Appadurai Daniel Reegan

Ovicidal and Oviposition Deterrent Activities of Medicinal Plant Extracts Against Aedes aegypti L. and Culex quinquefasciatus Say Mosquitoes (Diptera: Culicidae).

Objectives To evaluate the ovicidal and oviposition deterrent activities of five medicinal plant extracts namely Aegle marmelos (Linn.), Limonia acidissima (Linn.), Sphaeranthus indicus (Linn.), Sphaeranthus amaranthoides (burm.f), and Chromolaena odorata (Linn.) against Culex quinquefasciatus and Aedes aegypti mosquitoes. Three solvents, namely hexane, ethyl acetate, and methanol, were used for the preparation of extracts from each plant. Methods Four different concentrations—62.5 parts per million (ppm), 125 ppm, 250 ppm, and 500 ppm—were prepared using acetone and tested for ovicidal and oviposition deterrent activities. One-way analysis of variance (ANOVA) was used to determine the significance of the treatments and means were separated by Tukeys test of comparison. Results Among the different extracts of the five plants screened, the hexane extract of L. acidissima recorded the highest ovicidal activity of 79.2% and 60% at 500 ppm concentration against the eggs of Cx. quinquefasciatus and Ae. aegypti, respectively. Similarly, the same hexane extract of L. acidissima showed 100% oviposition deterrent activity at all the tested concentrations against Cx. quinquefasciatus and Ae. aegypti adult females. Conclusion It is concluded that the hexane extract of L. acidissima could be used in an integrated mosquito management program.

Larvicidal, Ovicidal, and Repellent Activities of Marine Sponge Cliona celata (Grant) Extracts against Culex quinquefasciatus Say and Aedes aegypti L. (Diptera: Culicidae)

Solvent extracts of marine sponge Cliona celata (Grant) were screened for larvicidal, ovicidal, and repellent properties against the filarial vector Culex quinquefasciatus Say and dengue vector Aedes aegypti L. Larvicidal and ovicidal activities of hexane, ethyl acetate, and methanol extracts were tested in four different concentrations ranging as 62.5, 125, 250, and 500 ppm. Among the three solvent extracts of C. celata, methanol extract showed the highest larvicidal activity at 500 ppm against both mosquito species. The LC50 and LC90 values of C. celata methanol extract were recorded as 95.63 and 242.16 ppm against C. quinquefasciatus larvae and 158.40 and 780.16 ppm against A. aegypti larvae, respectively. Ovicidal activity was high in methanol extract, in which 100% ovicidal activity was recorded in C. quinquefasciatus, and 72% ovicidal activity was recorded in A. aegypti at 500 ppm. The hexane extract was found to be the most effective protectant against the adult mosquitoes of both species. The mean protection time recorded in hexane extract was up to 273 and 165 min at 5 mg/cm2 dosage against C. quinquefasciatus and A. aegypti, respectively. Considering these bioactivities, C. celata could be used to obtain some novel pesticidal molecules.

Effect of niloticin, a protolimonoid isolated from Limonia acidissima L. (Rutaceae) on the immature stages of dengue vector Aedes aegypti L. (Diptera: Culicidae).

The aim of the present study was to evaluate the mosquitocidal activity of fractions and a compound niloticin from the hexane extract of Limonia acidissima L. leaves on eggs, larvae and pupae of Aedes aegypti L. (Diptera: Culicidae). In these bioassays, the eggs, larvae and pupae were exposed to concentrations of 2.5, 5.0, 7.5 and 10.0ppm for fractions and 0.5, 1.0, 1.5 and 2.0ppm for compound. After 24h, the mortality was assessed and the LC50 and LC90 values were calculated for larvae and pupae. Per cent ovicidal activity was calculated for eggs after 120h post treatment. Among the sixteen fractions screened, fraction 8 from the hexane extract of L. acidissima generated good mosquitocidal activity against Ae. aegypti. The LC50 and LC90 values of fraction 8 were 4.11, 8.04ppm against Ae. aegypti larvae and 4.19, 8.10ppm against Ae. aegypti pupae, respectively. Further, the isolated compound, niloticin recorded strong larvicidal and pupicidal activities. The 2ppm concentration of niloticin showed 100% larvicidal and pupicidal activities in 24h. The LC50 and LC90 values of niloticin on Ae. aegypti larvae were 0.44, 1.17ppm and on pupae were 0.62, 1.45ppm, respectively. Niloticin presented 83.2% ovicidal activity at 2ppm concentration after 120h post treatment and niloticin exhibited significant growth disruption and morphological deformities at sub lethal concentrations against Ae. aegypti. The structure of the isolated compound was identified on the basis of single XRD and spectral data ((1)H NMR and (13)C NMR) and compared with literature spectral data. The results indicate that niloticin could be used as a potential natural mosquitocide.

Current status of genome editing in vector mosquitoes: A review

Mosquitoes pose a major threat to human health as they spread many deadly diseases like malaria, dengue, chikungunya, filariasis, Japanese encephalitis and Zika. Identification and use of novel molecular tools are essential to combat the spread of vector borne diseases. Genome editing tools have been used for the precise alterations of the gene of interest for producing the desirable trait in mosquitoes. Deletion of functional genes or insertion of toxic genes in vector mosquitoes will produce either knock-out or knock-in mutants that will check the spread of vector-borne diseases. Presently, three types of genome editing tools viz., zinc finger nuclease (ZFN), transcription activator-like effector nucleases (TALEN) and clustered regulatory interspaced short palindromic repeats (CRISPR) and CRISPR associated protein 9 (Cas9) are widely used for the editing of the genomes of diverse organisms. These tools are also applied in vector mosquitoes to control the spread of vector-borne diseases. A few studies have been carried out on genome editing to control the diseases spread by vector mosquitoes and more studies need to be performed with the utilization of more recently invented tools like CRISPR/Cas9 to combat the spread of deadly diseases by vector mosquitoes. The high specificity and flexibility of CRISPR/Cas9 system may offer possibilities for novel genome editing for the control of important diseases spread by vector mosquitoes. In this review, we present the current status of genome editing research on vector mosquitoes and also discuss the future applications of vector mosquito genome editing to control the spread of vectorborne diseases.

Antimicrobial activity of some actinomycetes from Western Ghats of Tamil Nadu, India

Abstract Introduction Microbial diseases are increasing year by year and they are becoming a big threat to public health. There are more than 200 known diseases transmitted by bacteria, fungi, viruses, prions, rickettsia and other microbes to humans. The emergence of drug resistance to chemical drugs is the biggest threat in controlling human pathogens. Hence novel antimicrobial agents from actinomycetes are timely needed for the control of several human pathogens. Aim The aim was to find some actinomycetes with antimicrobial metabolites. Methods Soil samples were collected from Nilgiris district in Western Ghats of Tamil Nadu, India. Actinomycetes were isolated using serial dilution and plating techniques on actinomycetes isolation agar. Streptomycin and ketoconazole (25 μg/disc) were used as reference controls. The active strains were identified by 16S rRNA and phylogenetic tree was constructed; the sequences were submitted in the GenBank. Results Totally 106 actinomycete strains were isolated and cross streaked against various human microbial pathogens. Only 44 (41.50%) exhibited good antimicrobial activity against different pathogenic microbes. Five isolates (FMS-20, TGH-30, TGH-31, TGH-31-1 and IS-4) were chosen for secondary screening using filtrate. Among them FMS-20 filtrate showed good inhibition on the 16th day against all tested microbial pathogens. Further the intracellular methanol extract of FMS-20 showed maximum zone of inhibition against A. brasiliensis (22 mm) at 5 mg/disc. Similarly the extracellular ethyl acetate extract of FMS-20 showed maximum zone of inhibition against B. subtilis (25 mm). Conclusions The present work revealed that, among 106 actinomycetes screened, Streptomyces rimosus (FMS-20) (Accession No-KT827106) showed promising antimicrobial activity against all the tested human microbial pathogens.

Larvicidal, ovicidal and repellent activities of marine sponge Cliona celata (Grant) extracts against Anopheles stephensi Liston (Diptera: Culicidae)

OBJECTIVE To evaluate the larvicidal, ovicidal and repellent properties of solvent extracts of marine sponge Cliona celata (C. celata) (Grant) against the malarial vector Anopheles stephensi (An. stephensi) Liston. METHODS Marine sponge C. celata was thoroughly washed with distilled water and shade dried for 48 h. Then the sponges were homogenized and extracted sequentially with hexane, ethyl acetate and methanol. Larvicidal and ovicidal activities were tested at four different concentrations viz., 62.5, 125.0, 250.0 and 500.0 ppm. For repellent study extracts were taken in three different concentrations viz., 5.0, 2.5, 1.0 mg/cm at. RESULTS Among the three solvent extracts of C. celata, methanol extract showed the highest larvicidal activity at 500 ppm against the fourth instar larvae of An. stephensi. The LC50 and LC90 values of C. celata methanol extract were recorded as 80.61 and 220.81 ppm against An. stephensi larvae respectively. High ovicidal activity of 91.2% was recorded at 500 ppm concentration of methanol extract. The haxane extract was found to be the most effective protectant against the adult female mosquitoes of An. stephensi. The mean protection time recorded in hexane extract was up to 245 min at 5 mg/cm(2) dosage against An. stephensi adults. CONCLUSIONS The screening results suggest that the hexane and methanol extracts of C. celata are promising in mosquito control. Considering these bioactivities, C. celata could be probed further to obtain some novel pesticidal molecules.

Bioefficacy of ecbolin A and ecbolin B isolated from Ecbolium viride (Forsk.) Alston on dengue vector Aedes aegypti L. (Diptera: Culicidae)

Ecbolin A and ecbolin B were isolated from ethyl acetate extract of Ecbolium viride (Forsk.) Alston root and evaluated for larvicidal and growth disturbance activities against Aedes aegypti L. (Diptera: Culicidae). For larvicidal activity, the third instar larvae of A. aegypti were exposed to different concentrations viz., 1.0, 2.5, 5.0 and 10 ppm for each compound. Among the two compounds screened, ecbolin B recorded highest larvicidal activity with LC50 and LC90 values of 0.70 and 1.42 ppm, respectively. In control, the larval behaviour was normal. The active compound ecbolin B was tested for growth disruption activity at sub lethal concentrations viz., 0.5, 1.0 ppm and observed for malformation like larval gut elongation, larval longevity, intermediates, malformed adults, failed adult emergence and compared with methoprene. The results showed significant level of larva–pupa intermediates, pupa–adult intermediates, malformed adult emergence and less adult formation against A. aegypti. The histopathological results revealed a severe damage on the midgut epithelial columnar cells (CC) and cuboidal cells (CU) in ecbolin B treated larvae of A. aegypti. Similarly peritrophic membrane (pM) was also observed to be damaged in the treated larvae. The present results suggest that, ecbolin B could be used as a larvicidal agent against dengue vector A. aegypti.