Efficacy of Olea europaea leaves and propolis extracts in the control of experimentally induced infectious bronchitis in broiler chickens

Abstract

Infectious bronchitis (IB) is a viral disease that causes serious economic losses in the broiler industry. This study evaluated the effectiveness of Olea europaea leaves and propolis extracts (OLP) mixture at a rate of 400 μg and 100 mg/mL, respectively, in curing IB in broiler chickens. One-day-old Ross broiler chicks were randomized into four groups (G) of twenty-one chicks; G1 (control negative; no infection and treatment); G2 (no infection, treatment only), G3 (control positive; infection only and no treatment) and G4 (infection and treatment) that infected with IBv (106 EID50/ml) at 21 days old. The OLP treatment was applied for birds in G2 and G4 at a dose of 0.5 mL/liter drinking water for three successive days. The growth performance, clinical and pathological examinations and viral shedding were evaluated. The use of the OLP resulted in protection from IB infection through the significant improvement of performance parameters such as weight gain and feed conversion ratio, decrease in mortality rate, lowering disease severity, and rapid recovery from the observed clinical signs (mainly respiratory signs), gross and microscopic lesions in the trachea, lung, and kidneys as compared to those in the positive control (G3). Moreover, the viral shedding in the OLP-treated chicks (G4) was significantly decreased in tracheal and cloacal swabs to a rate less than 3×103 IBv genome copy number and became not detectable at 14-days post-infection (dpi) in their cloacal swabs. In conclusion, OLP can potentially display an antiviral effect against IB in broiler chickens. Therefore, adding OLP to the chicken drinking water is recommended to prevent and control IB.