The error-adjusted variance partition coefficient in the identification of critical control points for Salmonella carcass contamination

The variance partition coefficient (VPC) measures the clustering of Salmonella infection among pig carcasses with a specific combination of risk factors/processing steps (i.e., covariate pattern). Covariate-pattern-specific VPCs provide insight to the groups of carcasses that exhibit great heterogeneity and should be targeted for control. The imperfect accuracy of the diagnostic procedure bias VPC and other measures of clustering and should be analytically controlled. I applied a discrete mixed model for the estimation of VPC, via Markov-Chain Monte Carlo simulation, adjusting for imperfect accuracy, to data from a study aiming to identify critical control points (i.e. risk factors/processing steps) for Salmonella contamination of pig carcasses during the slaughtering process

Seroprevalence and antibiotic sensitivity of Salmonella enterica serotypes in Greek swine herds

Blood samples were taken from 50 pigs in each of 59 farrow-to-finish herds and from 40 gilts in each of 4/5 registered multiplying herds. Samples of feed and faeces were collected from 17 of the production herds and from the multiplying herds. The sera were tested for antibodies by the Danish-mix-ELISA (positive cut-off OD\u3e10 or OD\u3e40 %), and the organisms were isolated, serotyped and sensitivity tested by standard techniques. The average within herd seroprevalence was 15.6 or 3.4% and at least one pig tested seropositive in 52/59 or 21159 production herds at the low and the high cut-off values, respectively. All the multiplying herds had seroreactors at the low but only a single seroreactor was detected at the high cut-off. The salmonellae isolated were S. tennessee, S. typhimurium. S. bredeney, S. london and an untypable strain. The S. typhimurium and S. london had low sensitivity to streptomycin, kanamycin and neomycin. the former had low sensitivity also to amoxicillin, ticarcillin, piperacillin, cefalotin and cefoperazone. The other isolates were sensitive to the antimicrobial agents tested

Application of liquid chromatography coupled to high-resolution mass spectrometry to measure urinary cortisol in loose housed sows

Cortisol is the most common physiological parameter used to measure welfare in pigs. In field studies evaluating stress in individual pigs which are group housed, the collection of spontaneously voided urine is practical. The purpose of the study was to apply a liquid chromatography coupled to high-resolution mass spectrometry approach to observe the patterns of diurnal urinary cortisol excretion among loose sows of three herds. We applied the analytical method in spontaneously voided urine of thirty, repeatedly sampled within a day, multiparous sows of three Greek herds. We found the level of urinary cortisol being highest before morning feeding [geometric mean of urinary cortisol to creatinine ratio being 2.72 (95% confidence interval: 1.17, 6.30), 5.65 (3.15, 10.14) and 2.60 (1.50, 4.50) in sows of herds A, B, and C, respectively] and lowest at 19: 00 h [0.56 (0.27, 1.18), 1.24 (0.74, 2.07), 0.88 (0.55, 1.44)]. However, the patterns of diurnal urinary cortisol excretion appeared different among herds

Isolation of Salmonella enterica in seropositive classified finishing pig herds

The aim of this study was to assess the probability of detecting Salmonella from pen faecal samples in seropositive classified finishing pig herds. The study involved 77 herds from Denmark (20), the Netherlands (20), Greece (17) and Germany (20). The serological herd status was determined by the blood- sampling of 50 finishing pigs. Bacteriological sampling was performed by 20 pen faecal samples per herd. Over-all, 47 % of the blood samples had an OD% larger than 10 and 23 % larger than 40. Salmonella was isolated from 135 (9.3 %) pen faecal samples in 32 herds (42 %). Twenty-eight of these herds (87.5 %) had a within-herd seroprevalence larger than 50% at sample cut-off OD%\u3e10. A correlation coefficient of 0.62 was found between the proportion of culture positive- and seropositive samples in a herd at cut-off OD % \u3e 10 and of 0.58 at cut-off OD % \u3e 40. Due to the low sensitivity of culture methods, apparent ‘false positive’ serological results may well represent real infections not detected by bacteriological testing. In this study, there was an increasing probability of recovering Salmonella with increasing within-herd seroprevalence

Post harvest epidemioilogy of Salmonella enterica in pork: Prevalence in the environment, carcasses and by-products in two slaughterhouses in Greece (1996-1998)

In this study our objective was to estimate the prevalence of Salmonella enterica in the environment, on the pork carcasses and on several by-products in 2 industrial slaughterhouses over a 2-year period. In the period from 1/7/96 until 1/8/98, 1874 samples were obtained from the slaughterhouse environment (from the floor, the worker\u27s hands and their knives), product samples (from pork carcasses) and by products (livers and plucks). The prevalence of infection in pigs slaughtered at the sampling dates was estimated by testing samples from mesenteric lymph nodes and caecal content. Environmental samples were collected before the onset of slaughter. After the onset of slaughter and for every 50 pigs, a round of samplings of all sources mentioned above was repeated. Salmonella isolation and identification was carried out by standard cultural method. In total, based on the isolation method, 178/1874 (9.5%) samples were positive. The mean prevalence on floors, workers\u27 hands. workers\u27 knives, pork carcasses and by-products were 19.6% (range: 0%-100%), 5.2% (0%-50%), 3.1% (0%-37.5%), .3% (0%-88.9), 6.6% (0%-90%), respectively. The average prevalence of infection in pigs slaughtered at the sampling dates was 20.7% based on mesenteric lymph nodes and 15.2% based on caecal contents. Before the onset of slaughter, 37.5%, 6.3% and 8.7% of samples obtained from floors, worker hands and knives harbored Salmonella. This may reflect an inadequate plant hygiene. The frequent presence of Salmonella in the caecal contents and the lymph nodes may contribute to significant environmental contamination, including inspectors hands, eventually leading to final product contamination. The isolated salmonellae belonged to 22 serotypes. Among those, S. Derby and S. London were the most frequent representing 25.8% and 15.2% respectively. In conclusion, the frequent presence of Salmonella spp. in the lymph nodes, may indicate infection in the herd. Furthermore, the moderate prevalence of Salmonella on carcasses and by-products calls for further identification and institution of postharvest control options

Development of a LAMP assay for detection of Leishmania infantum infection in dogs using conjunctival swab samples

Background: Leishmania infantum infections in dogs play a crucial role in the transmission of pathogens causing visceral leishmaniasis to humans in the Gansu province, northwest China. To be able to control zoonotic transmission of the parasite to humans, a non-invasive loop-mediated isothermal amplification (LAMP) assay to specifically detect L. infantum infections in dogs was developed. Methods: The primers used in the LAMP assay were designed to target kinetoplast DNA minicircle sequences of the L. infantum isolate MCAN/CN/90/SC and tested using DNA isolated from promastigotes of different Leishmania species. The LAMP assay was evaluated with conjunctional swab samples obtained from 111 and 33 dogs living in an endemic and a non-endemic region of zoonotic visceral leishmaniasis in the Gansu province, respectively. The LAMP assay was also compared with conventional PCR, ELISA and microscopy using conjunctional swab, serum and bone marrow samples from the dogs, respectively. Results: The LAMP assay detected 1 fg of L. infantum DNA purified from cultured promastigotes which was 10-fold more sensitive than a conventional PCR test using Leishmania genus-specific primers. No cross reaction was observed with DNA isolated from promastigotes of L. donovani, L. major, L. tropica, and L. braziliensis, and the L. infantum reference strain MHOM/TN/80/IPT1. The L. infantum-positive rates obtained for field-collected samples were 61.3%, 58.6%, 40.5% and 10.8% by LAMP, PCR, ELISA and microscopy, respectively. As only one out of the 33 samples from control dogs from the non-endemic region of zoonotic visceral leishmaniasis was positive by the LAMP assay and the PCR test, the observed true negative rate (specificity) was 97% for both methods. Conclusion: This study has shown that the non-invasive, conjunctional swab-based LAMP assay developed was more sensitive in the detection of leishmaniasis in dogs than PCR, ELISA and microscopy. The findings indicate that the LAMP assay is a sensitive and specific method for the field surveillance of domestic dogs, particularly of asymptomatic canines, in ZVL-endemic areas in western China