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A survey of the relationship between bile staining and oesophagogastric lesions in slaughter pigs.

In 280 slaughter pigs, the oesophageal region of the stomach was examined to test the hypothesis that there is a (causal) relationship between the intensity of bile staining of oesophagogastric tissue due to bile regurgitation and the severity of oesophagogastric lesions. When the stomachs were opened, almost all stomachs contained bile and 99.6% of stomachs showed bile staining of the pars oesophagea. A total of 14.3% of the stomachs showed distinct erosions and/or ulceration. A considerable proportion of the stomachs (58.5%) had hyperkeratosis as the only lesion. Only two animals showed a completely intact epithelium. There was no evidence for an increased proportion of oesophagogastric lesions with an increased intensity of bile staining. No dark yellow to green staining was observed; a just detectable to an obvious yellow was seen. This is an indication for bile regurgitation of recent origin. Therefore, there is no evidence for the hypothesis that the regurgitation of bile into the stomach is positively linked to the occurrence of oesophagogastric lesions in fattening pigs. It is suggested that various factors associated with slaughter, such as fasting and slaughter procedure, are primarily responsible for the presence of bile and the staining of the pars oesophagea in the stomachs.

Abattoirs↗

In vivo porcine multi-omics integration identifies microbiome-driven histamine elevation and lasting gut perturbations following Ascaris suum infection and fenbendazole treatment.

Ascaris roundworms impair human and swine health. While treatments using anthelmintic drugs are generally effective in eliminating worms, their effects on the gut microenvironment remain poorly understood. Here we applied integrated multi-omics to characterize infection- and treatment-associated alterations in the pig-Ascaris system. In vitro anaerobic cultures were conducted as supportive validation of selected observations. Ascaris suum infection altered microbial composition and dysregulated 182 serum and fecal metabolites, including histamine and p-cresol sulfate. Compared with time-matched uninfected controls, infected pigs treated with fenbendazole showed marked differences in gut microbial composition 13&#x2009;days after confirmed worm clearance. Eleven microbial pathways were enriched in successfully treated pigs, including peptidoglycan biosynthesis and histidine metabolism, indicating that infection-associated alterations may persist after treatment. In vitro co-exposure of Lactobacillus reuteri to fenbendazole and A. suum proteins increased histamine production by approximately 79% at 48&#x2009;h (p&#x2009;<&#x2009;0.05), serving as supportive evidence of a microbiome contribution. Collectively, our in vivo findings support that host-microbiota-parasite interactions are multifaceted. Microbiota-derived metabolites were associated with regulation of host gene expression, such as TFF2 and IL8. Microbiota plasticity allows the exploitation of the niche differentiated upon infection, resulting in the proliferation of certain Lactobacillus strains in treated animals. Nevertheless, interpretations of treatment effects are made cautiously given the absence of an uninfected drug-only group and the cross-sectional design. Understanding these complex interactions will be important for the design of next-generation functional anthelmintics.

Animals↗

Japanese encephalitis virus in Bangkok: factors influencing vector infections in three suburban communities.

An unexpected outbreak of Japanese encephalitis (JE) in Bangkok in 1985 led us to investigate the vector ecology of urban JE from January 1986 to June 1987 at three suburban sites that displayed a wide range of factors imputed to influence JE transmission. Culex tritaeniorhynchus Giles and Cx. gelidus Theobald, suspected vectors, comprised 71-96% of all mosquitoes collected by CO2-baited CDC traps at the three sites. Mean of mosquito abundance per two trap-nights per month ranged from 28 to 5,728 mosquitoes at the sites of lowest and highest abundance, respectively. Cx. tritaeniorhynchus yielded more JE isolates (n = 16) than Cx. gelidus (n = 7), but the minimum infection rates of the two species (number of JE isolates per 1,000 mosquitoes tested; MIR, 0.17 and 0.47, respectively) were comparable and covaried with vector abundance. Moreover, the proportion of sentinel pigs that had JE antibodies generally increased proportionately with vector abundance at the sites. Vector abundance was high in monsoon (May-October), moderate in transition (March-April and November-December), and low in dry (January-February) seasons. Mosquitoes collected in monsoon seasons yielded 96% of the JE isolates, whereas 4 and 0% of the isolates were obtained from transition and dry season collections, respectively. More pigs seroconverted in monsoon and transition seasons than in dry seasons. Indices of JE transmission activity (vector abundance, pig seroconversions, and MIRs) increased proportionately with rainfall. Despite higher indices at the site of greatest vector abundance than elsewhere, the risk of human infection appeared greatest at the site with moderate vector abundance because of its greatest human population density.

Animals↗

The construction and analysis of epidemic trees with reference to the 2001 UK foot-and-mouth outbreak.

The case-reproduction ratio for the spread of an infectious disease is a critically important concept for understanding dynamics of epidemics and for evaluating impact of control measures on spread of infection. Reliable estimation of this ratio is a problem central to epidemiology and is most often accomplished by fitting dynamic models to data and estimating combinations of parameters that equate to the case-reproduction ratio. Here, we develop a novel parameter-free method that permits direct estimation of the history of transmission events recoverable from detailed observation of a particular epidemic. From these reconstructed 'epidemic trees', case-reproduction ratios can be estimated directly. We develop a bootstrap algorithm that generates percentile intervals for these estimates that shows the procedure to be both precise and robust to possible uncertainties in the historical reconstruction. Identifying and 'pruning' branches from these trees whose occurrence might have been prevented by implementation of more stringent control measures permits estimation of the possible efficacy of these alternative measures. Examination of the cladistic structure of these trees as a function of the distance of each case from its infection source reveals useful insights about the relationship between long-distance transmission events and epidemic size. We demonstrate the utility of these methods by applying them to data from the 2001 foot-and-mouth disease outbreak in the UK.

Algorithms↗

Modelling the initial spread of foot-and-mouth disease through animal movements.

Livestock movements in Great Britain (GB) are well recorded and are a unique record of the network of connections among livestock-holding locations. These connections can be critical for disease spread, as in the 2001 epidemic of foot-and-mouth disease (FMD) in the UK. Here, the movement data are used to construct an individual-farm-based model of the initial spread of FMD in GB and determine the susceptibility of the GB livestock industry to future outbreaks under the current legislative requirements. Transmission through movements is modelled, with additional local spread unrelated to the known movements. Simulations show that movements can result in a large nationwide epidemic, but only if cattle are heavily involved, or the epidemic occurs in late summer or early autumn. Inclusion of random local spread can considerably increase epidemic size, but has only a small impact on the spatial extent of the disease. There is a geographical bias in the epidemic size reached, with larger epidemics originating in Scotland and the north of England than elsewhere.

Animals↗

Analyses of the genomes of chlamydial isolates from ruminants and pigs support the adoption of the new species Chlamydia pecorum.

Analysis of the genomic DNAs of chlamydial isolates from sheep, cattle, and pigs was performed by Southern blot hybridization and by restriction endonuclease (RE) profiling of DNA amplified by PCR. The hybridization probes were derived from whole genomic DNA, the major outer membrane protein (MOMP) gene, the 16S rRNA gene, and an avian Chlamydia psittaci isolate plasmid. The PCR analysis used targets in the MOMP gene, the 16S rRNA gene, and the 60-kDa cysteine-rich protein gene. Together, the results showed that although there was considerable heterogeneity in the DNA sequence in the MOMP gene region, all the isolates had the same underlying total genomic RE profiles and yielded identical RE profiles for the rRNA and 60-kDa-protein gene regions. Most of the isolates were found to hybridize with the plasmid probe. Comparison of the MOMP sequence of one of the isolates (P787) with that of a known Chlamydia pecorum strain together with the results of the RE analyses allowed the conclusion that the isolates should all be classified within this new species.

Amino Acid Sequence↗

Experimental infection of calves, piglets and lambs with mixtures of invasive and enteropathogenic strains of Escherichia coli.

Mixtures of mutant organisms of an invasive (IN) strain, a strain enteropathogenic (EP) for calves, lambs and piglets, and a non-pathogenic (NP) strain of Escherichia coli, that could be differentiated from each other by their antibiotic resistances, were given orally to an immunoglobulin-negative (IG-) and an immunoglobulin-positive (IG+) calf, lamb and piglet. By the use of appropriate antibiotic-containing culture media, the concentrations of organisms of each of the three strains in the contents of the alimentary tracts and tissues (liver, spleen, kidney, blood and mesenteric lymph glands) of the animals were estimated when they were killed. In the three IG- animals, the IN strain proliferated in the tissues and the EP strain proliferated in the small intestines; in general, the concentrations of the IN strain in the small intestines and the EP strain in the tissues, apart from the mesenteric lymph glands, were as low as those of the NP strain in these sites. The only strain that proliferated in the small intestine of the IG+ animals was the EP strain, which proliferated in the small intestine of the calf and piglet; no organisms of either strain were isolated from the tissues of these three animals, except from their mesenteric lymph glands.

Agammaglobulinemia↗

Study of the population structure of Haemophilus parasuis by multilocus sequence typing.

Haemophilus parasuis is the aetiological agent of Glässer's disease in swine. In addition, this bacterium causes other clinical outcomes and can also be isolated from the upper respiratory tract of healthy pigs. Isolates of H. parasuis differ in phenotypic features (e.g. protein profiles, colony morphology or capsule production) and pathogenic capacity. Differences among strains have also been demonstrated at the genetic level. Several typing methods have been used to classify H. parasuis field strains, but they had resolution or implementation problems. To overcome these limitations, a multilocus sequence typing (MLST) system, using partial sequences of the house-keeping genes mdh, 6pgd, atpD, g3pd, frdB, infB and rpoB, was developed. Eleven reference strains and 120 field strains were included in this study. The number of alleles per locus ranged from 14 to 41, 6pgd being the locus with the highest diversity. The high genetic heterogeneity of this bacterium was confirmed with MLST, since the strains were divided into 109 sequence types, and only 13 small clonal complexes were detected by the Burst algorithm. Further analysis by unweighted-pair group method with arithmetic mean (UPGMA) identified six clusters. When the clinical background of the isolates was examined, one cluster was statistically associated with nasal isolation (putative non-virulent), while another cluster showed a significant association with isolation from clinical lesions (putative virulent). The remaining clusters did not show a statistical association with the clinical background of the isolates. Finally, although recombination among H. parasuis strains was detected, two divergent branches were found when a neighbour-joining tree was constructed with the concatenated sequences. Interestingly, one branch included almost all isolates of the putative virulent UPGMA cluster.

Alleles↗

Common swine leucocyte antigen (SLA) haplotypes in NIH and Sinclair miniature swine have similar effects on the expression of an inherited melanoma.

Mixed lymphocyte culture and serological typing of NIH and Sinclair miniature swine indicate that the two herds share a common SLA haplotype. NIH haplotype a (International Haplotype H10) appears identical to Sinclair haplotype B, which has significant effects on the penetrance of Sinclair swine cutaneous malignant melanoma (SSCM). Offspring of crosses between melanoma-bearing Sinclair swine homozygous for the B haplotype and non-melanoma NIH aa swine have tumour incidence identical to Sinclair melanoma BB x Sinclair non-melanoma BB offspring. Our results provide further support for the involvement of the swine leucocyte antigen (SLA) complex in the inheritance of SSCM, and identify a new source of non-tumour animals that have all of the genes for SSCM except those at the tumour-initiator locus.

Animals↗

Trimethoprim resistance plasmids in Escherichia coli isolated from cases of diarrhoea in cattle, pigs and sheep.

A total of 1572 isolates of Escherichia coli obtained from the faeces of young farm animals with diarrhoea over the period 1980-1983 were screened for resistance to trimethoprim (Tp). Resistance to Tp was detected in 263/954 (28%) of bovine isolates, 59/441 (13%) of porcine isolates and 15/177 (9%) of ovine isolates. Seventy-five resistant isolates from separate outbreaks of infection on farms within a 25 mile radius of Nottingham were examined in detail. Sixty-eight (91%) of the 75 isolates were resistant to greater than 1024 mg Tp/l and 34 (50%) of these 'highly resistant' isolates (45% of total resistant isolates) transferred their Tp resistance to E. coli K12. A further 13 (17%) isolates were demonstrated to carry non-self-transferable plasmids which were capable of being mobilized to E. coli K12 by the broad host range plasmid RP4. Thirty-one self-transferable Tp R plasmids were divided between the following incompatibility groups: IncB (14 plasmids), IncFII (4 plasmids), IncH2 (1 plasmid), IncI alpha (10 plasmids), IncI delta (1 plasmid) and IncP (1 plasmid). In terms of antibiotic resistance patterns and incompatibility properties, many of these plasmids closely resembled those isolated from human patients in the same area, suggesting that there may be a common pool of Tp R plasmids.

Animals↗