Spatial distribution & physicochemical characterization of the breeding habitats of Aedes aegypti in & around Kolkata, West Bengal, India.

Background & objectives: Dengue infection is endemic in several areas and the dengue virus is transmitted by Aedes mosquitoes. Thus, it becomes important to understand the breeding ecology of dengue vector and characterize the physicochemical parameters of its breeding habitat. The objective of this study was to analyze the physicochemical parameters of the breeding habitat of the dengue vector and to find out the nutrient composition of the habitat in and around Kolkata, West Bengal. In addition, a geographic information system (GIS) was used to map the disease prone areas for its effective management and prevention. Methods: Water samples were collected from various breeding habitats of Aedes mosquitoes of Kolkata and adjoining areas and were analysed for various physicochemical properties like acidity, alkalinity, hardness, electrical conductivity, total dissolved solids, concentration of chloride (Cl-), sodium (Na+), potassium (K+), fluoride (F-) in relation to larval prevalence. Results: Parameters like water pH, total dissolved solids, total hardness, electrical conductivity, concentration of chloride, sodium and potassium were seen to vary throughout the year. Certain parameters were found to be dependent on container type, like concentration of fluoride. Significant positive correlations were seen between per dip larval density and total dissolved solids (TDS) and electrical conductivity. Interpretation & conclusions: Water pH, electrical conductivity, total dissolved solids were seen to play a major role in the ovipositional preferences. Container type did not seem to affect TDS. Tyres had the highest TDS in most of the cases. Nutrient composition like sodium concentration was mostly found in the coconut shells, potassium concentration also showed the same. Thus, container type and various parameters and nutrients play a major role in determining where a gravid female mosquito will lay its eggs. It was observed that by altering various chemical and physical properties of breeding habitats it was possible to control the larvae survivability.

Characterization and Virulence of an Indigenous Soil Bacillus sp. Prospecting for Mosquito Control.

Aims: Aquatic habitat of the rice fields is the effective breeding site of the mosquitoes whose overcrowding would promote their pathogens. But no attention has been paid to these habitats for isolation and identification of the bacterial biocides. Therefore, the study was envisaged to isolate and identify the mosquitocidal bacteria from the unexplored rice field soil of the Burdwan district (a premier rice producer), West Bengal, India. It was also aimed to evaluate the virulence of the potent pathogenic organisms in the laboratory and field against the mosquitoes. Study Design: Laboratory and field study. Place and Duration of the Study: Parasitology and Microbiology Research Laboratory, Department of Zoology, The University of Burdwan, Burdwan 713104, West Bengal, India and Microbiology Laboratory, Crop Production Division, Central Rice Research Institute, Cuttack 753 006, Orissa, India. The study was conducted between June, 2011 to July 2012. Methodology: The soils were collected from the rice-fields, serially diluted up to 10-3 level, 100 μl suspension was plated on NA medium and incubated at 30±0.1ºC in the BOD incubator for 72 h. The colonies were checked under a phase-contrast microscope and those having spores were purified by dilution plating on NA plates. Phenotypic, biochemical and molecular characters of the bacteria were studied following standard methods. The mosquitocidal activity of the selected organism was assessed using different mosquito species both in the laboratory and field. Results: On the basis of phenotypic, biochemical and 16S rDNA (Acc. no. GU190368) analysis, the selected bacteria (Ts 116) was identified as Bacillus sp. In the laboratory, the LC50s of the Bacillus sp. Ts116 against late third instar larvae of An. subpictus, Ar. subalbatus and Cx. quinquefasciatus were (2.37, 2.2 and 9.6) X 106 bacteria/ml, respectively. After 7d, treatment with 100 ml suspension (containing 2.7x106 bacteria/ml) of bacteria/m3 breeding site effected 97.35, 95.65 and 100% mortality of An. subpictus, Ar. subalbatus and Cx. quinquefasciatus larvae, respectively. Conclusion: Indiscriminate use of chemical insecticides causes vector-resistance resulting in serious health and environmental hazards. The Bacillus sp. Ts116 (GU190368) of the rice fields had potential to be exploited in mosquito control programms.

Antibacterial potentiality of Argemone mexicana solvent extracts against some pathogenic bacteria

The sensitivity of two Gram positive (Staphylococcus aureus and Bacillus subtilis) and two Gram negative (Escherichia coli and Pseudomonas aeruginosa) pathogenic multi-drug resistant bacteria was tested against the crude extracts (cold aqueous, hot aqueous, and methanol extracts) of leaves and seeds of Argemone mexicana L. (Papaveraceae) by agar well diffusion method. Though all the extracts were found effective, yet the methanol extract showed maximum inhibition against the test microorganisms followed by hot aqueous extract and cold aqueous extract.