Killing poultry using hyperthermia

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Death caused by hyperthermia. This questionable method has been developed as a last resort option in case of a large-scale outbreak of High Pathogen Avian Influenza in the UK. Even in EU Regulation EU …

Death caused by hyperthermia. This questionable method has been developed as a last resort option in case of a large-scale outbreak of High Pathogen Avian Influenza in the UK. Even in EU Regulation EU 1099/2009 there is room for countries to use this kind of methods, when compliance is likely to affect human health or significantly slow down the process of eradication of a disease. (EU 1099/2009; article 18, under 3).

Hyperthermia means that the cause of death is overheating the shed of the birds. The normal core body (CB) temperature of a bird must remain within a narrow range around a mean value of 41.4°C if its welfare is to be safeguarded.

If the core body temperature rises above 45°C most poultry will die quickly. To ensure VSD is effective the temperature in the house must rise to 40°C or greater and remain at that level. Maintaining a relative humidity of at least 75% will help speed the onset of death through hyperthermia.

This DEFRA document provides procedures and instructions on using Ventilation Shutdown (VSD) as an emergency method of killing of poultry for disease control purposes.

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  • 1. www.defra.gov.uk GUIDELINES FOR KILLING POULTRY USING VENTILATION SHUTDOWN (VSD) September 2009 Version 9
  • 2. A. Introduction 1. This document provides instructions on using Ventilation Shutdown (VSD) as an emergency method of killing of poultry for disease control purposes as permitted under Schedule 9, paragraph 2 of the Welfare of Animals (Slaughter or Killing) Regulations 1995 as amended. 2. Authority to use Ventilation Shutdown (VSD) will not be given unless Highly Pathogenic Avian Influenza (HPAI) infection has been confirmed. VSD can only be used as a last resort. All other permitted killing methods must be explored and discounted first. 3. VSD must not be used unless written authority has been obtained from the Secretary of State. VSD cannot be used in Scotland or Wales. The National Disease Control Centre (NDCC) Joint Co-ordination Centre (JCC) Field Operations Team will inform the Local Disease Control Centre (LDCC) in writing when written authority has been given by the Secretary of State. It is anticipated that it could take up to 24 hours (although every attempt will be made to speed the approvals process up) to obtain written approval from the time the Field Report (see VO/ROD Instructions on the Preparations of a Field Report on the Suitability of Buildings for Whole House Gassing (WHG) or Ventilation Shutdown (VSD) to Kill Poultry During an Outbreak of Highly Pathogenic Avian Influenza)) is submitted to the NDCC. Where VSD is used it can  only  be  undertaken  under  the  “direct  supervision  of  an  official  of  the   Secretary  of  State”. 4. The aim is to quickly raise the temperature inside the house to 40°C or more within 30 minutes of the commencement of VSD operations by sealing the house, shutting down the ventilation and introducing heat (using supplementary heaters if required to achieve a rapid increase in temperature) and then maintaining that temperature for a minimum of three hours. 5. Death is caused by hyperthermia. The normal core body (CB) temperature of a bird must remain within a narrow range around a mean value of 41.4°C if its welfare is to be safeguarded. If the core body temperature rises above 45°C most poultry will die quickly. To ensure VSD is effective the temperature in the house must rise to 40°C or greater and remain at that level. Maintaining a relative humidity of at least 75% will help speed the onset of death through hyperthermia. 6. The results of modelling show that in optimum conditions for VSD, the time taken for 2kg broiler chickens to reach a lethal CB temperature of 45°C with supplementary heating supplied is 35 minutes. This assumes a leakage rate from the building of no more than 2 air changes per hour, an ambient temperature of 10°C and an ambient humidity of 70%. If day old chicks are substituted for 2kg broilers, then the time to reach a CB temperature of 45°C is 40 minutes with heaters operating.
  • 3. B. Pre killing planning 7. VSD should only be supervised by staff who are fully briefed on the VSD operating guidance and associated instructions. An Animal Health / Defra official must be nominated by the LDCC to undertake direct supervision of the VSD process. 8. It is anticipated that a team of at least 6 people will be required to seal a medium size poultry house and to install monitoring equipment and supplementary heaters (if required). The number of people required will depend on the type of ventilation system, the age and size of the building. 9. Where supplementary heaters are required the heaters used must be fan assisted, mobile, portable, have a self contained fuel supply and have a fuel capacity of at least 3 continuous hours. The unit must be equipped with the facility to allow remote thermostatic control (see more detailed specification at Annex A). 10. The coldest and draughtiest areas of the house are usually the end walls due to catching doors and the recent preference for tunnel ventilation where large fans are located. Heat will first migrate towards the roof space and then along the length of the house, heating from the ceiling downwards. Fan assistance from the heater is important for heat distribution. One heater must be located near each end wall, regardless of the further numbers that may be needed. To ensure good heat distribution there must not be excessive distance between the remaining heaters. This may require the use of several smaller heaters rather than a more limited number of higher capacity heaters. Further guidance on the location of heaters inside the house is given at Annex B. 11. Heaters will require a power supply. Where the site supply is not suitable backup generators will need to be provided (See Annex C). In addition temperature control and monitoring equipment will be required (See Annex D). C. Sealing the house 12. The building must be sealed sufficiently to ensure it is reasonably air tight. This will help ensure the quick build up of heat inside the building following VSD. Poultry houses are designed with ventilation systems to provide for the welfare of the stock and these systems have large numbers of fans and ventilation inlets. They are not air tight and frequently there are gaps around door frames, in the structure of the dwarf walls and often between roof and wall panels. Newer buildings tend to seal better than older ones. There are two components to be considered when sealing the building: sealing the ventilation inlets/outlets and sealing significant gaps in the structure of the building (e.g. gaps between doors and walls, holes in walls).
  • 4. Wherever possible the house must be sealed from outside to minimise exposure of personnel to infected birds and contaminated material. 13. Materials that can be used for sealing include: Heavy gauge plastic sheet (e.g. as used in the construction industry to form a water impermeable membrane in floors) Wooden battens (approximately 20mm x 5mm is adequate) to secure the plastic sheet, Nail guns and nails to secure battens (including spares to replace those that will jam/malfunction), Expanding foam (e.g. as used in the construction industry to fill gaps in walls between pipes and brick work etc) Duct tape 14. Poultry buildings are normally force-ventilated. Air may be drawn in through the walls or less commonly the roof and extracted, by fans through the walls or roof. The inlets and outlets normally have housings (e.g. ducts or so-called  ‘boxes’) associated with them that are external to the building. More modern ventilation inlets (e.g. Skov-type) may have dampers/deflectors that adequately seal the inlets. Older systems or systems that have inlets that cannot be sealed using the equipment fitted will need to be sealed by alternative means. 15. Sealing fan boxes using plastic sheet and battens is done most efficiently if teams work in pairs (assume approximately 3 - 4 minutes per box if all materials are to hand). Buildings can be prepared in advance as long as adequate ventilation is maintained until VSD commences. 16. All significant holes (e.g. larger than 25 cm2) in the walls/doors or exposed drains should be sealed. Plastic sheet should be used, if required to seal any significant gaps between doors and the walls etc. Ensure that all doors are securely closed. 17. A control point should be established. This should provide shelter from the elements, light, power and space to conduct briefings. It should also allow easy access to monitoring equipment. D. Sealing the ventilation system 18. Wind blowing across fan ducts on the roof of the building (or other similar apertures) will tend to draw air through the building reducing the temperature inside the house. Inlets set in the side walls may have flaps or dampers that can be positioned to seal the aperture. Inlets that do not have this arrangement and side (wall) outlets (which are unlikely to have this arrangement) will need to be sealed using plastic sheet and battens. 19. Most ducts set in the roof will have dampers, boxes or similar that can be winched into place. It is unlikely to be feasible to seal ventilation ducts set in the roof beyond using the dampers, boxes etc that are already available.
  • 5. 20. The ventilation system should not be sealed until immediately prior to full VSD however fan boxes can be sealed on three sides well in advance with the final side, that closes the gap over the duct, being secured when required. 21. The drinking system for the birds must not be shut off during VSD. E. Supplementary heating 22. House heaters should be switched on and set to operate at their maximum capacity during VSD. It might be necessary to override thermostat settings where these are set to turn the heaters off at a temperature below 40°C. The aim is to quickly raise the temperature inside the house to 40°C or more by sealing the house, shutting down the ventilation and introducing heat, using supplementary heaters if required and then maintaining that temperature for a minimum of three hours. Supplementary heaters will switch off when the house has reached 40°C. The results of modelling show that in optimum conditions for VSD, the time taken for 2kg broiler chickens to reach a lethal CB temperature of 45°C with supplementary heating is 35 minutes. If day old chicks are substituted for the broilers then the time taken to reach a CB temperature of 45°C is 40 minutes. 23. The NDCC JCC Field Operations will inform you of the supplementary heating capacity and number of heaters required. This assessment will have been made by the NDCC JCC Field Operations Veterinary Adviser in collaboration with the Defra Animal Welfare Team VA. The assessment will be based on the information provided in the field report, typical heat loss figures for poultry units and modelling data. Additional preparation time should be allowed where a large number of supplementary heaters have to be installed. 24. Calibrated temperature sensors should be installed at bird height in open floor based systems. For caged birds sensors should be placed in bottom / middle and top row cage positions. Ideally in medium to large houses there should be four sensors, one for approximately every 20m of house length. F. Other preparations 25. Ensure that there is enough suitable leak proof transport available on site (or big bags) to take all the carcases. This is dependent on numbers and the disposal method. 26. Ensure there are sufficient trained staff available to kill any birds remaining alive at the end of the VSD period and that there is sufficient equipment available to complete this task as quickly as possible. 27. Ensure personnel are available to disinfect the carcases and to load them into bags or a leak proof transport container. It will be particularly important to remove carcases as soon as possible after VSD has been completed as the elevated temperature involved will result in very rapid onset of decomposition.
  • 6. G. VSD process 28. At the commencement of VSD all remaining gaps should be sealed and all fans turned off. It may also be necessary to disable failsafe systems and alarms etc. designed to prevent accidental ventilation shutdown. When sealing the house, the system fan outlets at opposite ends of the building should be switched off last to maximise airflow across the birds immediately prior to the commencement of full VSD. Supplementary heaters / in situ heating systems should be turned on at their highest setting. The house should remain sealed for 3 hours and no one should enter the house during this period. 29. Monitor the temperature reached inside the house continuously. Record the temperature at the start of VSD and record the temperature at half hourly intervals whilst VSD is in progress. 30. Maintain VSD for 3 hours. At the end of this period the heaters should be turned off, vents should be uncovered and the ventilation system restarted to cool the house and vent any build up of ammonia. 31. Once the temperature inside the house has dropped below 30°C staff can enter the house. Birds should be inspected for signs of life and any surviving birds killed. Killing should be undertaken humanely using neck dislocation or other permitted method. 32. Once all the birds are dead enter the house and spray carcases with disinfectant. 33. Load carcases into bags / leak proof container for disposal. H. Post VSD report 34. A post VSD report using an EXD 64 form should be sent by the LDCC to NDCC and Defra AW Core Team within 24 hours of completion of VSD. In addition to the normal comments and observations the following data should be included: heaters used the capacity of the in situ / supplementary heaters used the measures taken to ensure the effective application of VSD duration of VSD ambient temperature and internal house temperature immediately before VSD commenced the temperature reached inside the house taken at half hourly intervals the approximate number of birds found alive at the end of the 3 hour VSD period the condition of those birds remaining alive at the end of the VSD period (conscious / unconscious etc.) the method used to kill any birds remaining alive
  • 7. recommendations to enhance the effectiveness of VSD Checklist Of Equipment Polythene sheeting or other material to seal the house Wooden battens 20mm x 5mm Nail guns, nails and spares Expanding foam Duct tape Supplementary space heaters (where NDCC Animal Welfare Team have advised the need for additional heaters) LPG / Fuel for supplementary heaters Generators to power heaters (if site supply not adequate) Fuel for generators Control equipment Temperature sensors and monitors Leak proof transport containers / big bags Disinfectant / knapsack sprayers Percussion or other permitted humane killer For each operator Respirator (typically FFP3 standard) Safety goggles Rubber boots Other PPE – based on site and disease specific risk assessment Key Reminders Always wear Safety glasses and appropriate PPE Always work with someone else and never on your own Visual checks by trained staff must be undertaken immediately after VSD is terminated to ensure that all birds are dead Remove carcases as soon as possible If something goes wrong notify the NDCC JCC Field Operations immediately
  • 8. Annex A SUPPLEMENTARY HEATER SPECIFICATION The basic specification for a suitable supplementary heater is as follows: o Mobile – they must have wheels, however, the wheel should not be so narrow as to sink into damp litter o Portable – 2 adults must be able to lift the unit, despite the wheels, as farms always offer obstacles. This limits the weight to about 70kg o Self contained fuel supply – as it is not feasible to use on-farm LPG supplies, supplementary LPG bottles should be provided or the heater must carry its own fuel o Fuel capacity - the fuel capacity must provide at least 3 hours continuous running o Type of fuel – The fuel required will be dependent on the heater type selected. Gas fired heaters require bottled of LPG. Oil-based heaters will use heating oil. o Control – the unit must be equipped with the facility to allow remote thermostatic control o Fan assistance – the size of the houses and heat capacity demand will require fan assisted heaters o Capacity – the higher the capacity, the larger the unit, but the fewer required. There will be a practical limit to capacity governed by the portability of the heater and the need to ensure an even spread of heat throughout the house A call off contract is in place for the supply of direct fired gas heaters. The operating characteristics are shown in the table below: Wt (kg) 28 G100TA 29 G260TA Output kW 102 77 Fuel Kg/hr 7.3 5.5 Cyls Kg 3x47 3x47 Duration Power (hours) (amps) 19 0.5 25 0.8 Thermostat An example of a suitable oil fired heater is made by Thermobile. The operating characteristics are shown in the Table below. Wt (kg) 48 TA 40 69 TA 80 Output kW 46 93 Fuel L/hr 4 8 Tank L 80 160 Duration Power (hours) (kW) 20 0.43 20 0.83 Thermostat
  • 9. To provide effective heat distribution, it is better to have more small units than a few large ones to meet the heat requirements. However, the setting up time will be longer.
  • 10. Annex B GUIDANCE ON LOCATION OF SUPPLEMENTARY HEATERS The coldest and draughtiest areas of the house are usually the end-walls, due to catching doors and the recent preference for tunnel ventilation where large fans are located. Heat will first migrate towards the roof space and then along the length of the house, heating from the ceiling downwards. Fan assistance from the heater is important for heat distribution. One heater must be located near each end-wall, regardless of the further numbers theoretically required. Also, if heat requirement only demands 3 heaters, but there is an excessive distance between the remaining heaters, an extra heater should be used to ensure good heat distribution. The basic specification for locating supplementary heaters is shown in Figure 1 (below):o One heater within 5m of each end-wall o Minimum: 1 x heater per 20m house length, between end-wall heaters o Heater positioned approximately 3m from alternate side-walls o Heat is directed across the house Figure 1 – Location of heaters and temperature probes < 20m 5m 5m < 20m 3m = heaters = temperature probe 3m = Heat direction
  • 11. Examples of heater distribution and layout Example 1 - location and distribution for 5 heaters Control 2 x HP15 Dual Zone controller 4 x probes 4 x heating zones = heater = temperature probe 40°C 40°C = HP 15 Controller = direction of heat = heater separation = <20m along house length = <5 m from end walls 40°C
  • 12. Example 2 - location and distribution for 14 heaters e.g.      ‘Very  large’  house  (90′  x  360′) 3 ACH, poor insulation = 1250 W 14 x 93kW = 1300kW Approximate centres: 9m Extra heater at ends of the house where heat loss can be greatest. 40°C Control 2 x HP15 Dual Zone Thermostat 4 x probes 4 x heating zones = heater = temperature probe 40°C = HP 15 Controller = direction of heat = heater separation = <20m along house length = <5m from end walls 40°C
  • 13. Annex C SPECIFICATION FOR BACK UP GENERATORS Whilst poultry farms have ample power capacity to run fans and equipment, with large back-up generators, they are notoriously badly supplied with power supply points to run accessories. Most equipment is hard-wired and protected from water ingress. What power points exist will be located in the control room and in discrete parts of the house and have limited current capacity. The requirement for multiple heater units that each demand a reliable power supply, at short notice, will mean that is impractical in nearly all cases to locate sufficient power supply points in the right location within the farm To maintain an independent approach to the procedure, it is necessary to provide portable generators. The basic specification for a suitable generator is as follows: o Portable – 2 adults must be able to lift the unit. This limits the weight to about 40kg o Self contained fuel supply – the generator must carry hold its own fuel o Fuel capacity - the fuel capacity must have at least 3 hours continuous running at maximum capacity, assuming that the generators are located in the houses. To ensure the generators are functioning, can be replaced and have fuel, they should be located outside the houses, with power supply leads running into the house via sidewall inlets or fan shafts o Power output - generators that are portable enough to use on a farm are limited in power output. For any given KVA rating (volts x amps), it must be assumed that only 70% is available to operate equipment, due to power-factor corrections. A 3KVA unit will provide: 3000 VA/240v 12.5 Amp x 0.7 = = 12.5 amps 8.75 amps o 1 x 3KVA generator could run 16 x G100TA heaters requiring 0.5 amps o 1 x 3KVA generator could run 2 x TA80 heaters requiring 3.5 amps (Note: it is always advisable to have at least two generators on site to guard against possible equipment failure. A suitable example is made by SIP, model Medusa 3KVA as described below:-
  • 14. Specification of a Medusa 3KVA generator Wt (kg) 3KVA 37 Output cont 3kVa Fuel Petrol Tank L 3.6 Duration (hours) 2.6 Other generators of a similar specification would be suitable. Power (kW) 0.43
  • 15. Annex D TEMPERATURE CONTROL AND MONITORING EQUIPMENT It is essential to have remote control of the heaters and remote monitoring of the environment. Simple digital controllers are available. The basic specification is as follows: o Temperature registration – the unit must be able to monitor temperature with a resolution to 0.1°C, with an easy-to-read display o Temperature sensor - monitors via a remote digital probe o Heater control – the unit must control the heaters in relation to a set temperature. It must be able to adjust the heating bandwidth. The heater and controller must be compatible and there must be sufficient cable to link to the control unit along very large houses o Zone control – Due to the size of poultry houses, more than one sensor should be used. The control unit should be able to accommodate more than one sensor. Ideally, in medium to large houses, there should be 4 sensors, i.e. one zone for approximately 30m of house length o Portable - to be portable, units will need a power lead and mounted in a suitable panel or box An example of a suitable control unit is an HP 15 – Dual zone thermostat supplied by Climatec. This controller can monitor and control 2 heating zones via two remote sensors. It can activate each group of heaters independently. In large and very large houses, 2 units should be used, providing a total of 4 zones with its own temperature registration and control, and 4 outputs to safely activate multiple heaters. The temperature probes should be in the centre line of the house but between the heaters, i.e. not in a direct line with the heater nozzles (see figure 1 at Annex B above).