Ventilation shutdown to expedite depopulation of flocks affected by avian influenza was first considered in August 2015, as the outbreaks continued to spread. With the recent re-emergence of avian influenza in the U.S., the shutdown protocol was able to be tested.
Quick depopulation of affected flocks is important because the sooner a flock is depopulated, the risk of the virus going into fans and out into the atmosphere becomes smaller.
In September 2015, the U.S. Department of Agriculture (USDA) approved ventilation shutdown as an emergency depopulation method to be used in flocks that have been affected by avian influenza.
Previously, the most effective and commonly used depopulation methods had been through use of carbon dioxide and water-based foam. However, at the height of outbreak detections, APHIS stated that the existing methods were insufficient for rapid depopulation and disposal. The longer the depopulation process takes, the greater the risk for the spread of the virus, the agency stated.
According to the APHIS documents, carbon dioxide and water-based foam methods will continue to be the primary methods first considered in an avian influenza response, but if these methods will not achieve depopulation of infected flocks within 24 hours, ventilation shutdown may be considered. However, ventilation shutdown should only be used after a full consideration of the epidemiologic threat posed concludes that no other method can achieve a sufficiently timely measure of assurance that the virus won’t spread. Further, ventilation shutdown can only be used to depopulate flocks if agreed upon by APHIS officials, state or tribal officials and the incident management team and national incident coordinator.
Earlier this month, at least 10 Indiana turkey flocks were affected by H7N8 avian influenza.
According to information provided by the National Turkey Federation, six of the 10 affected flocks were successfully depopulated by January 18, while depopulation efforts were underway in the other four. Ventilation shutdown was effectively utilized, according to NTF. In addition, depopulation by foaming was also done, but below freezing temperatures caused operational difficulties with foaming machines.
With a strong possibility that avian influenza might return to the United States in the fall, government and industry groups are considering using ventilation shutdown as a form of emergency depopulation of flocks that have been affected by highly pathogenic avian influenza.