Caring during crisis: animal welfare during pandemics and

natural disasters

Humane killing of animals for disease control purposes

Mohan Raj BVSc MVSc PhDDepartment of Clinical Veterinary Science

University of BristolLangford BS40 5DU, UK

M.Raj@bristol.ac.uk

Disease outbreaks

Intensions of humane killing of animals for disease control purposes• Protecting human health

• Eliminating suffering in diseased animals

• Preventing suffering in susceptible animals

• Maintaining healthy national heard or flock

• Sustaining or gaining disease free status and economic advantage over competitors

Physiological basis of stunning / killing

Stunning methods induce a pathological brain state that is incompatible with the persistence of consciousness and sensibility

Stunning methods should induce immediate loss of consciousness without causing animals avoidable pain and distress- animals should remain unconsciousness until death occurs through slaughter, destruction of brain, etc

Killing methods should induce immediate death without causing animals avoidable pain and distress- hence preferred during outbreaks of diseases

Scientific reports and guidelines

American Veterinary Medical Association (AVMA) http://www.avma.org/issues/animal_welfare/euthanasia.pdf

European Food Safety Authority (EFSA)http://www.efsa.europa.eu/en/science/ahaw/ahaw_opinions/495.html

World Organisation for Animal Health (OIE)http://www.oie.int/eng/normes/mcode/en_chapitre_3.7.6.htm

Methods (1)

• Free bullet (rifles, handguns and shotguns) -large animals

• Penetrating or non-penetrating captive bolt -large animals

• Manual blow to head - neonates• Neck dislocation / decapitation - poultry

species• Electrical stunning / killing - all animals

including poultry

Methods (2)

• Gas mixtures – pigs, lamb and poultry• Lethal injection of anaesthetics - all animals

including poultry• Maceration – newly hatched chicks /

unconscious poultry• Anaesthetics in feed or water - poultry and

other birds followed by killing• Exposure to gas mixture followed by

maceration• Foam with inert gases – poultry

Method selection criteria

Includes• Nature of disease (e.g. notifiable, zoonotic) or

disaster• Location of farm• Species, number, size and age of animals• Operators’ health and safety• Availability of resources and expertise• Biosecurity• Cost and efficacy of method

Existing threat of a pandemic

• Highly pathogenic avian influenza (HPAI)• H5 and H7 strains known to infect humans• Persistence of disease in birds remains to be a

potential global threat to human health• Previous flue outbreaks caused death in millions of

people– 1918 Spanish influenza – 40 to 50 m– 1957 Asian influenza – 2 m– 1968 Hong Kong influenza – 1 m

Sources of HPAI infection

PoultryDirect contact with

– Infected birds– Respiratory secretions from infected birds– Faeces of infected birds

HumansExposure to infected birds, their faeces or dust or soil

contaminated with faeces

Minimising human exposureVentilation shut down as a killing method

– No human contact with live or dead infected birds or infected materials

– Lung ventilation of birds seriously compromised due to AI, and therefore, shutting down the ventilation of house may not be a serious welfare concern?

Humane Slaughter Association (UK) “This method raises considerable welfare concerns and the

HSA looks to all concerned to take every step to avoid this situation ever arising”

www.opsi.gov.uk/si/si2006/20061200.htm

Previous experience

2003 AI outbreak in the Netherlands (example)

30 million birds were slaughtered within 3 km radius1242 commercial farms8000 hobby / back yard flocks

Revealed pros and cons of various killing methods

Gerritzen et al (2006) Veterinary Record, 159: 39-42

Limitations of established methods• Manual catching and handling can be distressing to

poultry, may cause injury• Lethal injection, captive bolt guns and electrical

methods need manual handling and severe restraint of birds

• Mobile electrical water bath system failed to kill all the birds, need slaughter to ensure death

• Shooting with captive bolts, neck dislocation and decapitation and slaughter causes blood spillage –biosecurity hazard

Gas mixtures

Carbon dioxide has been used in,

Skips and waste bins

Modified Atmosphere Killing (MAK) Carts

Containers

Skips and bins in use

Courtesy: Dr. Pam Hullinger, California, USA

Waste bins

Concerns with skips and bins

• Throwing batches of live birds into skips and bins could compromise bird welfare

• Birds may die due to compression and suffocation by other birds

• Labour intensive• Potential health and safety hazard when used

in confined spaces

Containerised gas killing system• Gas tight steel container• Transport module full of birds loaded and then gas

supplied• Welding gas mixture – 80% argon and 20% carbon

dioxide – least aversive to poultry– Sandilands et al. (2006) Proceedings of the 40th International

Congress of the ISAE, University of Bristol, August 8th – 12th 2006.

• 2% residual oxygen for ducks and geese• 5% residual oxygen for chickens and turkeys• Operating procedures and training DVD

Container in use

Manual or mechanical emptying of containers

• Used on three farms in Norfolk LPAI outbreak with about 48,700 birds killed in less than 48 hours

• Used for East Lothian NDV outbreak for 12745 birds (partridge, quail, pheasant chicken)

• Throughput of 4000 per hour achieved with safe operation and humane kill

Whole house gassing with CO2• Moderate sealing of

ventilation needed• Minimum 45% CO2 in air• 2 minutes exposure

adequate to kill birds• Takes about 10 minutes to

fill a UK poultry house• House emptied 1 hour after

gassing• Very steep learning curve

over the last 2 years

Evolution of gas injection system• 32 mm internal

diameter• Tip cut at 30

degree angle to the ground

• Mounted on a trolley - secured to avoid recoil

WHG – lance position for deep litter

1.5 meters from groundCO2 slurry directed towards ceilingUses heat in headspaceBirds excluded for 20 meters

WHG – deep litterBird dispersal before gassing

Bird clumping in small amount after gassing

Barrier excluded birds, some clumping seen around barrier

WHG battery cage9000 end-of-lay hens4 tiers, each 60 cages long8 rows of cages

WHG – battery cage - lance position

Pros and cons of WHG with CO2• Minimal contact with birds and faeces, improved

biosecurity• Gas administration made simple and quick• Lethal concentration achieved rapidly• Delayed rigor onset in carcasses helps depopulation

from cages• Extremely low temperature (-78.5oC)

– Triple point (solid, liquid and gas)– Heat produced in the house may be adequate to avoid frost

bite or cold burn– Difficult to estimate or predict heat production / loss, vary

according to housing and husbandry conditions

Other methods of CO2 admin into houses

• Dry ice blocks• Crushed dry ice• Delivered from cylinders

– No serious bird welfare concerns with these methods

WHG with nitrogen

Courtesy: Camilla Andersen, Denmark

Pros and cons of nitrogen• Cheap and readily available in large quantities• Non-aversive to poultry• Easy to vaporise using ambient temperature• 2% residual oxygen achieved in one trial• Birds killed within 20 minutes from start• Extremely low temperature (-196oC) of liquid

nitrogen• Only gaseous form should enter houses• Air-to-air vaporisers are also available

– www.cryoquip.com for details

Carbon monoxide

• Has been used in Europe, especially Belgium, for whole house gassing

• Remains to be a choice• 1.5 to 2.0% in air can kill poultry• Not readily available• Explosive at 12.5% in air

– Presence of fire brigade essential

• Health and safety hazard• Limited availability

Cyanide

• Has been used in Europe for killing poultry in houses• Kills poultry in less than 10 minutes• Convulsions may occur in conscious poultry

– Convulsive dose less than required to inducing loss of consciousness?

• Health and safety hazard• Adverse public opinion of the method• Rapid rigor development hinders depopulation from

cages

Inhalation anaestheticshalothane in a jam jar & fish tank aerator as

vaporiser

• Can be used in containers or houses

• Humane• Potential health and

safety and environmental hazard

• Costs

Fire fighting foam (USA)“Researchers and commercial poultry companies

recently established that non-toxic water-based foam with a certain bubble size presents a practical, effective, and humane method for mass depopulation. Foam of the right bubble size creates an occlusion in the trachea of birds, causing a rapid onset of hypoxia. The foam that blankets the broiler house induces physical hypoxia—the same cause of death as the approved method using carbon dioxide gas (CO2)”. – www.avi-foam.com/specs.php

Foam Vs CO2

• Exposure to carbon dioxide does not rely on hypoxia– 40% carbon dioxide in air with 15% residual

oxygen and 45% nitrogen works as well as a mixture of 50% carbon dioxide, 20% oxygen and 30% nitrogen

• Occlusion does not occur during exposure to carbon dioxide or other gas mixture

Welfare concerns

• Occlusion of trachea = suffocation• Suffocation = physical separation of the upper

respiratory tract from atmospheric air– Drowning – Chocking – Strangulation– Clamping nostrils or smothering

• Death by suffocation is prohibited / ethically unacceptable?

Fire fighting foam (UK)

UK trials with FFF

• Air, carbon dioxide or nitrogen was used• Carbon dioxide filled foam contained 100% but foam

failed to raise due to the denser than air gas• Nitrogen filled foam contained 100% nitrogen (0%

oxygen) and foam raised well due to lighter than air gas

• Nitrogen vaporised without difficulty• Carbon dioxide difficult to vaporise – frozen pipes• Decided to pursue nitrogen in dry foam

Foam maker & Perspex box

Mohan Raj, Gordon Hickman and Colin Smith

Foam made with shampoo & airFoam filled Perspex box rapidly

Bobbles burst due to bird movement

Bird survived with large air pocketsObservation ended after 5 minutes

Foam made with shampoo & nitrogen

Foam filled the Perspex box within seconds

Foam made with shampoo & nitrogen

Oxygen level dropped to less than 1% in the boxBird started to show anoxic convulsionsFoam depleted

Post mortem examination

Tiny amount of pin-head-sized bubbles found in larynx and one centimetre into upper trachea

Ante-mortem occlusion or post-mortem entry?

Promising results

Need research and development to• Ensure the foam is robust to hold gas and fill

houses to required width, length and height, but • Remain fragile enough so that bird movement

breaks bubbles and release nitrogen• Study bird reaction to foam / welfare

implications?

Overdose of anaesthetic in feed and water

• Alpha-chloralose has been tested– 3 to 6% recommended– Very bitter in taste– Birds need to consume lethal dose in one feeding

or drinking bout– Fasting (24 h) may force birds to consume– Need a killing method, e.g. containerised gassing

• Ideal for sedating all birds, including wild, under all conditions

Summary opinion

• Whole house and containerised gassing methods are feasible and better than conventional methods– Generic operating procedures and protocols exist

• Dry foam created using nitrogen is feasible but further research and development is urgently needed

• International resources could be pooled for this common cause?

Thank youAcknowledgements

Camilla Andersen, Danish Veterinary and Food Administration, Denmark

Lotta Berg, Swedish Animal Welfare Agency, Sweden

Gordon Hickman, Animal Health, UK

David Pritchard, Defra, UK