The impact of holding time on the likelihood of moving internally contaminated eggs from a highly pathogenic avian influenza infected but undetected commercial table-egg layer flock

Emergency response during a highly pathogenic avian influenza (HPAI) outbreak may involve quarantine and movement controls for poultry products such as eggs. However, such disease control measures may disrupt business continuity and impact food security, since egg production facilities often do not have sufficient capacity to store eggs for prolonged periods. We propose the incorporation of a holding time before egg movement in conjunction with targeted active surveillance as a novel approach to move eggs from flocks within a control area with a low likelihood of them being contaminated with HPAI virus. Holding time reduces the likelihood of HPAI-contaminated eggs being moved from a farm before HPAI infection is detected in the flock. We used a stochastic disease transmission model to estimate the HPAI disease prevalence, disease mortality, and fraction of internally contaminated eggs at various time points postinfection of a commercial table-egg layer flock. The transmission model results were then used in a simulation model of a targeted matrix gene real-time reverse transcriptase (RRT)-PCR testing based surveillance protocol to estimate the time to detection and the number of contaminated eggs moved under different holding times. Our simulation results indicate a significant reduction in the number of internally contaminated eggs moved from an HPAI-infected undetected flock with each additional day of holding time. Incorporation of a holding time and the use of targeted surveillance have been adopted by the U.S. Department of Agriculture in their Draft Secure Egg Supply Plan for movement of egg industry products during an HPAI outbreak.