Guidance Note for The Control of Salmonella for Pig farmers
Dear Herdowner
There are various measures that can be taken by pig producers to reduce the level salmonella at farm level. Salmonella in pig meat has long been associated with outbreaks of food borne illness. 20% of food borne illness is associated with pork and pork products in the EU.
It is in the interests of both industry and consumers to reduce the significance of Salmonella Typhimurium as a pig meat-associated food borne pathogen. This particular sero-type contains the most serious drug resistant strains, which can be difficult to treat in humans. Salmonella food poisoning is easily preventable by proper cooking handling and storage however consumers have a right to low risk or no risk food products. The information in this guidance note is aimed at helping pig farmers reduce the level of Salmonella on their farms.
This guidance note should be implemented in consultation with a nominated private veterinary practitioner. It is important to note that workers on pig farms should be aware that most salmonellas have the potential to cause illness in humans. The importance of good personal hygiene should be stressed e.g. hand-washing and drying facilities should be available and should be used frequently, in particular before eating.
All pig producers are registered under the National Pig Identification and Tracing System. All herds have a unique identification number and all herds presenting for slaughter are required under the Pig Salmonella Order to have a category that defines their risk in terms of the prevalence of Salmonella on their farms. Currently only 60% of pig herds have a valid category under this scheme and 10% of these are in category one. All pigs from farms deemed to be category three under the Pig Salmonella Order are subject to extra and additional hygiene measures at slaughter plant level. While it is acknowledged that there are issues identified which are impeding the progress of the Pig Salmonella Scheme DAFF is actively looking at more efficient data management systems and a web based system that will enable farmers to access and view their own sampling information and category allocation.
SALMONELLOSIS IN PIGS
Clinical salmonellosis is a relatively uncommon problem in pigs, causing septicaemia or enterocolitis. During this period affected pigs will excrete very large numbers of salmonella organisms during the course of the clinical problem and for several weeks afterwards. Farmer should seek veterinary advice in this regard.
Subclinical salmonellosis is a relatively common problem in pigs, usually causing no obvious animal health problems. Affected pigs are carriers of salmonella, and can excrete large numbers of salmonella organisms intermittently, and particularly when stressed.
Key elements have been identified which help to reduce the level of Salmonella on farms
· Accurate identification of pig herds at slaughter with a valid categorization under the Pig Salmonella Control Programme to facilitate implementation of slaughter controls
· Salmonella free feed which is achieved by effective heat treatment
· Good bio-security measures on farm in terms of rodent/bird/vermin control, footbaths, protective clothing
· Clean and adequate transport
· Stress free pigs in terms of no overcrowding (stress causes pigs to increase shedding of Salmonella)
· All in all out systems essential to allow proper cleaning and disinfection. A secure hygiene-barrier should operate between each sector for people/pigs and equipment
· Correct flow of pigs, people and equipment. Pigs at weaning are typically free of salmonella. This status should be maintained throughout their life
· Correct Antibiotic Usage
GENERAL MEASURES ON ALL PIG ENTERPRISES
· All producers should comply with the terms and conditions of NPITS to ensure traceability of pigs. All producers should have a valid and up to date category
· The feeding of salmonella free feed is an essential element in any salmonella control programme. All processed feed should be heat-treated to a minimum of 75° c for at least 1 minute (or equivalent). Where other feeding regimes apply (eg home mixing) producers should consult their Veterinary advisers in relation to salmonella control measures
· Wild birds can carry salmonella and other pathogens. All pig houses must be made bird proof.
· Rodent control is another essential element in any salmonella control programme. Rodents are important for two reasons: They are frequently carriers of salmonella, thus they introduce it into clean areas and they play a large part in carryover of infection from batch to batch on infected premises. A systematic approach to rodent control is necessary for success. The following minimum guidelines should be followed -
Ö Remove all rodent cover from around pig houses. The areas between and around houses should be completely clear of all vegetation, debris, rubbish, stored material etc. Ideally there should be a clear area of at least 30 metres around each pig house
Ö Prevent access; seal all structural holes, fit properly fitting doors etc and prevent access to stored or spilt feed
Ö A double perimeter baiting system should be employed (i.e. bait should be placed around the perimeter of the site and around the perimeter of each house)
Ö Bait should be placed approximately every 5-10 metres in a suitable container (e.g. concrete pipe) Bait should be checked weekly and replenished as needed. One employee on each pig farm should be given this responsibility
Ö A farm bait plan should be drawn up for each farm. This should give details of where each numbered bait point on the farm is located
Ö Ideally professional help should be sought and a professional rodent control company should service the site every two months (baits should be checked weekly as replenished as needed in the interim)
Ö Flies can mechanically transfer salmonellas within a pig unit. A systematic fly control programme must operate in all areas of the pig unit
Ö All other vermin/animals (including dogs and cats) should not be allowed access to pig farms and must not in any circumstances be allowed access to pig houses. Cats are totally unacceptable as a form of rodent control; in addition to the fact that they can carry salmonella, they can also be responsible for introducing other important diseases onto the pig unit
· Salmonella is often spread between houses on a site via manure and slurry material on boots/shoes. It is particularly important to understand the risks of spreading salmonella from a dirty area to clean areas via manure on footwear. Before entering each house, footwear should be cleaned (i.e. all material removed by washing or power-washing) and then disinfected (by dipping in clean disinfectant or by spraying with disinfectant) Most disinfectants are not effective in the presence of organic material hence the need to clean footwear first and then disinfect. Where footbaths are used, they must be replenished at least once daily using an approved disinfectant at the correct dilution
Ö All workers must wear suitable clean protective clothing and suitable footwear
Ö All visitors to a site must be issued with suitable clean protective clothing and suitable footwear. In addition all visitors to a site must be recorded in a visitors book. This can be vital in helping to trace disease outbreaks
Ö The water supply to the enterprise should be tested at least annually to ensure that it is uncontaminated. Internal header tanks in houses should be securely covered. Drinker design should be such that faecal cross contamination between pens is not possible
CLEANING/DISINFECTION OF TRANSPORT
Pigs should not be loaded onto any vehicle that has not been cleaned and disinfected prior to loading. Transport should be visibly clean (i.e. no organic debris). In DAFF approved slaughter plants all vehicles should not be allowed to leave the plant until they have been cleaned and disinfected to the satisfaction of DAFF personnel.
Producers should not allow vehicles containing pigs from other sources onto their premises and in particular transporters collecting pigs for slaughter from multiple sources.
STRESS REDUCTION
This point cannot be over emphasized. Stress on pigs is closely linked to disease outbreaks in general. Stress reduction is particularly important in salmonella control programmes in pigs. Stress on pigs will induce carrier pigs to start shedding salmonellas, leading to increased contamination of the environment.
For detailed advice contact the farms Veterinary adviser; the following are some of the key points in stress reduction:
Ö No overcrowding
Ö Smaller group sizes are preferable
Ö Pigs should be moved in a welfare friendly manner
Ö Pigs should not be mixed with animals of another age group
Ö Movement of pigs should be kept to a minimum
Ö All farms should have an isolation unit
Ö Sick pigs should be removed to a "hospital" pen immediately; for apparently minor ailments. Treatment can be undertaken in the normal pen, however if there has been no response to treatment within 24 hours these pigs must also be isolated.
Feed should be withdrawn for a minimum of 12 hours before slaughter. In addition to certain benefits in terms of meat quality fasting results in a lighter gastrointestinal tract at dressing, with less risk of accidental cutting leading to carcase contamination.
Water should never be withdrawn prior to slaughter.
ALL IN/ALL OUT CONCEPT
The all in /all out concept is another key element of Salmonella control. It is not possible on all farms due to capacity issues. However where possible it should be adhered to. It means that a room or a house must be totally emptied between batches to allow complete and proper cleaning and disinfection. Each sector on an enterprise should operate separately (dry sow, farrowing, first stage weaner, second stage weaner and finishers). A secure hygiene barrier must operate between each sector for people for pigs and equipment to prevent recontamination.
CLEANING AND DISINFECTION BETWEEN BATCHES
Thorough cleaning and disinfection of the entire room or house (using approved disinfectants at correct dilutions) must be carried out between batches in all sectors of the pig enterprise. In addition passageways and loading ramps should be cleaned and disinfected after each use. Particular attention should also be paid to cleaning and disinfection of the "hospital" pen. Drinking bowls and feeders should also be checked daily and cleaned and disinfected as needed. The veterinary adviser should be consulted for detailed advice.
HOUSE DESIGN AND LAYOUT AND MANAGEMENT
All new houses should be designed in such a way as to facilitate cleaning and disinfection and to facilitate all in all out systems and correct one-way flows of pigs, personnel and equipment. Existing defects should be identified and appropriate action taken. Solid pen partitions should be used to prevent spread of manure between pens.
Pigs at weaning are typically free of salmonella. In general salmonella levels increase as pigs move closer to finishing age. Pigs should move in a one-way flow from low salmonella areas (dry sow/farrowing) to areas of higher salmonella levels (i.e. grower/finisher areas). Pigs should never move in the opposite direction (e.g. from a house containing finishing pigs to a house containing weaners), similarly people/workers should never move from high salmonella areas to low salmonella areas. If it is unavoidable, they should take stringent precautions to prevent bringing salmonellas back to clean or low salmonella areas (particular care should be taken with boots/footwear). Equipment, e.g. power washers etc, should also follow a similar flow pattern. (Or ideally have separate, dedicated equipment for each compartment).
CORRECT ANTIBIOTIC USAGE
All antibiotic treatment should be based on sensitivity testing and antibiotics should only be used on veterinary advice. In relation to salmonella control in pigs, antibiotics should only be used in the case of clinical outbreaks of salmonellosis on veterinary advice. Medication is ineffective as al control strategy for sub-clinical Salmonellosis and should not be used. Incorrect and inappropriate usage of antibiotics can increase the development of salmonella carriers and can also lead to resistance problems.
VACCINATION
Salmonella vaccination of breeding sows should be considered in consultation with the Veterinary Adviser. Good maternal immunity in the piglets may help to reduce salmonella levels in weaners, it may help in particular in reducing outbreaks of clinical disease.
Meat Policy Division
October 2007