Structured approach to design of diagnostic test evaluation studies for chronic progressive infections in animals     

Nielsen SS  Toft N  Gardner IA 《Veterinary microbiology》2011,150(1-2):115-125

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Agricultural policy and social returns to eradication programs: the case of Aujeszky''s disease in Sweden     

Hans Andersson  Åsa Lexmon  Jan-Åke Robertsson  Nils Lundeheim  Martin Wierup 《Preventive veterinary medicine》1997,29(4):311-328

Economic-welfare analysis of animal disease prevention programs frequently ignore the constraints of the agricultural policy environment. Prevention programs affect producers, consumers and the government. The policy environment to a large extent determines the magnitude as well as the distribution of benefits of the program among these groups. The Swedish hog industry has been exposed to three major policy changes during the 1990–1995 period. These scenarios involve various degrees of government intervention in the agricultural sector including internal market deregulation and EU-membership. Aujeszky's disease is a virus disease with swine as the natural infection reservoir. Piglets are the most fragile and an outbreak of the disease results in symptoms such as shaking, cramps and convulsions with an increase in the mortality rate. Slaughter hogs suffer from coughing, fever and reduce their feed consumption. During the last 20–25 years the incidence of Aujeszky's disease (AD) has been increasing in Sweden. In 1989 an eradication program was undertaken. A model is developed to analyze social benefits of an eradication program given variations in agricultural policy. The model refers to the specifics of the AD-program implemented in Sweden. The expected benefits of the program are evaluated using a welfare-economic analysis applying cost-benefit analysis. Total benefits of the program are evaluated across herd and size categories and different regions. Data concerning the frequency of the virus among various categories of herds prior to enacting the program were used (Wahlström et al., 1990). In addition, data from an agricultural insurance company were used to estimate the conditional probability of an outbreak given that the herd is infected. Biological and technical parameter values were collected from a variety of sources. The results of the analysis indicate that the program is economically viable given a social rate of discount in the range of 3–5% without considering non-monetary aspects such as animal ethics. A scenario where the Swedish agricultural sector is deregulated provides the maximum benefits of the program. Consumers obtain about 50% of the benefits excluding program costs. The deregulation scenario would correspond closely to a case where a reformed Common Agricultural Policy (CAP) is applied across member countries. In the current case where Sweden is a member of the EU, the benefits are reduced mainly due to lower prices of inputs and pork.  相似文献   

Chronic Copper Poisoning in Sheep: Structural Changes in Erythrocytes and Organs     

Nils E. Sli  Inger Nafstad 《Acta veterinaria Scandinavica》1976,17(3):316

Four cases of experimental copper poisoning in sheep were examined. Light microscopical and ultrastructural alterations of erythrocytes were observed a few hours before a significant haemolysis was evident. Heinz body formation in otherwise unchanged red cells was the first morphological alteration observed. The Heinz bodies were predominantly membrane-attached. During the haemolytic crisis severe erythrocytic distortion, structural membrane alteration and Heinz body-containing ghost cells were observed. Erythrophagocytosis was mainly located to the RE cells of the spleen. Intrafollicular necroses were found in all histological sections from the spleen. Pathological changes in liver and kidney were comparable to those of earlier reports, comprising hepatocellular and renal tubular necrosis.  相似文献   

Assessing the convergence of Markov Chain Monte Carlo methods: an example from evaluation of diagnostic tests in absence of a gold standard     

Toft N  Innocent GT  Gettinby G  Reid SW 《Preventive veterinary medicine》2007,79(2-4):244-256

The accessibility of Markov Chain Monte Carlo (MCMC) methods for statistical inference have improved with the advent of general purpose software. This enables researchers with limited statistical skills to perform Bayesian analysis. Using MCMC sampling to do statistical inference requires convergence of the MCMC chain to its stationary distribution. There is no certain way to prove convergence; it is only possible to ascertain when convergence definitely has not been achieved. These methods are rather subjective and not implemented as automatic safeguards in general MCMC software. This paper considers a pragmatic approach towards assessing the convergence of MCMC methods illustrated by a Bayesian analysis of the Hui–Walter model for evaluating diagnostic tests in the absence of a gold standard. The Hui–Walter model has two optimal solutions, a property which causes problems with convergence when the solutions are sufficiently close in the parameter space. Using simulated data we demonstrate tools to assess the convergence and mixing of MCMC chains using examples with and without convergence. Suggestions to remedy the situation when the MCMC sampler fails to converge are given. The epidemiological implications of the two solutions of the Hui–Walter model are discussed.  相似文献   

Aggression and cortisol levels in three different group housing routines for lactating sows     

Ola Thomsson  Ann-Sofi Bergqvist  Ylva Sjunnesson  Lena Eliasson-Selling  Nils Lundeheim  Ulf Magnusson 《Acta veterinaria Scandinavica》2015,57(1)

Background

Lactating sows in Swedish organic piglet production are commonly group-housed with piglets in a multi-suckling pen within 14 days after farrowing. Nursing behaviour may be disturbed when lactating sows are moved to a new environment and mixed with other sows, as they spend more time fighting with other sows and exploring the new surroundings. This can disrupt the inhibitory effect of suckling on ovarian activity and increase the risk of lactational oestrus, making efficient reproductive management difficult. Therefore this study evaluated aggression and levels of the stress hormone cortisol in lactating sows group-housed together with their piglets at one (W1), two (W2) or three (W3) weeks post farrowing.

Results

There was no significant difference (P > 0.05) between the three management routines (W1, W2, W3) regarding number of attacks initiated or received in the mixed group. After mixing, W2 sows had a lower number of shoulder scratches (P < 0.05) than W3 sows. Among the W3 sows, there was a lower (P < 0.01) cortisol concentration in saliva when sows were group housed compared to when they were individually housed. The cortisol response, measured as variation in cortisol concentration in saliva, was also lower (P < 0.05) in group-housed W3 sows compared with W1 sows.For all management routines, sows already living in the new environment (resident sows) initiated more attacks (P < 0.001) and received fewer attacks (P < 0.01) than sows entering the new environment (intruder sows). Overall, multiparous sows initiated more attacks and received fewer attacks than primiparous sows (P <0.001).

Conclusions

Overall, the results suggest that mixing and group housing sows at three weeks post farrowing is less stressful than mixing and group housing sows at one week post farrowing. The results also indicate that parity and whether a sow is a resident or intruder in the group housing environment may have an effect on aggression levels when sows are group-housed.  相似文献   

Weaner production with low antimicrobial usage: a descriptive study     

Mette Fertner  Anette Boklund  Nana Dupont  Claes En?e  Helle Stege  Nils Toft 《Acta veterinaria Scandinavica》2015,57(1)

Background

Health, productivity and antimicrobial use in the production of pigs are expected to be interrelated to some extent. Previous studies on register-based data have investigated these correlations with a subsequent large variation residing at the farm level. In order to study such farm factors in more detail we designed an elaborate interview-guide. By in-depth interviews of farmers with well-managed 7–30 kg (weaner) productions we sought to describe a set of common key-factors characterizing their management practices. Identification of such common practices could be used in follow-up projects, investigating whether identified factors really are characteristic for good-practicing famers.

Results

Eleven farms were selected for a farm visit and in-depth interview. Participating farms used less antimicrobials than the national median (8.2 animal daily doses/100 weaners/day), had a mortality below the national average (2.9%) and an average daily weight gain above the national average (443 g/day). Similarities were observed among participating farms, including the sectioning of farms, use of all-in-all-out procedures with subsequent cleaning, purchasing 7 kg weaners from only one source, as well as active participation in management by a committed farm owner. Most farmers had a specific point of focus in their management, and were convinced that this was the reason for their success. This included; feeding, treatment strategy, refurbishment of facilities and presence in the shed.

Conclusion

According to register data, participating farms were alike; in the good league regarding use of antimicrobials, mortality and daily growth. However, on-farm interviews elucidated more heterogeneity among farmers than expected. Most of the farmers had a specific point of focus, which they considered to be crucial for their good results. These results indicate the importance of non-registerable factors, highlighting the value of qualitative study techniques in the understanding of human actions. Further studies on the effect of various farmer types are recommended.  相似文献   

Assessment of the diversity of comfrey (Symphytum officinale L. and S. × uplandicum Nyman)     

Ruzicka  Joana  Berger-Büter  Karin  Esslinger  Nils  Novak  Johannes 《Genetic Resources and Crop Evolution》2021,68(7):2813-2825

Genetic Resources and Crop Evolution - Comfrey Symphytum officinale L. (true comfrey) and S.?×?uplandicum Nyman (a hybrid between S. asperum Lepech?×?S. officinale...  相似文献   

Heat flux anomalies in Antarctica revealed by satellite magnetic data   总被引：1，自引：0，他引：1  

Maule CF  Purucker ME  Olsen N  Mosegaard K 《Science (New York, N.Y.)》2005,309(5733):464-467

The geothermal heat flux is an important factor in the dynamics of ice sheets; it affects the occurrence of subglacial lakes, the onset of ice streams, and mass losses from the ice sheet base. Because direct heat flux measurements in ice-covered regions are difficult to obtain, we developed a method that uses satellite magnetic data to estimate the heat flux underneath the Antarctic ice sheet. We found that the heat flux underneath the ice sheet varies from 40 to 185 megawatts per square meter and that areas of high heat flux coincide with known current volcanism and some areas known to have ice streams.  相似文献   

Measuring specialization in species interaction networks     

Nico Blüthgen  Florian Menzel  Nils Blüthgen 《BMC ecology》2006,6(1):9-12

Background  

Network analyses of plant-animal interactions hold valuable biological information. They are often used to quantify the degree of specialization between partners, but usually based on qualitative indices such as 'connectance' or number of links. These measures ignore interaction frequencies or sampling intensity, and strongly depend on network size.  相似文献   

A critique of models for freshwater and soil acidification     

John O. Reuss  Nils Christophersen  Hans M. Seip 《Water, air, and soil pollution》1986,30(3-4):909-930

Four types of models quantifying effects of acid deposition on freshwaters are reviewed. These include Henriksen's empirical model, an adsorption isotherm model, soil-oriented charge balance models (Reuss-Johnson, Birkenes, MAGIC, ILWAS), and the Trickle Down model. Emphasis is on an assessment of critical assumptions; no attempt has been made to run the various models and compare results. The models range from simple to very complex and from empirical to highly process oriented. The various types have all proven useful and there has been a significant convergence concerning key processes. The importance of anion mobility, sulfate adsorption, ion exchange, dissolution of Al bearing minerals and weathering seems to be accepted by most workers. Future model improvement, however, relies to a large extent on further checking against observations.  相似文献