Control and surveillance of salmonella in Sweden is carried out in the whole chain from “farm to fork. Photo: SVA.
Control/Surveillance in feed
The feed manufacturer is responsible for producing a salmonella-free feed. Heat-treatment of poultry feed is a legal requirement*. This legal requirement does not include other animal feed. Today, however, almost all feed is heat-treated - even for cattle and pigs. The control of feed production is under the responsibility of the Board of Agriculture (www.jordbruksverket.se) which is also responsible for unannounced inspections.
It is a legal requirement for all feed manufacturers to take a certain number of salmonella samples along the production line every week. The number of samples depends on the type of feed being produced. Establishments that produce poultry feed must take a minimum of five samples, while those producing feed for other food-producing animals must sample at least twice per week. The salmonella samples are collected at given control points, according to HACCP principles. The purpose of the weekly sampling is to ensure the absence of salmonella. All the legislated weekly samples shall be analysed at SVA. In addition to mandatory samples, the feed manufacturers take their own control samples to ensure that their feed does not contain salmonella. These samples can be analysed at any accredited laboratory of choice. However, all findings of salmonella (no matter where they are found) must be sent to SVA for serotyping.
* SJVFS 2006:81 (last updated version SJVFS 2009:53)
Feed materials are classified according to salmonella risk: feed material of animal origin (S1) and feed material of vegetable origin (S2 –soybean flour and some rapeseed products and S3 –rice and some rapeseed products)**. All imported feed materials that are classified as S1, S2, and S3 must be sampled for salmonella. The commodities are often sampled at the point of entry into the European Union. The rationale behind this is that the test result is available at the time of the products’ arrival in Sweden, so proper action can be taken if the consignment is contaminated. Only feed material with negative test results may enter production, and if a consignment is contaminated with salmonella it is stored separately and usually acid-treated before being re-sampled. If the re-sampling is negative, the feed material may enter the production but is only allowed to be used in compound feed that is heat-treated. The sampling scheme for feed material is estimated to detect salmonella with 99% certainty.
If the used feed materials are classified as S2 or S3, the feed company is obliged to have a salmonella control program to ensure that the manufactured feed material is safe to use.
** SJVFS 2006:81 appendix 4 (last updated version SJVFS 2009:53)
Control/surveillance of animals
The Board of Agriculture is the authority responsible for the mandatory control- and surveillance program for salmonella in food-producing animals.
Mandatory control program for food-producing animals
In case of a suspicion of salmonella in a food producing animal, the veterinarian is obliged to take samples to verify the suspicion and to take measures to prevent the spread of the infection. Whenever salmonella is isolated in a laboratory, the laboratory must notify the Board of Agriculture and the concerned County Administrative Board. The county veterinary officer shall inform other relevant parties. The salmonella sample, if analysed at another laboratory, shall always be confirmed and typed at SVA. SVA informs the Board of Agriculture, the animal owner and the county veterinary officer and the other laboratory.
When suspecting salmonella in a herd, the Board of Agriculture makes an investigation to verify possible infection. If salmonella is re-isolated in a herd, the herd is put under restriction and animal movements to or from the herd are prohibited. An epidemiological investigation is made and a plan is drawn up to, if possible, eliminate the salmonella from the herd.
In case of salmonella outbreak in a poultry farm all birds are euthanized regardless of the serotype of salmonella found. The entire premises that may be contaminated are mechanically cleaned and thoroughly disinfected. Before new poultry are introduced, all environmental samples for salmonella have to be negative.
In case of a salmonella outbreak in a pig- or cattle herd, the plan to eliminate the infection is done stepwise by systematic relocation of the animals in combination with cleaning and repeated sampling and strict hygiene to avoid the spread of infection. No salmonella positive animals are allowed in the cleaned and disinfected parts of the stables. The plan should be adapted to the production form and the extent of salmonella infection. For groups of animals in cattle herds, various measures are taken to reduce the infection pressure, such as letting the animal out to pasture during the warm season or relocation in temporary stables. Animals for slaughter cannot be sent to normal slaughter. Slaughter must be carried out under certain provisions with extra hygiene measures and sampling of every carcass. In some herds “stamping out” may be used, e.g. in highly infected calf groups, in systems where the animals are kept during a short period of time. The restrictions are lifted when cleaning and disinfection is completed and when salmonella cannot be isolated from any animal in two consecutive herd samplings four weeks apart.
Mandatory surveillance program for food-producing animals
Whenever salmonella is suspected in a herd, an investigation is made to verify the suspicion. If salmonella is detected in samples from animals in the herd, tracing is performed to identify the source of infection and possible spread. Investigation to identify possible spread of infection is also made when salmonella is detected in feed establishments, in food, in other animals and in humans. It is the responsibility of the Board of Agriculture to decide what measures to be taken. For example, when salmonella is detected in lymph node samples from slaughterhouses or in samples from autopsied animals, the whole herd is usually sampled. The herd of origin is also sampled after isolation of salmonella from carcasses at slaughter (swab samples) when isolates of salmonella with specific antibiotic resistance patterns are detected, or other special circumstances.
Routines have been established for continuous sampling of poultry flocks with more than 250 birds and of all laying hens in establishments that sell eggs for consumption. Moreover, all poultry flocks with more than 500 birds are sampled 1-2 weeks before slaughter.
Herds of breeding pigs and gilt-producing herds are randomly sampled annually for salmonella and sow pools are sampled twice every year Samples are taken as a routine procedure at autopsies of food-producing animals if there is suspicion of salmonella. Furthermore, all calves less than 6 months of age are routinely sampled at autopsy.
Voluntary control program for food-producing animals
In addition to the mandatory control of salmonella, there are voluntary control programs of poultry, cattle, and pigs. Farmers’ organizations for the various animal species have been assigned responsibility for the programs for their members.
Within the wildlife disease surveillance carried out at SVA, supported by grants from the Wildlife Management Fund, all dead wild animals sent in to the SVA, in sufficiently good condition, are examined for salmonella.
Control/Surveillance in food
The responsibility for the control and surveillance of salmonella in food is shared between the National Food Administration (www.slv.se) and the municipalities. The National Food Administration performs controls in slaughterhouses and most of the cutting plants, while the Environmental and Health Protection Units in the municipalities are responsible for any other sectors of food control like retailers. In addition, sampling is performed within the companies’ own control programs.
Mandatory control- and surveillance programs in slaughterhouses and cutting plants
The National Food Administration is the authority responsible for the mandatory control of the Swedish salmonella program at slaughter. Since Sweden’s membership in the European Union there has been a continuous and systematic surveillance at slaughter. To document the prevalence of salmonella in food of animal origin, samples are taken from carcasses (about 9000 swab samples and 9000 lymph node samples from cattle and pigs per year and about 4000 neck skin samples from poultry per year). Furthermore, about 3000 samples are taken every year in cutting plants to control the presence of salmonella in raw meat or in the environment in which it is handled.
Control/Surveillance of human cases
The surveillance of human cases of salmonella infection is based on clinical sampling and reports of infected people to the Swedish Institute for Communicable Disease Control, which, in collaboration with the County Councils infectious disease units and municipalities, handles investigations of disease outbreaks. These investigations are made in cooperation with the Board of Agriculture, SVA, and the National Food Administration if the outbreaks are linked to feed, animals or food.
Monitoring of antibiotic resistance
Monitoring of antibiotic susceptibility of salmonella is an important part of the Swedish salmonella control. SVA is responsible for monitoring and analysis of the development of antimicrobial resistance in bacteria from animals and from food of animal origin. This is carried out in the Swedish Veterinary Antimicrobial Resistance Monitoring Programme (SVARM) which has been running since 2000. Results of SVARM, i.e. data on antimicrobial resistance in bacteria from animals and data on sales of antimicrobials for use in animals, are published in a yearly report.