An experimental study on broiler chicken co-infected with the specimens containing avian influenza (H9 subtype) and infectious bronchitis (4/91 strain) viruses

This experimental study was carried out to induce a co-infection of H9 AIV and IBV with inoculums prepared from tracheal scrubbed epithelium tissues in natural co-infected birds to rule out the effect of field undesired environmental conditions and also other infectious causative agents. Eighty 1-day-old broilers were randomly divided into four equal groups. At 21 days of age, three test groups were inoculated intranasally with prepared inoculums containing IBV and H9 AIV alone and a co-infected group. The fourth group remained uninfected as a control group. The results showed that experimental co-infection of AIV and IBV increased the severity of clinical signs, mortality rate and gross lesions. The HI titer against AIV infection in the co-infected group was significantly higher than the Ill titer of other groups, which may indicate that IBV could promote the propagation of H9N2 AIV or stimulate the immune response.