دراسات وأبحاث  Studies & Research

2من اصل2

The HA0 precursor proteins of avian influenza viruses of low virulence for poultry have a single arginine at the cleavage site and another at position-4. these viruses are limited to cleavage by host proteases such as trypsin-like enzymes and thus restricted to replication at sires in the host where such enzymes are found. i.e. the respiratory and intestinal tracts.

But HPAI viruses possess multiple basic amino acids (arginine and lysine) at their HA0 cleavage sites either as a result of apparent insertion or apparent substitution and appear to be cleavable by a ubiquitous protease(s), probably one or more proprotein-processing subdivision-related endoproteases.

The clinical signs and PM lesions of H9N2 infection may be hidden with no obvious pathognominic characters so we called it (the hidden fun) but generally we can see head swelling with respiratory signs and decreased feed intake with low performance in broilers and gradually decreased egg production in layers and breeders associated with laying of small size eggs.

Grissly, we can only intestinal inflammation and ballooning, rachitic with caseated plug at the bronchial branch, pancreatitis and nephritis with oiphoritis in laying hens.