Infectious Bronchitis (IB) is a highly contagious respiratory disease in chickens caused by Infectious Bronchitis Virus (IBV), which belongs to the genus Gammacoronavirus. The virus can spread through aerosols (airborne transmission), direct contact, and contaminated equipment, including footwear, vehicles, and farm tools. In both broiler and layer chickens, the disease commonly causes coughing, sneezing, gasping, reduced feed and water intake, and reduced body weight gain. In laying hens, IBV infection can also lead to decreased egg production and impaired egg quality. Gross pathological lesions may include tracheitis characterized by mucus or exudate accumulation, hyperemia, and damage to the tracheal epithelium and cilia, accompanied by changes in the lungs. In addition, the QX-like strain is associated with more pronounced pathogenic effects on the reproductive system and kidneys. Infectious Bronchitis infection can lead to significant production losses, poor eggshell quality, and an increased risk of false layer syndrome when infection occurs during the early growth phase. Reproductive disturbances can be recognized by noticeable changes in egg quality, particularly when the eggs are broken open. The egg white becomes thinner and less viscous, and blood spots may occasionally be present. Other clinical signs include a characteristic penguin-like posture, which may result from abdominal enlargement due to oviduct dilation and fluid accumulation within the oviduct, a condition known as hydrosalpinx.
Source: AHTS Mensana and Diseases of Poultry: A Colour Atlas by Dinev (2007)
(a) Eggs with thin, rough shells and abnormal shapes; b) Watery albumen with a blood spot; c) Tracheitis; d) Nephritis characterized by enlarged kidneys and urate accumulation in the kidneys and ureters; e) Oviduct cysts.
Cases of Infectious Bronchitis (IB) infection continue to occur despite vaccination. Infectious Bronchitis Virus (IBV) has a high capacity for mutation and recombination, resulting in the emergence of numerous genotypes and new variants in different regions worldwide over the past decade. This genetic variability presents a major challenge in IB control because cross-protection between strains is not always optimal. According to Santoso et al. (2023) and Wibowo et al. (2019), the IBV variants reported in Indonesia to date include the Classical strain, the QX-like strain, and the 793B/4-91 strain. Phylogenetic mapping conducted by the SANBIO team from 2020 to September 2026 showed that the majority of field cases were identified as the 793B strain, followed by QX-like, with no classical strain confirmed variant detected during this period. In 2025, the mapping results showed an equal distribution between the two strains, with each accounting for 50% of the cases.
IBV control requires an integrated approach supported by strict biosecurity measures. Key practices include restricting personnel access and disinfecting poultry houses before and after each production cycle. Proper ventilation management is also essential minimize stress associated with poor air quality. IBV can spread rapidly through aerosols between neighboring poultry houses. Major risk factors commonly encountered in the field include high stocking density, inadequate ventilation, insufficient biosecurity measures, and stress caused by extreme weather conditions. Temperature fluctuations and high humidity can exacerbate respiratory problems and increase the risk of IBV exposure within poultry houses.
Effective IB prevention relies not only on vaccination but also on a combination of strict biosecurity, proper sanitation, optimal ventilation management, and an appropriate vaccination program. Combining live and inactivated (killed) vaccines can be one of the strategies used to improve protection. Live vaccines primarily stimulate both humoral and cellular immune responses, whereas inactivated vaccines stimulate humoral immunity and may induce longer-lasting antibody responses. Live vaccine boosters may be administered every 6–8 weeks depending on the vaccination program and antibody titer monitoring results. Inactivated vaccine boosters may be administered every 12–16 weeks or based on antibody titer monitoring results. Because Infectious Bronchitis Virus comprises numerous genotypes and serotypes that continue to evolve, vaccine selection should be guided by the genetic characteristics of the viruses circulating in the region. The use of vaccines combining classical and variant strains may provide improved protection. Even minor changes in the spike protein, particularly in the S1 subunit, can alter antigenic characteristics and affect the level of vaccine protection.
Post-vaccination monitoring should include routine clinical observations and serological testing to ensure that an adequate immune response has developed in the chicken population. The results should be evaluated alongside poultry house management, biosecurity practices, and disease history to facilitate timely corrective action.