Introduction
Avian metapneumovirus (aMPV) infections in Europe have been an
issue since its first appearance both in turkeys, chickens and in other
minor species (Toquin, Bayon-Auboyer, Eterradossi, & Jestin, 1999;
Catelli et al., 2001; Cecchinato, Ferreira, Munir, & Catelli, 2017;
Cecchinato et al., 2018), causing economic losses mainly due to
respiratory or reproductive problems (Cecchinato et al., 2012), often
exacerbated by secondary bacterial infections (Giovanardi et al., 2014).
First aMPV isolations in Europe date back to the second half of the
1980s, when Turkey Rhinotracheitis (TRT) outbreaks appeared in the
United Kingdom (McDougall and Cook, 1986) and France (Giraud, Bennejean,
Guittet, & Toquin, 1986). As the virus was spreading all over Europe
and the clinical problems in poultry farms became increasingly serious,
during the early 1990s (Cook et al. 1989a e 1989b) live attenuated
vaccines were developed and became commercially available. By analysing
strains circulating in Europe, Juhasz and Easton (1994) reported
differences in the G gene between aMPV isolates and proposed the
classification into A and B subtypes and confirmed the co-circulation of
both subtypes. After this initial study, and due to the increasing use
of sequence analysis, two further subtypes, named C and D, were
identified in France (Bayon-Auboyer, Arnauld, Toquin, & Eterradossi,
2000; Toquin et al., 2006).
Despite these reports, molecular data on aMPV strains circulating in
Europe are still poor and scattered (Catelli et al., 2004; Cecchinato et
al., 2013a; Listorti et al., 2014; Franzo et al., 2017; Tucciarone et
al., 2017 a 2018; Ball, Forrester, & Ganapathy, 2018; Andreopoulou et
al., 2019), as most of them originate from few countries. In the last
decades, subtype B has been generally the most frequently encountered
subtype in Europe, although subtype A has been sporadically reported
(Lupini et al., 2011).
In order to update the epidemiological picture of circulating strains,
the present study was designed to molecularly characterize, by partial G
gene sequencing, aMPV subtype B strains detected in Europe in the last
years.