Experimental production of ascites in broiler chickens using infectious bronchitis virus and Escherichia coli

Common commercial strain male broilers were intratracheally inoculated with 0.3 ml of fluid containing 10(3.7) embryo infective doses of infectious bronchitis virus (IBV) at 14 days of age and 7.5 x 10(6) colony-forming units of Escherichia coli at 18 days of age. Ascites was detected in 15 out of 100 infected birds, which was significantly higher than in a control group of 100 mock-infected birds (P < 0.01). Some parabronchi were blocked by copious exudate containing heterophils and fibrin in the infected birds at 22 days of age although these findings were not seen in the infected birds at 35 days of age or in birds with ascites. The erythrocyte packed cell volume and right ventricle/total ventricle (RV/TV) ratio of birds with ascites were higher than in birds without ascites. The RV/TV weight ratio for the infected group at the age of 35 days was higher than that of the control group. No IBV or E. coli were recovered from the ascitic birds. These findings suggest that these infectious agents induce ascites in the broilers, and then disappear until the birds suffer from ascites.