Epidemiological and entomological aspects of malaria in forestfringed villages of Sonitpur district, Assam

Background & objectives : Detailed epidemiological and entomological studies were undertaken inforest-fringed villages and a Tea Estate in Sonitpur, Assam to assess the malaria situation.Methods : Door-to-door active surveillance was carried out to collect blood samples. Thick and thinblood smears stained with Giemsa were used for malaria parasite detection. Mosquito collectionswere made using CDC miniature light-traps and hand catch methods from dusk-to-dawn.Results : 48% SPR, 49.1 Pf % was recorded from the study villages. Children between 10 and 14 yearswere most sufferers. Per trap night density of mosquitoes in human dwellings was 204.3 and incattlesheds — 908.7, An. minimus accounted for 20.7% of total malaria vectors.Interpretation & conclusion : The results showed high malaria risk in the study villages. High vectordensity with high parity rate, poor socio-economic conditions, lack of awareness, poor sanitation andcongenial atmosphere for mosquito proliferation are aggravating the malaria situation more complex inthe study area

Preliminary evaluation of mosquito larvicidal efficacy of plant extracts

Mosquitoes are the most important single group ofinsects in terms of public health importance, whichtransmit a number of diseases, such as malaria, filariasis,dengue, Japanese encephalitis, etc. causing millionsof deaths every year. Repeated use of syntheticinsecticides for mosquito control has disrupted naturalbiological control systems and led to resurgencesin mosquito populations. It has also resulted in thedevelopment of resistance1, undesirable effects onnon-target organisms and fostered environmental andhuman health concern2, which initiated a search foralternative control measures. Plants are considered asa rich source of bioactive chemicals3 and they may bean alternative source of mosquito control agents.Natural products of plant origin with insecticidalproperties have been tried in the recent past for controlof variety of insect pests and vectors. Essentialoils of leaf and bark of Cryptomeria japonica demonstratedhigh larvicidal activity against Aedesaegypti (Diptera: Culicidae) larvae4. Insecticidalactivity of plant essential oils has been well-describedby Isman5. Azadiractin, the active ingredient of neemhas long been recognised for its mosquito larvicidalcapability. The extracts of Murraya koenigii, Coriandrumsativam, Ferula asafetida and Trigonella foenumgraceum were found to be effective and showedencouraging results against Ae. aegypti6 and Culex(Diptera: Culicidae) mosquito larvae7. It is also reportedthat many compounds with insecticidal potentialhave been isolated from the genus Piper—Pipercide,isolated from Piper negrum (black piper) hasbeen found to be just as active against adjuki beanweevils as the pyrethroides8. Phytochemicals derivedfrom plant sources can act as larvicide, insect growthregulators, repellent and ovipositor attractant andhave different activities observed by many researchers9–11. However, insecticides of plant origin havebeen extensively used on agricultural pests and to avery limited extent, against insect vectors of publichealth importance.Northeastern region of India is considered as a majorbiodiversity hot spot. The eastern Himalayas range,which extends all through the northern border ofAssam, is a rich treasure house of many promisingmedicinal and aromatic plants. In the present communication,an attempt has been made to evaluate themosquito larvicidal efficacy of methanol and ethanolextracts of different parts of five indigenous plantsagainst Ae. albopictus (Diptera: Culicidae) and Culexquinquefasciatus larvae in laboratory conditions.Plant materials were collected from the foothill forestsof Sonitpur district, Assam bordering ArunachalPradesh during April and May 2005. They were segregatedas leaf, stem, bark, root and fruit/pericarp andair-dried in a shady place. Dried materials wereground in a table model grinder. The ground plant materialswere dipped in solvents (methanol and ethanol)Short Research Communications146 J VECT BORNE DIS 44, JUNE 2007in tightly capped jars separately for 48 h. The solventsalong with extracts were drained out, filtered andsemisolid extracts were obtained in vacuum usingrotary evaporator. The semisolid extracts were lyophilisedto obtain solid extracts. Stock solutions of desiredconcentration were prepared in distilled waterusing 1 ppm teepol as emulsifying agent and subsequentdilutions were made as per requirement. Larvicidalbioassay was carried out as per standard WHOtechniques in 500 ml glass beakers containing 250 mlof water and 25 numbers of late III or early IV instarmosquito larvae for various concentrations. Threedifferent concentrations of each extract were tried outat a time with six replicates. One control was kept witheach set of experiment and mortality was recordedafter 24 h. Five sets of experiments were conductedfor each extract. Tests were carried out under controlledlaboratory conditions (temperature 27 ± 2oC)against laboratory reared Ae. albopictus and Cx. quinquefasciatus(Diptera: Culicidae) larvae. Values obtainedwere subjected to log probit regression analysisto obtain LC50 and LC90 values with 95% confidencelimit12.The results showed that the larvicidal activity ofmethanol and ethanol extracts of five aromatic plantspecies against Ae. albopictus and Cx. quinquefasciatuslarvae varied according to plant species (Tables 1& 2). Methanol extract of Aristolochia saccata rootswas found to be the most effective against Ae. albopictuslarvae followed by ethanol extracts of A. saccata,Annona squamosa leaf and methanol extract ofA. squamosa leaf respectively. LC90 values of methanolextract of fruit/pericarp of Gymnopetelumcochinchinensis, bark of Caesalpinea species andethanol extract of stem of Piper species were obtainedat <200 ppm but methanol extract of seeds of G.cochinchinensis and stem of Piper species gave at<358 ppm against Ae. albopictus larvae (Table 1).Ethanol extract of leaf of A. squamosa was found tohave the most promising larvicidal activity againstCx. quinquefasciatus larvae. Methanol and ethanolextracts of A. saccata (root), methanol extract of A.squamosa (leaf) showed LC90 values at <100 ppmwhile methanol extract of G. cochinchinensis (fruit/pericarp), methanol and ethanol extract of Piper speciesshowed at <200 ppm and methanol extract of G.cochinchinensis (seed) showed at >302 ppm againstCx. quinquefasciatus larvae (Table 2).Long before the advent of synthetic insecticides,plants and their derivatives were used to kill pest ofagriculture, veterinary and public health. Sosan et al13reported larvicidal activities of essential oils of Ocimumgratissium, Cymbopogon citrus and Ageratumconyzoides against Ae. aegypti and achieved 100%mortality at 120, 200 and 300 ppm concentrationsrespectively. Similarly, it was reported that the essentialoil of Ipomoea cairica Linn. possesses remark-Table 1. Larvicidal efficacy of plant extracts against Ae. albopictus larvaeName of plant Part used Solvent used LC50 LC90 Regression equationAristolochia saccata Root Methanol 14.52 42.68 Y = 2.5683 *X+2.0164-do- Root Ethanol 17.30 58.51 Y = 2.3633 *X+2.0721Annona squamosa Leaf Methanol 20.26 86.59 Y = 1.9392 *X+2.4637-do- Leaf Ethanol 20.70 76.73 Y = 2.1991 *X+2.1020Gymnopetelum cochinchinensis Fruit/Pericarp Methanol 50.67 155.12 Y = 2.5821 *X+0.5927-do- Seed Methanol 100.42 312.45 Y = 2.3014 *X+0.3481Caesalpinea species Bark Methanol 53.66 169.41 Y = 2.3429*X+0.8638Piper species Stem Methanol 144.22 357.32 Y = 3.1826 *X–1.9688-do- Stem Ethanol 76.35 180.42 Y = 3.2525 *X–1.1333DAS et al : HERBAL MOSQUITO LARVICIDES 147able larvicidal properties as it could produce 100%mortality in the larvae of Cx. tritaeniorhynchus, Ae.aegypti, An. stephensi and Cx. quinquefasciatus mosquitoesat concentrations ranging from 100 to 170ppm14. Dwivedi & Kawasara15 found acetone extractof Lantana camara to be most effective against Cx.quinquefasciatus larvae at the dose of 1 ml/100 ml.Latha et al16 reported Piper longum and Zingiberwightianum extracts at 80 mg/l causing completemortality in Cx. quinquefasciatus and 60 mg/l for Cx.sitiens. In the present investigation LC90 values ofmethanol and ethanol extracts of roots of A. saccata,leaf of A. squamosa and fruits/pericarp of G.cochinchinensis against Ae. albopictus and Cx. quinquefasciatuslarvae ranged between 31.80 and 155ppm. Studies with essential oil of Ocimum americansand O. gratissium showed LC50 at 67 and 60 ppmrespectively against Ae. aegypti larvae17. In contrast,in the present study methanol and ethanol extracts ofroots of A. saccata, leaf of A. squamosa and fruits/pericarp of G. cochinchinensis against Ae. albopictusand Cx. quinquefasciatus larvae showed LC50 valuesbetween 6.96 and 57.4 ppm. Larvicidal activities ofthe plant extracts vary according to the plant species,the parts of the plant, the geographical location wherethe plants were grown and the application method.Plant could be an alternative source for mosquitolarvicides because they constitute a potential sourceof bioactive chemicals and generally free from harmfuleffects. Use of these botanical derivatives inmosquito control instead of synthetic insecticidescould reduce the cost and environmental pollution.Further studies on identification of active compounds,toxicity and field trials are needed to recommend theactive fraction of these plant extracts for developmentof eco-friendly chemicals for control of insect vectors.AcknowledgementThe authors are thankful to Dr. S.N. Dube, Director,Defence Research Laboratory, Tezpur, Assam, Indiafor extending necessary facilities, continuous supportand guidance in the study.References1. Brown AWA. Insecticide resistance in mosquitoes:pragmatic review. J Am Mosq Control Assoc 1986; 2: 123–40.2. Hayes JB Jr, Laws ER Jr. Handbook of pesticidetoxicology, v. 1. San Diego, CA: Academic Press 1991.3. Wink M. Production and application of pytochemicalsfrom an agricultural perspective. In: Van Beek TA, BretelerH, editors. Phytochemistry and agriculture. Oxford, UK:Clerendon Press 1993; p. 171–213.Table 2. Larvicidal efficacy of plant extracts against Cx. quinquefasciatus larvaeName of plant Part used Solvent used LC50 LC90 Regression equationAristolochia saccata Root Methanol 31.91 81.06 Y = 3.3086 *X-0.0062-do- Root Ethanol 19.83 60.44 Y = 2.5791 *X-1.6605Annona squamosa Leaf Methanol 17.70 64.29 Y = 2.1180 *X+2.3457-do- Leaf Ethanol 6.96 31.80 Y = 1.9441 *X+3.3592Gymnopetelum cochinchinensis Fruit/pericarp Methanol 57.4 108.3 Y = 4.1627 *X+2.3501-do- Seed Methanol 199.0 301.6 Y = 1.7586 *X+11.0557Caesalpinea species Bark Methanol 42.27 207.13 Y = 1.7586 *X+2.0573Piper species Stem Methanol 70.10 113.90 Y = 5.669 *X+5.4992-do- Stem Ethanol 57.4 108.3 Y = 4.1627 *X+2.3501148 J VECT BORNE DIS 44, JUNE 20074. Cheng SS, Chang HT, Chang ST, Tsai KH, Chen WJ.Bioactivity of selected plant essential oils against theyellow fever mosquito Aedes aegypti larvae. BioresTechnol 2003; 89(1): 99–102.5. Isman MB. Pesticides based on plant essential oils.Pesticide Outlook 1999; p. 68–72.6. Harve G, Kamath V. Larvicidal activity of plant extractsused alone and in combination with known syntheticlarvicidal agents against Aedes aegypti. Indian J ExptlBiol 2004; 42: 1216–9.7. Desai ST. Potency of larvicidal properties of plantextracts against mosquito larvae under laboratoryconditions (M.Sc. Dissertation submitted to MumbaiUniversity Mumbai, India 2002).8. Mwangi RW, Mukiama TK. Evaluation of Melia volkensiextract fractions as mosquito larvicides. J Am MosqControl Assoc 1988; 4: 442–7.9. Babu R, Murugan K. Interactive effect of neem seed kernaand neem gum extract on the control of Culex quinquefasciatusSay. Neem Newsletter 1998; 15(2): 9–11.10. Venketachalam MR, Jebasan A. Repellent activity ofFerronia elephantum Corr. (Rutaceae) leaf extract againstAedes aegypti. Biores Technol 2001; 76(3): 287–8.11. Venketachalam MR, Jebasan A. Larvicidal activity ofHydrocotyl javanica Thunb (Apiaceae) extract against Cx.quinquefasciatus. J Exptl Zool India 2001; 4(1): 99–101.12. Finney DJ. Probit analysis, III edn. Cambridge: CambridgeUniversity Press 1971.13. Sosan MB, Adewoyin FB, Adewunmi CO. Larvicidalproperties of three indigenous plant oils on the mosquitoAedes aegypti. Nigerian J Natl Prod Med 2001; 5: 30–3.14. Thomas TG, Rao S, Lal S. Mosquito larvicidal propertiesof an indigenous plant, Ipomoea cairica Linn. JapaneseJ Infect Dis 2004; 57: 176–7.15. Dwivedi SC, Karwasara K. Larvicidal activity of fiveplants extracts against Culex quinquefasciatus. Indian JEntomol 2003; 65(3): 335–8.16. Latha C, Vijhayakumar PD, Velayudhan S, Joseph A.Biological activity of indigenous plant extracts as mosquitolarvicides. Indian J Exptl Biol 1999; 37: 206–8.17. Cavalcanti ESB, Morais SM, Lima MAA, Santana EWP.Larvicidal activity of essential oils from Brazilian plantsagainst Aedes aegypti L. Mem Inst Oswaldo Cruz 2004;99(5): 541–4.Corresponding author: Dr. N.G. Das, Medical Entomology Division, Defence Researc

Seamounts : characteristics, formation, mineral deposits and biodiversity

Seamounts represent crust-mantle activities and are areas of petrological deviations, biodiversity, seismicity and hydrothermal events. An estimated ~50 million tons/year of basalts are required to produce seamounts suggesting intense oceanic volcanism. Seamounts either occur as chains perpendicular to the ridge or as isolated entities or in clusters. Seamounts may host basalts, hyaloclastites, gabbros and serpentinites and these variants perhaps evolve from multiple melting domains as a consequence of large-scale thermal structure and mantle lithology. Nonhotspot seamounts on a young, thin and hot lithosphere host tholeiites whereas the plume related ones on thick, older lithosphere may be either tholeiitic or alkaline. Seamounts may bear hydrothermal deposits (Fe, Mn, Co) rare metals and phosphorites. The resistance of seamounts to subduction could trigger slides; while shearing of seamounts buried in subduction zones leads to seismicity, both of which could cause tsunamis. Seamounts greatly affect the circulation patterns and currents, which in turn influence the surrounding biota. We review here the seamounts in terms of discovery, characteristics, distribution and their influence on the marine environment

Synergistic mosquito-repellent activity of Curcuma longa, Pogostemon heyneanus and Zanthoxylum limonella essential oils

SummaryMosquito repellents play an important role in preventing man–mosquito contact. In the present study, we evaluated the synergistic mosquito-repellent activity of Curcuma longa, Pogostemon heyneanus and Zanthoxylum limonella essential oils. The mosquito repellent efficacies of three essential oils were evaluated separately and in combination under laboratory and field conditions. N,N-Diethylphenylacetamide (DEPA) and dimethylphthalate (DMP) were used for comparison of the protection time of the mixture of essential oils. At an optimum concentration of 20%, the essential oils of C. longa, Z. limonella and P. heyneanus provided complete protection times (CPTs) of 96.2, 91.4 and 123.4min, respectively, against Aedes albopictus mosquitoes in the laboratory. The 1:1:2 mixture of the essential oils provided 329.4 and 391.0min of CPT in the laboratory and field trials, respectively. The percent increases in CPTs for the essential oil mixture were 30 for DMP and 55 for N,N-diethylphenylacetamide (DEPA). The synergistic repellent activity of the essential oils used in the present study might be useful for developing safer alternatives to synthetic repellents for personal protection against mosquitoes

Sustainable management practices for broodstock development, incubation and hatching of Macrobrachium rosenbergii using probiotics in a model hatchery of Bangladesh

The influences of probiotics Sanolife MIC comparing with antibiotics OTC were tested in both water quality and growth parameters for the brood-stock development, incubation and hatching of Macrobrachium rosenbergii. The study was to find out a sustainable practice of hatchery management applying probiotics instead of using antibiotics frequently. Influences of the application of three doses, Sanolife MIC @0.50, 0.65 and 0.80 ppm in water were checked in egg incubation, spawning and hatching phases. Sanolife Pro-1 @4 ppm was used in the feed of brood-stock as a supporting gut-probiotic in all the three trials with MIC. Findings of MIC based trials were compared with a control group of treatments with antibiotic OTC (@4.0 ppm in favor of the objectives of the study. Among three doses as 0.50, 0.65 and 0.80 ppm of MIC, the dose 0.65 ppm was found to be best in respect to the findings of the study. Water pH, DO, NH3, NO3 and NO2 level were found to be comparatively more stable and more favorable in probiotics based trials than that of antibiotic. Increased feeding appetite of spawners, earlier (4 days) embryonic development, higher (9%) hatching rate, 3% less disability of new hatchlings, better physical condition and higher (10%) rate of attraction to illumination of new hatchlings and absence of disease contamination in probiotic based trial (trial with 0.65 ppm) revealed much better efficiency and sustainability of using probiotics than that of antibiotic in rearing phases of berried prawn brood-stocks

Diffusion of particles moving with constant speed

The propagation of light in a scattering medium is described as the motion of a special kind of a Brownian particle on which the fluctuating forces act only perpendicular to its velocity. This enforces strictly and dynamically the constraint of constant speed of the photon in the medium. A Fokker-Planck equation is derived for the probability distribution in the phase space assuming the transverse fluctuating force to be a white noise. Analytic expressions for the moments of the displacement $$ along with an approximate expression for the marginal probability distribution function $P(x,t)$ are obtained. Exact numerical solutions for the phase space probability distribution for various geometries are presented. The results show that the velocity distribution randomizes in a time of about eight times the mean free time ($8t^*$) only after which the diffusion approximation becomes valid. This factor of eight is a well known experimental fact. A persistence exponent of $0.435 \pm 0.005$ is calculated for this process in two dimensions by studying the survival probability of the particle in a semi-infinite medium. The case of a stochastic amplifying medium is also discussed.Comment: 9 pages, 9 figures(Submitted to Phys. Rev. E

Invisible decays of Higgs and other mesons in models with singlet neutrinos in large extra dimensions

In light of current atmospheric neutrino oscillation data, we revisit the invisible decay of the standard model Higgs boson and other pseudoscalar mesons which can be enhanced because of large number of KK modes in models with right handed singlet neutrinos in large extra dimensions. We find that the invisible decay rate of Higgs can be as large as $H\to b \bar b$ decay rate only for a very restricted region of parameter space. This parameter space is even further restricted if one demands that the dimensionless neutrino Yukawa coupling \l is O(1). We have also studied the scenarios where singlet neutrino propagate in a sub-space, which lowers the string scale $M_{\ast}$ and keeps neutrino Yukawa coupling O(1). We have also considered decays of other spin-0 mesons to $\nu \bar\nu$ and found the rates to be too small for measurement.Comment: 14 pages, Latex, 4 postscript figures. Includes further discussions of invisible decay of Higgs and other mesons in the asymmetric scenario, where singlet neutrinos propagate in extra-dimensions with the largest size. Final conclusion remain unchanged. More references added, version to appear in PL

The outer halos of elliptical galaxies

Recent progress is summarized on the determination of the density distributions of stars and dark matter, stellar kinematics, and stellar population properties, in the extended, low surface brightness halo regions of elliptical galaxies. With integral field absorption spectroscopy and with planetary nebulae as tracers, velocity dispersion and rotation profiles have been followed to ~4 and ~5-8 effective radii, respectively, and in M87 to the outer edge at ~150 kpc. The results are generally consistent with the known dichotomy of elliptical galaxy types, but some galaxies show more complex rotation profiles in their halos and there is a higher incidence of misalignments, indicating triaxiality. Dynamical models have shown a range of slopes for the total mass profiles, and that the inner dark matter densities in ellipticals are higher than in spiral galaxies, indicating earlier assembly redshifts. Analysis of the hot X-ray emitting gas in X-ray bright ellipticals and comparison with dynamical mass determinations indicates that non-thermal components to the pressure may be important in the inner ~10 kpc, and that the properties of these systems are closely related to their group environments. First results on the outer halo stellar population properties do not yet give a clear picture. In the halo of one bright galaxy, lower [alpha/Fe] abundances indicate longer star formation histories pointing towards late accretion of the halo. This is consistent with independent evidence for on-going accretion, and suggests a connection to the observed size evolution of elliptical galaxies with redshift.Comment: 8 pages. Invited review to appear in the proceedings of "Galaxies and their Masks" eds. Block, D.L., Freeman, K.C. & Puerari, I., 2010, Springer (New York

Transfer measurements for the Ti plus Ni systems at near barrier energies

Large enhancements have been observed in the sub-barrier fusion cross sections for Ti + Ni systems in our previous studies. Coupled channel calculations incorporating couplings to 2(+) and 3(-) states failed to explain these enhancements completely. A possibilty of transfer channels contributing to the residual enhancements had been suggested. In order to investigate the role of relevant transfer channels, measurements of one- and two-nucleon transfer were carried out for Ti-46,Ti-48 + Ni-64 systems. The present paper gives the results of these studies

Bulk dynamics for interfacial growth models

We study the influence of the bulk dynamics of a growing cluster of particles on the properties of its interface. First, we define a {\it general bulk growth model} by means of a continuum Master equation for the evolution of the bulk density field. This general model just considers arbitrary addition of particles (though it can be easily generalized to consider substraction) with no other physical restriction. The corresponding Langevin equation for this bulk density field is derived where the influence of the bulk dynamics is explicitly shown. Finally, when it is assumed a well-defined interface for the growing cluster, the Langevin equation for the height field of this interface for some particular bulk dynamics is written. In particular, we obtain the celebrated Kardar-Parisi-Zhang (KPZ) equation. A Monte Carlo simulation illustrates the theoretical results.Comment: 6 pages, 2 figure