Pathogenesis of H9N2 virus in Chukar partridges.

Low-pathogenic avian influenza virus (H9N2) is circulating in the poultry industry of many countries in the Middle East and Asia, causing serious economic damage. In this study the clinical signs, antibody response, viral shedding and efficacy of oil emulsion vaccines in Chukar partridges were investigated until 9 days post inoculation (d.p.i.). Seventy-five Chukar partridges (Alectoris chukar) were divided randomly in three groups of challenged (Group C), vaccinated and challenged (Group VC) and control (non-vaccinated and non-challenged [Group NC]), 25 birds/group. Groups C and VC were inoculated with 0.4 ml allantoic fluid containing 10(7) median embryo infective dose/bird of A/Chicken/Iran/772/1998(H9N2) avian influenza virus. Clinical signs, antibody response, viral shedding and vaccine efficacy were evaluated and compared among these groups over 9 days. Clinical signs such as coughing and sneezing with depression and decreased feed and water consumption were observed in Group C. In Group VC only a slight decrease in food and water consumption was observed. Both Groups C and VC showed maximum antibody titre at 9 d.p.i. At 1 d.p.i. the virus was detected from all tissues in challenged group, but the virus was not detected from the spleen and caecal tonsil of Group VC. Group C showed the longest period of viral shedding in the trachea and kidney.