Avian Influenza: Welfare During Outbreaks

Avian Influenza Outbreaks: Animal Welfare Implications

Highly pathogenic avian influenza (HPAI) is both a devastating disease for poultry and a massive welfare challenge. The disease itself causes severe suffering, while mass culling operations — the primary control method — raise profound welfare concerns of their own.

Disease Welfare Impact

HPAI H5N1 and related strains cause severe systemic disease in poultry. Clinical signs include respiratory distress, neurological signs, severe depression, and hemorrhagic lesions. Mortality rates in affected flocks can reach 90-100%, with birds experiencing significant suffering before death. The speed of disease progression — from first clinical signs to widespread mortality in 24-48 hours — limits treatment options but does not eliminate the welfare imperative of prompt action.

Mass Culling: Welfare Challenges

When HPAI is detected, rapid depopulation of affected and exposed flocks is the primary biosecurity and control measure. In the 2021-2024 HPAI outbreaks, over 200 million birds were culled globally. The welfare implications of mass culling are significant:

• Speed requirements can compromise individual welfare assessments
• Culling methods used in emergency conditions — including CO2 gassing, ventilation shutdown (VSD), and foam application — vary widely in humaneness
• VSD (turning off ventilation) causes hyperthermia and prolonged distress and is widely condemned by animal welfare scientists
• Worker capacity constraints can lead to delays that extend suffering of sick birds

Welfare-Preferred Culling Methods

Welfare science has evaluated culling methods extensively. Preferred methods for different species include:

• High-concentration CO2 (≥35% CO2) for poultry in containers
• Electrical stunning followed by cervical dislocation for small numbers
• Maceration for day-old chicks (instantaneous)
• Water-based foam application (WBF) — evidence of effectiveness but some controversy remains

Ventilation shutdown (VSD+) with additional heat is conditionally accepted in the US but remains controversial. VSD without supplemental heat is unacceptable from a welfare standpoint.

Wild Bird Welfare

HPAI has caused catastrophic mortality in wild bird populations, particularly seabirds. The 2022 Fulmarus glacialis die-off in the UK caused an estimated 35,000+ deaths in a single population. Welfare interventions for wild birds are limited but include: not disturbing sick birds, reporting cases for surveillance, and supporting rehabilitation facilities for recoverable individuals.

Prevention and Biosecurity

Preventing HPAI outbreaks is the most welfare-positive approach. Enhanced biosecurity on farms — wild bird exclusion, controlled access, monitoring programs — reduces transmission risk. Vaccination programs for poultry, now approved in several countries including France and Mexico, offer promise for reducing both disease burden and the scale of culling operations.