of natural or vaccine-induced immunity and should be accounted for when planning control measure implementation. On the contrary, while a significant strain exchange was proven among turkey, guinea fowl and chicken, no evidence of differential selective pressures or specific amino-acid mutations was observed, suggesting that no host adaptation is occurring.
Highlights
Avian Metapenumovirus is a well-known pathogen affecting turkeys and chickens, other avian species including guinea fowls [1], pheasants [2] and ducks [3] can be infected. aMPV has been associated with upper respiratory tract infections in turkeys and chickens, which can lead to relevant clinical signs and economic losses, especially in presence of secondary infections [4].aMPV is an icosahedral, enveloped virus belonging to the family Pneumoviridae, genus Metapneumovirus, and is featured by a single-stranded negative-sense RNA genome approximately 15 kb-long encoding for 8 genes located in the following order: 3′-Nucleoprotein (N), Phosphoprotein (P), Matrix (M), Fusion (F), Matrix 2 (M2), Small hydrophobic (SH), attachment (G) and large polymerase (L)-5′ [5]
*Correspondence: giovanni.franzo@unipd.it 1 Department of Animal Medicine, Production and Health, University of Padua, Legnaro, PD, Italy Full list of author information is available at the end of the article aMPV is an icosahedral, enveloped virus belonging to the family Pneumoviridae, genus Metapneumovirus, and is featured by a single-stranded negative-sense RNA genome approximately 15 kb-long encoding for 8 genes located in the following order: 3′-Nucleoprotein (N), Phosphoprotein (P), Matrix (M), Fusion (F), Matrix 2 (M2), Small hydrophobic (SH), attachment (G) and large polymerase (L)-5′ [5]
The phylogeographic reconstruction demonstrated a tendency of aMPV-B strains to form mainly country-specific clusters, being single introduction events able to explain most of the genetic variability observed within country (Figure 2A and Additional file 2)
Summary
Avian Metapenumovirus (aMPV) is a well-known pathogen affecting turkeys and chickens, other avian species including guinea fowls [1], pheasants [2] and ducks [3] can be infected. aMPV has been associated with upper respiratory tract infections in turkeys and chickens, which can lead to relevant clinical signs and economic losses, especially in presence of secondary infections [4].aMPV is an icosahedral, enveloped virus belonging to the family Pneumoviridae, genus Metapneumovirus, and is featured by a single-stranded negative-sense RNA genome approximately 15 kb-long encoding for 8 genes located in the following order: 3′-Nucleoprotein (N), Phosphoprotein (P), Matrix (M), Fusion (F), Matrix 2 (M2), Small hydrophobic (SH), attachment (G) and large polymerase (L)-5′ [5]. AMPV has been associated with upper respiratory tract infections in turkeys and chickens, which can lead to relevant clinical signs and economic losses, especially in presence of secondary infections [4]. The research has focused especially on the G protein, a glycoprotein involved in the viral attachment, and the F one, a fusion protein fundamental for the fusion of the viral envelope with the cell membrane. Franzo et al Vet Res (2020) 51:88 studies investigating the interaction of these proteins with the host receptors and immune response are largely lacking. They are considered likely targets of the host immunity because of their location on the virus surface [6, 7]. The higher genetic heterogeneity of the G gene compared to others, including the F one, makes it suitable for molecular epidemiological studies and strain characterization and has promoted a more intensive sequencing activity over time
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