ULTRASTRUCTURAL STUDY OF THE TRACHEA IN EXPERIMENTALLY INFECTED BROILERS WITH IBV SEROTYPE 4/91

Avian infectious bronchitis virus (IBV) is a globally distributed Coronavirus that causes tremendous economic loss in the poultry industry. The primary target cells of the virus are located in the respiratory tract. Strain-dependent, IBV may spread to other epithelia and cause nephritis or drop in egg production. Subcellular changes in broilers trachea induced by infectious bronchitis virus serotype 4/91 were examined by transmission electron microscopy (TEM). Seventy 1-day-old commercial broiler chicks were divided randomly into two groups (control and experimental), and at the age of 21 days, all birds in the experimental group were challenged intranasally with the virus. Four birds from challenge group and two birds from the control group were euthanized at 1, 2, and 4 days post inoculation (PI) and tracheae were isolated after necropsy and examined with TEM. Mild tracheal rales, coughing and gasping were seen in the experimental group. As gross lesions, hyperemia and edema in tracheal mucosa were observed. IBV infection resulted in hypertrophy of goblet cells, their rupture, and the formation of excess mucus. At the level of the ciliated cells, complete deciliation of the tracheal surface was observed. Swelling and increase in the amount of endoplasmic reticulum was seen in infected birds.