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.