Soil erosion and redistribution on cultivated and uncultivated land near las bardenas in the central Ebro river Basin,Spain

The semiarid regions of Spain, including the central part of the Ebro River basin, are under threat due to desertification. Severe erosion, as a result of poor land management, has led to degradation of the soil resource, and there is a clear need for quantitative erosion rate data to evaluate the problem. This study aimed to examine the potential for using caesium-137 to identify the patterns and rates of soil erosion and redistribution within this semiarid environment. Samples for the determination of caesium-137 were collected from uncultivated slopes and cultivated valley floor sites near the head and outlet of a small representative basin in the Las Bardenas area. The measured patterns of caesium-137 mobilization, redistribution and export provide a semiquantitative indication of the variation in erosion within the study site. Calibration of the caesium-137 measurements, taking account of the differing behaviour of radiocaesium on cultivated and uncultivated land, allows estimation of the actual rates of erosion and deposition involved. The results show (1) the erosion rates on the cultivated land (1.6–2.5 kg m⁻² yr⁻¹) are typically more than five times those seen on the uncultivated land (0.2–0.4 kg m⁻² yr⁻¹), and (2) erosion on the uncultivated land is significantly less severe at the head of the basin than at the outlet. Study of the vegetation cover suggests that lower growing shrubs and grasses may be more effective in reducing erosion in this environment than trees.     

First isolation of Tenacibaculum maritimum from wedge sole, Dicologoglossa cuneata (Moreau)

The first isolation of Tenacibaculum maritimum from wedge sole, Dicologoglossa cuneata, is reported. The pathogen was recovered from ulcers of cultured fish, from three different outbreaks. The six isolates obtained were biochemically and serologically characterized and diagnosis was confirmed by polymerase chain reaction using specific primers and partial 16S rRNA gene sequencing. The isolates constituted a homogeneous phenotypic group; however, they belong to two of the different serotypes described within this species. A virulence evaluation of the isolates using Wedge sole fry was also performed.     

Assessing soil erosion and control factors by the radiometric technique in the Boussouab catchment,Eastern Rif,Morocco

In the Eastern Rif of N Morocco, soil conservation is seriously threatened by water erosion. Large areas of soil have reached an irreversible state of degradation. In this study, the ¹³⁷Cs technique was used to quantify erosion rates and identify the main factors involved in the erosion process based on a representative catchment of the Eastern Rif. To estimate erosion rates in terms of the main factors affecting soil losses, samples were collected taking into account the lithology, slope and land use along six selected transects within the Boussouab catchment. The transects were representative of the main land uses and physiographic characteristics of that Rif sector. The reference inventory for the area was established at a stable, well preserved, matorral site (value of 4250 Bq m^− 2). All the sampling sites were eroded and ¹³⁷Cs inventories varied widely (between 245 and 3670 Bq m^− 2). The effective soil losses were also highly variable (between 5.1 and 48.8 t ha^− 1 yr^− 1). Soil losses varied with land use. The lowest average values were on matorral and fallow land (10.5 and 15.2 t ha^− 1 yr^− 1, respectively) but much higher with alfa vegetation or cereal crops (31.6 and 27.3, respectively). The highest erosion rate was on a badland transect at the more eroded part of the catchment, with rates exceeding 40 t ha^− 1 yr^− 1 and reaching a maximum of 48.8 t ha^− 1 yr^− 1.The average soil losses increased by more than 100% when the slope increased from 10° (17.7 t ha^− 1 yr^− 1) to 25° (40. 8 t ha^− 1 yr^− 1). Similar results were obtained when comparing erosion rates in soils that were covered by matorral with respect to those under cultivation. Lithology was also a key factor affecting soil loss. Soils on marls were more erodible and the average erosion rates reached 29.36 t ha^− 1 yr^− 1, which was twice as high as soils on the glacis and old fluvial terraces (average rates of 14.98 t ha^− 1 yr^− 1). The radiometric approach was very useful to quantify erosion rates and to examine the pattern of soil movement. The analysis of main erosion factors can help to promote rational soil use and establish conservation strategies in the study area.     

Changes in antimicrobial susceptibility of Actinobacillus pleuropneumoniae isolated from pigs in Spain during the last decade

A total of 229 Spanish Actinobacillus pleuropneumoniae isolates recovered from diseased pigs with pleuropneumonia from 1997 to 2004 was tested for their susceptibility to 11 antimicrobials in a broth microdilution method. All the isolates were susceptible to florfenicol and most of them to cephalothin; however, a high rate of resistance was observed to tetracycline. A bimodal or multimodal distribution of isolates over the MIC range were observed for penicillins, tetracycline, trimethoprim, sulfisoxazole and nalidixic acid, suggesting the development of acquired resistance. Eight resistance patterns were established, and 21.1% of the isolates were resistant to at least two antimicrobials. In addition, a considerable increase in the resistance to tetracyclines was observed during the last decade in Spain, when compared with other A. pleuropneumoniae strains isolated during 1987-1988 (Gutiérrez, C.B., Píriz, S., Vadillo, S., Rodríguez Ferri, E.F., 1993. In vitro susceptibility of Actinobacillus pleuropneumoniae strains to 42 antimicrobial agents. Am. J. Vet. Res. 54, 546-550); this finding was also observed for gentamicin in minor percentage.     

Molecular characterization of Haemophilus parasuis ferric hydroxamate uptake (fhu) genes and constitutive expression of the FhuA receptor

Bacteria have evolved a set of highly specialized proteins to capture iron in iron-depleted environments. The acquisition and uptake of iron present in the extracellular milieu of eukaryotic organisms is indispensable for the growth and survival of microbial pathogens in the course of infection. Haemophilus parasuis is the causative agent of Gl?sser disease, which is responsible for considerable financial losses in pig-rearing worldwide. To gain insight into the mechanisms involved in siderophore-mediated iron uptake in H. parasuis, genes in the H. parasuis ferric hydroxamate uptake (Fhu) region were amplified in the work being reported here. As has been described in A. pleuropneumoniae, an Fhu genomic region was also present in H. parasuis, being composed of four potential consecutive open reading frames (ORF) designated as fhuC, fhuD, fhuB, and fhuA, respectively. By immunoblotting, using a cross-reactive polyclonal antibody raised against Actinobacillus pleuropneumoniae FhuA protein, it was demonstrated that this protein was constitutively expressed in H. parasuis and its level of expression was not modified under conditions of restricted iron availability. This is the first report describing the presence of the fhu genes in H. parasuis. Our results indicate that FhuA protein expression is not affected under iron-restricted conditions, however, it is one of the targets of the humoral immune response.     

Antimicrobial susceptibility patterns of Haemophilus parasuis from pigs in the United Kingdom and Spain

A total of 30 British and 30 Spanish Haemophilus parasuis isolates were tested for their susceptibility to 19 of the antimicrobials currently used in swine practice with a broth microdilution method in order to know the emergence of resistance against these compounds in this porcine pathogen. All the British isolates were susceptible to penicillin, ceftiofur, erythromycin, tilmicosin, enrofloxacin, and florfenicol, and most of them were susceptible to the remaining antimicrobials (the highest resistance rate found was of 20% to neomycin). In contrast, all the Spanish isolates were susceptible exclusively to florfenicol, and high proportions of resistance were encountered for penicillin, ampicillin, oxytetracycline, erythromycin, tilmicosin, tiamulin and trimethoprim+sulphamethoxazole; in addition, a bimodal or multimodal distribution, or tailing of Spanish isolates over the MIC range was observed for clindamycin, sulphonamides and tylosine tartrate, suggesting the development of acquired resistance. In addition, several multiresistance patterns were found among the Spanish isolates, 23.3% of them being resistant to at least eight antimicrobials, the same rate as that encountered for those being susceptible to all antimicrobials tested. This study showed that in general British H. parasuis isolates are susceptible to antimicrobial agents routinely used for treatment of porcine respiratory diseases; however, the Spanish isolates need a more continuous surveillance of their susceptibility patterns.     

Prevalence,geographic distribution and phenotypic differences of Piscirickettsia salmonis EM‐90‐like isolates

Early reports accounted for two main genotypes of Piscirickettsia salmonis, a fish pathogen and causative agent of piscirickettsiosis, placing the single isolate EM‐90 apart from the prototypic LF‐89 and related isolates. In this study, we provide evidence that, contrary to what has been supposed, the EM‐90‐like isolates are highly prevalent and disseminated across Chilean marine farms. Molecular analysis of 507 P. salmonis field isolates derived from main rearing areas, diverse hosts and collected over 6 years, revealed that nearly 50% of the entire collection were indeed typed as EM‐90‐like. Interestingly, these isolates showed a marked host preference, being recovered exclusively from Atlantic salmon (Salmo salar) samples. Although both strains produce undistinguishable pathological outcomes, differences regarding growth kinetics and susceptibility to the antibiotics and bactericidal action of serum could be identified. In sum, our results allow to conclude that the EM‐90‐like isolates represent an epidemiologically relevant group in the current situation of piscirickettsiosis. Based on the consistency between genotype and phenotype exhibited by this strain, we point out the need for genotypic studies that may be as important for the Chilean salmon industry as the continuous surveillance of antimicrobial susceptibility patterns.     

Physiological responses of juvenile wedge sole Dicologoglossa cuneata (Moreau) to high stocking density

Physiological responses to a high stocking density were tested in juvenile wedge sole Dicologoglossa cuneata (Moreau). Fish were kept at low (1 kg m⁻²), medium (3 kg m⁻²) and high (9 kg m⁻²) stocking densities for 22 days. No differences in the weight, length, survival and hepatosomatic index were observed among treatments. Basal plasma cortisol and osmolality were found to be directly and positively related to stocking density. A mild increase in plasma glucose was seen at medium density, and plasma protein was elevated at medium and high densities. The liver glucose and glycogen content was inversely related to stocking density. The liver triglyceride level was significantly elevated at the highest density, and the α-amino acid content decreased at the highest density. In muscle, glucose levels were significantly higher in fish kept at the lowest density; the α-amino acid content was elevated in fish kept at high density. In conclusion, plasma cortisol levels indicated an increasing stress level depending on the culture density, but significant changes in energy reserves did not occur in tissue (mainly liver and muscle glycogen and glucose reserves were significantly affected).