Landscape Ecology - In landscapes where natural habitats have been severely fragmented by intensive farming, survival of many species depends on connectivity among habitat patches. Spatio-temporal... 相似文献
Increased transport and trade as well as climate shifts play an important role in the introduction, establishment and spread of new pathogens. Arguably, the introduction of bluetongue virus (BTV) serotype 8 in Benelux, Germany and France in 2006 is such an example. After its establishment in receptive local vector and host populations the continued spread of such a disease in a suitable environment will mainly depend on movement of infected vectors and animals. In this paper we explore how wind models can contribute to explain the spread of BTV in a temperate eco-climatic setting. Based on previous work in Greece and Bulgaria filtered wind density maps were computed using data from the European Centre for Medium-Range Weather Forecasts (ECMWF). Six hourly forward wind trajectories were computed at pressure levels of 850hPa for each infected farm as from the recorded onset of symptoms. The trajectories were filtered to remove wind events that do not contribute to possible spread of the vector. The suitable wind events were rastered and aggregated on a weekly basis to obtain weekly wind density maps. Next to this, cumulated wind density maps were also calculated to assess the overall impact of wind dispersal of vectors. A strong positive correlation was established between wind density data and the horizontal asymmetrical spread pattern of the 2006 BTV8 epidemic. It was shown that short (<5km), medium (5-31km) and long (>31km) distance spread had a different impact on disease spread. Computed wind densities were linked to the medium/long-distance spread whilst short range spread was mainly driven by active Culicoides flight. Whilst previous work in the Mediterranean basin showed that wind driven spread of Culicoides over sea occurred over distances of up to 700km, this phenomenon was not observed over land. Long-distance spread over land followed a hopping pattern, i.e. with intermediary stops and establishment of local virus circulation clusters at distances of 35-85km. Despite suitable wind densities, no long range spread was recorded over distances of 300-400km. Factors preventing spread Eastwards to the UK and Northwards to Denmark during the 2006 epidemic are discussed. Towards the east both elevation and terrain roughness, causing air turbulences and drop down of Culicoides, were major factors restricting spread. It is concluded that the proposed approach opens new avenues for understanding the spread of vector-borne viruses in Europe. Future developments should take into consideration both physical and biological factors affecting spread. 相似文献
1. Most samples of field bean, irrespective of their genetic origin, induced a decrease in the mean egg weight when included in the diet at a rate of 300 g/kg: the relative sizes of yolk, albumen and shell were unchanged.
2. Lipoxygenase was not involved in this phenomenon since addition of linoleic acid to the diets containing field beans did not improve egg weight.
3. The depressing effect of the field beans was proportional to the proanthocyanidine content of the seed extracted with absolute methanol.
4. In a longer trial (252d) field beans rich in these kinds of tannin decreased laying rate, efficiency of food utilisation and tended to increase mortality.
5. The removal of the hulls from the field beans did not prevent the reduction in egg weight. 相似文献
Past land use is an important factor determining vegetation in temperate deciduous forests. Little is known about the long-term
persistence of these impacts on vegetation but especially on the seed bank. This study assessed whether soil characteristics
remain altered 1,600 years after human occupation and if this yielded persistent differences in forest plant communities and
their seed bank in particular. Compiègne forest is located in northern-France and has a history of continuous forest cover
since the end of Roman times. Twenty-four Gallo-Roman and 24 unoccupied sites were sampled and data were analysed using paired
sample tests to investigate whether soil, vegetation and seed bank still differed significantly. The soil was persistently
altered on the Gallo-Roman sites resulting in elevated phosphorus levels and pH (dependent on initial soil conditions) which
translated into increased vegetation and seed bank species richness. Though spatially isolated, Gallo-Roman sites supported
both a homogenized vegetation and seed bank. Vegetation differences were not the only driver behind seed bank differences.
Similarity between vegetation and seed bank was low and the possibility existed that agricultural ruderals were introduced
via the former land use. Ancient human occupation leaves a persistent trace on forest soil, vegetation and seed bank and appears
to do so at least 1,600 years after the former occupation. The geochemical alterations created an entirely different habitat
causing not only vegetation but also the seed bank to have altered and homogenized composition and characteristics. Seed bank
differences likely persisted by the traditional forest management and altered forest environment. 相似文献
This study was designed to compare the efficacy of oral prednisolone and intramuscular (IM) dexamethasone in heaves-affected horses with environmental control. A total of 16 horses, aged 8-20years, with heaves were included in the study. Complete examinations were performed on Day 0 (before treatment), Day 13 (after treatment) and Day 30. Clinical variables, arterial blood gases, mucus scoring and carina evaluation (during endoscopy), and bronchoalveolar lavage (BAL) cytological analysis were all assessed. The horses were randomly assigned to receive either oral prednisolone (1mg/kg) or IM dexamethasone (0.1mg/kg). The animals were clinically scored and mucus accumulation evaluated. Results were analysed by repeated measures ANOVA with time (days of treatment) and treatment as the main effects. When combined with environmental control, prednisolone and dexamethasone treatments had similar effects on heaves score, blood gases and endoscopic scores. However, dexamethasone had a more beneficial effect on BAL cytology. 相似文献
1. Apparent (AME) and true (TME) metabolisable energy values of four diets, containing 50 or 150 g animal fat or maize oil/kg, were estimated in young and adult chickens. The diets were given with and without a supplement of 5 g bile salts/kg. Three feeding rates, ad libitum, and l/6th or 1/3rd of ad libitum were compared.
2. In younger birds, endogenous energy losses were higher when measured in starved birds than when estimated by regression analysis.
3. In young birds, feeding rate had no effect on AME of diets containing 50 g lipids/kg but it significantly affected TME. These results were reversed in adults. AME and TME values of diets containing 150 g lipids/kg were affected by the feeding rate in both young and adult birds.
4. Bile salts increased metabolisable energy values of diets containing high concentrations of saturated fatty acids and their effect was more pronounced in young birds. 相似文献
Fusarium head blight (FHB) of wheat and other small-grain cereals is a disease complex caused by several fungal species. To monitor and quantify the major species in the FHB complex during the growing season, real-time PCR was developed. TaqMan primers and probes were designed that showed high specificity for Fusarium avenaceum, F. culmorum, F. graminearum, F. poae and Microdochium nivale var. majus. Inclusion of an internal PCR control and serial dilutions of pure genomic DNAs allowed accurate determination of the concentration of fungal DNA for each of these species in leaves, ears as well as harvested grains of winter wheat. The DNA concentration of F. graminearum in grain samples correlated (r2= 0.7917) with the incidence of this species on the grain as determined by isolation from individual kernels. Application of the TaqMan technology to field samples collected in 40 wheat crops in the Netherlands during the growing season of 2001 revealed that M. nivale var. majus predominated on leaves early in the season (GS 45-65). Ears and harvested grains from the same fields, however, showed F. graminearum as the major species. In 2002, grain samples from 40 Dutch fields showed a much wider range of species, whereas in ears from 29 wheat crops in France, F. graminearum was the predominant species. The concentration of DON correlated equally well with the incidence of the DON-producing species F. culmorum and F. graminearum in the grain samples (r2= 0.8232) as well as with total DNA of both these species (r2= 0.8259). The Fusarium TaqMan technology is an important tool to quantify and monitor the dynamics of individual species of the complex causing FHB in cereals during the growing season. This versatile tool has been applied in a comparison of different genotypes, but can also be applied to other disease management systems, e.g. fungicide treatments. 相似文献
Reference values have been established for serum biochemical parameters in sows from high producing pig herds. In total, 132 clinically healthy sows from eight breeding herds were serially sampled three weeks and one week before farrowing, and at one week and three weeks after farrowing. Fourteen serum biochemical parameters, focusing mainly on energy and protein metabolism, hepatobiliary and kidney function and inflammation, were investigated. The reproductive state significantly influenced the investigated parameters, other than for urea and non-esterified fatty acids. First parity sows showed higher concentrations of gamma-glutamyltransferase, phosphorus and haptoglobin, and higher albumin/globulin and haptoglobin/albumin ratios compared to sows with 2 parities. The concentrations of creatinine, globulin and total protein however were lower in first parity sows. Between-herd variations were especially high (>50%) for gamma-glutamyltransferase, alkaline phosphatase and non-esterified fatty acids. Serum biochemical parameters constitute an important diagnostic tool to assess the health status of sows, but to interpret the outcome properly, it is important to consider reproductive state and parity. 相似文献
PURPOSE: To evaluate the efficacy of using a porcine small intestinal submucosa (SIS) graft for the surgical repair of deep melting ulcers in dogs and cats. METHODS: Two cats and five dogs presented with deep and large melting ulcers of the cornea. In each case, the necrotic and collagenolytic tissue of the cornea was removed by keratectomy. A SIS graft, 1 mm greater than the corneal defect, was rehydrated in sterile saline and sutured to the edges of the ulcer with a simple interrupted pattern of 9/0 polyglactin 910. A nictitating membrane flap was utilized in two cats and four dogs for 2 weeks. All cases were treated postoperatively with topical and systemic antibiotics, a systemic anti-inflammatory drug and topical atropine. All animals were re-evaluated 15 days, 4 weeks, 35-45 days, 2-3 months and 6 months postsurgery. RESULTS: At 15 days postsurgery, a superficial intense corneal neovascularization surrounded the SIS graft. No ocular discomfort was present and fluorescein staining was negative in all cases. At 4 weeks the SIS graft was thick and opaque in all cases, although in one cat the SIS graft had partially detached. Between 35 and 45 days, SIS graft integration was evident in all eyes, and corneal neovascularization had decreased progressively. All eyes healed without complications and retained corneal transparency. This occurred even in the presence of corneal perforation in two cases: one prior to and one during surgery. CONCLUSION: Results of our study suggest the SIS graft may be an effective alternative surgical treatment to the traditional conjunctival grafts commonly used to repair melting ulcers in dogs and cats. The advantages of using a SIS graft include good corneal transparency, preservation of corneal integrity and maintenance of vision. 相似文献