Cleaning down after Avian Influenza

If a notifiable strain of Avian Influenza (AI) is confirmed, DEFRA will take action on the infected premises to reduce the risk of the disease spreading. This includes movement restrictions and culling all susceptible birds. Premises are then cleaned and disinfected with strict rules on re-stocking. The aim of the article is to provide information on what is involved in a clean down following AI and implications on the cost of production.

Cleaning protocols

Preliminary cleansing and disinfection (C&D) is the responsibility of government, and is performed by the Animal and Plant Health Agency (APHA), at their cost. At this time restrictions will remain in place, as there is an assumption that the influenza virus will still be present on the farm. It takes time for viruses to decay naturally, the length of which depends on factors including, exposure to sunlight and the ambient temperature. The final (secondary) C&D is the responsibility of the farmer but must be carried out according to procedures outlined by the APHA.

Initial cleansing and disinfection

Once the hens on the infected farm have been culled, production of the virus ceases. Initial C&D will be carried out following the removal of carcasses and eggs for disposal. APHA staff will spray disinfectant on:

• All parts of the premises (other than parts where disinfectants would have no effect, such as fields).

Steve Birchall
Steve Birchall

• All equipment which the hens have had access to.

• Anything that was contaminated during culling.

Litter will usually be removed at this point and is most commonly burnt to remove the risk of disease transmission. Farm clothing, the overalls used by those involved in culling and C&D procedures; also is required to be disposed of in a bio-secure manner.

Secondary Cleansing and disinfection

A thorough secondary C&D should be carried out by the farmer or more likely by a contracted agricultural cleaning service. This process should involve cleansing, degreasing and disinfecting. Following a drying period a secondary disinfection is also often carried out. A representative of the AHPA has to approve the work and may be present on site to offer guidance. It is important to carry out the secondary C&D immediately following the initial C&D. This both reduces viral load on the infected premises as well and reducing the risk of the disease spreading to other farms.

The secondary C&D should follow the same basic principles of any poultry house cleaning protocol: clean, dry and disinfect. The poultry houses, anterooms and moveable equipment should all be subject to the same procedures. Anything that can’t be effectively disinfected should be safely disposed off.

It is essential that all faecal material is removed effectively as the virus can persist at a high level in organic material. The next cleaning step is the application of soap/detergent to walls, floors and equipment. Steam cleaning is then sometimes carried out before the application of disinfectant. For most products a contact time of 10 minutes is required and the use of a foaming type product can help to achieve this. Fumigation should be considered to kill the virus present in hard to reach areas.

It is of paramount importance that the buildings and equipment are allowed to thoroughly dry before re-stocking, as drying will help to kill off any remaining virus. Ideally one to two days should be allowed, depending on the weather. Using un-washed equipment or staff wearing dirty clothing, can bring the virus back into the building. Foot dips and other biosecurity procedures should remain in place during cleaning.

Depending on the specifics of the site and environmental conditions, exact protocols for the secondary C&D will vary. An initial clean down and disinfection onto the litter before it’s removal may be recommended. Another C&D would then follow. Or if the C&D had been carried out after litter removal, another application of disinfectant may be done following drying. Decisions on exact procedures will be made by the APAH representative on site.

Disposal of infective material

Part of the additional cost of this secondary C&D is from the disposal of the litter, manure and wash-water. The disinfectant laden wash-down water cannot be spread on farmland straight away, as it normally would be. The water is collected in sealed containers and taken to holding tanks away from the farm. There it is tested until shown to be free of the virus, at which time it can be disposed of as normal.

Similarly manure and litter from an AI infected farm cannot be spread on land straight away or taken to power stations for burning. In the latter case this is to minimize the risk of cross-contamination with trucks moving litter from non-infected farms. Trailers moving litter from infected farms have to be sheeted or sealed containers used. Again the manure is held for a period of time until it is free of the virus and then disposed of.

An important consideration when cleaning down following an AI outbreak is the weather. Litter removal will be delayed if it is windy to reduce the risk of spreading the virus to nearby farms. Although heat can be used to speed the drying process this isn’t generally recommended following a disease outbreak as it could increase the chance of re-infection. Instead the preferred method is natural drying, which will take longer in the winter or during wet weather.

Managing the range

The big challenge on free range egg farms is how to effectively remove the AI virus from the range. Actions that will help include; scraping off heavy faecal load close to pop-holes, cutting pasture short to allow drying and exposure to the sun. The virus doesn't like desiccation or UV light so exposure to the elements is of benefit for the de-contamination of ranges. The longer the period of time that the range is left un-stocked will also be an advantage.

There are some specific products that can be used to ‘dress’ pasture, absorbing moisture and containing an anti-viral disinfectant. Alternatively a heavy lime application, following scraping and mowing will also help to reduce pathogen growth. The producers themselves, following the secondary C&D, normally carry out these procedures.

Products and services

The AI virus is susceptible to disinfectants and as such it will be effective following thorough cleaning. By law you must use a DEFRA approved disinfectant when there is a case of a notifiable disease. This extensive list is available on the DEFRA website: http://disinfectants.defra.gov.uk The page also details the concentration that is appropriate for each product, in the case of a notifiable avian disease. The AHPA may also recommend a particular type of disinfectant dependant on risk or situation.

If you are using a cleaning contractor they similarly need to be approved by DEFRA to carry out C&D following a disease outbreak. In order to do this, contractors provide details of the companies’ experience, staff and procedures in order to show that they are capable of and proficient in the tasks involved. Then once a contractor is working at an AI infected farm they are under the supervision of the AHPA. Procedures, timings and products used will all be decided by the AHPA and compliance monitored

Steve Birchall explained the additional costs involved in a secondary C&D. “We charge approximately 25% more for a C&D following an AI outbreak over a normal end of cycle clean-down. This takes account for the extra time spent and the more thorough cleaning required.” His company will work in conjunction with the APHA, to take the swabs and get them tested for the presence for AI. If the results are still positive then Steve charges 50% of the cost of a standard clean down to repeat the process.

Downtime and re-stocking

The secondary C&D may need to be repeated to ensure that the virus has been eliminated from the farm. In most cases the decision to carry out a third C&D process would be decided based on laboratory tests. Following the secondary C&D swabs from the poultry housing are taken; floor, walls, equipment etc. These are then send to the AHPA laboratory to determine the presence or absence of the AI virus. Results take approximately three weeks to obtain, during which time disease restrictions remain in place. If the tests come back negative and the AHPA are satisfied with the C&D that has been carried out, then they will give the go ahead for re-stocking. During the following 21 days a veterinary officer will examine the new flock and samples may be sent for testing. Restrictions on the premises will remain in place until at least the completion of the following:

• Clinical surveillance showing no evidence of infection. ?

• Any samples taken have returned negative test results for AI. ?

The cost of the secondary C&D is a significant burden on free range egg producers.

However, the most significant cost is that of the increased down time, which can be as long as two to three months. There is therefore, the loss of egg income during this time, as well as overheads that still need to be paid. For example; staff pay, utilities, loan re-paid etc.

Insurance

Various brokers and underwriters do offer policies to free range egg producers that cover the risk of disease outbreaks, including AI. This is usually in the form of extensions and as such, additional liability will incur an additional premium. The cost of these is specific to the farm and is calculated based on the type and size of farm as well as the location; in terms of previous outbreaks and density of the poultry population. Therefore, careful calculation is needed to decide if it is financially worthwhile to extend insurance cover. Cover will be on the condition that producers meet minimum standards in terms of biosecurity.

An example policy could include top-up cover for the following; in relation to an AI outbreak:

• Difference in price of hens culled paid by the government and their commercial value

• Increased cost of working e.g. Secondary C&D, disposal of infective material

• Loss of income e.g. Lost egg sales (this is calculated based on turnover and will include any saved costs)

Conclusions

In general a farm that is suspected of being infected with AI will be subject to an initial C&D immediately. Completing the process is important because secondary C&D is the more rapid method for the UK to regain its official disease free status. Not being able to carry this out or delays in completing the procedure could have implications on trade with other countries.

Although we haven’t had an AI outbreak in the UK for several months, it is still on producers’ minds. It is a worthwhile exercise to consider what would happen if an outbreak occurred on your farm. Calculating the additional costs involved and deciding whether additional insurance makes economic sense. There also be implications regarding supplying customers, or the ordering of feed and poults. If producers are selling their own branded eggs, are relationships in place with other producers to fulfil orders.

This article provides the generalities of requirements for clean-downs on AI infected farms. However, the government veterinary inspectors present at the time will specify the details and supervise the secondary C&D; to make sure it is completed to their satisfaction. Time is the big factor with this process, with clean-downs taking up to twice as long. And depending on the weather, test results etc. the downtime could be four or five times as long.