Histopathological Changes in Lungs and Tracheas of Broiler Chickens Infected With Infectious Bronchitis Virus

Infectious bronchitis is an acute extremely infectious respiratory illness caused by the avian gamma-corona virus. Infection with the infectious bronchitis virus predisposes the bird to secondary bacterial infection, worsening the situation. The infection causes severe morbidity and variable mortality in broilers, as well as a significant decrease in the layer production of eggs. This study was conducted to evaluate the pathological changes that occur in natural infection with the infectious bronchitis virus. Samples were collected from clinical cases submitted for necropsy at local veterinary clinics in Anbar province, Iraq. Tissues for molecular detection included tracheas, lungs, and kidneys. Samples confirmed infection by PCR used in the histopathological study. Histopathological sections from samples that tested positive showed variable lesions from one farm to another. In some cases, there was mild heterophilic infiltration and some times accompanied by deciliation and sometimes accompanied by subepithelial edema. In more severe cases there was congestion of blood vessels along heterophilic infiltration along with desquamation of the epithelial layers. The histopathological section in a lung of infected birds showed inflammatory cells infiltration consisting mainly of heterophils in the interstitial tissue. In some samples, there was extensive hemorrhage filling the atrial lumen and infiltration of eosinophils and heterophils along with interstitial hemorrhage. From this study, we concluded that viruses circulating in Iraq causes more pulmonary lesions when compared to lesions in the trachea.