A Cross-Sectional Survey of the Prevalence and Associated Risk Factors of Infectious Bronchitis Virus in Poultry Farms in Northern Vietnam

Do Duy Hoa^1†, Bui Van Dung^2†, Nguyen Hoai Nam² , Nguyen Duc Truong², Nguyen Van Phuong¹, Dan The Ngo¹, Tran Thi Duc Tam³, Pham Thi Lan Huong⁴, Ha Xuan Bo⁵, Le Van Truong⁶, Le Van Phan⁶, Mai Thi Ngan^6*

¹Boehringer Ingelheim Animal Health Vietnam Limited Liability Company, Ho Chi Minh, Vietnam
²Department of Animal Surgery and Theriogenology, Faculty of Veterinary Medicine, Vietnam National University of Agriculture, Ha Noi, Viet Nam
³ Department of Veterinary Anatomy, Histology and Embryology, Faculty of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi, Vietnam
⁴Department of Pharmacology, Toxicology, Internal Medicine and Diagnostics, Faculty of Veterinary Medicine, Vietnam National University of Agriculture, Ha Noi, Vietnam
⁵Department of Animal Genetics and Breeding, Faculty of Animal Science, Vietnam National University of Agriculture, Hanoi, Vietnam
⁶Department of Veterinary Microbiology and Infectious Diseases, Faculty of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi, Vietnam
^† These authors contribute equally
^* Corresponding author

Dr. Mai Thi Ngan, Department of Veterinary Microbiology and Infectious Diseases, Faculty of Veterinary Medicine, Vietnam National University of Agriculture, Hanoi, Vietnam
Email address: mtngan@vnua.edu.vn

Abstract
Infectious bronchitis virus (IBV) remains a major respiratory pathogen of economic concern in the poultry industry. This study investigated the farm-level prevalence of IBV and evaluated associated risk factors in northern Vietnam by a cross-sectional study. A total of 69 poultry farms were surveyed, and pooled tracheal swab samples were tested using RT-qPCR for IBV detection. The overall IBV farm-level prevalence was 34.78%. No significant variation in prevalence was observed across provinces or production types. A total of 22 potential risk factors were initially assessed using univariate logistic regression. Of these, six variables with P < 0.1, including farm size, number of poultry houses, presence of multiple age groups, vaccination at day-old, frequency of disinfection before chick placement, and proximity to live bird markets and residential areas, were selected for multivariable logistic regression. The final multivariable model retained two independent predictors: performing more than one disinfection before chick placement (P = 0.035), and administration of a live IB vaccine at one day of age (P = 0.006), both of which were significantly associated with reduced the odds of IBV infection at the farm level. These findings suggest that strategic vaccination and careful calibration of disinfection protocols are critical to minimizing IBV transmission at the farm level.

Keywords: Cross-sectional study, Infectious bronchitis virus, risk factors, prevalence, Vietnam

DOI: https://doi.org/10.1016/j.prevetmed.2025.106734