Epidemiology of gastrointestinal nematode parasitism in a commercial sheep flock and its implications for control programmes

The epidemiology of nematode infections in a uk commercial crossbred sheep flock was studied from January 2004 to January 2005. The ewes were treated orally with moxidectin when they were turned out of the lambing shed on to nematode-contaminated pasture, and the lambs were treated orally with ivermectin throughout the summer in accordance with the farm's usual practice, with the aim of near-suppressive nematode control. The lactating ewes experienced a significant increase in faecal egg count during the early summer, after the period of persistence of the moxidectin treatment had ended. The ewes' and lambs' egg outputs were dominated by Teladorsagia species, despite the persistence of the effect of moxidectin against this genus. The gimmers (primiparous two-year-old ewes) had a significantly greater faecal egg count at lambing than the three- to four-year-old ewes, but the older ewes had significantly greater post-treatment increases. The population of Trichostrongylus species appeared to follow accepted epidemiological patterns, with no evidence of summer trichostrongylosis. In late summer and autumn the faecal egg output of the ewes was primarily due to large intestinal nematodes.     

Physico-chemical characteristics and total quality of date palm varieties grown in the southern of Tunisia

The date palm, Phoenix dactylifera, is a palm extensively cultivated for its edible fruit. The chemical composition and the water content of ten Tunisian date varieties were determined. For all analysis, the Deglet Nour variety was taken as reference. Compositional analysis showed that the littoral varieties were very rich in reducing sugars (26 to 51%) than Deglet Nour which was rich in sucrose (54%). The relative results of the moisture content showed that the littoral varieties were classified as soft dates. The vitamin C analysis showed that the littoral varieties were very rich in this compound (24 to 46 mg/100 g) than Deglet Nour (1.12 mg/100 g). The mineral analysis showed that the littoral dates were relatively rich in potassium (283 to 733 mg/100 g) and presented a weak content in sodium (0.06 to 0.09 mg/100 g).     

Relative impact of soil, metal source and metal concentration on bacterial community structure and community tolerance

In a study to assess the sustainable use of sewage sludge application to land, the long-term effect of Zn and Cu contaminated sludge additions on the structure of the bacterial communities (using T-RFLP analysis) and their tolerance to additional metal exposure through pollution-induced community tolerance (PICT) assays was assessed. This used two soils that received metal-rich sludge cake (SC), liquid sludge (LS) or metal salts (MS) additions more than 10 years previously. Soil type had the predominant influence on bacterial community structure and PICT. The source of the metal contamination also had a large influence on community structure and PICT, greater than the effects due to metal concentrations. Nevertheless, in both Zn and Cu contaminated soils, PICT was observed and decreased in the order MS > LS > SC. Within a metal source and site, there was evidence of increased PICT with increasing Zn or Cu contamination, however few differences were significant as a result of high variability between sample replicates. These results highlight the importance of considering soil physico-chemical properties and the source of metal contamination as well as total metal concentrations when considering the long-term effects of metals on soil microbial communities. Further, the matrix that a metal is associated with prior to addition may play an important factor in determining levels of toxicity. This could have consequences for the interpretation and use of data from metal spiking experiments when considering metal limits for sludge application to land.     

Long-term impacts of zinc and copper enriched sewage sludge additions on bacterial, archaeal and fungal communities in arable and grassland soils

Long-term impacts of metal contamination derived from sewage sludge on soil microbial communities have been widely evaluated, but confounding effects have made it difficult to draw firm conclusions and thus to advise on safe metal limits. Here we used Multiplex-terminal restriction length fragment polymorphism (M-TRFLP) to assess the long-term impact of sludge-borne Zn and Cu contamination on the structure of bacterial, fungal and archaeal communities across seven different soils at metal levels relevant to current guideline limits. Despite strong effects of site on microbial community structure, analysis of similarity (ANOSIM) demonstrated a small but significant effect of Zn on bacteria (P < 0.001), archaea (P < 0.001), and fungi (P < 0.001). Significant effects of Cu on bacteria (P < 0.001), archaea (P < 0.001) and fungi (P < 0.001) were also observed. Several bacterial and fungal T-RFs were identified as responding to Zn or Cu. For example the bacterial T-RF 72 was negatively correlated with Zn and Cu, and T-RF 259 was positively correlated with Zn. Attempts to identify these bacterial markers of Zn and Cu contamination suggest a negative impact of Cu on Acidobacteria in arable soils. These results demonstrate for the first time, that despite a strong influence of site on microbial community structure, effects of Zn and Cu derived from sewage sludge can be detected as shifts in bacterial, fungal and archaeal communities indicating a common response more than 11 years after sludge addition.     

Plasma somatolactin levels in coho salmon (Oncorhynchus kisutch) during smoltification and sexual maturation

Somatolactin (SL) is a novel pituitary hormone recently characterized in several fish species. Structural analyses have shown that SL belongs to the growth hormone/prolactin family, and that it is a highly conserved protein. SL is synthesized by the periodic acid/Schiff-positive cells in the pars intermedia, but has an as yet unidentified function(s). We have recently developed a homologous radioimmunoassay for coho salmon SL and measured plasma levels of SL during two stages of the coho salmon life cycle, smoltification and sexual maturation. During smoltification, plasma levels of SL changed almost in parallel with plasma levels of thyroxine; levels increased as morphological indices of smoltification appeared and decreased as smoltification was completed. Following this period, SL levels remained low until the spring prior to spawning. In a separate study, plasma levels of SL were measured in sexually maturing coho salmon that remained in fresh water throughout their life cycle. During the year of sexual maturation, plasma levels of SL gradually increased from the spring onward, reaching peak levels at the time of spawning in November and December. These data are similar to those previously reported for sexually maturing coho salmon that were maintained in seawater prior to spawning (Rand-Weaver et al. 1992). Therefore, increases in plasma SL levels occurred in sexually maturing fish irrespective of whether they were maintained in fresh water or seawater. Peak levels at spawning were higher than those observed during smoltification. Possible roles for SL in metabolism and reproduction are discussed.     

Relationship between metabolic and reproductive hormones in salmonid fish

Circulating concentrations of estradiol (E₂), vitellogenin (VTG), thyroxine (T₄), triiodothyronine (T₃) and insulin were measured in reproductively maturing four and five year-old Atlantic salmon. Blood samples were collected from the fish in seawater for one year prior to their spawning in November in fresh water. In females, E₂ and VTG were low but detectable from December to July, and then increased to peak levels in September and October. Plasma levels of T₄ and T₃ were relatively constant in winter and spring, and decreased in July. Plasma concentration of T₄ increased in November when the fish returned to fresh water. Plasma T₃ levels remained low during the autumn. Both T₄ and T₃ levels tended to be higher in males than in females during September through November. Plasma insulin concentrations increased during the spring to peak values in May, and then decreased in June and July in fish of both sexes. There was a significant elevation of plasma insulin in males during October, and the levels in males tended to be higher than those found in females during final maturation.