Update on laboratory diagnosis of subclinical salmonella infection in pigs

Detection of Salmonella is a key point in veterinary salmonella research and surveillance programmes. The chosen method of detection, direct or indirect, highly affects our conclusions in any examination or investigation. The perfect test is characterized by having a very high specificity, sensitivity and predictive value, being easy to perform, cheap, rapid and having the possibilty oflarge scale examination by automation. So far no single test has been able to fulfil all these requirements

The occurrence of S. enterica serotypes in animal feed, pigs, pork and man

In Denmark, national surveillance systems have been established with the aim of monitoring the level of salmonella infection in animal feed, pig herds and pork. The human infections are monitored at Statens Serum Institute. All Salmonella isolates identified are serotyped according to the Kauffmann-White scheme. The results of the surveillance allow a comparison of the serotypes occurring in the different levels

Antibiotic resistance in S. enterica isolated from Danish pig herds

An increase in the occurence of antibiotic resistance in Salmonella enterica and other patogenic bacteria has been observed in several countries during the last years. This development is cause for concern as it complicates the therapeutic use of antibiotics in both human and veterinary medicine. Antibiotic resistance is correlated to the use of antibiotics for therapeutic, prophylactic or growth promoting purposes. In Denmark, the occurence of resistance in Salmonella enterica is monitored as a part of the diagnostic work. The objective of this paper is to describe the level and type of antibiotic resistance in Salmonella enterica isolated from Danish pig herds in 1996

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

The emergence of nalidixic acid resistant, multiresistant S. typhimurium DT104 in Denmark. An outbreak in humans traced back to pork

Infection with the zoonotic Salmonella enterica serovar typhimurium DTI04 has been recognised since the beginning of the 90\u27s as a health problem in several industrialised countries. The present investigation demonstrates that results of surveillance of Salmonella infection in food animals, food production and among humans enabled identification of an outbreak of human salmonellosis caused by a nalidixic acid resistant strain of S. typhimurium DTJ 04. The source of infection was traced back to a single slaughterhouse and two pig herds

Outbreak of Salmonella manhattan associated with a ready-to-eat pork product in Denmark in 1998

Salmonella Manhattan is rarely found in Denmark. Since 1980, only 0-3 human cases have been registered annually. However, in the first 4 weeks of 1998, 19 cases of this serotype were registered suggesting an outbreak. S. Manhattan isolates from 18 human cases were typed using pulsedfield gel electrophoresis. Twelve of these isolates were identical and 3 were closely related, whereas the remaining isolates from humans in 1997 were clearly different. This indicated an outbreak with a common source. Further typing of S. Manhattan isolates collected as a part of the routine surveillance of domestic animals and food suggested a link to pork. Of 17 isolates from broilers, pigs and imported poultry, 6 isolates from breeder pigs imported from an internationally operating pig-production company were indistinguishable from the outbreak strain, whereas the remaining were different. A matched case-control study of 16 cases and 45 controls was carried out. The results suggested that cured and smoked ready-to-eat fillet of pork was the most likely source. Ten of 16 cases had consumed this product within three days before onset of disease, compared with 4 of 45 matched controls (OR 17,

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

Bacteriological and serological characterisation of slaughter pigs from 25 serologically identified salmonella high risk herds

Danish finishing herds are routinely screened for antibodies to Salmonella in random samples of meat juice from slaughter pigs. The herds are categorized by the seroprevalence of samples from the preceding three months into three infection levels (1, 2 and 3). Herds are allocated to level 3 ( Salmonella high risk herds) at seroprevalences exceeding 33-50% depending on herd size (larger herds lower limit) (Mousing et al., in press)

Host defence responses in pigs experimentally infected with S. typhimurium

Salmonella Typhimurium may induce persistent infections (organ carriers) in pigs, and healthy carriers seems to be a problem in controling the infection (8). Evasion or disturbance of the host defence responses may be nessesary for establishment of a persistent infection. Functional changes in circulating neutrophils from pigs infected with Salmonella Typhimurium have been demonstrated (1). The aim of the study was to investigate host defence mechanisms in pigs that have cleared the infection, persistently infected pigs and uninfected pigs, studies that may contribute to the explanation of how the carrier-state is established. Phagocytosis and oxidative burst in peripheral blood or cells isolated from peripheral blood were investigated in three inoculation experiments