Avian influenza, commonly known as bird flu, is a highly contagious viral disease that can infect birds such as chickens, turkeys, and ducks. There are two main types of bird flu viruses that cause concern: H5N1 and H7N9. Both can cause severe disease in poultry and have the potential to occasionally spread to humans. When there is an outbreak of avian influenza on a poultry farm, measures must be taken to contain and eradicate the disease. This includes the humane culling and disposal of infected birds in a biosecure manner.
Why Culling is Necessary
Culling refers to the depopulation or killing of animals in response to an infectious disease outbreak. For avian influenza, culling is necessary for several reasons:
– To prevent further spread of the virus to other poultry – Avian influenza spreads rapidly among birds through contact with infected feces, respiratory secretions, and other fluids. Culling removes infected animals that can transmit the virus to other birds.
– To prevent transmission to humans – Some strains of avian flu, like H5N1 and H7N9, have the potential to infect humans exposed to infected birds. Culling flock helps protect human health.
– To control and contain the outbreak – Quickly culling all infected/exposed birds is key to getting an avian flu outbreak under control before it spreads more widely.
– To meet trade requirements – Many countries ban poultry imports from countries with avian flu. Culling helps resume trade.
Culling Methods
Infected flocks are culled using humane methods that result in rapid death with minimal pain or distress. The main methods are:
– Gassing with carbon dioxide, argon, or nitrogen – Birds are placed in a sealed chamber and gas is released, causing unconsciousness and death.
– Ventilation shutdown – Foam or other sealants are used to seal off poultry housing ventilation fans. Birds die as oxygen levels drop and carbon dioxide builds up.
– Water-based foam – Foam that cuts off air supply is pumped into the birds’ housing, causing quick suffocation.
– Cervical dislocation – The bird’s neck is separated from the spine using a rod or blade, severing the spinal cord. Used on smaller flocks.
– Electrocution – An electric current is passed through the bird’s brain, causing loss of consciousness and cardiac arrest.
– Gunshot – A captive bolt, firearm, or similar device is used to destroy the bird’s brain.
Carcass Disposal Methods
Proper disposal of culled birds is critical to prevent further disease spread. The most common disposal methods are:
Burial
Carcasses are transported to an approved landfill or other burial site and covered with dirt. Burial pits must be at least 6 feet deep and slopes present to prevent ground water contamination. Lime or other disinfectants may be added to accelerate decomposition. Burial is a simple, low-cost option if there is sufficient land available.
Incineration
Carcasses are burned in an incinerator designed for animal disposal. Incineration effectively destroys viruses and pathogens and reduces volume significantly. Requires special equipment and facilities that may not be readily available in all areas. Ash must be disposed of properly as well.
Rendering
Carcasses are transported to a rendering facility which cooks down the material to destroy pathogens. The resulting rendered fats and proteins can be used for non-animal feed applications. Requires access to a rendering plant and coordination of transport.
Composting
Carcasses are layered with carbon sources like wood chips or sawdust in long piles known as windrows. Natural microbiological heating destroys pathogens as the material decomposes. Compost windrows must be monitored and turned for proper pathogen treatment. Results in a useful soil amendment product.
Alkaline Hydrolysis
Carcasses are digested using a combination of heat, pressure, alkali chemicals, and water, leaving only bones and fluid. The process effectively sterilizes material. Specialized equipment is expensive however.
Landfilling
If approved landfills are unavailable, specially designed avian influenza landfills may be constructed. Carcasses are layered with lime and soil in a lined pit. Landfilling requires considerable land area and controls to prevent groundwater contamination with runoff.
Culling Logistics
When culling infected flocks, careful planning and coordination is required for efficient disposal. Steps typically include:
1. Planning
– Determine extent of outbreak and number of birds to be culled
– Select preferred culling and disposal methods
– Identify locations for culling activities and disposal sites
– Estimate resources needed for culling crews, transportation, equipment, supplies, etc.
– Develop detailed plans and protocols for each step of the process
2. Mobilization
– Assemble culling personnel and train for duties
– Alert disposal sites like landfills, incinerators, composting operations
– Prepare required equipment and supplies for culling and carcass handling
– Arrange necessary transportation for culling crews, equipment, and carcass removal
– Alert local authorities regarding road usage, traffic control, and community impacts
3. Depopulation
– Restrict access to infected premises during culling
– Humanely cull birds using selected method and approved protocols
– Place carcasses in approved containers, trucks, dumpsters for transport
– Thoroughly clean and disinfect premises after removal of birds
4. Disposal
– Transport carcasses to selected disposal locations
– Manage carcass disposal according to method protocols (burial, incineration, etc.)
– Clean, disinfect and inspect all equipment, vehicles, PPE after disposal tasks
– Follow all biosecurity procedures throughout process
Proper planning helps ensure culling and disposal can be carried out quickly, safely, and effectively to control the outbreak. Close coordination between government authorities, culling contractors, disposal sites and others is key.
Environmental Considerations
Culling and disposing of large numbers of birds must be done with care to avoid environmental impacts. Considerations include:
Ground and Surface Water Contamination
– Line burial pits and prevent runoff from landfills
– Monitor compost windrows for leachate
– Divert clean water from entering disposal areas
Soil Contamination
– Test soils after burial or composting operations
– Spread composted materials thinly to prevent nutrient buildups
Air Pollution
– Use incinerators designed to meet air quality standards
– Position compost windrows to avoid nuisance odors
Wildlife Disturbance
– Cover disposal pits, compost piles to prevent scavenging
– Use noise control devices around burial or disposal sites if needed
Community Impacts
– Notify nearby residents regarding operations and schedule
– Clean vehicles and monitor for dust, noise on public roads
– Address community concerns and complaints promptly
Following best management practices can help mitigate environmental risks during outbreak disposal activities.
Health and Safety
The health and safety of both birds and humans must be carefully considered when culling infected flocks. Precautions include:
Worker Health and Safety
– Provide PPE for culling crews including protective suiting, respirators, face shields, gloves, rubber boots, etc.
– Establish decontamination procedures for personnel and equipment
– Address physical hazards of culling methods like noise exposure
– Monitor crews for signs of heat stress and fatigue
Biosecurity
– Restrict access to infected premises with security personnel
– Provide foot baths, hand sanitizer, and cleaning stations
– Disinfect equipment, vehicles, and PPE after use
– Safely dispose of used culled materials and debris
Disease Monitoring
– Closely monitor workers for any influenza-like illness
– Conduct medical surveillance of personnel during outbreak
– Provide antiviral medications to workers as recommended
Humane Euthanasia
– Use only approved, humane methods for culling
– Minimize bird stress during handling and transport
– Ensure proper training of all culling personnel on procedures
Psychological Support
– Offer mental health services to aid workers with emotional distress
– Provide breaks and temporary assignment rotations as needed
– Address worker concerns and respects their wellbeing
Following health and safety protocols protects both the workers tasked with bird culling and the surrounding community.
Financial Considerations
Culling and safely disposing of millions of birds is an extremely costly endeavor. Economic considerations include:
Indemnity Payments
– Government compensation to producers for euthanized birds and flock cleanup costs. A single farm outbreak can equal payments of several million dollars.
Culling Activities
– Contract fees for culling personnel, equipment rentals, PPE, supplies, utilities, security, etc. can tally hundreds of thousands per site.
Carcass Disposal
– Fees for transportation, incineration, rendering, landfilling, etc. based on volume and locality. Burial costs depend on land values.
Monitoring and Testing
– Expenses for veterinary oversight, sample collection and analysis during and after culling. Routine surveillance is expensive.
Cleaning and Disinfection
– Costs for sanitizers, decontamination supplies and labor to cleanup infected sites after culling.
Community Impacts
– Local economic losses in jobs, business revenue, and poultry production until restocking can occur.
– Public costs for communications, traffic control and community health monitoring.
While culling costs may seem high, they are small compared to the costs of allowing avian influenza to spread more widely. Fast containment protects poultry producers, associated industries, exports and human health.
Case Studies
Reviewing past avian influenza outbreaks provides lessons in effective culling and disposal.
Indiana Turkey Outbreaks 2002-2003
Over 27 million turkeys across 157 farms in Indiana were culled due to H7N2 avian influenza. Foam was used to cull flocks, followed by composting and burial of carcasses on site. The coordinated response successfully contained the outbreak with no human cases.
Netherlands H7N7 Outbreak 2003
Around 30 million chickens were gassed with carbon dioxide and disposed of by rendering, burying, and burning during this widespread outbreak. The fast, coordinated culling effort has been credited with preventing greater spread across densely populated poultry areas.
British Columbia H7N3 Outbreak 2004
Approximately 17 million birds on 42 farms were humanely killed using carbon dioxide, cervical dislocation, and firearms. Carcasses were buried in approved landfills. The outbreak was contained with no human illness.
Nigeria H5N1 Outbreaks 2006-2008
Over 1 million birds were culled during multiple avian flu outbreaks by methods like gassing, neck cutting, suffocation, and drowning. Carcasses were buried or burned. Outbreak management suffered from inadequate resources, compensation, and oversight.
US Upper Midwest H5N2 Outbreak 2015
Over 48 million chickens and turkeys on 211 commercial farms were gassed and composted, rendered or landfilled to control outbreaks across 15 states. Strict biosecurity and coordination between producers, contractors and state/federal authorities were credited with the response.
Reviewing past successes and failures aids preparedness efforts for the rapid detection of avian influenza, humane culling, and proper disposal required to contain future outbreaks.
Conclusion
The quick and humane culling of infected poultry flocks, paired with safe disposal, is critical for controlling avian influenza outbreaks. While the killing of millions of birds is an enormous and sobering undertaking, the public health and economic risks of allowing the virus to spread are far greater. Avian flu outbreaks require extensive coordination between producers, government regulators, and private contractors to manage surveillance, tracing, biosecure depopulation, transportation, and treatment of carcasses. Adequate compensation and resources must be provided to poultry owners to ensure cooperation. With sound science guiding disease response protocols, and proper precautions taken, outbreaks can be contained to protect animal and human health, the environment, and the sustainability of the poultry supply chain. Continued vigilance, planning, and training is essential to prepare for the next inevitable avian influenza emergency.