04 October 2026
A recent publication in the World Organisation for Animal Health (WOAH) Scientific and Technical Review highlights the growing importance of vaccination as a strategic complement to traditional control measures against high pathogenicity avian influenza (HPAI). Authored by a collaborative team of researchers from the United States Department of Agriculture’s Animal and Plant Health Inspection Service (USDA APHIS), the University of Minnesota’s Secure Food Systems Team, and the USDA Agricultural Research Service’s National Poultry Research Center, the study examines the emerging challenges of surveillance in immunized poultry. The authors explain that while vaccination reduces clinical disease and limits virus transmission within and between flocks, the resulting reduction in viral shedding can make detection more difficult, necessitating enhanced and carefully designed surveillance strategies.
To explore these dynamics, the researchers developed a stochastic within-flock model to simulate HPAI transmission across different levels of flock immunity. Their analysis confirms that targeted sampling of dead birds remains a highly sensitive and effective surveillance approach in vaccinated flocks, substantially outperforming random sampling of live birds. The study further demonstrates that increasing the frequency of sampling substantially reduces the time required to detect the virus and decreases the number of infectious birds present at the time of detection, thereby reducing the risk of lateral transmission between farms.
However, the researchers emphasize that surveillance protocols should be tailored to flock size, transmission rates, and baseline mortality levels. For example, larger flocks require more samples to reliably detect infection against the background of normal daily mortality. In smaller flocks with slower virus transmission, distributing sampling efforts across two consecutive days may improve detection efficiency. Ultimately, the study concludes that optimizing surveillance strategies to balance timely detection with efficient use of resources is essential for mitigating the risk of undetected HPAI transmission.
Malladi et al. (2026) Targeted surveillance for high pathogenicity avian influenza in vaccinated birds. Sci. Tech. Rev. 2026;45:3790.
