Biological control of Biomphalaria tenagophila (Mollusca, Planorbidae), a schistosomiasis vector, using the fish Geophagus brasiliensis (Pisces, Cichlidae) in the laboratory or in a seminatural environment

In order to investigate a possible method of biological control of schistosomiasis, we used the fish Geophagus brasiliensis (Quoy & Gaimard, 1824) which is widely distributed throughout Brazil, to interrupt the life cycle of the snail Biomphalaria tenagophila (Orbigny, 1835), an intermediate host of Schistosoma mansoni. In the laboratory, predation eliminated 97.6% of the smaller snails (3-8 mm shell diameter) and 9.2% of the larger ones (12-14 mm shell diameter). Very promising results were also obtained in a seminatural environment. Studies of this fish in natural snail habitats should be further encouraged.

Sulphate-reducing bacteria associated with biocorrosion: a review

Biocorrosion means any process of corrosion in wich microorganisms are somehow involved. As far as the petroleum industry is concerned, the anaerobic type is the more important, with Sulphate-Reducing Bacteria (SRB) accouting for half of the described processes. SRB are obligate anaerobs that use sulphur, sulphate or other oxidized sulphur compounds as oxidizing agents when decomposing organic material. A typical product of SRB metabolism, hydrogen sulphide -H2S-, is extremely toxic. In the present work we review the literature on mechanisms underlying biocorrosive process in wich SRB are involved and summarize some of the ultrastructural and eletrochemical work developed using SRB obtained from water injection flow in wells located on PETROBRAS offshore marine plataforms, sampled directly in the field over metallic probes, or cultured under laboratory conditions. Biofilms develop when SRB adhere to inert surfaces. A high diversity of morphological types is found inside these biofilms. Their extracellular matrix is highly hydrated and mainly anionic, as shown by its avid reaction with cationic compounds like ruthenium red. We have noted that variations in iron contet lead to interesting changes in the ultrastructure of the bacterial cell coat and also in the rate of corrosion induced in metallic test cupons. Since routine methods to prevent and treat SRB contamination and biodeterioration involve the use of biocides that are toxic and always have some environmental impact, an accurate diagnosis of biocorrosion is always required prior to a treatment decision. We developed a method that detects and semi-quantifies the presence of living or dead SRB by using free silver potentials as an indicator of corrosive action by SRB-associated sulphides. We found a correlation between sulphide levels (determined either by spectrophotometry, or using a silver electrode -E(Ag)- that measured changes in free potentials induced by the presence of exogeneously added sulphide) and SRB concentration (enumerated by a culturing method). E (Ag) was characterized under a variety of conditions andwas found to be relatively immune to possible interference resulting from aeration of media or from the psence of iron corrosion products. The method offers a simple, rapid, and effective means of diagnosing biocorrosive processes prior to their control.

Genetic Structure of Triatoma sordida (Hemiptera: Reduviidae) Domestic Populations from Bolivia: Application on Control Interventions

The genetic population of Triatoma sordida group 1, a secondary vector of Chagas disease in Bolivia, was studied by multi-locus enzyme electrophoresis. A total of 253 nymphal and adult specimens collected from seven neighbouring localities in the Velasco Province, Department of Santa Cruz, were processed. The relatively low genetic variability was confirmed for this species (rate of polymorphism: 0.20). The absence of genetic disequilibrium detected within the seven localities was demonstrated. A geographical structuration appears between localities with distances greater than 20 km apart. Although T. sordida presents a relatively reduced dispersive capacity, its panmictic unit is wider than compared with T. infestans. Genetic distances between T. sordida populations were correlated with geographic distance. Gene flow between geographic populations of T. sordida provides an efficient framework for effective vigilance and control protocols.

Developing new approaches for detecting and preventing Aedes aegypti population outbreaks: basis for surveillance, alert and control system

A new approach to dengue vector surveillance based on permanent egg-collection using a modified ovitrap and Bacillus thuringiensis israelensis(Bti) was evaluated in different urban landscapes in Recife, Northeast Brazil. From April 2004 to April 2005, 13 egg-collection cycles of four weeks were carried out. Geo-referenced ovitraps containing grass infusion, Bti and three paddles were placed at fixed sampling stations distributed over five selected sites. Continuous egg-collections yielded more than four million eggs laid into 464 sentinel-ovitraps over one year. The overall positive ovitrap index was 98.5% (over 5,616 trap observations). The egg density index ranged from 100 to 2,500 eggs per trap-cycle, indicating a wide spread and high density of Aedes aegypti (Diptera: Culicidae) breeding populations in all sites. Fluctuations in population density over time were observed, particularly a marked increase from January on, or later, according to site. Massive egg-collection carried out at one of the sites prevented such a population outbreak. At intra-site level, egg counts made it possible to identify spots where the vector population is consistently concentrated over the time, pinpointing areas that should be considered high priority for control activities. The results indicate that these could be promising strategies for detecting and preventing Ae. aegypti population outbreaks.

Insecticide treated mosquito nets for malaria control in India-experience from a tribal area on operational feasibility and uptake

The study assessed the operational feasibility and acceptability of insecticide-treated mosquito nets (ITNs) in one Primary Health Centre (PHC) in a falciparum malaria endemic district in the state of Orissa, India, where 74% of the people are tribes and DDT indoor residual spraying had been withdrawn and ITNs introduced by the National Vector Borne Disease Control Programme. To a population of 63,920, 24,442 ITNs were distributed free of charge through 101 treatment centers during July-August 2002. Interview of 1,130, 1,012 and 126 respondents showed that the net use rates were 80%, 74% and 55% in the cold, rainy and summer seasons, respectively. Since using ITNs, 74.5-76.6% of the respondents observed reduction of mosquito bites and 7.2-32.1% reduction of malaria incidence; 37% expressed willingness to buy ITNs if the cost was lower and they were affordable. Up to ten months post-treatment, almost 100% mortality of vector mosquitoes was recorded on unwashed and washed nets (once or twice). Health workers re-treated the nets at the treatment centers eight months after distribution on a cost-recovery basis. The coverage reported by the PHC was only 4.2%, mainly because of unwillingness of the people to pay for re-treatment and to go to the treatment centers from their villages. When the re-treatment was continued at the villages involving personnel from several departments, the coverage improved to about 90%.Interview of 126 respondents showed that among those who got their nets re-treated, 81.4% paid cash for the re-treatment and the remainder were reluctant to pay. Majority of those who paid said that they did so due to the fear that if they did not do so they would lose benefits from other government welfare schemes. The 2nd re-treatment was therefore carried out free of charge nine months after the 1st re-treatment and thus achieved coverage of 70.4%. The study showed community acceptance to use ITNs as they perceived the benefit. Distribution and re-treatment of nets was thus possible through the PHC system, if done free of charge and when personnel from different departments, especially those at village level, were involved.

Spatial and temporal changes in Lutzomyia longipalpis abundance, a Leishmania infantum vector in an urban area in northeastern Argentina

This study aimed to analyse changes in the spatial distribution of Lutzomyia longipalpis in Posadas, an urban area located in northeastern Argentina. Data were obtained during the summer of 2007 and 2009 through two entomological surveys of peridomiciles distributed around the city. The abundance distribution pattern for 2009 was computed and compared with the previous pattern obtained in 2007, when the first human visceral leishmaniasis cases were reported in the city. Vector abundance was also examined in relation to micro and macrohabitat characteristics. In 2007 and 2009, Lu. longipalpis was distributed among 41.5% and 31% of the households in the study area, respectively. In both years, the abundance rates at most of the trapping sites were below 30 Lu. longipalpis per trap per night; however, for areas exhibiting 30-60 Lu. longipalpis and more than 60 Lu. longipalpis, the areas increased in both size and number from 2007-2009. Lu. longipalpis was more abundant in areas with a higher tree and bush cover (a macrohabitat characteristic) and in peridomiciles with accumulated unused material (a microhabitat characteristic). These results will help to prioritise and focus control efforts by defining which peridomiciles display a potentially high abundance of Lu. longipalpis.

Aphid parasitoids (Hymenoptera, Braconidae, Aphidiinae) and their associations related to biological control in Brazil

This study evaluated the parasitoid-aphid-plant associations in Brazil with the objective of developing a useful research database for further studies of aphid parasitoid ecology and aphid management. The original material was obtained from collections made in Paraná, Rio Grande do Sul, Minas Gerais, and São Paulo states. The published information on the Aphidiinae in Brazil is revised. The general features of the target parasitoid fauna of Central and South America is summarized and promising biological control programs of some aphid species in Brazil is discussed.

Organic material decomposition and nutrient dynamics in a mulch system enriched with leguminous trees in the Amazon

The new techniques proposed for agriculture in the Amazon region include rotational fallow systems enriched with leguminous trees and the replacement of biomass burning by mulching. Decomposition and nutrient release from mulch were studied using fine-mesh litterbags with five different leguminous species and the natural fallow vegetation as control. Samples from each treatment were analyzed for total C, N, P, K, Ca, Mg, lignin, cellulose content and soluble polyphenol at different sampling times over the course of one year. The decomposition rate constant varied with species and time. Weight loss from the decomposed litter bag material after 96 days was 30.1 % for Acacia angustissima, 32.7 % for Sclerolobium paniculatum, 33.9 % for Iinga edulis and the Fallow vegetation, 45.2 % for Acacia mangium and 63.6 % for Clitoria racemosa. Immobilization of N and P was observed in all studied treatments. Nitrogen mineralization was negatively correlated with phenol, C-to-N ratio, lignin + phenol/N ratio, and phenol/phosphorus ratios and with N content in the litterbag material. After 362 days of field incubation, an average (of all treatments), 3.3 % K, 32.2 % Ca and 22.4 % Mg remained in the mulch. Results confirm that low quality and high amount of organic C as mulch application are limiting for the quantity of energy available for microorganisms and increase the nutrient immobilization for biomass decomposition, which results in competition for nutrients with the crop plants.

Use of steel slag to neutralize acid mine drainage (AMD) in sulfidic material from a uranium mine

Acid Mine Drainage (AMD) is one of the main environmental impacts caused by mining. Thus, innovative mitigation strategies should be exploited, to neutralize acidity and prevent mobilization of trace elements in AMD. The use of industrial byproducts has been considered an economically and environmentally effective alternative to remediate acid mine drainage. Therefore, the objective of this study was to evaluate the use of steel slag to mitigate acid mine drainage in a sulfidic material from a uranium mine, as an alternative to the use of limestone. Thus, increasing doses of two neutralizing agents were applied to a sulfidic material from the uranium mine Osamu Utsumi in Caldas, Minas Gerais State. A steel slag from the company ArcelorMittal Tubarão and a commercial limestone were used as neutralizing agents. The experiment was conducted in leaching columns, arranged in a completely randomized, [(2 x 3) + 1] factorial design, consisting of two neutralizing agents, three doses and one control, in three replications, totaling 21 experimental units. Electrical conductivity (EC), pH and the concentrations of Al, As, Ca, Cd, Cu, Fe, Mn, Ni, S, Se, and Zn were evaluated in the leached solutions. The trace element concentration was evaluated by ICP-OES. Furthermore, the CO2 emission was measured at the top of the leaching columns by capturing in NaOH solution and titration with HCl, in the presence of BaCl2. An increase in the pH of the leachate was observed for both neutralizing agents, with slightly higher values for steel slag. The EC was lower at the higher lime dose at an early stage of the experiment, and CO2 emission was greater with the use of limestone compared to steel slag. A decrease in trace element mobilization in the presence of both neutralizing agents was also observed. Therefore, the results showed that the use of steel slag is a suitable alternative to mitigate AMD, with the advantage of reducing CO2 emissions to the atmosphere compared to limestone.

Antibacterial activity of essential oils on Xanthomonas vesicatoria and control of bacterial spot in tomato

The objective of this work was to evaluate the effects of plant essential oils (EOs) on the growth of Xanthomonas vesicatoria, on bacterial morphology and ultrastructure, and on the severity of tomato bacterial spot. EOs from citronella, clove, cinnamon, lemongrass, eucalyptus, thyme, and tea tree were evaluated in vitro at concentrations of 0.1, 1.0, 10, and 100% in 1.0% powdered milk. The effect of EOs, at 0.1%, on the severity of tomato bacterial spot was evaluated in tomato seedlings under greenhouse conditions. The effects of citronella, lemongrass, clove, and tea tree EOs, at 0.1%, on X. vesicatoria cells were evaluated by transmission electron microscopy. All EOs showed direct toxic effect on the bacteria at a 10%-concentration in vitro. Under greenhouse conditions, the EOs of clove, citronella, tea tree, and lemongrass reduced disease severity. EOs of clove and tea tree, and streptomycin sulfate promoted loss of electron-dense material and alterations in the cytoplasm, whereas EO of tea tree promoted cytoplasm vacuolation, and those of citronella, lemongrass, clove, and tea tree caused damage to the bacterial cell wall. The EOs at a concentration of 0.1% reduce the severity of the disease.

Flow analysis by using solenoid valves for As(III) determination in natural waters by an on-line separation and pre-concentration system coupled to a tungsten coil atomizer

A flow system coupled to a tungsten coil atomizer in an atomic absorption spectrometer (TCA-AAS) was developed for As(III) determination in waters, by extraction with sodium diethyldithiocarbamate (NaDDTC) as complexing agent, and by sorption of the As(III)-DDTC complex in a micro-column filled with 5 mg C18 reversed phase (10 µL dry sorbent), followed by elution with ethanol. A complete pre-concentration/elution cycle took 208 s, with 30 s sample load time (1.7 mL) and 4 s elution time (71 µL). The interface and software for the synchronous control of two peristaltic pumps (RUN/ STOP), an autosampler arm, seven solenoid valves, one injection valve, the electrothermal atomizer and the spectrometer Read function were constructed. The system was characterized and validated by analytical recovery studies performed both in synthetic solutions and in natural waters. Using a 30 s pre-concentration period, the working curve was linear between 0.25 and 6.0 µg L-1 (r = 0.9976), the retention efficiency was 94±1% (6.0 µg L-1), and the pre-concentration coefficient was 28.9. The characteristic mass was 58 pg, the mean repeatability (expressed as the variation coefficient) was 3.4% (n=5), the detection limit was 0.058 µg L-1 (4.1 pg in 71 µL of eluate injected into the coil), and the mean analytical recovery in natural waters was 92.6 ± 9.5 % (n=15). The procedure is simple, economic, less prone to sample loss and contamination and the useful lifetime of the micro-column was between 200-300 pre-concentration cycles.

Estudo de homogeneidade de lote de material silício metálico candidato a material de referência

From the perspective of the uncertainties in chemical measurements all uncertainty sources should be part of the uncertainty of the reference material. When the primary methods are not available, interlaboratorial comparisons are used as a means of certification. The material to be distributed to the laboratories should have its homogeneity confirmed. The uncertainty due to this factor will be added to the characterization uncertainty. This work presents a homogeneity study of a lot of silicon metal of chemical degree where the uncertainty due to inhomogeneity is obtained using analysis of variance.

Design and evaluation of a continuous flow, integrated nebulizer-hydride generator for flame atomic absorption spectrometry

An evaluation of the performance of a continuous flow hydride generator-nebulizer for flame atomic absorption spectrometry was carried out. Optimization of nebulizer gas flow rate, sample acid concentration, sample and tetrahydroborate uptake rates and reductant concentration, on the As and Se absorbance signals was carried out. A hydrogen-argon flame was used. An improvement of the analytical sensitivity relative to the conventional bead nebulizer used in flame AA was obtained (2 (As) and 4.8 (Se) µg L-1). Detection limits (3σb) of 1 (As) and 1.3 (Se) µg L-1 were obtained. Accuracy of the method was checked by analyzing an oyster tissue reference material.

Caracterização detalhada de material de referência certificado de carvão brasileiro

The use and characterization of the first Certified Reference Material (CRM) of Brazilian coal for analytical quality control are presented. All results were determined within the limits of repeatability and reproducibility allowed under the standards. Notable among the characterization parameters was the mineral matter content (45.39%) obtained by an alternative procedure showing a low relative error (-2.1%) compared to the standard technique (low ashing temperature). The possible expanded application of this CRM application in national laboratories, beyond the certificated and reference parameters, has advantages such as lower cost and easy availability, but round robin tests must be performed.

Automatic and manual spray bar sections control

The use of precision farming tools in pesticide application technology can improve the techniques effectiveness during the spraying. Thus, this study aimed to compare automatic and manual systems to interrupt the syrup flow in the spray bar sections when applied in overlapped areas. The sprayings were carried out in eight places in completely randomized design. It was compared the spray consumption and the sprayed area in relation to the total area. The results indicated that in sprays performed with the automatic system there was an average savings of 17.2% of the sprayed volume. The sprayed area using the bar section's automatic control was an average 6.1% lower than the sprayed area with manual control.