A new VLA/e-MERLIN limit on central images in the gravitational lens system CLASS B1030+074

We present new VLA 22-GHz and e-MERLIN 5-GHz observations of CLASS B1030+074, a two-image strong gravitational lens system whose background source is a compact flat-spectrum radio quasar. In such systems we expect a third image of the background source to form close to the centre of the lensing galaxy. The existence and brightness of such images is important for investigation of the central mass distributions of lensing galaxies, but only one secure detection has been made so far in a galaxy-scale lens system. The noise levels achieved in our new B1030+074 images reach 3 microJy/beam and represent an improvement in central image constraints of nearly an order of magnitude over previous work, with correspondingly better resulting limits on the shape of the central mass profile of the lensing galaxy. Simple models with an isothermal outer power law slope now require either the influence of a central supermassive black hole, or an inner power law slope very close to isothermal, in order to suppress the central image below our detection limit. Using the central mass profiles inferred from light distributions in Virgo galaxies, moved to z=0.5, and matching to the observed Einstein radius, we now find that 45% of such mass profiles should give observable central images, 10% should give central images with a flux density still below our limit, and the remaining systems have extreme demagnification produced by the central SMBH. Further observations of similar objects will therefore allow proper statistical constraints to be placed on the central properties of elliptical galaxies at high redshift.Comment: Accepted by Monthly Notices of the Royal Astronomical Society. 16 pages, 8 figure

Salmonella enterica prevalence and serotype distribution in swine at slaughter

The objective of this cross-sectional study was to analyze data available from multiple studies conducted by our research team estimating the prevalence of S. enterica, and the serotype d1stribution in swine at slaughter, based on different sample types A total of 1,110 pigs from three large capacity abattoirs located in the Midwestern U S. were individually sampled at slaughter. Individually paired samples collected mcluded. cecal contents and ileocecal lymph nodes. Samples were collected on multiple occasions in all three abattoirs, transported to the laboratory, and processed for the isolation and identification of S. enterica. The overall prevalence of S. enterica, based on cecal contents, mesentenc lymph nodes, and any of the samples (i.e., cecal contents and/or mesenteric lymph nodes) was 54.7%, 27.9%, and 62.6%, respectively. There was a Significant difference (P\u3c0.05) between prevalence estimates based on cecal contents and mesenteric lymph node samples in all three abattoirs, and overall. A variety of S. enterica serotypes was isolated m all abattoirs The average number of serotypes isolated per group was 3.48. This study confirms that the S. entenca prevalence at slaughter in swine is high, requiring attention due to the associated risk of contamination of the abattoir environment. Moreover, our results demonstrate the common occurrence of a high diversity of serotypes in swine at slaughter. This study also shows that both cecal contents and mesenteric lymph nodes should be considered for a better estimate of S. enterica prevalence at slaughter

Salmonella prevalence in first pull versus close out market pigs

Identifying potential risk factors to direct intervention strategies is fundamental to reduce the risk of pork contamination with Salmonella. This study was designed to compare the Salmonella prevalence in the first group of pigs selected for slaughter (uFirst pull ) versus the last group of pigs selected for slaughter ( Close out ) from typical commercial finishing barns containing 800 - 1,000 animals. Nine finishing barns from two production sites were included in the study {4 paired samplings from site A, and 5 paired samplings from site B). Each paired sampling consisted in matched groups of pigs from the same barn as the first pair and the close out with a 4-week interval between groups. From each group, individual fecal samples (n = 45) and meat samples (n = 50) were collected, on-farm and at slaughter, respectively. In the laboratory, fecal samples were selectively enriched, and analyzed for the presence of Salmonella by a commercially available antigen-capture ELISA. Meat samples were kept frozen, and thawed for processing. The resulting liquid ( meat juice ) was collected and analyzed for the presence of antibodies against Salmonella by a commercially available ELISA. All lots of pigs housed in the finishing barns studied were Salmonella-positive, based on sampling from first pull and close out . 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 9.3% (P\u3c0.05) in bacteriologic prevalence, and 25.1% (P\u3c0.05) in serologic prevalence from first pull to close out groups. This study demonstrates that a significant increase of Salmonella prevalence occurs between the first and the last group of pigs from a finishing barn shipped to slaughter. In conclusion, close out groups of finishing pigs constitute a higher risk for Salmonella contamination of pork products

Quantity and Distribution of Salmonella Recovered from Three Swine Lairage Pens

The quantity of Salmonella recoverable from three lairage pens in a swine abattoir was determined. Using dry four-ply cotton gauze pads measuring 10 by 10 cm, 100 fecal slurry samples were collected from each of the three pens. Salmonella recovery was expressed as the log CFU per milliliter of sample. Mean values were 2.5 log CFU/ml in pen A, 2.7 log CFU/ ml in pen B, and 0.89 log CFU/ml in pen C. Median values were 2.6 log CFU/ml in pen A, 2.0 log CFU/ml in pen B, and below the detectable limit in pen C. In pen C, Salmonella was not recoverable from a high number of samples. Pen B results suggested spatial dependency, i.e., samples close together were more similar than samples farther apart. These results indicate that Salmonella concentrations vary within and between lairage pens. Because of the limited number of pens assessed, it was not possible to identify factors that were associated with the observed variation in Salmonella concentrations within and between pens. However, this variation suggests that numerous samples are required to adequately describe the concentration of Salmonella in a lairage pen

Eliminating the Abattoir Pen Lairages to Decrease the Prevalence of Salmonella in Cull Sows

The study objective, to determine the role of abattoir antemortem pens in preharvest Salmonella enterica contamination, was conducted over 4 sampling periods, February-April 2002. A total of 40 sows were selected for each period at the same collection point and transported to the abattoir. Twenty (20) were unloaded and sent directly to harvest and 20 held in antemortem pen for 2 h before harvest. Samples collected included ileocecal and subiliac lymph nodes, cecal and transverse colon contents, pre-rinse carcass sponge swabs for the right and left carcass sections and chopped meat blocks composited from these carcasses. The percentage of positive samples (all tissues) and cecal content from sows held in the antemortem pens (59%, 55 %, respectively) were significantly higher (P \u3c 0.05) compared to direct delivered (44%, 39 % respectively). This study demonstrates that normal antemortem holding practices contributed to increased Salmonella enterica contamination of the digestive tract

The Association between Cleaning and Disinfection of Lairage Pens and the Prevalence of Salmonella enterica in Swine at Harvest

A series of four field trials were conducted to evaluate the ability of a cleaning and disinfection procedure in swine lairage pens to reduce the prevalence of Salmonella enterica in slaughtered pigs. A cleaning and disinfection procedure was applied to lairage pens at a large Midwest abattoir. Each trial consisted of a cleaned (alkaline chloride detergent) and disinfected (H2O2 plus peracetic acid sanitizer) pen (treated) and a control pen, each holding 90 to 95 pigs for 2 to 3 h before slaughter. Ileocecal lymph nodes, cecal contents, and rectal contents were collected from 45 pigs from each study pen at harvest and cultured for S. enterica. In all trials, cleaning and disinfection reduced the prevalence of S. enterica–positive floor swabs in the treated pen (P , 0.05). However, the postharvest prevalence of S. enterica–positive pigs varied between trials. In trial 1, there was no significant difference in the prevalence of S. enterica in pigs between treatment and control groups. In trials 2 and 3, the prevalence of S. enterica was higher in pigs from treated pens versus pigs from control pens (91% versus 40%, P , 0.0001, and 91% versus 24%, P , 0.0001, respectively). In trial 4, the prevalence of S. enterica was lower in pigs from treated pens compared with pigs from control pens (5% versus 42%, P , 0.0001). This study indicates that cleaning and disinfection effectively reduces the amount of culturable S. enterica in lairage pens, but the ability of cleaned and disinfected pens to reduce the prevalence of S. enterica in market-weight pigs remains inconclusive

Sampling cecal contents or ileocecal lymph nodes: is it different?

The objective of this study was to compare the prevalence of Salmonella enterica in swine populations estimated by sampling cecal contents versus ileocecal lymph nodes. In each of two abattoirs, four groups of pigs (n=30 pigs per group) were studied. Cecal contents and ileocecal lymph nodes were individually collected and processed for isolation and identification of S. enterica. The overall prevalence found by cecal contents was 40%, whereas by ileocecal lymph nodes it was 22.9% (p\u3c0.05). Combining results from both samples, the prevalence found was 50.8%. The relative sensitivity of cecal content sampling was 79.3%, whereas for ileocecal lymph node sampling it was 45.5%. The agreement (Kappa statistic) between both sample types was 13.1%. This study demonstrates that sampling either cecal contents or ileocecal lymph nodes affects results of S. enterica epidemiological studies. It is recommended that both samples be used

Genetic relatedness of Salmonella enterica isolates from pens and swine at slaughter

The study aimed to determine if Salmonella enterica isolates from the floor of pre-slaughter holding pens were genetically related to isolates found in swine, held in those pens, post slaughter. Pulsed-field gel electrophoresis (PFGE) typing was used to determine genetic relatedness. On seven occasions, 100% homologous PFGE patterns were found, i.e. the pen and pig isolates were identical. This suggested that pen to pig transfer of Salmonella enterica occurred. Isolates from PFGE patterns associated with pig to pen transfers were more likely to occur in the S. Anatum, S. Heidelberg and S. Typhimurium serotypes. The ability of an isolate from a pen to rapidly infect animals housed in the pen may vary within serotype based on factors described by the PFGE pattern. This may explain why some S. enterica serotypes are prevalent in swine but not in pork products or humans

Slatted pen floors reduce Salmonella in market swine held in abattoirs

The objective of this study was to directly compare Salmonella isolation rates from pig slaughtered after 4 hours holding on slatted or solid concrete floors. Seven truckloads (replicates) of market swine ( 120 kg) from a fully integrated farrow-to-slaughter operation were studied. At unloading, groups of pigs (15-30) were sorted to 1) no-hold (20-45 minutes waiting), 2) pens with solid concrete floors (4 hours), 3) slatted concrete floors (4 hours). Postmortem samples were cultured for Salmonella. Those pigs held in pens with slatted floors (63.6%) had significantly (P \u3c 0.05) less Salmonella in their ceca than those held on solid floors (72.7%)