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Biosecurity is a vital tool to reduce the effect of infections and decrease the impact of diseases in livestock populations. Adopting biosecurity practices in livestock production can increase profitability by keeping viral diseases at bay and improving production efficiency. It is extremely important that poultry industry, in particular, implement a comprehensive biosecurity programme to ensure better quality production.
Biosecurity programmes must be strategically planned underpinned by basic principles and rules of good hygiene. Long-term success will only be achieved with clear-cut priorities and correctly sequenced steps.
Sustainable biosecurity means beginning with an absolutely disease-free environment and then erecting and maintaining a hermetic (sealed) cordon around the entire farm. As an extra precaution separate biosecurity cordons are established around each individual poultry house as additional barriers to infection. Poultry stock should always be bought from known disease-free sources. All incoming vehicles must be washed thoroughly and tyres and wheel arches sprayed with disinfectants. Drivers should remain in the vehicle or otherwise be provided with waterproof protective clothing and boots.
The focal point of any biosecurity programme is the provision of pest- and disease-free housing for birds. New birds brought onto the farm must be isolated from other birds for 14 days while blood tests, vaccination, preventative medication and anti-parasitic treatment are carried out. In the meantime, the existing flock should be removed from the intended house which is made biosecure before the new flock is installed.
Use of disinfectants
Disinfectant use may be essential but is not necessarily a panacea for all ills. Cleanness of surfaces and application methods employed rather than the actual chemical disinfectant used will usually determine whether a disease-free house is achieved.
Dirt and organic matter such as dried and hardened faeces, mucous, feathers and spilt feed will inhibit disinfectant action because there must be direct contact between the biocide and the pathogen.
Modern disinfectants are put through stringent laboratory tests such as the Kelsey Sykes Test that simulates real working conditions in the poultry house. These assess biocidal activity in the face of repeated ‘challenge’ by organic matter and effect of hard water caused by high levels of calcium or magnesium salts.
Many chemicals including strong acids and bases, chlorine generators, phenols, aldehydes, quaternary ammonium compounds, iodophors and peroxygen compounds possess disinfectant action. Some chemicals like iodine-based compounds have a long history of use but limited action and a relatively narrow range of killing. Others like formaldehyde though widely used in the past are now largely avoided for reasons of safety to both birds and poultry workers.
Modern disinfectants are potent biocides with broad-spectrum activity and a long contact time to kill pathogenic microbes. For instance, peroxygen compounds that disrupt and destroy microbes through oxidation reactions will destroy most types of pathogenic microbe. These include bacteria (e.g. Salmonella typhimurium and Escherichia coli) viruses (e.g. avian influenza and infectious bronchitis) and fungi (e.g. Aspergillus fumigatus and Canida albicans). Contact time is increased by the addition of a surfactant. Surfactants are surface-active chemicals that lower the surface tension of the diluted disinfectant mixture to increase penetration and spreading power of water-based biocides.
Facts about fogging
Power washing with detergent will remove dirt and organic matter from accessible surfaces and leave them clean and ready for disinfectant action by ‘wet’ spraying. But poultry houses are typically riddled with ‘nooks and crannies’ – fan shafts, ducts and other areas inaccessible to take up standard cleaning and disinfectant spray programmes. These out of the reach areas can only be ‘covered’ by space spraying using droplets small enough to penetrate into the smallest crack and corner. ‘Dry’ application of disinfectant by thermal (hot) fogging is the only application method that can realistically achieve this goal.
Thermal foggers operate by vapourising the liquid disinfectant mixture that subsequently issues through the fogging pipe as mixture of hot gases. On contact with cold air it condenses into a mass of tiny droplets which form the fog.
Benefits of hot fogging disinfectant arise from two basic laws of physics that relate droplet number to droplet size, and suspension time with droplet size:
• The number of droplets generated from a given volume of spray liquid is inversely related to the cube of the droplet diameter.
• The smaller its size (diameter), and therefore it’s mass, the longer a droplet will be suspended in the air.
Hot foggers produce droplets of 5-25 in diameter. The larger droplets cover the walls, floor and ceilings to provide residual disinfection. The smaller droplets stay suspended in the air for space disinfection, thus acting against airborne spores and dust-borne infections. Disinfectants with a relatively high vapour pressure perform best during hot fogging, although fog-enhancing chemicals are available to improve performance of a wide range of disinfectants. Disinfection by hot fogging may be achieved at very low volume application rates of 20 litres/1000 cubic metres.
Fogging may also be used to control insect pests and pathogenic microbes in bagged/sacked feed storage areas. Ideally it should be carried out when the store is empty. But it can also be used as an emergency measure when the store is full, provided the biocide is cleared for such use and the bags/sacks are stacked with ample space.
Thermal foggers can be operated in the hand-carried mode, in a stand-alone mode within the building, or from outside by fogging through ports in the walls. If hand-carried the operator should start at the far end of the building and retreat carefully to the exit. Full protective clothing including a respirator must be worn.
• Building is emptied of all poultry* and all litter removed
• Compressed air or brushing used to dislodge dust and dirt from beams and fittings and to clean the floor.
• All easily removable equipment are taken out to wash and disinfect outside
• Drinker lines are sanitised with disinfectant solution. Mixture is left in the system for at least 12 hours and then flushed through with clean water.
• Electricity power supply switched off.
• All surfaces are soaked with solution of an agricultural detergent applied through power washer at low pressure, so surfaces stay wet or foam stands for at least 20 minutes.
• All surfaces are washed with clean cold water at high pressure to remove soiling prior to application of disinfectant.
* Immediately after emptying the building of all birds, but before embarking on the cleaning programme, producers can make a short-time aerosol application of insecticide (pyrethroid or other appropriate active ingredient). This will control all arthropod (insect and mite) pests, including those that are air-borne or resting up in cracks and crevices. Swift application, while the building is still warm, ensures good control while the insect and mite pests are still present and active.
• Disinfectant is sprayed at recommended strength and at low pressure, covering all surfaces to ‘run-off’.
• Roadways and aprons are washed and disinfected.
• Re-introduce and assemble all clean and disinfected fittings.
• Litter added and house set up, ensuring all personnel entering the house have clean clothing and disinfected boots.
• Terminal disinfection is carried out by thermal fogging with house sealed for 1 hour and later with 30 minutes ventilation before restocking.
With the healthy new flock of birds safely installed in a pest- and disease-free building it is now up to the producer to see it stays that way using utmost caution coupled with a dose of ‘common-sense’ and good hygiene practice.
Keep visitors to an absolute minimum. Provide all authorised personnel with waterproof clothing and boots that can be easily and effectively cleaned and changed regularly.
Provide a ‘foot-bath’ of disinfectant at the entrance to each house and a brush for cleaning boots prior to immersion in the ‘foot-bath’. Renew the disinfectant daily. ‘Foot-baths’ are not a practical essential but also a constant reminder to staff about the need for constant vigilance to maintain biosecurity.
Schedule and route those vehicles unloading at multiple points on the farm so that they stop first in areas of highest vulnerability (young birds), and then move to areas of lower vulnerability (e.g. mature flocks). Scrub drinkers daily with an appropriate disinfectant and detergent. Iodine is good because it removes algae and slime, and is of low toxicity to birds. Remove all dead birds quickly and carefully. Seal in bags for disposal and incinerate well away from the poultry house to prevent cross contamination with feathers or ash.
One potential high risk that often goes unnoticed is sources of infection within the farm environment, outside of the poultry house posing threat of re-infection. For example, vegetation between houses should be well managed or preferably replaced by concrete that does not harbour infection so readily and can be easily cleaned. Rubbish and other vermin attracting material should be cleared from poultry houses. Hay, straw bales and other bedding materials should be stored in dry, closed places to ensure that poultry houses are not at risk from wind-borne fungal spores released from damp and musty material.
Biosecurity programmes, which need proper planning, encompass the entire farm environment as well as recognising hazards from outside. But even the best-laid plans will go awry if procedures are not followed to the letter. For instance, carrying non-disinfected fittings back into the fogged poultry house or introduction of litter after fogging will negate the whole programme.
Dr. Terry Mabbett