During the 2014-15 outbreak of highly pathogenic avian influenza, the U.S. poultry industry learned that rapid depopulation stops viral replication on an infected farm and reduces the likelihood of further spread of the virus. However, it can be difficult to quickly and humanely euthanize large numbers of caged layers or large turkeys.
At the time of the outbreak, the methods for depopulation of poultry acceptable to the American Veterinary Medical Association (AVMA) and the United States Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) included water-based foam, modified atmosphere euthanasia carts and whole house carbon dioxide (CO2). These are effective in providing a quick end to the suffering of diseased flocks and reducing the potential spread of the disease to healthy flocks. Nevertheless, they are not practical for use on all farms because of the type of housing, the type of birds or the weather. None of the processes work particularly well with caged layers, and severely cold weather can freeze foaming equipment.
Ventilation shutdown depopulation (VSD) may solve this dilemma. As the poultry industry learned through unfortunate experience throughout the years, when ventilation ceases in a modern poultry house – by accidental loss of electrical power, for example – the birds housed inside die fairly rapidly.
However, VSD is not considered an acceptable poultry depopulation method by AVMA or APHIS. It was not approved for use during the 2014-15 avian influenza outbreak. The process, the physiological changes in the birds and the animal welfare aspects of VSD are currently not well understood due to lack of research.
To begin understanding VSD, and perhaps find ways to improve it, the U.S. Poultry & Egg Association (USPOULTRY) is funding research at North Carolina State University focused on learning the details of the environmental changes occurring in the poultry house during VSD as well as the physiologic responses of the birds as the environment changes. N.C. State’s Dr. Ken Anderson, who is directing the research, and his colleagues completed the first research grant from USPOULTRY and are now working through a second VSD research grant.
Anderson’s group already learned a great deal. They confirmed the cause of death during VSD is hyperthermia. Additionally, VSD alone cannot be relied upon to provide 100 percent lethality in a timely or humane manner. By providing supplemental heat or CO2, the process becomes more rapidly lethal and more humane. They call this modification VSD+. They define VSD+ as increasing natural CO2 by shutting down ventilation in a sealed poultry house in combination with supplemental heat or CO2 (or both) to promote death by hyperthermia and hypoxia.
The industry may be able to use VSD+ for emergency disease depopulation in the future when other techniques aren’t practical. As the research progresses, both AVMA and APHIS show keen interest in the results. Hopefully, they will approve using the method in dire circumstances. VSD+ can help the poultry industry meet the timeline goal of depopulation within 24 hours of a confirmed diagnosis and will humanely end the suffering of infected flocks during a disease outbreak.
