Transmission of the microsporidian gill parasite, Loma salmonae

Since it was first reported in 1987 at a hatchery in British Columbia, Loma salmonae has become increasingly important as an emerging parasite affecting the Canadian salmonid aquaculture industry. L. salmonae causes Microsporidial Gill Disease of Salmon (MGDS) in farmed Pacific salmonids, Oncorhynchus spp., resulting in respiratory distress, secondary infections and high mortality rates. In the last decade, laboratory studies have identified key transmission factors for this disease and described the pathogenesis of MGDS. L. salmonae enters the host via the gut, where it injects sporoplasm into a host cell, which then migrates to the heart for a two-week merogony-like phase, followed by a macrophage-mediated transport of the parasite to the gill, with a final development stage of a spore-laden xenoma within the endothelial and pillar cells. Xenoma rupture triggers a cascade of inflammatory events leading to severe, persistent, and extensive proliferative branchitis. The development of robust and reliable experimental challenge models using several exposure methods in marine and freshwater environments with several fish hosts, is a primary reason for the success of scientific research surrounding L. salmonae. To date, demonstrated factors affecting MGDS transmission include host species, strain and size, the length of contact time between na?ve and infected fish, water temperature and flow rates.     

Thiamine and fatty acid content of walleye tissue from three southern U.S. reservoirs

We determined the thiamine concentration in egg, muscle, and liver tissues of walleyes Sander vitreus and the fatty acid content of walleye eggs from three southern U.S. reservoirs. In two Tennessee reservoirs (Dale Hollow and Center Hill), in which there were alewives Alosa pseudoharengus in the forage base, natural recruitment of walleyes was not occurring; by contrast in Lake James Reservoir, North Carolina, where there were no alewives, the walleye population was sustained via natural recruitment. Female walleye tissues were collected and assayed for thiamine (vitamin B1) and fatty acid content. Thiamine pyrophosphate was found to be the predominant form of thiamine in walleye eggs. In 2000, mean total egg thiamine concentrations were similar among Center Hill, Dale Hollow, and Lake James reservoirs (2.13, 3.14, and 2.77 nmol thiamine/g, respectively). Egg thiamine concentration increased as maternal muscle (r2 = 0.73) and liver (r2 = 0.68) thiamine concentration increased. Walleye egg thiamine does not appear to be connected to poor natural reproduction in Tennessee walleyes. Threadfin shad Dorosoma petenense, which are found in all three reservoirs, had higher thiaminase activity than alewives. Six fatty acids differed among the walleye eggs for the three reservoirs. Two were physiologically important fatty acids, arachidonic acid (20:4[n-6]) and docosahexaenoic acid (22:6[n-3]), which are important eicosanoid precursors involved in the regulation of biological functions, such as immune response and reproduction.     

Remote monitoring of a deep‐sea marine protected area: The Endeavour Hydrothermal Vents

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Binding of PF2 lectin from Olneya tesota to gut proteins of Zabrotes subfasciatus larvae associated with the insecticidal mechanism

Zabrotes subfasciatus (Boheman) is the main pest of common beans ( Phaselous vulgaris ). Wild legume seeds from Olneya tesota contain a lectin, PF2, that shows insecticidal activities against this insect. The binding of PF2 to midgut glycoproteins of 20-day-old larvae was evaluated using PF2 affinity chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the proteins retained on the gel revealed several putative glycoproteins, ranging in mass from 17 to 97 kDa. Subsequent protein digestion and analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS) provided amino acid fragments that identified an α-tubulin, cytochrome c oxidase subunit I, an odorant receptor, and a lysozyme from available insect sequence databases. The potential of these proteins to serve as part of the mechanisms involved in the insecticidal activity of PF2 to Z. subfasciatus is discussed.     

Entomopathogens (Beauveria bassiana and Steinernema carpocapsae) for biological control of bark-feeding moth Indarbela dea on field-infested litchi trees

BACKGROUND: The bark-feeding moth Indarbela dea (Swinhoe) is one of the major pests of litchi (Litchi chinensis Sonn.) in Asia. Effects on larval mortality and web production were tested by repeated, single and combined tree trunk applications of the entomopathogenic fungus Beauveria bassiana (Bals.) Vuill. and the entomopathogenic nematode Steinernema carpocapsae (Weiser). Two separate application trials were conducted in different seasons on young and older larvae respectively. RESULTS: In both trials, complete or nearly complete mortality (100% and 95%) of the larvae was achieved 3 weeks after application of S. carpocapsae alone and 2 weeks after the combined application of B. bassiana and S. carpocapsae (100% in both trials). However, in the combined application, all larvae were killed by one treatment, while the application of S. carpocapsae alone needed to be repeated to reach the same result. The effectiveness of the combined entomopathogen application and of the application of S. carpocapsae alone was not influenced by the age of the larvae. However, the single applications of B. bassiana were only effective on young larvae. In both trials, web production of surviving larvae was very significantly reduced by the application of S. carpocapsae in single and combined treatments. CONCLUSIONS: As the results show, only one application is necessary in the combined application of the two entomopathogens to control I. dea, which implies that such treatment is probably the economically most relevant solution.     

Disease development and mycotoxin production by the <Emphasis Type="Italic">Fusarium graminearum</Emphasis> species complex associated with South African maize and wheat

Fungal species comprising the Fusarium graminearum species complex (FGSC) may cause disease in maize and wheat. Host preference within the FGSC has been suggested, in particular F. boothii towards maize ears. Therefore, the disease development and mycotoxin production of five FGSC species in maize and wheat grain was determined. Eighteen isolates representing F. acaciae-mearnsii, F. boothii, F. cortaderiae, F. graminearum and F. meridionale were used. Each isolate was inoculated on maize ears and wheat heads to determine host preferences. Disease severity and disease incidence was measured for maize and wheat, respectively. Fungal colonisation and mycotoxins, deoxynivalenol (DON), nivalenol and zearalenone, was also quantified. Isolates differed significantly (P < 0.05) in their ability to produce symptoms on maize ears, however, no significant differences between FGSC species were determined. Similarly, significant differences (P < 0.05) between isolates but not between FGSC species in disease incidence on wheat were determined. The isolates also differed significantly (P < 0.05) in their ability to colonise maize and wheat grain. No significant differences in fungal colonisation, among the five FGSC species, were determined in field grown maize. However, under greenhouse conditions, F. boothii was the most successful coloniser of maize grain (P < 0.05). In wheat, F. graminearum colonised the grain more successfully and produced significantly more (P < 0.05) DON than the other species. Fusarium boothii isolates were the best colonisers and mycotoxin producers in maize, and F. graminearum isolates in wheat. The selective advantage of F. boothii to cause disease on maize was supported in this study.     

Effects of Rosmarinus officinalis L. essential oils supplementation on digestion,colostrum production of dairy ewes and lamb mortality and growth

The aim of this study was to evaluate the effect of rosemary essential oils (REO) and the forage nature on ewes' performances, immune response and lambs' growth and mortality. Forty‐eight dairy ewes (Sicilo‐Sarde) were fed oat‐hay or oat‐silage supplemented with 400 g of concentrate during pregnancy and 600 g during postpartum. The experimental concentrate contained the same mixture as the control (barley, soybean meal and mineral vitamin supplement) more 0.6 g/kg of REO. Two groups were obtained with each forage (Hay groups: H‐C and H‐REO; Silage groups: S‐C and S‐REO). REO increased the dry matter (DM) intake, the nitrogen intake and retention being higher with the silage groups (P < 0.05). REO increased solid non‐fat (P = 0.004) and fat contents of colostrum which was higher with hay (P = 0.002). REO decreased lamb mortality (P < 0.05) which averaged 21% for control groups and 6% for H‐REO, while no mortality was recorded with S‐REO. REO dietary supply improved forage intake and tended to ameliorate colostrum production; it could be a natural additive to improve ewes' performances.