RESUMO
The H9N2 subtype of avian influenza viruses [AIVs] has been isolated in multiple avian species in many European, Asian, African and American countries. Since the first outbreak of H9N2 virus in Iran in 1998, this virus has widely circulated throughout the country, resulting in major economic losses in chicken flocks. Several amino acids in the virus ribonucleoprotein [RNP] complex including the nucleoprotein [NP] and polymerase [PB2, PB1 and PA] proteins are associated with host range and virulence. Our aim was to understand the molecular characterization of RNP complex proteins of Iranian H9N2 subtype isolates. The full length nucleotide sequences of RNP complex genes of two strains designated as Ck/IR/ZMT-101/98 and Ck/IR/EBGV- 88/10 were amplified and sequenced. The phylogenetic analysis revealed that both strains were located in different sub-lineages. However, based on the genetic similarities, PB1, PA and NP genes of Ck/IR/EBGV-88/10 strain had a close relationship with a H7N3 subtype strain, isolated from Pakistan. Most positions of RNP proteins contained amino acids typical of avian determinants of host range. The results showed that the Iranian RNP complex genes have undergone genetic reassortment. Continuous AIV monitoring in poultry industry would help to obtain more information about genetic variation of H9N2 viruses and possible emergence of virulent and/or pandemic viruses
RESUMO
Understanding the distributions of poultry diseases will help planning for disease control and prevention more effectively. Studies on poultry diseases in Iran are scarce. We investigated the incidence of mortality in broiler chicken flocks in Iran as part of a national project. Specifically, documents from September 2004 to November 2005 related to the mortality of broilers that were covered by the national insurance scheme were analyzed retrospectively. Of the 439,188,406 broiler chickens that were covered by insurance services, 188,680,459 chickens were exposed to different diseases. The most common diseases [in descending order] were infectious bursal disease [IBD], infectious bronchitis [IB], chronic respiratory disease [CRD], colibacillosis and avian influenza [AI; subtype H9N2]. The mean mortality rate in broilers was 7.89%. Mortality rates were higher during chicks between the third to sixth weeks of age. AI [H9N2] produced the highest mean mortality rate of 26.1%, followed by IB with a mean mortality rate of 22.1%. Most of the mortalities were recorded from the southern provinces of Iran. The distributions of diseases were differed in different regions which could be related to regional conditions and management parameters