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K H Christiansen

Publications and source records attributed to K H Christiansen.

At least 19 recordsLinked to original sources
PubMed2007

Assessing the effect of interventions on the risk of cattle and sheep carrying Escherichia coli O157:H7 to the abattoir using a stochastic model.

Escherichia coli O157:H7 persists in being a threat to food safety. The mechanisms behind the spread of E. coli O157:H7 on the farm are complex and poorly understood. The objective of this study was to apply a Monte Carlo model, constructed to simulate the propagation of E. coli O157:H7 in cattle and sheep on the farm, to both test the effect of different interventions on the risk of animals carrying E. coli O157:H7 to the abattoir and to develop understanding of the underlying processes, including the identification of areas that could benefit from further research. An overview of the model including key assumptions is given. The output statistics from batches of 100 runs of the model were collected. From the model output, a cumulative frequency distribution of the prevalence and specific shedding level for the groups of cattle or sheep being sent to the abattoir were generated. Stochastic dominance was used to compare the results of the model outputs. Using the shorthand that "risk" means the likelihood of carrying E. coli O157:H7 to the abattoir, key conclusions from the study included: mixing sheep and cattle increases the risk in both groups; merging groups of animals of the same species into larger groups increases the risk substantially; increasing stocking density increases the risk independently of group size; decreasing the group size decreases the E. coli O157:H7 prevalence independently of stocking density; a very high level of barn hygiene reduces the risk; a shorter time between spreading farmyard manure and grazing and an increased background level of E. coli O157:H7 in the model increases the risk. The background level could be influenced by the presence of wild animals carrying the organism. The parameters to which the model is most sensitive are those related to transmission from grass and enclosures to animals, pathogen survival on grass, in slurry and in barns and contact between animals.

Abattoirs↗
PubMed2006

Ante mortem diagnosis of tuberculosis in cattle: a review of the tuberculin tests, gamma-interferon assay and other ancillary diagnostic techniques.

The early, preclinical stages of bovine TB can be detected in live animals by the use of tests of cellular immunity (the skin, gamma-interferon and lymphocyte transformation tests). Tests of humoral (antibody) immunity, Mycobacterium bovis PCR probes on early tissue cultures or live cattle specimens, and tests based on "electronic nose" technology have been developed more recently. The key measure of diagnostic test accuracy is the relationship between sensitivity and specificity, which determines the false-positive and false-negative proportions. None of the tests currently available for the diagnosis of bovine TB allow a perfectly accurate determination of the M. bovis infection status of cattle. Although various factors can reduce the sensitivity and specificity of the skin tests, these remain the primary ante mortem diagnostic tools for TB in cattle, providing a cost-effective and reliable means of screening entire cattle populations. Despite the inescapable limitations of existing diagnostic tests, bovine TB has been effectively eradicated from many developed countries and regions with the implementation of sound programmes of regular tuberculin skin testing and removal of reactors, coupled with slaughterhouse surveillance for undetected infections, repeat testing and culling of infected herds, cattle movement restrictions to prevent introduction of infected animals and occasional slaughter of entire herds with intractable breakdowns. This is likely to remain the mainstay of bovine TB control programmes for the foreseeable future. Additionally, newer ancillary in vitro diagnostic assays are now available to TB control programme managers to supplement the skin tests in defined circumstances according to the specific disease situation in each country or region. The strategic deployment of ancillary in vitro tests alongside the primary skin tests has enhanced the detection of M. bovis-infected cattle and reduced the number of animals slaughtered as false positives.

Animals↗
PubMed1999

Determination of farm-level risk factors for abnormalities observed during post-mortem meat inspection of lambs: a feasibility study.

To investigate the feasibility of using information about the health and management of lambs on farms to predict the risk of gross abnormalities at post-mortem meat inspection, 6732 lambs from 30 different farms in Great Britain were followed through to slaughter in 1995/6. The farm-level data were collected during farm visits at the beginning of the study. Routine meat inspection findings for the lambs were obtained from the 10 participating abattoirs. The most common abnormalities found during post-mortem inspection were pneumonia/pleurisy (53% of cohorts), lungworm (40%), abscesses (30%), liver fluke (27%) and nephritis/nephrosis (27%). The farm-level risk factors associated with abnormalities at slaughter varied with the type of lesion. The most significant risk factor was the age of the lambs at slaughter. Lambs slaughtered at an older age were more likely to have an abnormality, especially pneumonia, abscesses and liver fluke. After age, environmental factors appeared to be better predictors of those cohorts that would have lesions at slaughter than health and disease control variables. However, a much larger study would be required to identify a set of farm-level factors that adequately discriminated between lambs with high and low risks of lesion at slaughter. At the end of the study, the farmers were informed of the meat inspection findings for their lambs and a third indicated that they would improve their animal husbandry as a result of the information.

Animals↗
PubMed1998

Prevalence of antibodies to bovine virus diarrhoea virus and other viruses in bulk tank milk in England and Wales.

Bulk tank milk samples from 1070 dairy herds in England and Wales were tested by ELISA for antibodies to bovine virus diarrhoea virus (BVDV). A subset of 341 herds was tested by ELISA for antibodies to bovine herpesvirus 1 (BHV-1), bovine respiratory syncytial virus (BRSV) and bovine coronavirus (BCV). None of the herds had less than 40 dairy cows and none had been vaccinated against BVDV. The prevalence of BVDV antibody-positive herds in the national population was estimated at 95 per cent and approximately 65 per cent of the herds had a high level of bulk tank antibody suggestive of recent infection with BVDV. Dairy herds in East Anglia and the south-east of England had a significantly lower risk of being BVDV antibody-positive than herds in the rest of England and Wales. However, these regional differences tended to diminish with increasing herd size. Around 69 per cent of the herds were BHV-1 antibody-positive and all the herds were antibody positive to BRSV and BCV. Comparison with earlier serological surveys revealed that there had been little change in the prevalence and distribution of BVDV antibody-positive herds in England and Wales over the last 20 years, but that there had been an increase in the prevalence of BHV-1 antibody-positive herds.

Animals↗
PubMed1991

Serum and saliva sex hormone levels in !Kung San men.

Serum concentrations of testosterone (Tser), 5 alpha-dihydrotestosterone (DHT), estradiol 17 beta (E2), and free testosterone in saliva (Tsal) were determined by means of the radioimmunoassay method in 114 !Kung San men living in the Bushmanland district of Namibia. The healthy men (mean age 26.4 years) were asked about their dietary habits over the last two months and their acute alcohol intake during the 24 hours preceding the blood and saliva sampling. Although the sex hormone status of the !Kung lies within the range of normal men reported for Caucasoid samples, both Tser and Tsal exhibit relatively low concentrations in comparison to the great majority of published mean values. On the other hand, comparatively high DHT levels point to an elevated 5 alpha-reduction of testosterone to DHT in our sample. Estradiol concentrations show no deviation from normal values reported elsewhere for healthy young men. Different dietary habits of the !Kung lead to significant differences in their sex hormone status: both levels of Tsal and the androgen ratio Tsal/Tser decrease with increasing supplement of the traditional hunter-gatherer diet with domestic and Western food products. The amount of alcohol consumed during the day before the blood and saliva sampling shows a significant effect on the DHT metabolism, and the shorter the time after drinking, the greater decrease of DHT and DHT/E2 can be observed.

Adult↗
PubMed1988

Acute monocular disturbances mimicking optic neuritis in pituitary apoplexy.

Three patients with acute monocular central scotoma and headache had the initial diagnosis of optic neuritis. Computed tomography showed large pituitary adenomas with necrosis and cyst formation consistent with the clinical symptoms of a previous pituitary apoplexy. After transsphenoidal adenomectomy the visual disturbances disappeared.

Adenoma↗
PubMed1986

A survey of excessively worn incisors and periodontal disease in sheep in Dunedin City, Silverpeaks, Bruce and Clutha Counties.

To determine the prevalence of excessively worn incisors (XSW) and periodontal disease (PD) in sheep in Dunedin City, Silverpeaks, Bruce and Clutha Counties, the incisors of 4049 mixed age ewes on 83 farms selected at random were examined between December 1983 and February 1984. Of these ewes, 14.9% had XSW (11.7% moderate, 3.2% severe), 13.7% had PD (10.5% moderate, 3.2% severe) and 71.4% had sound mouths. An additional 43 ewes had miscellaneous incisor faults, and these were excluded from the survey. Seventeen (>20.5%) and 25 (>30.1%) farms had 20% ewes with XSW and PD respectively. On two farms only did XSW and PD each occur at a prevalence of 15%. No association was found between the prevalence of XSW or PD and body condition score, breed or farm topography.

Journal Article↗