Mortality of wild swans associated with naturally infection with highly pathogenic H۵N۱ avian influenza virus in Iran

In the February ۲۰۰۶ 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 in pancreas, 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 moderate multifocal 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 detected more 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, but seldom in the lung. The RT-PCR tests showed the presence of H۵, N۱ and NP genes of influenza virus in trachea, lung, liver, kidney, spleen, and cerebellum. Deduced amino acid sequence at cleavage site was PQGERRRKKR G which is typical for highly pathogen avian influenza viruses. The phylogenetic analysis of HA(heamagglutinin) protein showed a very close similarity of Z/۱۰۱(H۵N۱) virus with HA proteins of H۵ 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. The high HA protein sequence similarity among H۵N۱ viruses from various geographical areas of the word shows that the wild aquatic birds are the major cause of worldwide spreading of H۵N۱ viruses.

کلیدواژه ها:

Influenza ، Swan ، H۵N۱ ، RT ، PCR ، immunohistochemistry ، Histopathology