Abstract
Outbreaks of highly pathogenic avian influenza (HPAI) in domestic birds have been increasing in Europe since 2020. From 2020 to 2023, Denmark experienced 36 outbreaks of HPAI, resulting in the deaths of more than half a million domestic birds. Meanwhile, the HPAI virus was detected in over 700 dead wild birds in Denmark as part of the EU compulsory passive surveillance program. It is often difficult to infer the route of infection, even though competent authorities conduct thorough epidemiological investigations.
Using a case-control study, we assessed potential risk factors for HPAI outbreaks in poultry farms in Denmark, including factors related to the environment and farm management, staff and visitors, biosecurity measures, ventilation, wild bird and rodent observations, and trade of poultry and their products. We included 29 farms with primary outbreaks of HPAI from October 2020 to September 2023. Each case was matched with two control farms based on farm size, bird species and distance to coast or wetlands.
In the source population, 38% of the case owners and 45% of the control owners declined to participate due to time constraints, concerns about legislative restrictions, and compliance issues with the veterinary authorities. Using Monte Carlo integration to estimate relevant odds ratios (OR) in a Bayesian framework, we found that observing wild waterfowl or gulls was more common near case farms (OR: 19, 95% credible interval: 3–148, Bayesian p-value: 0.02). This finding can improve future risk-based surveillance and control actions, as well as placement of farms.
Using a case-control study, we assessed potential risk factors for HPAI outbreaks in poultry farms in Denmark, including factors related to the environment and farm management, staff and visitors, biosecurity measures, ventilation, wild bird and rodent observations, and trade of poultry and their products. We included 29 farms with primary outbreaks of HPAI from October 2020 to September 2023. Each case was matched with two control farms based on farm size, bird species and distance to coast or wetlands.
In the source population, 38% of the case owners and 45% of the control owners declined to participate due to time constraints, concerns about legislative restrictions, and compliance issues with the veterinary authorities. Using Monte Carlo integration to estimate relevant odds ratios (OR) in a Bayesian framework, we found that observing wild waterfowl or gulls was more common near case farms (OR: 19, 95% credible interval: 3–148, Bayesian p-value: 0.02). This finding can improve future risk-based surveillance and control actions, as well as placement of farms.
Co-Author(s)
Helene Ane Jensen (University of Copenhagen, Denmark), Søren Saxmose Nielsen (University of Copenhagen, Denmark), Carsten Thure Kirkeby (University of Copenhagen, Denmark), Matthew Denwood (University of Copenhagen, Denmark), Lene Jung Kjær (University of Copenhagen, Denmark), Yuan Liang (University of Copenhagen, Denmark), Charlotte Kristiane Hjulsager (Statens Serum Institut, Denmark), Anette Ella Boklund (University of Copenhagen, Denmark)
Abstract Category
Biosecurity, mitigation, control, and post-epidemic considerations in poultry