Avian metapneumovirus subtype B (aMPV-B)

Avian metapneumovirus subtype B (aMPV-B) is a single-stranded, non-segmented, negative-sense RNA virus in the Pneumoviridae family that primarily infects turkeys and chickens, causing turkey rhinotracheitis (TRT), swollen head syndrome (SHS), mild upper respiratory symptoms, and reduced egg production. Its genome spans about 13.5-15 kb and encodes eight genes in the order 3'-N-P-M-F-M2-SH-G-L-5', producing structural proteins like the attachment glycoprotein (G) for host cell binding, fusion protein (F) for membrane fusion and virulence, small hydrophobic protein (SH), matrix protein (M), and nucleocapsid components (N, P, M2, L) that form infectious ribonucleoprotein complexes. The G protein is highly variable and used for subtyping, while F is more conserved and determines host tropism limited to avian species like poultry. aMPV-B shows weak pathogenicity with low mortality, brief viral shedding peaking at 2-3 days post-infection mainly in nasal turbinates, trachea, and lungs, and mild mucosal inflammation without severe tissue damage. It spreads via respiratory secretions and direct contact, with recent detections in wild birds suggesting potential spillover, though sequences often resemble vaccine strains. No approved antiviral drugs target aMPV-B directly; control relies on vaccination and biosecurity, as the virus evades immunity via G protein variability but maintains stable F-driven antigenicity.

Other names

aMPV subtype BAvian metapneumovirus type BAMPV-B