Paul A. Brown and Nicolas Eterradossi
from: Avian Virology: Current Research and Future Trends (Edited by: Siba K. Samal). Caister Academic Press, U.K. (2019) Pages: 119-132.
Avian metapneumoviruses (AMPV), discovered in the late 1970s in South Africa, and now detected in almost all parts of the world, are classified in the order Mononegavirales, family Pneumoviridae, genus Metapneumovirus, together with the more recently identified human metapneumovirus (HMPV). AMPVs are responsible for respiratory diseases in poultry resulting in high morbidity and variable mortality depending on the severity of bacterial secondary infections. In breeding birds, a drop in egg production, and quality of egg, can often follow. To date, four subgroups have been defined (A, B, C and D) based on genetic and antigenic properties for which differential laboratory diagnostic tools have been developed. The principal host species of AMPV are turkeys, chickens and ducks, although other bird species can be infected. Subgroup susceptibility changes with bird species. Subgroup C viruses appear to have the broadest host range and, interestingly, show a closer genetic relationship to HMPV than to other AMPV subgroups. This cross-species genetic resemblance between AMPV-C and HMPV reflects common ancestry and a comparative virological approach may improve our understanding of both viruses within the frame of future 'one health' metapneumovirus projects. Conversely, significant differences between AMPV subgroups A, B, D and AMPV-C suggest that knowledge gained from studies of either group of AMPVs may not be readily transferred to the other. A good level of protection against AMPV infection can be achieved in chickens or turkeys by careful vaccination using a combination of live attenuated and inactivated vaccines, together with good farm practices; however, several studies have shown that some live vaccines can revert to virulence causing problems in the flock. To address this, attempts have been made to generate more stable live vaccines with reverse genetics, yet still no recombinant AMPV vaccine has been commercialised since the development of the first system in 2004. This chapter gives an up-to-date review of the literature and perspectives for AMPV read more ...