Pathogenesis of Avian Metapneumovirus
In turkeys the incubation period is relatively short, with the disease spreading rapidly through an entire flock. In chickens this is less clearly defined and may not be always associated with clinical signs.
In chickens a condition known as “Swollen Head Syndrome”, so named due to the presence of swollen infraorbital sinuses or submandibular swelling is often associated with aMPV infections. It has however not been possible to reproduce this disease experimentally and flocks positive for aMPV infection may show no clinical signs. It is probable that aMPV is one of the factors involved in SHS, but only together with other agents which may be bacterial or viral.
In birds in lay aMPV has two important sites of replication, the respiratory and the reproductive tract.
It has been reported that concomitant infections of aMPV and bacteria (Escherichia coli, Pasteurella spp, Bordetella avium, Ornithobacterium rhinotracheale, etc) or Mycoplasma will enhance the clinical effect of these agents.
aMPV has two important sites of replication, the respiratory and the reproductive tract.