Prevalence and Seroprevalence of Infectious Bronchitis Virus and Infectious Laryngotracheitis Virus in Backyard Poultry in Central Chile.

Backyard production systems (BPSs) are common in Chile and play an important role in food access and local trade. However, these systems often lack basic biosecurity and disease prevention practices, which increases the risk of disease spreading. In this study, we evaluated the presence of two major avian respiratory viruses, infectious bronchitis virus (IBV) and infectious laryngotracheitis virus (ILTV), in BPSs located near wetlands in central Chile. These areas are known as the country's main poultry production zones. We collected 449 poultry serum samples from 88 BPSs and performed serological tests using ELISA. Additionally, we analyzed 250 poultry tracheal swabs from 31 BPSs using qPCR. The results showed high seroprevalence levels: 95.5% of BPSs tested positive for IBV and 85.2% for ILTV. At the animal level, 82.2% were positive for IBV and 57.2% for ILTV. Most birds had antibodies to both viruses. However, active infections were less frequent, with 4.3% of tracheal swabs testing positive for IBV and 14.1% for ILTV during 2021 and 0.6% and 3.8% for IBV and ILTV, respectively, during 2024. This is the first serological and molecular evidence of IBV and ILTV circulation in backyard poultry in central Chile. Since this region includes most of the country's poultry industry, these findings raise concern about the risk of virus transmission to commercial farms. The high circulation rates suggest that backyard poultry could act as reservoirs and may contribute to decreased productivity. Our results highlight the need for improved disease surveillance and enhancement of biosecurity in BPSs in Chile.