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