High diversity of salmonella serotypes found in an experiment with outdoor pigs

Little is known about the risk of Salmonella infection in outdoor pig production, but seroprevalence data has indicated a higher occurrence of Salmonella in outdoor production systems than in conventional indoor systems. This is perhaps due to the increased exposure to the surrounding environment including contact with wildlife. An unexpected high diversity of Salmonella serotypes, as e.g. S. Uganda and S. Goldcoast, which are not normally isolated from pigs, was detected in connection with an experimental study on transmission of Salmonella in outdoor organic pigs. In order to elucidate the potential source of the different Salmonella serotypes, a small-scale examination of wildlife was performed. Salmonella was not detected in any of a total of 22 rats, mice and shrews or in 21 birds (mainly crowbirds). The unidentified source of these Salmonella serotypes implies inadequate control possibilities and may therefore pose a problem for outdoor pig production in terms of food safety

Probing scattering phase shifts by attosecond streaking

Attosecond streaking is one of the most fundamental processes in attosecond science allowing for a mapping of temporal (i.e. phase) information on the energy domain. We show that on the single-particle level attosecond streaking time shifts contain spectral phase information associated with the Eisenbud-Wigner-Smith (EWS) time delay, provided the influence of the streaking infrared field is properly accounted for. While the streaking phase shifts for short-ranged potentials agree with the associated EWS delays, Coulomb potentials require special care. We show that the interaction between the outgoing electron and the combined Coulomb and IR laser fields lead to a streaking phase shift that can be described classically

Detection of S. enterica in subclinically infected herds

The nation-wide salmonella control program is based on serological monitoring of swine herds (meat juice samples taken at the slaughter line) and classification of the herds on the basis of serology (Mousing eta!. 1997). When a herd is classified as a level 2 or level 3 herd (moderate or high sera-prevalence), a follow-up program is instituted. From August 1996, the follow-up program comprises: (1) a letter to the individual herd with information about the assigned salmonella level and the follow-up program (the injunction); (2) mandatory visits by veterinary advisors including a profile of the salmonella occurrence in the herd. The profile must comprise pen samples for bacteriological examination for Salmonella enterica.; (3) a plan for interventions; and (4) penalties if the herd does not comply with the program. On the submission forms to the Danish Veterinary Laboratory DVL the individual samples can be marked. Materials from swine are typically marked with sow number, stable, unit, or age-group

Salmonella reduction at the farm level

An important part of the Danish salmonella program is surveillance of all Danish pig herds with a yearly deliverance of more than 100 slaughter pigs. Herds categorized in infection level 2 or 3 are obliged to take effort to reduce the seroprevalence of slaughter pigs to an acceptable level. It has been shown, that it is possible to remove pigs from infected herds and raise them to the normal age of slaughter without detectable salmonella infection (Dahl and others, 1996). Based on these results, a model for salmonella reduction on herd level was established. The model consisted of a microbiological survey in the herd to locate infected parts of the herd. Based on the microbiological results a plan for reduction of salmonella was described for each individual farm. A typical plan consisted of hygienic measures combined with all in-all out measures on either pen-level or section level, in combination with an attempt to improve colonization resistance by using organic acids in water or feed

Subclinical salmonella infection in Danish finishing pig herds - the effect of salmonella contaminated feed

As part of the integrated salmonella programme in the pig production, feed produced in Danish feed mills is examined for salmonella after heat treatment. The results of the bacteriological examination have shown that the prevalence of salmonella in the finished feed products has been \u3c 0.1% (Annual Report on Zoonoses in Denmark, 1996). Since feed may be contaminated during transport, storage or in the feeding systems at the farms, and only the concentrate part of homemixed feed is being heat treated and examined, the actual occurrence of salmonella in the feed when fed to the pigs is unknown. The aim of this study was to determine the prevalence of salmonella in feed at the outlets in the pens, to establish whether certain feeding systems or types of feed were more likely to be contaminated and to assess the possible association between salmonella detected in feed and salmonella infection of pig herds

Detection of S. enterica in different materials from the environment of pig herds

Salmonella contamination of pork carcasses as a result of subclinical salmonella infection in pig herds constitutes a menace to human health. Since 1993 there has been a national surveillance system in Denmark with the aim of monitoring and controlling salmonella infections in pig herds (Mousing et al., 1997). Application of the HACCP principles in control of salmonella infection at herd level depends on the possibility of characterizing the bacteriological status of the different sections of the herd in order to define the critical control points of the production. The objective of the present study was to characterize the microbiological status of the environment in pig herds with respect to different types of salmonella infection, and to evaluate the availability of material which is easy to collect and sensitive in the bacteriological examination

Strategies for elimination of S. typhimurium

Four different strategies were employed to try to eliminate Salmonella typhimurium from infected herds or pigs. Only strategic removal of pigs prior to entering infected sections of the herd was found to be beneficial. Strategies involving efforts to eliminate salmonella from infected pigs or herds by medication were found to be inefficient, and a vaccination strategy using a killed salmonella vaccine did not reduce subclinical infection

An outbreak of salmonellosis in Denmark caused by pork from a single slaughterhouse

Due to a rise in the endemic level of Salmonella Typhimurium infections in humans in Funen county, an outbreak of this serotype was discovered in the first week of September 1996. During the outbreak period (28 August - 14 October 1996) approximately 170 culture confirmed cases were registered at Statens Serum Institut. Almost all isolates were of phage type 12, which is frequently found in pork in Denmark - about 60% of S. Typhimurium isolates from pork are of DT 12 (Anon., 1997)

Salmonella in Swine Research Projects in Denmark and EU

Salmonella spp. in pork has become recognized as a major source for human salmonellosis in Denmark. Consequently, a number of research activities, surveillance and control programs have been initiated during the last 4 years

Dose dependent establishment of subclinical S. typhimurium infection in pigs and protection against homologous re-challenge

The fact that the majority of Salmonella infected pig herds are subclinically infected is accepted worldwide. In subclinically infected herds shedding of salmonella from infected pigs and the contamination of the environment is markedly below the level known from herds having experienced a clinical outbreak (Baggesen et al., 1996)