排序方式： 共有49条查询结果，搜索用时 343 毫秒
31.
Poetri O Bouma A Claassen I Koch G Soejoedono R Stegeman A van Boven M 《Veterinary research》2011,42(1):74
ABSTRACT: Vaccination of chickens has become routine practice in Asian countries in which H5N1 highly pathogenic avian influenza (HPAI) is endemically present. This mainly applies to layer and breeder flocks, but broilers are usually left unvaccinated. Here we investigate whether vaccination is able to reduce HPAI H5N1 virus transmission among broiler chickens. Four sets of experiments were carried out, each consisting of 22 replicate trials containing a pair of birds. Experiments 1-3 were carried out with four-week-old birds that were unvaccinated, and vaccinated at day 1 or at day 10 of age. Experiment 4 was carried out with unvaccinated day-old broiler chicks. One chicken in each trial was inoculated with H5N1 HPAI virus. One chicken in each trial was inoculated with virus. The course of the infection chain was monitored by serological analysis, and by virus isolation performed on tracheal and cloacal swabs. The analyses were based on a stochastic SEIR model using a Bayesian inferential framework. When inoculation was carried out at the 28th day of life, transmission was efficient in unvaccinated birds, and in birds vaccinated at first or tenth day of life. In these experiments estimates of the latent period (~1.0 day), infectious period (~3.3 days), and transmission rate parameter (~1.4 per day) were similar, as were estimates of the reproduction number (~4) and generation interval (~1.4 day). Transmission was significantly less efficient in unvaccinated chickens when inoculation was carried out on the first day of life. These results show that vaccination of broiler chickens does not reduce transmission, and suggest that this may be due to the interference of maternal immunity. 相似文献
32.
Matthijs MG Ariaans MP Dwars RM van Eck JH Bouma A Stegeman A Vervelde L 《Veterinary immunology and immunopathology》2009,127(1-2):77-84
Colibacillosis results from infection with avian pathogenic Escherichia coli bacteria. Healthy broilers are resistant to inhaled E. coli, but previous infection with vaccine or virulent strains of Infectious Bronchitis Virus (IBV) predisposes birds for severe colibacillosis. The aim of this study was to investigate how IBV affects the course of events upon infection with E. coli. Broilers were inoculated with IBV H120 vaccine virus or virulent M41 and challenged 5 days later with E. coli 506. A PBS and E. coli group without previous virus inoculation were included. Sections of trachea, lung and airsacs were stained for CD4, CD8, gammadelta-TCR, alphabeta1-TCR, and for macrophages (KUL-01) and both pathogens. Changes in the mucociliary barrier of trachea, lung and airsacs did not predispose for bacterial superinfection. The disease in the lungs of the E. coli group and both IBV/E. coli groups was similar. Lesions in the airsacs were more pronounced and of longer duration in the IBV/E. coli groups. The immunocytological changes differed substantially between the E. coli group and both IBV/E. coli groups. In trachea, lungs and airsacs the CD4+ and CD8+ populations were significantly larger than in the E. coli and PBS groups. In the lungs and the airsacs the macrophages were more numerous in the IBV/E. coli and the E. coli groups than in the PBS group. The presence of high numbers of T cells and macrophages in IBV infected birds most likely induced an altered immune response, which is responsible for the enhanced clinical signs of colibacillosis. 相似文献
33.
Improved knowledge on the swimming physiology of fish and its application to fisheries science and aquaculture (i.e., farming
a fitter fish) is currently needed in the face of global environmental changes, high fishing pressures, increased aquaculture
production as well as increased concern on fish well-being. Here, we review existing data on teleost fish that indicate that
sustained exercise at optimal speeds enhances muscle growth and has consequences for flesh quality. Potential added benefits
of sustained exercise may be delay of ovarian development and stimulation of immune status. Exercise could represent a natural,
noninvasive, and economical approach to improve growth, flesh quality as well as welfare of aquacultured fish: a FitFish for
a healthy consumer. All these issues are important for setting directions for policy decisions and future studies in this
area. For this purpose, the FitFish workshop on the Swimming Physiology of Fish () was organized to bring together a multidisciplinary group of scientists using exercise models, industrial partners, and
policy makers. Sixteen international experts from Europe, North America, and Japan were invited to present their work and
view on migration of fishes in their natural environment, beneficial effects of exercise, and applications for sustainable
aquaculture. Eighty-eight participants from 19 different countries contributed through a poster session and round table discussion.
Eight papers from invited speakers at the workshop have been contributed to this special issue on The Swimming Physiology
of Fish. 相似文献
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35.
Charles Hillyer John Bolte Frits van Evert Arjan Lamaker 《European Journal of Agronomy》2003,18(3-4):333-343
Simulation models of agro-ecological systems are typically written in a manner that precludes reusability of parts of the model without a significant amount of familiarity with and rewriting of existing code. Similarly, replacing a part of a model with a functionally equivalent part from another model is typically difficult. The objective of this study was to develop a method to enable the assembly of simulation models from previously and independently developed component models. Recent advances in software engineering have enabled the development of software applications from smaller parts (called components) on the basis of an abstract decomposition of the relevant domain (called a framework). Based on a requirements analysis of existing simulation models we developed the ModCom simulation framework. ModCom provides a set of interface specifications that describe components in a simulation. ModCom also provides implementations of the core simulation services. The framework interfaces use well-defined binary standards and allows developers to implement the interfaces using a broad range of computer languages. Using this framework, simulation models can be assembled by connecting component models in much the same way that Lego blocks are put together to assemble a house. ModCom thus allows modelers to create models and modeling tools that are easily exchanged (in binary form or source code) with colleagues across the hall or across the globe. 相似文献
36.
A considerable fraction of the poultry carcasses becomes contaminated with Campylobacter by cross-contamination from the digestive tract of colonized broilers at slaughter. Campylobacter in the crop may serve as a possible source of cross-contamination, because the crop may contain high numbers of Campylobacter and is more likely to rupture during the slaughtering process than intestines. In this study, the correlation between Campylobacter colonization levels in crop and cecum was assessed in 48 broilers of 31 days of age. In addition, the effect of drinking water supplemented with 0.2% volatile fatty acid (VFA) on these Campylobacter colonization levels was studied. No correlation between crop and cecal colonization levels was found (p = 0.09; P = 0.71), indicating that future studies on cross-contamination should include an examination of not only cecal colonization levels but also crop colonization levels. Supplementation of drinking water with VFA did not result in a significant reduction of colonization levels in either the crop (P = 0.50) or the ceca (P = 0.92), indicating that this is not an effective measure to reduce cross-contamination at slaughter. 相似文献
37.
Fitzgerald DJ Stratford M Gasson MJ Narbad A 《Journal of agricultural and food chemistry》2005,53(5):1769-1775
The aim of the present study was to evaluate which structural elements of the vanillin molecule are responsible for its observed antifungal activity. MICs of vanillin, its six direct structural analogues, and several other related compounds were determined in yeast extract peptone dextrose broth against a total of 18 different food spoilage molds and yeasts. Using total mean MICs after 4 days of incubation at 25 degrees C, the antifungal activity order was 3-anisaldehyde (1.97 mM) > benzaldehyde (3.30 mM) > vanillin (5.71 mM) > anisole (6.59 mM) > 4-hydroxybenzaldehyde (9.09 mM) > phenol (10.59 mM) > guaiacol (11.66 mM). No correlation was observed between the relative antifungal activity of the test compounds and log P(o/w). Furthermore, phenol (10.6 mM) was found to exhibit a greater activity than cyclohexanol (25.3 mM), whereas cyclohexanecarboxaldehyde (2.13 mM) was more active than benzaldehyde (3.30 mM). Finally, the antifungal order of isomers of hydroxybenzaldehyde and anisaldehyde was found to be 2- > 3- > 4- and 3- > 2- > 4-, respectively. In conclusion, the aldehyde moeity of vanillin plays a key role in its antifungal activity, but side-group position on the benzene ring also influences this activity. Understanding how the structure of natural compounds relates to their antimicrobial function is fundamentally important and may help facilitate their application as novel food preservatives. 相似文献
38.
Arjan Stegeman 《The Veterinary quarterly》2013,33(4):150-156
Summary This article reviews the rationale for using marker vaccines and companion diagnostic tests in the eradication of pseudorabies virus (PRV). Recent advances in vaccinology and epidemiology indicate that, despite the inability to induce complete immunity, vaccination is a useful tool in the battle against PRV. This review focuses on the effectiveness of vaccination under field conditions and on herd, management and regional factors that are associated with PRV introduction or transmission. 相似文献
39.
Salmonella is a cause of concern in the cattle industry, because it is a zoonosis causing severe invasive infections in humans and because it causes economic and welfare losses in infected herds. In general, cattle in the Netherlands are infected with two types; Salmonella Dublin and Salmonella Typhimurium. Both types cause clinical signs but S. Dublin outbreaks are more prevalent and clinical signs are more severe than S. Typhimurium outbreaks. Our knowledge of the transmission of Salmonella within herds is still limited, while this is an essential component for modelling the success of intervention strategies to control Salmonella. The aim of our study was to estimate the basic reproduction ratio (R(0)), the number of secondary cases produced from each primary case in a totally susceptible population, for S. Dublin and S. Typhimurium in dairy herds. Serological data were obtained from eight farms with a clinical outbreak of Salmonella, two with an outbreak of S. Dublin and 6 of S. Typhimurium. R(0) was estimated from the serological data of the herds that were in an endemic state of the infection. R(0) across herds was estimated to be 2.5 (95% CI 1.7-9.8) and 1.3 (95% CI 1.1-1.7) for S. Dublin and S. Typhimurium, respectively. The between herd variation was significant and fairly large. The results of the sensitivity analysis showed that the R(0) estimate was not sensitive for changes in the latent, infectious or seropositive periods. The R(0) estimates indicated that the infection would not spread very extensively in susceptible populations under management systems similar to the ones in the study herds. 相似文献
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