Risk factors for equine laminitis: a systematic review with quality appraisal of published evidence

Epidemiological studies into the risk factors for naturally-occurring equine laminitis are limited. There are a small number of such studies, although the results are inconsistent and remain disputed. The reasons for the conflicting results remain unclear. The aim of this review was to critically evaluate previous research in order to identify publications which provide the best evidence of risk factors for naturally-occurring equine laminitis. A systematic review of English language publications was conducted using MEDLINE (1950-2010), CAB Direct (1910-2010) and IVIS (1997-2010). Additional publications were included by searching bibliographies. Search terms included laminitis, equine, risk factors and epidemiology. Publications which compared a case population to a control population and made inferences about parameters as risk factors for naturally-occurring equine laminitis were included. Information was extracted using predefined data fields, including 18 study quality indicators. In total, 17 publications were fully appraised. Six were considered to provide the most reliable information about risk factors for naturally-occurring laminitis. Information on signalment was well researched and there was good evidence for an association with chronic laminitis and increasing age. There remain inconsistent results for many other horse-level risk factors including gender, breed and bodyweight. Previous publications estimating risk factors for equine laminitis were of reasonable quality, although they were limited in the number and scope of the risk factors studied. High-quality, evidence-based studies are needed to identify further risk factors and to establish consensus over previously identified risk factors for different equine populations.     

Streptococcus suis type 2 infections in pigs in the Netherlands (Part two)

Since 1983 some pig breeding and fattening farms in the Netherlands have been faced with a considerable mortality in pigs due to Streptococcus suis type 2 infections. The most predominant clinical feature of S. suis type 2 infection is meningitis, although sudden deaths often occur. It was noted that some affected farms had imported breeding stock from the United Kingdom. Tonsils of slaughter pigs were collected from herds with and without a history of S. suis type 2 infections. Bacteriological examination was done by using an elective-selective medium. No significant difference was found in carrier rates of S. suis type 2 between clinically healthy and affected herds (38% vs. 45%). A cohort study was carried out by regular bacteriological examination of tonsil biopsies on a farm with a high incidence of streptococcal meningitis. Twenty-seven percent of the pigs were carriers of S. suis type 2 at nine weeks of age. Possible methods for disease control are discussed.     

Training-related factors associated with dorsometacarpal disease in young Thoroughbred racehorses in the UK

REASONS FOR PERFORMING STUDY: Dorsometacarpal disease (DMD) is common in young Thoroughbred (TB) racehorses, often interfering with their training programme. No reports exist on incidence rate or associated risk factors in the UK. OBJECTIVES: To estimate the incidence rate of DMD in TB horses in training for flat racing in the UK and identify associated risk factors, particularly in relation to training regimens. METHODS: Data were drawn from a large prospective study in which TB horses in 13 training yards were monitored for a period of up to 2 years, recording daily training information and details of musculoskeletal injury, including DMD. The incidence of DMD was calculated and survival analysis performed to determine features of the training regimen related to the risk of disease. RESULTS: A total of 335 horses provided 4235 months at risk of DMD. Seventy-nine first episodes were recorded, resulting in an incidence rate of 1.87/100 horse months (95% confidence interval 1.50-2.33). Increasing exercise distances at canter and high speed in short periods (up to 1 month) were associated with an increasing risk of DMD. However, increasing cumulative exercise distances since entering training were associated with a decreasing risk of the disease. CONCLUSIONS: The risk of DMD in young TBs decreases with accumulation of distances exercised at canter and high speed; this reflects the adaptive response of the third metacarpal bone to the loads placed upon it. However, increasing exercise distances in short periods (up to 1 month) increases the risk of DMD, probably as a consequence of microdamage and its associated remodelling response, and should therefore be avoided. POTENTIAL RELEVANCE: Training regimens for young TBs can be adjusted to prevent the occurrence of DMD. Early but gradual introduction of small amounts of high-speed exercise may be beneficial. Canter exercise should be kept minimal on high-speed work days and large amounts of both cantering and high-speed work per week, 2 weeks or per month should be avoided, particularly during the early stages of training, in order to minimise the risk of DMD.     

Influence of amylovoran production on virulence of Erwinia amylovora and a different amylovoran structure in E. amylovora isolates from Rubus

The amylovoran structures of five Erwinia amylovora isolates from Malaceae sp. and four isolates from Rubus sp. host plants were fully established, mainly by NMR. The structural data on one E. amylovora isolate from a Malaceae sp. host, which had been previously suggested by mass and NMR (Nimtz et al., 1996), were completed. E. amylovora strains infective on Malaceae sp. host plants had an amylovoran composed of pentasaccharide and 30–40% hexasaccharide repeating-substructures, whereas amylovoran from E. amylovora isolates from Rubus sp. host plants had only the pentasaccharide substructures. On the other hand, the exopolysaccharide (EPS) production differed in wild-type E. amylovora strains. Data on in vitro amylovoran production per cell could account for the differences in aggressiveness found in E. amylovora strains, as deduced from a pilot test with highly, moderately, and weakly aggressive strains. This correlation was confirmed with several other wild-type E. amylovora strains from different origin.     

Nutrient supply at the local tree level in mixed forests of sessile oak and beech

In mixed-species forests, tree species composition can affect nutrient return through litter fall. This in turn is expected to have an effect on soil available nutrients, which could influence the nutrient status at the local tree level. Using ion-exchange resins, we estimated resin available soil nutrients at two depths beneath target trees of sessile oak and beech in the Belgian Ardennes. First we tested whether resin available nutrients were related to tree nutrition, using foliar nutrient concentrations as a proxy. In a second step, we tested whether local litter fall, through total nutrient return or litter species composition, affected resin available nutrients. In a final stage, we tested the impacts of local stand composition, as an integrated proxy of above- and belowground processes, and compared them to those of litter composition. With the exception of P for oak, nutrient supply was only poorly related to foliar nutrient concentrations for both target species. The effects of litter fall on nutrient supply were driven by litter species composition and not by total nutrient inputs. Litter composition and local stand composition effects were in close agreement. Our results show that nutrient supply to target trees in mixed-species stands is affected by local neighbourhoods, yet to a limited extent. Direct translation of resin available nutrients into foliar concentrations is probably hampered by complex capture patterns.     

Spatio-temporal litterfall dynamics in a 60-year-old mixed deciduous forest

Introduction  

To increase our understanding of litterfall dynamics in mixed-species forests, seasonal and annual variations in litterfall mass and nutrient concentrations were assessed for a 60-year-old spontaneously developed forest dominated by silver birch (Betula pendula Roth), pedunculate oak (Quercus robur L.), and northern red oak (Quercus rubra L.) in Belgium.     

Gradual forest edges can mitigate edge effects on throughfall deposition if their size and shape are well considered

For the protection and promotion of biodiversity in forest edges and interiors, forest edge management practices are put forward like the creation of gradual forest edges (i.e., edges with a gradual increase of vegetation height from open area to forest, e.g., by means of a fringe, a belt, and a mantle). In this study, we tested the mitigating effect of gradual forest edges on the atmospheric deposition of inorganic nitrogen (N) and the potentially acidifying pollutants SO₄²⁻, NO₃⁻, and NH₄⁺ (N + S). We conducted field experiments at three exposed forest edges in Flanders and the Netherlands and compared throughfall deposition at steep edges (i.e., edges with an abrupt transition from open area to forest) and at adjacent gradual edges. Along transects perpendicular to the edges, during three months in both winter and summer, throughfall deposition of Cl⁻, SO₄²⁻, NO₃⁻, and NH₄⁺ was monitored in the forest between 0 and 64 m from the edges and in the gradual edge vegetation. At the smoothest and best fitting gradual edge, the extra N + S throughfall deposition the forest received due to edge effects was lower than at the adjacent steep edge, with on average 80 and 100% in winter and summer, respectively. This was due to a halving of the depth of edge influence and an almost full reduction of the magnitude of edge influence. This decrease in throughfall deposition in the forest was not compensated by the additional throughfall deposition on the gradual edge vegetation itself, resulting in a final decrease in throughfall deposition in the forest edge by 60% in winter and 74% in summer. While this result confirms that gradual edges can mitigate edge effects on atmospheric deposition, the results of the other sites indicate the importance of size and shape of the gradual edge vegetation in mitigating edge effects on deposition: due to insufficient height (‘size’) or inadequate shape of the gradual edge vegetation, only small or insignificant decreases in throughfall deposition were observed. Hence, for mitigating edge effects on N + S and N deposition, our results support the recommendation of creating gradual edges at forests with poorly developed, abrupt edges, but it stresses the importance of a thorough consideration of the shape and size of the gradual edge vegetation in the design and management of gradual forest edges.     

Origin of the superflock of cichlid fishes from Lake Victoria,East Africa

Lake Victoria harbors a unique species-rich flock of more than 500 endemic haplochromine cichlid fishes. The origin, age, and mechanism of diversification of this extraordinary radiation are still debated. Geological evidence suggests that the lake dried out completely about 14,700 years ago. On the basis of phylogenetic analyses of almost 300 DNA sequences of the mitochondrial control region of East African cichlids, we find that the Lake Victoria cichlid flock is derived from the geologically older Lake Kivu. We suggest that the two seeding lineages may have already been lake-adapted when they colonized Lake Victoria. A haplotype analysis further shows that the most recent desiccation of Lake Victoria did not lead to a complete extinction of its endemic cichlid fauna and that the major lineage diversification took place about 100,000 years ago.