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In the present study, one hundred and sixteen partial G gene sequences of Avian metapneumovirus (aMPV) subtype B, obtained during routine diagnostics in different European Countries in the last few years (2014–2019), were analysed by sequence and phylogenetic analyses in order to draw an updated picture of the molecular characteristics of circulating strains. Nucleotide sequences were compared with other sequences of European and non‐European aMPV‐Bs collected prior to that period or retrieved from GenBank. Phylogenetic relationships among the aMPV‐B strains, reconstructed using the maximum likelihood method implemented in MEGA X, demonstrated that aMPV‐B has evolved in Europe from its first appearance, frequently displaying a clear relation with the geographic area of detection. The 40% of aMPV‐B viruses analysed were classified as vaccine‐derived strains, being phylogenetically related, and showing high nucleotide identity with live commercial vaccine strains licensed in Europe. The remaining 60% were classified as field strains since they clustered separately and showed a low nucleotide identity with vaccines and vaccine‐derived strains. The phylogenetic tree showed that the virus has continued to evolve from its first appearance in the '80s since more recently detected strains belonged to clades phylogenetically distant from the older strains. Unlike vaccine‐derived strains, field strains tended to cluster according to their geographic origin and irrespective of the host species where the viruses had been detected. In conclusion, the molecular characterization of aMPV‐B and the differentiation between vaccines and field strains through G gene sequence analysis can be a useful tool towards correct diagnosis and should be routinely applied in order to better address the control strategies. [ABSTRACT FROM AUTHOR]

Recently, a new genotype of infectious bursal disease virus (IBDV), named ITA, was detected in IBD‐vaccinated Italian broilers. Genome characterization revealed ITA to be a genetically different IBDV, belonging to genogroup 6 according to a recently proposed IBDV classification. The currently available clinical data do not allow any definition of the degree of pathogenicity of the ITA‐IBDV isolates. In the present study, a pathogenicity trial was conducted by the oral inoculation of specific‐pathogen‐free (SPF) chickens. Birds were housed in poultry isolators and inoculated at 35 days of age with an ITA‐IBDV isolate (35 birds) or a strain belonging to the G1a genogroup as a comparison (35 birds). Control birds (25 birds) were contextually mock‐inoculated with sterile water. Birds were observed daily for clinical signs and at 0, 7, 14, 21 and 28 days post‐inoculation (dpi) were bled for IBDV antibody detection. At 2, 4, 7, 14, 21 and 28 dpi, five birds from each of the inoculated groups, and three from the control group, were euthanized and subjected to a post‐mortem examination; the bursa:body weight and thymus:body weight ratios were calculated. Microscopic lesions of the bursa and thymus were scored on the basis of lymphoid necrosis and/or depletion or cortex atrophy, respectively. Both viruses induced a subclinical course of disease, as neither clinical signs nor mortality were recorded during the study, even in the presence of typical IBDV gross and microscopic lesions. Bursal damage, measured by the bursa:body weight ratio, was more noticeable and precocious after ITA‐IBDV inoculation. Histopathology scores of the bursa, indicative of rapid lymphoid depletion, confirmed the aggressiveness of the ITA‐IBDV strain in this organ. This study showed that, although the ITA‐IBDV strain tested causes infection with a subclinical course, it induces severe damage to lymphoid tissues. Therefore, its circulation in birds might be a threat for the poultry industry and may jeopardize the success of the production cycle. [ABSTRACT FROM AUTHOR]

Infectious Bronchitis virus (IBV) genotype Q1 was detected for the first time in China in 1996, and then spread worldwide. The first report of Q1 genotype in Italy occurred in 2011 and a deep molecular investigation of a Q1 isolated in Italy in 2013 has led to speculation regarding the origin of this genotype. Phylogenetic analysis of the S1 sequence of a Q1 Italian strain revealed a close relationship with sequences of the 624I strains circulating in Italy in the early 1990s and this led to the idea that 624I was an ancestor of the Q1 genotype. Despite the fact that most heterogeneity of IBVs occurs in the S1 gene, the sequence analysis of this gene alone was not sufficient to confirm or deny this hypothesis. In the present study, an Italian 624I (gammaCoV/AvCov/Ck/Italy/IP14425/96) was fully sequenced for the first time and compared to all available complete Q1 genome sequences. This analysis confirmed the genetic correlation between GammaCoV/AvCov/Ck/Italy/IP14425/96 and Q1 strains, suggesting a common origin between 624I and Q1 genotypes. [ABSTRACT FROM AUTHOR]