Histopathological Study of Intratracheally Inoculated A/Chicken/Iran/259/1998 (H9N2) Influenza Virus in Chicken

The type, severity and frequency of gross lesion, histopatholgic change, and tissue tropism of A/Chicken/Iran/259/1998(H9N2) avian influenza virus following intratrachealy (IT) inoculation were studied in chickens. Twenty, 5-week-old chickens (hatched from SPF eggs) were inoculated with this virus. Another twenty chickens were inoculated with sterile chorio allantoic fluid. Tracheitis, pneumonia and tubulointerstital nephritis were the most frequent specific histopathologic changes. Influenza nucleoproteins were demonstrated in epithelium of trachea, secondary bronchi and cecal tonsile of an inoculated chicken. Common non-specific histopathologic changes were lymphoid and reticuloendothelial cell hyperplasia in spleen, cecal tonsil and leukocyte cell infiltration in myocardium. These results indicate that the low-pathogenic avian influenza virus is epithliotropic in chicken. In IT route of inoculation, it has tissue tropism and pathogenicity for trachea, lung (pneumotropic) and kidney (nephrotropic).