Page 126 - Avian Virology: Current Research and Future Trends

Avian Metapneumoviruses

Paul A. Brown* and Nicolas Eterradossi 4

VIPAC (Virology, Immunology and Parasitology in Poultry & Rabbits) Unit, ANSES (French Agency for Food, Environmental
and Occupational Health Safety), Ploufragan-Plouzané-Niort Laboratory, Ploufragan, France.
*Correspondence: paul.brown@anses.fr
https://doi.org/10.21775/9781912530106.04

Abstract flocks in South Africa. Shortly after, the disease was reported in
Avian metapneumoviruses (AMPV), discovered in the late 1970s Europe were the virus was isolated (Giraud et al., 1986; McDou-
in South Africa, and now detected in almost all parts of the world, gall and Cook, 1986; Wilding et al., 1986) and later classified as
are classified in the order Mononegavirales, family Pneumoviridae, avian pneumovirus (APV) (Cavanagh and Barrett, 1988; Collins
genus Metapneumovirus, together with the more recently identi- and Gough, 1988; Ling and Pringle, 1988). This initial classifica-
fied human metapneumovirus (HMPV). AMPVs are responsible tion was based on its close genetic and structural relationships to
for respiratory diseases in poultry resulting in high morbidity and respiratory syncytial virus (RSV) which had been discovered 30
variable mortality depending on the severity of bacterial second- years previously in cases of respiratory infection in chimpanzees
ary infections. In breeding birds, a drop in egg production, and (Blount et al., 1956). Two notable differences however, were
quality of egg, can often follow. To date, four subgroups have observed between APV and RSV: (i) the absence of approxi-
been defined (A, B, C and D) based on genetic and antigenic mately 1000 nucleotides in the APV genome which in RSV were
properties for which differential laboratory diagnostic tools have known to encode two biologically active, non-structural proteins
been developed. The principal host species of AMPV are turkeys, NS1 and NS2 (Randhawa et al., 1997) (see ‘Viral proteins’,
chickens and ducks, although other bird species can be infected. below) and (ii) the order in which the genes appeared in the
Subgroup susceptibility changes with bird species. Subgroup C genome (Ling et al., 1992) (see ‘Genome structure and organi-
viruses appear to have the broadest host range and, interestingly, zation’, below). In 2001 a new respiratory virus in humans was
show a closer genetic relationship to HMPV than to other AMPV detected that had the same genome composition, structure and
subgroups. This cross-species genetic resemblance between organization as APV (van den Hoogen et al., 2001). The discov-
AMPV-C and HMPV reflects common ancestry and a compara- ery and isolation of several of these viruses from humans and in
tive virological approach may improve our understanding of both consideration that they, together with the APV isolates, emerged
viruses within the frame of future ‘one health’ metapneumovirus after the discovery of RSV, led to the addition of the Greek prefix
projects. Conversely, significant differences between AMPV sub- Meta (equivalent to post or ad in Latin) to the genus pneumovirus
groups A, B, D and AMPV-C suggest that knowledge gained from and thus the classification: avian and human Metapneumoviruses
studies of either group of AMPVs may not be readily transferred in the family Pneumoviridae, order Mononegavirales (Afonso et al.,
to the other. A good level of protection against AMPV infection 2016).
can be achieved in chickens or turkeys by careful vaccination To date four subgroups have been defined for the avian
using a combination of live attenuated and inactivated vaccines, metapneumoviruses (AMPV-A, B, C and D) based on genetic
together with good farm practices; however, several studies have and antigenic differences (Brown et al., 2014) and two sub-
shown that some live vaccines can revert to virulence causing groups for the human metapneumoviruses (HMPV-A and B).
problems in the flock. To address this, attempts have been made Genetic sublineages have been defined within HMPV subgroups
to generate more stable live vaccines with reverse genetics, yet and AMPV-C, the latter forming two genetic lineages: one in
still no recombinant AMPV vaccine has been commercialized Muscovy ducks in France and Asia (Toquin et al., 1999a; Sun
since the development of the first system in 2004. et al., 2014;) and another in turkeys and wild birds in the USA
This chapter gives an up-to-date review of the literature and per- (Senne et al., 1997; Cook et al., 1999; Shin et al., 2000; Bennett
spectives for AMPV. et al., 2004; Toquin et al., 2006b; Turpin et al., 2008). Recently
an AMPV-C has also been isolated from chickens in China (Wei
et al., 2013). Several studies have shown that the subgroup C
Introduction and history viruses are more closely related to HMPV than they are to the
Respiratory disease resulting from Avian Metapneumovirus other avian subgroups (Yunus et al., 2003; Govindarajan et al.,
(AMPV) infection was first described in the late 1970s in turkey 2004; Govindarajan and Samal, 2004, 2005; Brown et al., 2014)