Rats: control on livestock units

Transcription

1 Rats and mice are particularly attracted to farms with livestock and can thrive in the environment provided by such holdings. In the absence of adequate control measures serious infestations may develop. The presence of rodents can cause a number of significant problems, which should prompt occupiers and managers to take appropriate action to control any existing infestations and prevent new ones from becoming established. Rats may move between farms and can act as carriers of livestock diseases. Their control is one of the biosecurity measures necessary on a livestock unit. Rats also carry diseases that pose a health threat to farm workers and others who may be exposed at infested locations. Leptospirosis, or Weils Disease, is potentially fatal in humans and needs to be considered when carrying out a risk assessment under COSHH Regulations. Rodents may also cause structural damage and gnaw electrical wiring creating a fire hazard. They may contaminate foodstuffs and stored crops with droppings and urine, resulting in products failing to meet hygiene and quality standards. Biology and behaviour In deciding on the measures that should be taken to reduce the number of rats on the farm, aspects of rodent biology and behaviour need to be taken into account. These include: Rats require food, water and shelter. If these can be denied to them then infestations will be significantly reduced In suitable conditions rodents are prolific breeders and capable of increasing their numbers within a short period of time. Monitoring for their presence needs to be undertaken regularly. Favoured harbourage sites are voids and dead spaces in buildings, stacks or stores of feeding stuffs including straw, hay, bagged silage and clamps, accumulations of materials around building perimeters and ditches, banks and hedgerows that are located close to the farm complex and in manure heaps and rubbish dumps. Infestations are likely to build up in the autumn as rats move in from field locations seeking the cover and food offered by agricultural holdings. Rats burrow, climb, swim and can squeeze through small apertures. They feed predominantly on grain based materials but where necessary, will exploit vegetable and animal matter. Rats are creatures of habit and this is apparent in the field signs that indicate their presence. They are suspicious of new objects appearing in their territory and will react to disturbance or other apparent threats by moving to alternative habitats. Preventative measures Farm premises should be made as unattractive and Third Edition Published August 2006

2 Page 2 uninviting as possible to rats. This will help prevent the initial establishment of infestations and assist when control measures are undertaken. Practical measures to take are to store bagged material on pallets, ensure that bulk bins are structurally sound and avoid spilt food finding its way into gaps and dead spaces. The accumulation of rubbish and stored materials in vulnerable areas, particularly in and around buildings, provides harbourage for rats and should be removed. Vegetation around livestock accommodation, storage areas and associated banks and ditches also provides cover and should be removed. Within buildings, voids in walls, faults in the structure and flooring and access points provided by damaged drain covers and open pipes or ducts all provide routes by which rats can enter. Block or repair these as appropriate. Rubbish dumps or sites used for incineration, particularly where these are located close to farm buildings and which are not managed effectively, can act as a source of infestation. Make sure that these sites are kept tidy and free of material that might attract rats. The priority should be to prevent infestations by the combined use of these measures. This will reduce the need for control with rodenticides, thereby cutting costs and reducing risks to domestic animals and wildlife. Less reliance on poison baiting may contribute to preventing the development of resistance to anticoagulant rodenticides. In addition, when control using rodenticides is necessary this will be more effective as there will be less alternative food for the rats. Control Farms are most likely to suffer from rat problems during the autumn and winter period when the cold, wet conditions in field or other outdoor locations encourage rats to enter holdings. However, on intensive rearing units or in other situations it may be necessary to take control measures throughout the year. Survey Before attempting to deal with a rodent problem it is essential to identify the full extent and level of the infestation and establish where rats are living, travelling and feeding. This can be achieved by carrying out a full survey of the site including the building complex and associated areas such as silage clamps, slurry lagoons, manure storage areas, straw and hay stacks, ditches, banks and hedgerows. The main signs of rodent presence are: Holes or burrows. These may be found in a number of locations including earth banks, around the outside of walls or other structures and in unmade floors. Rats will also burrow into stacks, accumulations of manure and bedding and wall cladding or insulation panels. They can exploit gaps and faults in all sections of buildings. Runs and tracks. Where rats have become established, well defined tracks will link their living sites with feeding areas. These may be combined with greasy smear marks and worn surfaces left by rodents as they move around their territory. Droppings. Rats tend to deposit droppings at various specific points and the presence of fresh evidence is an important indicator of current activity. Damage signs. The gnawing and chewing habits of rodents and subsequent impact on building structures, and stored materials provides useful, if costly, information on their movement and distribution. Footprints and other marks. The existence of prints in soft mud, dust or bulk grain can often be used as an indication of existing rat activity. Tail swipes on the surface of grain heaps can help to confirm that rats are present. Other signs. These include sightings of live and dead rodents and a characteristic smell betraying their presence. The site survey should also be used to identify suitable baiting or trapping locations, indicate any specific hazards or potential treatment problems and provide information on non-target animal risks. The survey may identify hygiene deficiencies or structural faults that can then be put right. A rodenticide treatment In most situations where infestations occur, the use of one of the anticoagulant rodenticide baits will be the most appropriate control technique. Rodenticide options There are a number of compounds approved for use against rats in farm premises and these fall into two main groups. Those that were originally developed are known as first generation anticoagulants and when used correctly, can still be effective in most situations. They include products based on warfarin, chlorophacinone and coumatetralyl. Primarily in response to localised problems with resistance to first generation compounds, the second

3 Page 3 generation anticoagulants were introduced. These are difenacoum, bromadiolone, brodifacoum and flocoumafen. It is important to be aware that both brodifacoum and flocoumafen must not be used out of doors and so this restriction places significant limitations on the use of these compounds in dealing with typical farm rat infestations. All of these rodenticides are available as ready to use baits that are formulated in a number of presentations. These include meals, chopped cereals, whole grains, pellets and wax blocks. As a general rule, rats find loose cereal baits more palatable. However, formulation options are necessary to meet the wide range of circumstances in which rodent problems are encountered. Cellulose-based products (which interfere with rodents water absorption, thus causing dehydration) are also available. Zinc phosphide is no longer approved for use as a rodenticide. Safety precautions All rodenticides have the potential to cause harm to other animals and humans. These products have statutory label instructions which must be complied with. Directions for use should also be followed. It is therefore important that all the information contained on the label is read and understood. Users of rodenticides should be adequately instructed and trained in their use and must be competent. Before undertaking a treatment using rodenticides the following points should be considered: Baits must be placed so that they are not accessible to children, domestic pets, livestock and wildlife. Monitor the treatment regularly. The frequency of inspections will depend upon a number of factors including the severity of the infestation, the vulnerability of bait points to disturbance and the environmental conditions. At all visits, search for and safely dispose of rodent carcasses. On completion of a treatment clear up uneaten bait and dispose of according to the product label instructions. Where rodenticides are used in connection with a business or by professional users, rodent carcasses and bait residues must be treated as controlled waste. Disposal requirements include suitable packaging of these materials and arranging for their disposal at a recognised landfill or other disposal facility. This action has to be documented by the use of an appropriate consignment note. Keep records of the type of rodenticide used, the quantity of bait laid and where this has been placed. A simple site plan indicating the location of bait points will help to keep track of the treatment. The rodenticide should be stored safely in the original container. If bait must be decanted for use, the bucket or tub used should be labelled appropriately. Wear suitable waterproof gloves during treatments and when handling rodent carcases. This is primarily to protect against rodent borne diseases. Baiting Procedures It will normally take at least 3-4 weeks to achieve a reasonable level of control by using anticoagulant rodenticides. During this period it is essential that an adequate number of bait points are used and that these are kept topped up, so that bait is always available to the rodents. Control failures are usually due to poor treatment technique. Aim to place baits in as natural a state as possible making use of available site cover to provide protection against non-target species access. These should be placed where the initial survey indicated that the rats are living, moving and feeding. Avoid placing bait where it is likely to become wet or otherwise spoiled. The product label will give guidance on the quantity of bait to be used and the number of bait points required. Useful sites include wall voids and gaps, under corrugated or other sheeting, making use of the cover provided by stored materials and equipment and in buildings or structures that can be closed or secured against entry by other animals. Burrow or hole baiting can be particularly effective but regular checks will be needed to deal with bait that might have been ejected by rats. Placing the bait well down the burrow, covering the treatment area and heeling in the holes will all help to reduce this problem. More regular inspections are likely to be necessary to reduce the risks posed by exposed bait. Mark the location of all baiting points; numbering these can be helpful. The use of aerosol spray stock marker is a practical, easy to apply option. In some situations especially where there is a lack of on site materials, suitably secure locations or there are specific safety concerns, it may be necessary to use bait boxes or containers. These can be either produced locally or purchased from rodenticide or equipment suppliers. Users need to be aware that rats will shy away from new objects placed in their territory and as a result, may be reluctant to feed from such points. This

4 Page 4 can have the effect of prolonging the treatment or reducing its effectiveness. Deal with exposed bait or spillages as soon as they occur. Rats may remove bait from where it has been placed and this can create a hazard for other animals or children. This is most likely to arise where unsecured bagged, sachet or block formulations are used. Take care that bait is not exposed as bales or bags of food are moved. Continue baiting until takes cease and there is no further evidence of rat activity. Pick up as much of the unused bait as is possible and dispose of this according to the product label instructions. Preventative Baiting This technique involves establishing bait points that are then maintained with the aims of preventing rodent populations from developing and dealing with any rats that might move into the unit. Baits provided with a high level of protection such as by the use of tamper resistant boxes, can be installed at key locations where rats are likely to enter the farm. These would include ditch or hedge junctions that provide a safe access route into the building complex and around ponds, rubbish tips, banks or other features that may provide initial harbourage and attraction for rats seeking to establish in the area. Empty bait boxes or other bait protection can be left in position following treatments or put in place prior to taking control action. This may speed up bait acceptance by rats. The use of this approach should be limited to times of the year and situations where rodents pose the greatest threat. The long term placement of rodenticide bait is not recommended as this presents an increased risk to non-target animals and could encourage the development of anticoagulant compound resistance problems. Other control techniques The use of methods such as trapping or shooting may have a role in certain situations when dealing with rat infestations on farms. Further details of these techniques can be found in the Defra leaflet Rats: Options for controlling infestations (TAN 34). Measures such as chemical, physical or electronic deterrents are unlikely to provide practical and effective rodent control. Legal aspects Under the Prevention of Damage by Pests Act 1949, local authorities are responsible for ensuring that their districts are kept, as far as practicable, free from rats and mice. In addition, the Act requires that occupiers of non-agricultural land must notify the local authority if "substantial numbers" of rats and mice are living on or resorting to the land. There is no requirement, however, for occupiers of agricultural land to notify the local authority of the presence of rats and mice. The Act gives local authorities the power to require landowners and occupiers to control rat and mouse infestations on their land. Local authorities can also, where necessary, carry out the control work in default and recover the cost of such action from the landowner or occupier. The Health and Safety at Work Act 1974 places responsibilities on employers for the health and safety of their employees. This has relevance to the risks of rodents transmitting disease and on the safe use of rodenticides. This Act also places a responsibility on employees to work in a safe manner. Under the Control of Substances Hazardous to Health Regulations (COSHH), employers whose staff may come into contact with rodents must ensure that an assessment is carried out of the risks to human health from rodent borne diseases and with regard to the use of pesticides. Suitable precautions must be taken to prevent or control any hazards. The Control of Pesticides Regulations 1986, as amended, place a general obligation on all users of pesticides to take all reasonable precautions to protect the health of humans, creatures and plants, to safeguard the environment and, in particular, to avoid the contamination of water. They also prohibit the advertisement, sale, supply, storage or use of a pesticide unless it has been approved. All users of pesticides must comply with the statutory conditions of use shown on the product label. Further information If you do not wish to deal with the rodent problem yourself, you may be able to call upon the help of the local authority Environmental Health Department or seek the services of a pest control company. In England, further advice on dealing with rat problems, as well as problems caused by other mammals and birds, can be obtained by contacting the Department for Environment, Food and Rural Affairs (Defra) National Wildlife Management Team at: Address: Wildlife Administration Unit, Defra, Burghill Road, Westbury-on-Trym, Bristol, BS10 6NJ Telephone: (local rate) enquiries.southwest@defra.gsi.gov.uk

5 Page 5 This leaflet was produced by the Defra Rural Development Service (RDS) National Wildlife Management Team. A range of leaflets on wildlife topics is available online at: