A physical map for an Asian malaria mosquito, Anopheles stephensi

Physical mapping is a useful approach for studying genome organization and evolution as well as for genome sequence assembly. The availability of polytene chromosomes in malaria mosquitoes provides a unique opportunity to develop high-resolution physical maps. We report a 0.6-Mb-resolution physical map consisting of 422 DNA markers hybridized to 379 chromosomal sites of the Anopheles stephensi polytene chromosomes. This makes An. stephensi second only to Anopheles gambiae in density of a physical map among malaria mosquitoes. Three hundred sixty-three (363) probes hybridized to single chromosomal sites, whereas 59 clones yielded multiple signals. This physical map provided a suitable basis for comparative genomics, which was used for determining inversion breakpoints, duplications, and origin of novel genes across species.     

Larvicidal and pupicidal activity of spinosad against the malarial vector Anopheles stephensi

ObjectiveTo investigate the larvicidal and pupicidal activity of spinosad against Anopheles stephensi Listen.MethodsSpinosad from the actinomycete, Saccharopolyspora spinosa was tested against Anopheles stephensi at different concentrations (0.01, 0.02, 0.04, 0.06 and 0.08 ppm.), and against first to fourth instar larvae and pupae.ResultsThe larval mortality ranged from 36.1±1.7 in (0.01 ppm) to 79.3±1.8 (0.08 ppm) the first instar larva. The LC₅₀ and LC₉₀ values of first, second, third and fourth instar larva were 0.001, 0.031, 0.034, 0.036 and 0.0113, 0.102, 0.111, 0.113, respectively. The pupal mortality ranged from 33.0±2.0 (0.01 ppm) to 80.0±0.9 (0.08 ppm). The LC₅₀ and LC₉₀ values were 0.028 and 0.1020, respectively. The reduction percentage of Anopheles larvae was 82.7%, 91.4% and 96.0% after 24, 48, 72 hours, respectively, while more than 80% reduction was observed after 3 weeks.ConclusionsIn the present study spinosad effectively caused mortality of mosquito larvae in both the laboratory and field trial. It is predicted that spinosad is likely to be an effective larvicide for treatment of mosquito breeding sites.     

Wild chive oil is an extremely effective larvicide against malaria mosquito vector Anopheles stephensi

Objective: To assess the chemical composition and mosquito larvicidal potentials of essential oil of wild chive(Allium schoenoprasum L.) against Anopheles stephensi.Methods: In the search for an environmentally safer alternative mosquitoes control, the larvicidal efficacy of essential oil obtained from the leaves of Allium schoenoprasum L. against Anopheles stephensi was determined. The composition of chive essential oil was analyzed by gas chromatography–mass spectrometry. Results: In toxicity assays, the essential oil demonstrated substantial larvicidal activity against larvae of Anopheles stephensi with LC_(50) and LC_(90) values of 2.60, and 7.31 ppm after 24 h of exposure, respectively. Gas chromatography–mass spectrometry analysis of chive essential oil identified 35 components representing more than 97.31% of the total essential oil. The main constituents were sulfur compounds, including diallyl trisulfide(13.72%), 2-ethyl[1,3]dithiane(8.93%), allyl methyl trisulfide(8.77%), and trimethylene trisulfide(6.64%), respectively. Conclusions: This study demonstrated that wild chive essential oil has a rich source of eco-friendly bioactive compounds for use as a mosquito larvicide. The main reason for its extraordinary properties may be related to the high percentage of sulfur compounds.     

Effect of Vetiveria zizanioides L. Root extracts on the malarial vector,Anopheles stephensi Liston

ObjectiveTo evaluate the ovicidal and oviposition deterrent potential of the ethanolic extract from Vetiveria zizanioides (V. zizanioides) roots against the malarial vector, Anopheles stephensi (A. stephensi).MethodsThe dried clean V. zizanioides roots were powerdered and extracted with ethanol for 8 h in a soxhlet apparatus. After evaporation, the residue was dissolved in acetone. One hundred freshly laid eggs of A. stephensi were exposed to the extract at differnt concentrations for 48 h, and the hatch rate was calculated to evaluate the ovicidal activity. Those exposed to actone aqueous solution were used as control. The egg laying behavior of gravid female A. stephensi was also observed using oviposition deterrent test. Effective repellency (ER) was used to evaluate the oviposition deterrent activity.ResultsExposure to the crude ethanol extract of V. zizanioides reduced the hatchability rate of A. stephensi eggs, and zero hatchability was exerted at 375 ppm. In the oviposition deterrent test, the extract alleviated the egg laying with an ER of 78.9% at the highest concentration of 375 ppm and even 53.7% at the lowest concentration of 125 ppm. Moreover, the negative values of oviposition active index also suggests the extract was a good deterrent agent.ConclusionsThe ethanolic extract of V. zizanioides roots may be used an alternative pesticide to control A. stephensi at the early stage of life history, possibly due to the presence of various active chemical compounds.     

Mosquito adulticidal and repellent activities of botanical extracts against malarial vector, Anopheles stephensi Liston (Diptera: Culicidae)

ObjectiveTo determine the adulticidal and repellent activities of different solvent leaf extracts of Eclipta alba (E. alba) and Andrographis paniculata (A. paniculata) against malarial vector, Anopheles stephensi (An. stephensi).MethodsAdulticidal efficacy of the crude leaf extracts of E. alba and A. paniculata with five different solvents like benzene, hexane, ethyl acetate, methanol and chloroform was tested against the five to six day old adult female mosquitoes of An. stephensi. The adult mortality was observed after 24 h under the laboratory conditions. The repellent efficacy was determined against An. stephensi mosquito species at three concentrations viz., 1.0, 2.5 and 5.0 mg/cm² under laboratory conditions.ResultsAmong the tested solvents the maximum efficacy was observed in the methanol extract. The LC₅₀ and LC₉₀ values of E. alba and A. paniculata against adults of An. stephensi were 150.36, 130.19 ppm and 285.22, 244.16 ppm, respectively. No mortality was observed in controls. The chi-square values were significant at P<0.05 level. Methanol extract of E. alba and A. paniculata was produce maximum repellency against An. stephensi.ConclusionsFrom the results it can be concluded the crude extract of E. alba and A. paniculata was an excellent potential for controlling An. stephensi mosquitoes.     

Spinosad and neem seed kernel extract as bio-controlling agents for malarial vector, Anopheles stephensi and non-biting midge, Chironomus circumdatus

ObjectiveMidge egg masses are reported to support non-pathogenic strains of the cholera pathogen, Vibrio cholera (V. cholera). Mosquito born diseases have been reported to cause millions of death worldwide. The present research reveals the toxicity effect of spinosad and neem seed kernel extract (NSKE) against different larval stages of Anopheles stephensi (An. stephensi) and Chironomus circumdatus (Ch. circumdatus).MethodsThe neem seeds were collected from Marudamalai hills, Bharathiar University, Coimbatore, India. Neem seed kernels were powdered, extracted and diluted for different concentrations (2 ppm to 10 ppm). Spinosad was purchased from Kalpatharu pesticide Limited, Coimbatore, Tamil Nadu, India and thoroughly mixed with distilled water to prepare various concentrations (0.01 to 0.08 ppm) and used for bioassay.ResultsThe results depict that spinosad is more toxic in lower concentrations when compared to NSKE and mosquitoes are more susceptible than chironomids. Lethal concentrations were evaluated using the observed mortality. The lowest LC₅₀ value obtained from spinosad against An. stephensi and Ch. circumdatus were 0.002 05 ppm and 0.008 91 ppm. This study investigated on effect of Spinosad and NSKE on the biology of mosquito. The immature stages of both species were susceptible to Spinosad and NSKE. Spinosad and NSKE in individual as well as combined treatment provided additional days in development for mosquitoes.ConclusionsThe results conclude that Spinosad and NSKE are potential larvicides against An. stephensi and Ch. circumdatus.     

Effect of leaf essential oil of Coccinia indica on egg hatchability and different larval instars of malarial mosquito Anopheles stephensi

ObjectiveTo assess the larvicidal and egg hatching inhibition property of the leaf essential oil of Coccinia indica (C. indica) against Anopheles stephensi (An. stephensi).MethodsThe larvicidal potential of C. indica leaf essential oil was evaluated against 1st, 2nd, 3rd and 4th instars larvae of An. stephensi using WHO protocol. The 24h LC₅₀ and LC₉₀ values of the essential oil were determined following probit analysis. The egg hatching inhibition activity was also tested at 10, 20, 40, and 60 mg/L. The IC₅₀ value of essential oil was determined against eggs of An. stephensi.ResultsThe essential oil extracted from C. indica possessed excellent larvicidal and egg hatching inhibition activity against An. stephensi. The bioassays showed LC₅₀-LC₉₀ of 54.3-140.3, 65.5-155.6, 86.8-180.7 and 95.3-192.6 for 1st, 2nd, 3rd, and 4th larval instars, respectively. The 50% egg hatching inhibition concentration (IC₅₀) was noted at 16.5 mg/L.ConclusionsThe present finding suggest that the C. indica leaf essential oil provided an excellent potential for controlling An. stephensi mosquito at earlier stage of their life cycle.     

Genetic analysis of three new eye colour mutations in the mosquito, Anopheles stephensi

Three new eye colour mutants, scarlet eye (wsca), red-spotted eye (prs) and pigmentless eye (p) were isolated in the malaria vector, Anopheles stephensi. Genetic analysis revealed that all three mutants are sex-linked and recessive to the wild type. Scarlet eye is allelic to white eye but is not to either red-spotted eye or pigmentless eye, which are allelic to each other; 5.7% recombination was observed between the white eye and pigmentless eye loci.     

Selection of permethrin resistance in the malaria vector Anopheles stephensi.

The laboratory strain of Anopheles stephensi, a well-known urban malaria vector, was selected with permethrin, a synthetic pyrethroid at LD90 level up to five generations. The selection resulted in the development of resistance in F5 generation to the tune of 13-fold to permethrin and cross-resistance to the tune of 7-fold to cypermethrin, 9-fold to alphamethrin, and 10-fold to deltamethrin. The development of cross-resistance to 4% DDT was also noticed. The susceptibility status against 5% malathion was maintained throughout the five generations. The synergistic effect of piperonyl butoxide with permethrin did not overcome the development of resistance. The development of resistance showed a significant relationship between hatchability and different generations.     

Morphological and genetic characteristics of the malarial mosquito Anopheles beklemishevi (Diptera, Culicidae)

The paper presents morphological and genetic data on the malarial mosquito Anopheles beklemishevi Stegnii et Kabanova, 1976. It also provides morphological accounts of eggs, age stage IV larvae, and, firstly, pupae and imagoes. The paper considers it possible to use cytogenetic and molecular markers to identify An. beklemishevi.     

Indication of pyrethroid resistance in the main malaria vector, Anopheles stephensi from Iran

ObjectiveTo investiagte insecticide resistance in target species for better insecticide resistance managemnet in malaria control programs.MethodsThe status of insecticide resistance to different imagicides in Anopheles stephensi (An. stephensi) including DDT 4%, lambdacyhalothrin 0.50%, deltamethrin 0.05%, permethrin 0.75%, cyfluthrin 0.15% and etofenprox 0.50% was performed according to WHO standard method.ResultsThe mortality rate to lambdacyhalothrin, permethrin, cyfluthrin, deltamethrin, etofenprox and DDT was (88.0±3.2), (92.0±2.7), (52.0±5.0), (96.0±2.2), (90.0±3.0) and (41.0±5.7) percent, respectively at diagnostic dose for one hour exposure time followed by 24 h recovery period.ConclusionsThese results showed first indication of pyrethroid resistance in An. stephensi in a malarious area, from southern Iran. There is widespread, multiple resistances in the country in An. stephensi to organochlorine and some report of tolerance to organophosphate insecticides and recently to pyrethroids. However, results of this paper will provide a clue for monitoring and mapping of insecticide resistance in the main malaria vector for implementation of any vector control.     

Dark larva a new autosomal larval colour mutant in the malaria mosquito, Anopheles stephensi Liston

Anopheles stephensi is an important urban malaria vector, which is widely distributed throughout the Indian subcontinent. The said vector species has developed resistance to various insecticides and therefore, it is desirable to develop alternative strategies including genetic methods for its control. One of the requirements for such strategy is to establish morphological mutants and to establish the genetic basis of the same. Such mutant markers could be used in the construction of genetically modified strain/s in the genetic control programme of An. stephensi. The dark colour expresses in all larval stages and pupae with full penetarence and uniform expression in both the sexes. The viability of the mutant is as good as the wild type. The genetic studies of the dark larva revealed that the gene da is mono-factorial, autosomal and recessive to the wild type. The gene da is an excellent marker for An. stephensi.     

The feeding characteristics of mosquito larvae of the genus Anopheles]

Studies carried out on 6 species of malaria mosquitos revealed a relationship between the larval activity to scratch the substrate and their morphological and physiological features and also their development at different depth of feed immersion. The development of scratching capacity was compared in different species of Anopheles and Cellia subgenera.     

Astrodaucus persicus as a new source of bioinsectisides against malaria vector,Anopheles stephensi

Objective: To determine the larvicidal activities of petroleum ether, chloroform, ethyl acetate and methanol fractions of roots and fruits extracts of Astrodaucus persicus from Apiaceae family against malaria vector, Anopheles stephensi(An. stephensi).Methods: Twenty five third instar larvae of An. stephensi were exposed to various concentrations(10–160 g/L) of fractions and were assayed according to World Health Organization protocol. The larval mortality was calculated after 24 h treatment.Results: Among tested fractions, the highest larvicidal efficacy was observed from ethyl acetate fraction of fruits extract with 50% and 90% mortality values(LC_(50) and LC_(90)) of34.49 g/L and 108.61 g/L, respectively. Chloroform fraction of fruits extract was the second larvicidal sample with LC_(50) of 45.11 g/L and LC_(90) of 139.36 g/L. Petroleum ether fractions of fruits and roots and methanol fraction of fruits showed moderate toxicity against An. stephensi.Conclusions: Astrodaucus persicus is a potential source of valuable and natural larvicidal compounds against malaria vector, An. stephensi and can be used in mosquitoes control programs as an alternative to synthetic insecticides.