Our aim was to determine the Salmonella enterica prevalence in 96 randomly selected Danish pig herds, based on serological examination of blood samples and bacteriological examination of faecal samples (collected simultaneously from the same pens). For comparison, 39 high-seroprevalence herds were included in the study. The representativeness of the selected herds was assessed, based on descriptive statistics of herd size and type. Totals of 1330 pen samples and 6814 blood samples were examined.The results from the meat-juice screening in the Danish S. enterica Control Programme were available for 3372 meat-juice samples from 91 of the 96 randomly selected herds and 1195 meat-juice samples from 37 of the 39 high-seroprevalence herds. Of the 96 randomly selected herds, 23 herds had no positive pen samples (out of 10), no positive blood samples (out of 50) and no positive meat-juice samples (out of approximately 30-40 samples in 6 months). Ten herds had one or more positive meat-juice samples but were otherwise negative. S. Typhimurium was isolated from 30 of the 39 high-seroprevalence herds. Our conclusions were: (1) The within-herd seroprevalence among the 96 randomly selected Danish pig herds was low (average within-herd seroprevalence=2%, maximum=32%). (2) Among the 39 high-seroprevalence herds (recently assigned level 3 in the S. enterica Control Programme), S. enterica was isolated from 77% of the herds when 10 pen samples were examined bacteriologically. (3) Seropositivity tended to be related to the presence of S. Typhimurium.
"It is uncertain whether the observed difference between STM and other serovars in respect of an association with herd size is genuine. However, evidence from elsewhere [32, 33] suggests that infections with STM may be more long lasting in growing pigs than those with other serovars, which may interact with herd immunity effects discussed above to reduce the likelihood that infections will spontaneously recede or resolve in larger herds. "
[Show abstract][Hide abstract] ABSTRACT: To examine patterns of Salmonella herd infections in units linked by common sources of pigs, the study examined pooled pen faeces samples from 161 nursery and finishing units in a UK integrated pig enterprise. An epidemiological questionnaire was also completed by investigators for each farm. Salmonella was isolated from 630 (19.5%) of the samples: S. Typhimurium was found in 387 (12%) and S. Derby in 157 (4.9%) samples; 111 units yielded at least one sample containing Salmonella. The proportion of Salmonella-positive samples from positive farms ranged from 5% to 95%. In a univariable risk factor analysis, increasing length of time as a pig farm was positively associated with the detection of Salmonella in a herd. Larger farms (>500 pigs) were significantly more likely to be positive for S. Typhimurium than smaller farms. There was an association between Salmonella serovars isolated in the present study and those subsequently isolated in breeding herds linked to the integration.
"The survey embraced two objectives, the evaluation of the prevalence of Salmonella spp., and determines the specific prevalence of the multiresistant S. Typhimurium DT104. Similarly, in 1999 a subclinical prevalence study was performed (Stege et al., 2000). That study comprised 96 farms selected randomly and 36 high-seroprevalence herds which were evaluated by both bacteriology and serology. "
[Show abstract][Hide abstract] ABSTRACT: The objective of this paper is to analyse in further detail the Danish results of the EFSA baseline studies in slaughter pigs and breeding herds, and compare them with the results obtained in (1) the pre-implementation study that was carried out to establish the initial prevalence values in fattening herds as part of the Danish Salmonella control programme, and (2) the study performed four years later in breeding and finishing herds to obtain information about the prevalence in breeding farms and the status of the finishers after the first years of the National Salmonella Control Programme. In the slaughter pigs Salmonella was detected in a 7.4% of 1218 ileocaecal lymph nodes and on 3.2% of 438 carcasses examined. Among the breeding herds examined by floor faecal or swab samples 122 of 298 (40.9%) were positive in at least one of the ten samples collected. The most prevalent serotypes were Salmonella Typhimurium in finishers and Salmonella Derby in breeding herds while the most prevalent phage types of the S. Typhimurium isolates were DT 12 and DT 120. The antimicrobial resistance analysis yielded a 35.2% of the isolates from the slaughter pigs resistant to one or more antimicrobials while 19.3% were resistant to four or more antimicrobials. A significantly higher percentage of resistance to antimicrobials was found in the S. Typhimurium isolates (χ(2)=4.72, p=0.029), where 42.9% presented resistance to one or more compounds. In breeding herds, just S. Typhimurium and S. 4,5],12:i: - isolates were tested. As many as 56.8% of the S. Typhimurium-like strains positive breeding farms had resistant strains, while 27% had multidrug resistant strains. The distribution of the isolates in regions showed that S. Derby is at present the predominant serotype in breeding farms from most of the regions of the country.
Research in Veterinary Science 04/2013; 95(2). DOI:10.1016/j.rvsc.2013.04.001 · 1.41 Impact Factor
"More importantly, it is possible that animals with positive serological status (which has been shown to persist for several weeks; Nielsen et al., 1995) do not continue to shed Salmonella in the feces and, therefore, would not be detected with bacteriologic analysis. This scenario would explain the common finding of higher serologic prevalence estimates, as reported here, and by others (Stege et al., 2000; Lo Fo Wong et al., 2003; Hurd et al., 2004; Funk et al., 2005). Studies with experimentally infected pigs have shown that the onset of serologic response and peak seroprevalence occur at approximately 7 and 30 days postinoculation , respectively (Wood et al., 1989, 1991; Nielsen et al., 1995; Srinand et al., 1995). "
[Show abstract][Hide abstract] ABSTRACT: On-farm reduction of Salmonella carriage prevalence in pigs requires the identification of risk factors to direct interventions development. This study was designed to determine if split marketing of finishing pigs constitutes a risk factor for Salmonella infections, by comparing Salmonella prevalence in the first group of pigs selected for harvest ("first pull") versus the prevalence in the last group of pigs selected for harvest ("close out") from multiple commercial finishing lots. Nine paired samplings were conducted consisting in matched groups of pigs from individual barns as the first pull and the close out with a 4-week interval between groups. From each group, fecal and meat samples were collected, on-farm and at harvest, respectively. Fecal samples were selectively enriched, and analyzed for the presence of Salmonella, whereas meat juice samples were analyzed for the presence of antibodies against Salmonella. In 7/9 (77.8%) of the studied barns, an increase in Salmonella prevalence was observed, based on both bacteriologic and serologic analysis. Overall, there was an increase of 9.2% (p < 0.05) in bacteriologic prevalence, and 31.3% (p < 0.05) in serologic prevalence from first pull to close out groups. This study demonstrates that a significant increase in Salmonella prevalence occurs between the first and the last group of pigs harvested from finishing lots, with close out groups of market pigs posing a higher risk for Salmonella contaminations.
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