Investigation on some clinical characteristics and risk factors for infectious bronchitis in broiler chickens in the Mekong Delta area

Abstract

An investigation on the prevalence of infectious bronchitis virus (IBV) in the broiler chickens was carried out by symptom and gross lesion observations, and combining with PCR test from 20 chicken flocks suffering from respiratory problems in Vinh Long and Soc Trang provinces. The studied results showed that there were 7 chicken flocks infected with IBV (35%). Clinical diagnosis was determined combining with PCR assay because clinical signs showed only 53.84% of accuracy in diagnosis. The symptoms and gross lesions were mainly found in the respiratory tract, including tracheal rales when breathing, sneezing, dyspnea, nasal discharge, sinusitis, conjunctivitis, tracheal petechial hemorrhage with exudate mucus, pulmonary hemorrhage and congestion, airsacculitis and swollen kidney. The mortality of the IBV infected chickens was 14.93%. The higher IBV infection rate was found in the chicken flocks vaccinated only one or two times with 1 vaccine serotype (Massachusetts - H120) (50%), followed by the chicken flocks vaccinated two times with 2 serotypes (Massachusetts - H120
and 793B - 4/91) (25%). The comparison of different age groups showed that the highest infection flocks rate was from the chickens at 5 to 7 weeks of age (71.43%). There was no significant difference for the infection rate of the chickens in the different farm types as well as in the dry seasons, but the IB disease of chicken showed the tendency to increase in the captive farms and in the rainy season