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Avian Influenza – Autumn Migration Signals New Risk

by 5m Editor
9 October 2006, at 12:00am

By Dr Stephen Lister MRCVS and published by DuPont Animal Health Solutions - Autumn is on the way and with it comes the continued threat of spread of the H5N1 avian influenza virus.

As temperatures begin to drop, the migration of vast numbers of wild birds starts to get underway bringing with it a heightened risk of possible spread of infection. With all poultry-producing areas of the world either currently experiencing the virus or still in fear of its appearance, the upcoming migratory season is a stark reminder that avian influenza remains a global threat against which vigilance and preparedness must be maintained.

Impact on Farming and the Food Industry

Not only is avian influenza a potentially devastating poultry health disease, but the effects on consumer confidence in poultry meat and products can be dramatic and even more damaging. Whatever the comforting advice, however accurate, from medical authorities and food safety organisations, about the very small risk of human exposure from eating poultry products, the appearance of the infection in, or close to, a particular country undermines public confidence in the safety of such products.

As a result, it is essential that each and every poultry-producing country has a structured and effective control strategy. This strategy should include effective surveillance and detection of the H5N1 virus in commercial poultry or wild birds, but more importantly, procedures aimed at preventing the arrival of the virus in the first place.

These strategies must be implemented at international, national, regional and farm levels. All those involved in poultry production from Government to individual flock farmers must play their part. The aim must be to increase awareness of how and where infection might be introduced and target control strategies to prevent this primary introduction and any possible secondary spread.

DuPont Animal Health Solutions (DAHS) and its local partners around the world are currently working with international governments and independent organisations to help prevent and control the spread of highly pathogenic avian influenza H5N1. DuPont will assist in the development and implementation of biosecurity programmes, in addition to providing training for the appropriate use of its biosecurity products and equipment, including the disinfectant Virkon® S.

Whilst strategies are developed at Government level, individual flock farmers and poultry producers should also be organising their own contingency plans which clearly state the farm’s biosecurity procedures. The farm management team must then ensure that the biosecurity plan is accurately implemented.

Biosecurity Best Practice Measures

As a first step, poultry producers must establish a secure biosecurity perimeter to ensure that the farm is limited to one combined entrance and exit. The site entrance and the farm house/office must have a means of contact e.g. a bell or whistle which should be provided and numbers of visitors should be minimised. Where possible, visitors should be provided with “farm-only” boots and overalls and a shower-in policy should be in place, along with hand-washing facilities.

On entry to the farm site, all visitors must use footdips and vehicle wheel disinfection baths filled with an independently approved disinfectant. The disinfectant must be changed on a daily basis. All vehicles must be cleaned and disinfected prior to arrival on site with only essential vehicles being allowed to enter. All other cars (staff, service vehicles etc) should be kept outside the biosecurity perimeter and adjacent loading bays, paths and roadways should be disinfected using an independently approved disinfectant.

When cleaning and disinfecting poultry houses and farm buildings in accordance with a terminal biosecurity programme, personnel must be provided with and wear personal protective equipment comprising of; respirator face mask, eye protection, coveralls such as (DuPontTM Tychem®), heavy duty rubber gloves and rubber or polyurethane boots.

Table 1

In summary, some of the important aspects of setting up a biosecurity contingency plan and strategy must include:

  1. Choice of high quality efficacious, easy-to-use disinfectants, with adequate emergency stocks on site
  2. Implementation of an effective external biosecurity programme aimed at addressing the known risk factors:
    • Reduce vehicle and visitor movements
    • Provide shower facilities prior to entry to high value stock
    • Cleanse and disinfect all vehicles and equipment which must enter a site
    • Effective use of protective clothing, boots and foot dips
    • Use hand sanitisers before and after handling birds
    • Exclusion of wild birds from houses to prevent contact with commercial stock (difficult/impossible in extensive free range systems)
    • Clean up all feed spillages under feed bins to discourage wild birds
    • Avoid standing water, and do not use surface water which may be faecally contaminated by wild birds as a source of drinking water for commercial stock
    • It should be noted that the avian influenza virus survives well in water so simple washing with water alone may assist transmission.

Selecting a Disinfectant

The United Nations’ Food and Agriculture Organisation (FAO) recently selected Virkon® S as a precautionary measure to help combat the avian influenza threat. Supplies were requested to meet short-term requirements in 81 nations, where the disinfectant was needed most to help governments and farmers prevent the virus from spreading. These 81 countries were primarily located in Eastern Europe, the Middle East and Africa.

Vehicle Disinfection

Transmission of the virus has been strongly linked to moving live birds, contaminated carcasses or litter in vehicles and has highlighted the importance of vehicle-related biosecurity. Producers have often had difficulty in justifying this action as time must be spent ensuring that vehicles are adequately disinfected which may have a commercial impact on the producer. However any vehicles or associated equipment coming into contact with poultry or litter may become grossly contaminated with organic material containing large numbers of infective bacterial and viral particles.

Although notoriously difficult to police, vehicle disinfection protocol can help to reduce the potential spread of the virus. The guidelines include:

  • Wash wheels and wheel arches between visits
  • Avoid walking onto a farm unless your footwear has been disinfected by use of foot bath or similar
  • Use protective clothing as supplied by the farm
  • Follow the site's own biosecurity instructions
  • Clean and disinfect vehicles after each journey, including the driver's cab
  • Use a combination approach to first clean and degrease the vehicle and all contaminated surfaces, followed with the use of a disinfectant with proven activity against the pathogens of concern to the particular enterprise
  • Select a disinfectant which has been tested by a motor industry association for suitability on vehicle moving parts
  • Use products with known efficacy in removing bio-films from surfaces. These may be difficult to clean and can harbour and protect many micro-organisms
  • Wash and disinfect the vehicle at the end of the day.

Conclusions

The risk of introduction of the potentially devastating H5N1 avian influenza virus into poultry-producing areas around the world is likely to remain with us for some time and particularly at times such as the forthcoming migratory season.

Reducing the likelihood of infection, as well as eventually bringing this global threat under control, will depend on effective contingency planning and efficiently applied biosecurity programmes. The approach must include consideration of the following:

  • Decisions based on good science
  • Effective surveillance
  • Effective diagnosis
  • Excellent communication
  • Well planned contingency systems
  • Effective and sufficient veterinary manpower
  • An effective partnership between legislators, state veterinary personnel, field veterinarians and the poultry industry
  • Biosecurity programmes aimed at preventing the introduction of the virus into a specific country/region, and the control and elimination of infection once it has arrived in a country.

Achieving these goals depends on a coordinated approach of continuous routine biosecurity, using proven effective products which are applied properly. DuPont is currently assisting Government and Veterinary bodies in the development and implementation of biosecurity programmes, in addition to providing training for the appropriate use of its biosecurity products and equipment.

September 2006