Sweden has achieved efficient control of Salmonella, despite the industrialisation of animal production. Due to the control, both red and white meat produced in Sweden can today be claimed to be virtually free from Salmonella.
Salmonella control started with a governmental regulation in 1961. Earlier a voluntary programme for the control of fowl typhoid (Salmonella Gallinarium/Pullorum) had been running since 1941. Severe Salmonella epidemics during 1953- 54 demonstrated the need for a more comprehensive control programme. The control and its applications are continuously being revised.
The objective of the Salmonella control is that animal products delivered for human consumption shall be free from Salmonella. The concept is that animals delivered for slaughter shall be free from Salmonella.
The strategies are:
1. Prevent Salmonella contamination of all parts of the production chain
2. Monitor the production chain at critical points to detect if Salmonella contamination occurs
3. Undertake actions necessary to fulfil the objective of the control when Salmonella contamination is detected. It is also found to be of basic importance to create a legal framework and motivations to ensure co-operations and compliance with the programme.
All veterinary laboratories are required to immediately report isolations of Salmonella to the Swedish Board of Agriculture (SBA) and to the County Administration. All isolations, regardless of serotype, from index cases are sent to the National Veterinary Institute (NVI) for confirmation and registration. In all suspected and confirmed Salmonella cases SBA will instruct a veterinary officer to investigate the outbreak and supervise the clearance of the farm from Salmonella infection or contamination.
Infected farms are subjected to restrictions which include a total ban on movement of animals, except for transport to sanitary slaughter. The veterinary officer, supervising the clearance of a farm, will give specific instructions to each farm. The restrictions remain in place until all animals are declared free from Salmonella following bacteriological examination. As the shedding period for Salmonella in broilers, in contrast to the case in cattle and swine, is usually longer than the rearing period, destruction of the infected flock has been the only alternative to clear Salmonella from an infected flock.
Antibiotics are not used to control Salmonella. This principle, in combination with the low prevalence of Salmonella, is reflected in a relatively low frequency of antibiotic resistance in isolated strains of Salmonella.
Of basic importance for the control of Salmonella in food-producing animals is that meat products contaminated by any serotype of Salmonella are by law and consequently forbidden to sell (Food Act. SFS 1971:511) declared unfit for human consumption.
Today we have a mandatory and a voluntary Salmonella control. The mandatory Salmonella control includes testing preslaughter and at the hatcheries in accordance with the Zoonosisdirective in force. The voluntary Salmonella control includes the animal environment, the houses, hygienprogram etc.
Salmonella in poultry
General principles in 1970, the rapid increase in broiler production and some severe outbreaks of human salmonellosis originating from chickens, necessitated the initiation of a Salmonella control programme in poultry. 90 % of the costs for the control were covered by the State until 1984. Since 1984/85 the producer pays the control with the aid of an insurance programme. To obtain economic compensation for destruction of animals, in case of Salmonella contamination, the insurance companies, as did the State before 1984, require that the chickens are delivered from hatcheries and breeder flocks participating in the voluntary Salmonella control programme. The basic principle of the control programme is the no acceptance of Salmonella contaminated poultry or poultry meat. The primary objective is to stop Salmonella contaminated animals from entering the abattoir. The chosen strategy is to prevent Salmonella introduction through breeders, feed or the environment. The quality of the programme is controlled by bacteriological monitoring after slaughter.
Salmonella control in broilers for slaughter
Testing for Salmonella is done one to two weeks before slaughter. Two pair of sock samples per flock are taken, pooled and examined. By this method a prevalence of Salmonella contamination above five percent are calculated to be detected. If any serotype of Salmonella is isolated, the flock is destroyed. Cost for destruction of Salmonella contaminated flocks is paid by the producers through insurance. The demand for insurance participation is that the chickens and their parents are affiliated to the voluntary Salmonella control programme. The cost for the mandatory testing before slaughter is also paid by the producer.
There are detailed rules for hygiene and management procedures in the different forms of productions which have to be followed. Highest demands apply to breeder-flocks and hatcheries. A veterinary officer is appointed to be in charge of the control for each farm. He has to visit the farm at least yearly and ensure that the rules of the control programme are followed and to take the official samples. Special controls are carried out after the clean-up of a poultry house contaminated with Salmonella. We always apply the "all in - all out" principle with depopulation of the whole house, before new birds arrive. Although no Salmonella has been found in a previous flock the house always must be cleaned and disinfected very thoroughly.
The following requirements should be met to avoid Salmonella contamination:
* Salmonella-free breeders producing non-infected chicks
* Measures to prevent any domestic or wild animals from gaining access to the premises
* Provision of protective clothing
* Effective cleaning and disinfection of equipment and house in between flocks
* An appropriate "resting" period for each house between successive crops of birds
* Use of Salmonella free feed and litter
* Avoidance of spreading slurry or manure too near the premises
Imported birds and grandparent flocks
When importing to Sweden, all poultry (broilers, turkeys, ducks, geese and layers) have to stay in quarantine. The quarantine station is authorised by SBA. There are strict rules concerning the location and construction of the building and the management of the birds. All commercial poultry are imported as day-old grandparents (GP) or in rare cases, as parents (P). All breeders have to be sampled frequently and found free from Salmonella before they are released from the quarantine. The breeders and hatcheries are kept in strict isolation and the general hygiene rules in the control programme are applied very rigorously. The birds are destroyed if Salmonella is isolated, regardless of serotype.
Every second week, from each breeder flock, 5 pair of sock samples are sent to the laboratory and examined for Salmonella. The eggs intended for hatching should be collected twice a day and fumigated with an approved disinfectant as soon as possible after collection. The use of dirty eggs as hatching eggs is prohibited.
The control, to prevent Salmonella introduction into the hatchery, is based on the control of breeders. The eggs should be disinfected before they are set into the brooders and fumigated on the third day of brooding and in the hatcheries.
Control of feed factories
Since 1960 a voluntary control programme has been running for feed factories producing feed for farm animals. All Swedish factories participate in the control. The current strategy for the control is to detect, as early as possible in the production chain, when Salmonella contaminated raw material has entered the factory. All samples are examined at NVI. Salmonella has been isolated after heat treatment only on rare occasions. The primary objective is that Salmonella contaminated feed must not leave the factory. Actions are taken when Salmonella is isolated in different parts of the production.
All costs for the Salmonella control have to be paid by the producers and also for the measures taken as a result of Salmonella positive samples. This is also the case when factories have to be closed in order to control a Salmonella contamination. The costs have to be paid by the owners of the factories even though such decisions have been made in agreement between the owners and the authorities.
The poultry meat production in Sweden, opposite to nearly every other food or meat production in the country, does not receive any financial compensation from the state in case of a Salmonella-outbreak.