INFECTIOUS BRONCHITIS IN A 30-WEEK-OLD BROILER BREEDER FLOCK (ARBOR ACRE PARENT STOCK): A CASE REPORT

Abstract

Infectious bronchitis (IB), caused by the avian gammacoronavirus Infectious Bronchitis Virus (IBV), is a highly contagious poultry disease that causes significant economic losses globally. This report describes an outbreak in a 30-week-old Arbor Acre parent stock breeder flock of 1,250 birds in Oyo State, Nigeria. Clinical signs included a sharp decline in egg production, misshapen and rough-shelled eggs, reduced feed intake, diarrhea, and increased mortality, mainly in females. Post-mortem findings were tracheal catarrh, ovarian follicle degeneration, bluish combs and wattles, and watery albumen. Bacterial culture confirmed Escherichia coli as a complicating infection, showing multidrug resistance but susceptibility to gentamicin. Serological testing demonstrated high IBV titres above the protective range with a narrow coefficient of variation, indicating uniform exposure to a circulating field strain despite prior vaccination with the H120 strain. Supportive management, nutritional supplementation, and gentamicin therapy improved flock performance, with egg production rising from 64% to between 74% and 88%. This case illustrates the persistence of IBV in breeder flocks despite vaccination and the potential role of colibacillosis in worsening outcomes. It further underscores the importance of strict biosecurity, adoption of strain-specific or updated vaccination strategies, and supportive care in reducing losses linked to IB outbreaks in Nigeria and similar production settings.