Caring during crisis: Animal welfare during pandemics andnatural disastersHumane killing of animals for diseasecontrol purposes.

1. Caring during crisis:
animal welfare during pandemics and
natural disasters
Humane killing of animals for disease
control purposes
Mohan Raj BVSc MVSc PhD
Department of Clinical Veterinary Science
University of Bristol
Langford BS40 5DU, UK
M.Raj@bristol.ac.uk

2. Disease outbreaks

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. Sources of HPAI infection
Poultry
Direct contact with
– Infected birds
– Respiratory secretions from infected birds
– Faeces of infected birds
Humans
Exposure to infected birds, their faeces or dust or soil
contaminated with faeces

11. Minimising human exposure
Ventilation 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

12. Previous experience
2003 AI outbreak in the Netherlands (example)
30 million birds were slaughtered within 3 km radius
1242 commercial farms
8000 hobby / back yard flocks
Revealed pros and cons of various killing methods
Gerritzen et al (2006) Veterinary Record, 159: 39-42

13. 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

14. Gas mixtures
Carbon dioxide has been used in,
Skips and waste bins
Modified Atmosphere Killing (MAK) Carts
Containers

15. Skips and bins in use
Courtesy: Dr. Pam Hullinger, California, USA

16. Waste bins

17. 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

18. 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

19. Container in use

20. 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

22. 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

23. 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

24. WHG – lance position for deep litter
1.5 meters from ground
CO2 slurry directed towards ceiling
Uses heat in headspace
Birds excluded for 20 meters

25. WHG – deep litter
Bird dispersal
before gassing
Bird clumping in
small amount
after gassing
Barrier excluded
birds, some
clumping seen
around barrier

26. WHG battery cage
9000 end-of-lay hens
4 tiers, each 60 cages
long
8 rows of cages

27. WHG – battery cage - lance position

28. 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

29. Other methods of CO2 admin into
houses
• Dry ice blocks
• Crushed dry ice
• Delivered from cylinders
– No serious bird welfare concerns with these
methods

30. WHG with nitrogen
Courtesy: Camilla Andersen, Denmark

31. 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

32. 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

33. 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

34. Inhalation anaesthetics
halothane 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

35. 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

36. 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

37. 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?

38. Fire fighting foam (UK)

39. 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

40. Foam maker & Perspex box
Mohan Raj, Gordon Hickman and Colin Smith

41. Foam made with shampoo & air
Foam filled Perspex box rapidly
Bobbles burst due to bird movement
Bird survived with large air pockets
Observation ended after 5 minutes

42. Foam made with shampoo & nitrogen
Foam filled the Perspex box within seconds

43. Foam made with shampoo & nitrogen
Oxygen level dropped to less than 1% in the box
Bird started to show anoxic convulsions
Foam depleted

44. 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?

45. 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?

46. 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

47. 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?

48. Thank you
Acknowledgements
Camilla Andersen, Danish Veterinary and Food
Administration, Denmark
Lotta Berg, Swedish Animal Welfare Agency, Sweden
Gordon Hickman, Animal Health, UK
David Pritchard, Defra, UK