Mortality of wild swans associated with naturally infection with highly pathogenic H5Nl avian influenza virus in Iran.

In the february 2006 in two wetlands in northern iran, the mortality among wild swans was observed. paralysis was the most prominent feature of the disease. histologically , diffused necrosis of acinar cells inpancreas, degeneration and necrosis of some neurons in central nervous system (cns), sever necrotic and hemorrhagic enteritis, foci of haemorrahge and myocardial cell necrosis in the heart, mild to moderatemultifocal hepatocytic necrosis, limited focal necrosis in the kidney and testis and morphological evidence of apoptosis in the spleen were observed. immunohistochemically, influenza virus antigen were detectedmore often in the acinar cells of pancreas, some neuron and glial cells in cns, renal tubule of kidney and hepatocytes of the liver. moreover, antigen was seen in the meisner plexus of the intestine and testis, butseldom in the lung. the rt-pcr tests showed the presence of h5, n1 and np genes of influenza virus in trachea, lung, liver, kidney, spleen, and cerebellum. deduced amino acid sequence at cleavage site waspqgerrrkkr g which is typical for highly pathogen avian influenza viruses. the phylogenetic analysis of ha (heamagglutinin) protein showed a very close similarity of z/101 (h5n1) virus with ha proteins ofh5 influenza viruses isolates from cat, wild duck, chicken, ostrich and turkey in various geographical regions. our data confirmed that these new emerging viruses are systemically able to infect wild swans. thehigh ha protein sequence similarity among h5n1 viruses from various geographical areas of the word shows that the wild aquatic birds are the major cause of world wide spreading of h5n1 viruses.