Insecticidal efficacy of nanomaterials used to control mosquito, Culex quinquefasciatus Say, 1823 with special reference to their hepatotoxicity in rats.

The present study aimed to develop a novel methodology for controlling the mosquito larvae using different nanoparticles, with special reference to their effect on rats (a non-target mammalian model). The mosquito species of Culex quinquefasciatus was reared in the laboratory. Chitosan, silver nanoparticles and their combination as well as lavender (Lavandula officinalis) nanoemulsion with different concentrations were tested as biological insecticides against the mosquito larvae. Mammalian toxicity of the used nanoparticles were evaluated using 27 adult male rats, experimental rats were divided into 9 equal groups (n=3). The nanoparticles were added to the drinking water for 30 days. At the end of the study, blood and tissue samples were collected to assess the levels of the serum alanine aminotransferase and aspartate aminotransferase, different genes expression as interleukin 6 (IL-6) and IL-1ß activity. Histopathological and immunohistochemical studies using two markers (TNF-α and BAX expression) were also applied. The LC50 and LC90 were recorded for each tested nanoparticles, and also the changes of the treated mosquito larvae cuticle were assessed using the scanning electron microscopy. Green nanoemulsion (Lavandula officinalis) was more effective than metal (silver) or even biodegradable (chitosan) nanoparticles in controlling of Culex quiquefasciatus mosquito larvae, and also it proved its safety by evaluation of the mammalian hepatotoxicity of the tested nanoparticles.

Susceptibility of Culex quinquefasciatus (Say) Larvae to Methanolic Extracts of Annona reticulata.

<b>Background and Objective:</b> Environment pollution and resistance of many pests to the most frequently used chemical insecticides gave the rationale of altering to replace them with natural herbal extracts for pests and vector control. This study investigated the effect of methanolic extract of <i>Annona reticulata</i> on the mortality and development of larvae of <i>Culex quinquefasciatus</i>. <b>Materials and Methods:</b> Methanolic herbal extracts were analyzed using Reverse-Phase High-Performance Liquid Chromatography (RP-HPLC) to identify the phytochemical compounds in them. Ten mosquito larvae were used as replicates and exposed to each of the five concentrations of the plant extract (30, 100, 150, 200 and 250 mg mL¹) and ten larvae were exposed to double distilled water and considered as control. <b>Results:</b> Phytochemical analysis revealed the presence of phenols, steroids, quinones, tannins and saponins. Statistical analysis showed a significant strong correlation and regression between exposure to the different concentrations of the extract and mortality of <i>Culex quinquefasciatus</i> larvae where R² = 0.982, the Correlation value is 0.991099 (p<0.05). Results also showed that the extracts affect the development of larvae more than mortality. The effect of the extracts on the early larval stages was significantly high compared to the late stages of larvae. <b>Conclusion:</b> According to our knowledge results of this study has been reported for the first time in Saudi Arabia where <i>Annona reticulata</i> is neglected regionally and no study approved its efficacy as a botanical herbal extract against mosquitoes.

Exploring essential oils of Slovak medicinal plants for insecticidal activity: The case of Thymus alternans and Teucrium montanum subsp. jailae.

Thymus alternans and Teucrium montanum subsp. jailae are medicinal and aromatic plants, typical of Slovakian flora, producing bioactive essential oils. In the present study, we evaluated the insecticidal potential of the essential oils, obtained by hydrodistillation from the plant aerial parts and analysed by GC-MS, as insecticidal agents. For the purpose, they were assayed against three insect species acting as agricultural pests or vectors of medical relevance, such as the common housefly, Musca domestica L., the lymphatic filariasis vector, Culex quinquefasciatus and the Egyptian cotton leafworm Spodoptera littoralis; α-cypermethrin was tested as positive control. The two essential oils exhibited a different chemical profile, with monoterpenes and sesquiterpenes being the main fractions in the essential oils from Th. alternans and T. montanum subsp. jailae, respectively. Insecticidal tests showed that the T. montanum essential oil was effective against S. littoralis (LD50(90) = 56.7 (170.0) µg larva-1) and Cx. quinquefasciatus larvae (LC50(90) = 180.5 (268.7) mg L-1), whereas T. alternans essential oil displayed good toxicity against M. domestica adults (LD50(90) = 103.7 (223.9) µg adult-1). Overall, our results add useful knowledge about the potential of Slovakian flora as a source of botanicals for the eco-friendly management of insect pests and vectors.

Larvicidal potential of Nerium indicum and Thuja oriertelis extracts against malaria and Japanese encephalitis vector.

Ethanolic and acetone extracts of Nerium indicum and Thuja orientelis have been studied against III instar larvae of Anopheles stephensi and Culex quinquefasciatus. Ethanolic extract of N. indicum is found more effective than its acetone extract against anopheline larvae with LC50 values of 185.99 and 148.05 ppm for former and 229.28 and 149.43 ppm for the later after 24 and 48 hrs of exposure. The acetone extract with LC50 values of 209.00 and 155.97 ppm is more effective in case of culicine larvae than its ethanolic extract with LC50 494.07 and 194.49 ppm after 24 and 48 hours of treatment. Ethanolic extract of T. orientelis is more effective against both the larval species with LC50 values of 13.10 and 9.02 ppm after 24 and 48 hours for anopheline and 22.74 and 16.72 ppm against culicine larvae. The acetone extract showed LC50 values of 200.87 and 127.53 ppm against anopheline and 69.03 and 51.14 ppm against culicine larvae. Thus ethanolic extract of T. orientelis is an ideal potential larvicide for both types of mosquito larvae.

Larvicidal efficacy of Pavonia zeylanica L. and Acacia ferruginea D.C. against Culex quinquefasciatus Say.

Larvicidal efficacy of leaf extracts of Pavonia zeylanica and Acacia ferruginea were tested against the late third instar larvae of Culex quinquefasciatus. The larval mortality was observed after 24 h of treatment. The LC50 values of P. zeylanica and A. ferruginea were 2214.7 and 5362.6 ppm, respectively.

Loss of the membrane anchor of the target receptor is a mechanism of bioinsecticide resistance.

The mosquitocidal activity of Bacillus sphaericus is because of a binary toxin (Bin), which binds to Culex pipiens maltase 1 (Cpm1), an alpha-glucosidase present in the midgut of Culex pipiens larvae. In this work, we studied the molecular basis of the resistance to Bin developed by a strain (GEO) of C. pipiens. Immunohistochemical and in situ hybridization experiments showed that Cpm1 was undetectable in the midgut of GEO larvae, although the gene was correctly transcribed. The sequence of the cpm1(GEO) cDNA differs from the sequence we previously reported for a susceptible strain (cpm1(IP)) by seven mutations: six missense mutations and a mutation leading to the premature termination of translation. When produced in insect cells, Cpm1(IP) was attached to the membrane by a glycosylphosphatidylinositol (GPI). In contrast, the premature termination of translation of Cpm1(GEO) resulted in the targeting of the protein to the extracellular compartment because of truncation of the GPI-anchoring site. The interaction between Bin and Cpm1(GEO) and the enzyme activity of the receptor were not affected. Thus, Bin is not toxic to GEO larvae because it cannot interact with the midgut cell membrane, even though its receptor site is unaffected. This mechanism contrasts with other known resistance mechanisms in which point mutations decrease the affinity of binding between the receptor and the toxin.