Detection of Infectious Bronchitis Virus in Multicausal Respiratory Disease in Vaccinated and Unvaccinated Broilers in Bushehr Province

In recent years, the multicausal respiratory disease has caused severe economic losses in poultry industry, particularly in broiler flocks. A variety of viral and bacterial factors are involved in the incidence of this disease, one of the most prominent of which is infectious bronchitis virus (IBV). Despite the vaccination program, this disease is still regarded as the most prevalent virulence factor in poultry industry throughout the world. Recently, the outbreak of multicausal respiratory disease has led to an increase of considerable losses in broiler flocks in Bushehr province. In order to detect the infectious bronchitis virus in vaccinated and unvaccinated broilers with multicausal respiratory disease, 8 flocks, vaccinated against infectious bronchitis and 7 as unvaccinated flocks were selected as samples. For all vaccinated broilers, the Massachusetts Serotype Vaccine was used as bronchitis vaccine. During the study, representative samples showed respiratory problems including coughing, sneezing, and respiratory rales. In the present survey, 135 tracheal swabs and 150 blood samples of 15 flocks with respiratory infection and with high mortality rate were collected and examined using RT-PCR method and ELISA. Out of 15 sampled broilers, 12 (80%) were positive for IBV, and 3 were negative for molecular detection. All unvaccinated broilers were positive for IBV, while 3 among vaccinated ones were negative. In serological assay, it was elucidated that all unvaccinated flocks were positive, demonstrating correlation with molecular results. The findings revealed a high incidence of infectious bronchitis virus in broilers with multicausal respiratory disease; especially in unvaccinated flocks, showing an immediate action in controlling infectious bronchitis disease as to decrease the damages caused by multicausal respiratory disease.