Seasonality of hydrographic variables in a coastal lagoon: Mar Chiquita,Argentina

• 1. The concentration and distribution of several hydrographical variables from Mar Chiquita coastal lagoon, Argentina, were measured monthly over a year in order to quantify their seasonal variations. Temperature, salinity, inorganic nutrient concentrations (nitrate, nitrite, phosphate, silicate) in the water column, and photosynthetic pigments (chlorophyll a and phaeopigments) in suspended particulate matter (SPM), were measured using internationally standardized analytical methods.
• 2. Agricultural use of land surrounding the coastal lagoon has been shown to be the main nutrient source, owing to the use of fertilizers for farming and the consequent leaching of the soils by freshwater runoff.
• 3. Two different hydrographical areas were identified within the coastal lagoon, one showing marine influence and the other dominated by inland influence (due to catchment and freshwater inputs), both with different characteristics and ecological behaviour.
• 4. The frequent occurrence of phytoplankton blooms has also been identified within the coastal lagoon. There was significant biological production (in terms of chlorophyll a) within the lagoon throughout the year. The lagoon appears to function as a transitional system, opportunistically benefiting from extra nutrient inputs which, together with other environmental conditions, results in a continuous food supply, useful to both marine and estuarine organisms. Consequently the system is important for numerous fish and shellfish species as a nursery area.

Copyright © 2005 John Wiley & Sons, Ltd.     

PCR diagnosis of Fasciola hepatica in field-collected Lymnaea columella and Lymnaea viatrix snails

Fasciolosis, caused by the trematode Fasciola hepatica, is a zoonosis of economic importance in livestock that is emerging as a chronic disease in humans. The intermediate hosts are lymnaeid snails, in which diagnosis of infection is traditionally based on cercarial shedding, tissue sectioning and crushing. We developed a PCR assay for the sensitive and specific detection of F. hepatica in field-collected Lymnaea sp. snails. A primer pair was designed to amplify a 405 bp fragment of the cytochrome c oxidase subunit 1 gene of F. hepatica. The PCR assay showed a limit of detection of 10 pg of genomic F. hepatica DNA. No cross-reactions were observed with samples from other related trematode species or from the snail hosts Lymnaea columella and Lymnaea viatrix. DNA sequencing of the amplicon showed 100% homology with F. hepatica, and 75-89% homology with other trematodes on regions that did not include the entire set of primers. Two samples from Argentina were analysed. For snails in sample 1 (n = 240), identified as L. columella, the infection rate was 17.5 and 51.3% by direct examination and PCR, respectively. For snails in sample 2 (n = 34), identified as L. viatrix, the infection rate was 2.9 and 61.8% by direct examination and PCR, respectively. Differences in infection rates between these diagnosis methods were significant for both samples. Our PCR technique showed to be effective for detecting specific F. hepatica infections of low intensity in the intermediate host, and hence it could be used to study the epidemiological situation in a given area, as well as to assess host suitability for the parasite.     

Initial evaluation of a technique for complete cecal bypass in the horse

OBJECTIVE: To describe a novel stapling technique for creation of a complete cecal bypass, without ileal transection in horses. STUDY DESIGN: Experimental study. ANIMALS: Four adult horses. METHODS: Through a ventral median celiotomy, jejunocolostomy was made with an intraluminal anastomosis device (ILA-100) and oversewn with a Cushing pattern to reinforce the staple line. Immediately distal to the anastomosis, 4 rows of staples were applied using a thoracoabdominal stapling device (TA-90) to occlude the lumen of the distal jejunum and proximal ileum. Necropsy exams were performed at least 60 days after surgery. RESULTS: No intraoperative complications occurred. Cecal bypass was functional in all horses at necropsy. The most oral staple line across the ileum partially failed in 1 horse; however cecal bypass was functional. CONCLUSIONS: Complete cecal bypass without ileal transection is a viable alternative to traditional methods of complete cecal bypass. Two sets of staple lines across the ileum are recommended. Longer term follow-up is warranted before clinical use of this technique. CLINICAL RELEVANCE: Cecal bypass without ileal transection is technically simple and effectively bypasses the cecum. It also should intuitively require less time and have a reduced risk of contamination compared with complete cecal bypass with ileal transection.     

Manipulating the soil microbiome to increase soil health and plant fertility

A variety of soil factors are known to increase nutrient availability and plant productivity. The most influential might be the organisms comprising the soil microbial community of the rhizosphere, which is the soil surrounding the roots of plants where complex interactions occur between the roots, soil, and microorganisms. Root exudates act as substrates and signaling molecules for microbes creating a complex and interwoven relationship between plants and the microbiome. While individual microorganisms such as endophytes, symbionts, pathogens, and plant growth promoting rhizobacteria are increasingly featured in the literature, the larger community of soil microorganisms, or soil microbiome, may have more far-reaching effects. Each microorganism functions in coordination with the overall soil microbiome to influence plant health and crop productivity. Increasing evidence indicates that plants can shape the soil microbiome through the secretion of root exudates. The molecular communication fluctuates according to the plant development stage, proximity to neighboring species, management techniques, and many other factors. This review seeks to summarize the current knowledge on this topic.     

Genetic and phenotypic diversity in a germplasm working collection of cultivated tropical yams (Dioscorea spp.)

A working collection of yam (Dioscorea spp.) comprising 53 landraces and seven improved cultivars of four species (D. alata L., D. cayenensis Lam., D. dumetorum (Kunth) and D. rotundata Poir.) was evaluated for phenotypic and genetic diversity. The evaluation involved field assessment of 24 morphological traits and DNA analysis with 32 Simple sequence repeat (SSR) polymorphic markers. Diversity was greater between species than within species; highest in D. rotundata and lowest in D. alata and D. cayenensis. Analysis based on combined phenotypic and SSR marker data sets revealed a close relationship between D. rotundata and D. cayenensis, but D. alata and D. dumetorum remained as distinct species. D. alata was related genetically to D. rotundata and D. cayenensis, but phenotypically to D. dumetorum. The study showed that cultivars obtained from different farmers may bear the same name but be genetically different. Polymorphic SSR markers were identified that may be used for genetic analysis across yam species. The working collection assessed in this study represents a good gene pool for intra- and inter-specific hybridization in yam genetic improvement.     

Phenotypic–genotypic resistance in Salmonella spp. isolated from cattle carcasses from the north central zone of the State of Mexico

Salmonella is a public and animal health problem due to the generation of strains multiresistant to antimicrobial products. The objective of this study was to determine prevalence and antimicrobial phenotypic and genotypic resistance of Salmonella spp. isolated from beef cattle carcasses killed in slaughterhouses of the north central zone of the State of Mexico. Sampling was carried out according to the European Directive 2001/471/EC; isolation and identification of the strain was carried out according to the Mexican Official Standard NOM-114-SSA1-1994; resistance was established by CMI according to the National Committees for Clinical Laboratory Standards (NCLS) and multiplex PCR according to Ahmed et al. (Journal of Applied Microbiology 106:402–409, 2009) with PSE-1, tetG, qnrS, FloR, STR, and sul1 oligonucleotides. Twenty-seven strains of Salmonella spp. were obtained from 327 samples (prevalence of 0.083); 19 strains (70 %) were resistant to 10 μg/ml of ampicillin, 15 of these (79 %) had the PSE-1 gene; 22 strains (84 %) were resistant to 30 μg/ml streptomycin, 14 of these (63.6 %) had the STR gene. Genes PSE-1 and STR were factors in the presence of resistance, the rest of the genes (tetG, qnrS, FloR, and sul1) were not factors of resistance in the studied strains.     

First report of seroprevalence of Toxoplasma gondii and Neospora caninum in dairy sheep from Humid Pampa, Argentina

The aim of this study was to describe the occurrence of antibodies to Toxoplasma gondii and Neospora caninum in dairy sheep from the Humid Pampa region, Argentina. Blood samples from 704 dairy sheep belonging to six flocks were collected. Using a cut off titer of 1:50, an indirect fluorescence antibody test was used. Antibodies to T. gondii or N. caninum were detected in 17.3 % (n?=?122) and 3 % (n?=?21), respectively. All the flocks had at least one seropositive animal to T. gondii but two of them had no seropositive sheep to N. caninum. Fifty-two of 122 (42.6 %) positive samples to T. gondii had antibody titers higher than 1:400. There was a significantly higher proportion of T. gondii seropositive animals in females and older sheep (p?<?0.05). Ten of 21 (52.3 %) positive samples to N. caninum had antibody titers higher than 1:400. This is the first report of seroprevalence of T. gondii and N. caninum in dairy sheep from Humid Pampa, Argentina. Further research is required for a better understanding of the role of toxoplasmosis and neosporosis in dairy sheep in Argentina.