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41.
Tijs J Tobias Annemarie Bouma Angeline JJM Daemen Jaap A Wagenaar Arjan Stegeman Don Klinkenberg 《Veterinary research》2013,44(1):2
A better understanding of the variation in infectivity and its relation with clinical signs may help to improve measures to control and prevent (clinical) outbreaks of diseases. Here we investigated the role of disease severity on infectivity and transmission of Actinobacillus pleuropneumoniae, a bacterium causing respiratory problems in pig farms. We carried out transmission experiments with 10 pairs of caesarean-derived, colostrum-deprived pigs. In each pair, one pig was inoculated intranasally with 5 × 106 CFUs of A. pleuropneumoniae strain 1536 and housed together with a contact pig. Clinical signs were scored and the course of infection was observed by bacterial examination and qPCR analysis of tonsillar brush and nasal swab samples. In 6 out of 10 pairs transmission to contact pigs was observed, but disease scores in contact infected pigs were low compared to the score in inoculated pigs. Whereas disease score was positively associated with bacterial load in inoculated pigs and bacterial load with the transmission rate, the disease score had a negative association with transmission. These findings indicate that in pigs with equal bacterial load, those with higher clinical scores transmit A. pleuropneumoniae less efficiently. Finally, the correlation between disease score in inoculated pigs and in positive contact pigs was low. Although translation of experimental work towards farm level has limitations, our results suggest that clinical outbreaks of A. pleuropneumoniae are unlikely to be caused only by spread of the pathogen by clinically diseased pigs, but may rather be the result of development of clinical signs in already infected pigs. 相似文献
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Detection and quantification of classical swine fever virus in air samples originating from infected pigs and experimentally produced aerosols 总被引:3,自引:0,他引:3
During epidemics of classical swine fever (CSF), neighbourhood infections occurred where none of the 'traditional' routes of transmission like direct animal contact, swill feeding, transport contact or transmission by people could be identified. A hypothesized route of virus introduction for these herds was airborne transmission. In order to better understand this possible transmission route, we developed a method to detect and quantify classical swine fever virus (CSFV) in air samples using gelatine filters. The air samples were collected from CSFV-infected pigs after experimental aerosolization of the virus. Furthermore, we studied the viability of the virus with time in aerosolized state. Three strains of CSFV were aerosolized in an empty isolator and air samples were taken at different time intervals. The virus remained infective in aerosolized state for at least 30 min with half-life time values ranging from 4.5 to 15 min. During animal experiments, concentrations of 10(0.3)-10(1.6)TCID(50)/m(3) CSFV were detected in air samples originating from the air of the pig cages and 10(0.4)-10(4.0)TCID(50)/m(3) from the expired air of infected animals. This is the first study describing the isolation and quantification of CSFV from air samples originating from infected pigs and their cages, supporting previous findings that airborne transmission of CSF is feasible. 相似文献
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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
46.
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
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Arjan?P.?PalstraEmail author Guido?E.?E.?J.?M.?van?den Thillart 《Fish physiology and biochemistry》2010,36(3):297-322
The European eel migrates 5,000–6,000 km to the Sargasso Sea to reproduce. Because they venture into the ocean in a pre-pubertal
state and reproduce after swimming for months, a strong interaction between swimming and sexual maturation is expected. Many
swimming trials have been performed in 22 swim tunnels to elucidate their performance and the impact on maturation. European
eels are able to swim long distances at a cost of 10–12 mg fat/km which is 4–6 times more efficient than salmonids. The total
energy costs of reproduction correspond to 67% of the fat stores. During long distance swimming, the body composition stays
the same showing that energy consumption calculations cannot be based on fat alone but need to be compensated for protein
oxidation. The optimal swimming speed is 0.61–0.67 m s−1, which is ~60% higher than the generally assumed cruise speed of 0.4 m s−1 and implies that female eels may reach the Sargasso Sea within 3.5 months instead of the assumed 6 months. Swimming trials
showed lipid deposition and oocyte growth, which are the first steps of sexual maturation. To investigate effects of oceanic
migration on maturation, we simulated group-wise migration in a large swim-gutter with seawater. These trials showed suppressed
gonadotropin expression and vitellogenesis in females, while in contrast continued sexual maturation was observed in silver
males. The induction of lipid deposition in the oocytes and the inhibition of vitellogenesis by swimming in females suggest
a natural sequence of events quite different from artificial maturation protocols. 相似文献
49.
Palstra AP Guerrero MA de Laak G Klein Breteler JP van den Thillart GE 《Fish physiology and biochemistry》2011,37(2):285-296
The onset of downstream migration of European eels is accompanied by a cessation of feeding and the start of sexual maturation
which stresses the link between metabolism and sexual maturation, also suggesting an important role for exercise. Exercise
has been tested with eels in swim tunnels and was found to stimulate the onset of sexual maturation. In this study, we have
investigated the interplay between migration and maturation in the field during the downstream migration of female silver
eels. Temporal changes in migratory status and sexual maturation among silver eels of the upstream Rhine River system over
3 months of the migration season (August, September and October) were determined in biometrical parameters, plasma 17β-estradiol
and calcium levels, oocyte histology and gonadal fat levels. Furthermore, the ecological relevant parameters age as determined
by otolithometry and health aspects indicated by haematocrit, haemoglobin and swim-bladder parasite load were measured. Silver
eels were estimated to be 14 years old. A strong temporal progression in migratory stage was shown over the months of downstream
migration. Catches probably represented a mix of reproductive migrants and feeding migrants of which the ratio increased over
time. Furthermore, this study confirmed our hypothesis linking the migratory stage to early maturation as indicated by enlargement
of the eyes, oocyte growth and fat deposition in the oocytes, exactly the same changes as found induced by exercise but not
ruling out environmental influences. Migrants show extensive fat uptake by the oocytes, probably stimulated by the swimming
exercise. In addition, at least 83% of the silver eels in this spawning run may have suffered from negative effects of swim-bladder
parasites on their swimming performance. 相似文献