Larvicidal and adulticidal activity of essential oils from plants of the Lamiaceae family against the West Nile virus vector,Culex pipiens (Diptera: Culicidae)

Culex pipiens mosquitoes are the most widely distributed primary vector of the West Nile virus worldwide. Many attempts for investigation of botanical pesticides to avoid the development of pesticide resistance to conventional synthetic pesticides that are recognized as a threat to the diversity of ecosystems. The study aimed to determine the components of three essential oils of Lamiaceae family, lavender (Lavandula angustifolia), peppermint (Mentha piperita L.), and rosemary (Rosmarinus officinalis L.) by gas chromatography-mass spectrometry (GC–MS) analysis. Furthermore, aimed to validate the insecticidal activities of these oils as larvicidal agents against the third instar larvae of Culex pipiens using five different concentrations (62.5, 125, 250, 500, and 1000 ppm) for each oil in five replicates and as an adulticidal agent against approximately three-day-old female adults of Cx. Pipiens using 0.5, 1, 2, 4, and 5% concentrations in three replicates. The results generally showed a dose-related response. At 1000 ppm, rosemary oil showed the highest larvicidal (100%) (LC₅₀, 214.97 ppm), followed by peppermint oil (92.00% mortality and LC₅₀ (269.35 ppm). Lavender oil showed the lowest efficacy with 87.20% mortality and LC₅₀ (301.11 ppm). At 5% oil concentration, the highest knockdown rate at 1 h was recorded for lavender oil (95.55%), followed by peppermint oil (88.89%) and lastly rosemary oil (84.44%). After 24 h, rosemary oil showed the lowest adult mortality rate (88.89%; LC₅₀, 1.44%), while lavender and peppermint oils both showed a 100% mortality rate, with (LC₅₀, 0.81% and 0.91%, respectively). The chemical constituents of the oils consisted of monoterpenes and sesquiterpenes that determined their insecticidal activities against the target insect stage. The study proposed that rosemary essential oil may be useful for the control of Cx. pipiens larvae as part of an integrated water treatment strategy, and lavender and peppermint oils may be used in an integrated plan for adult’s control.     

Larvicidal effects of some natural products on the Aedes aegypti mosquito,a vector of dengue fever and Zika virus

Natural products are considered a good choice in the biological control of mosquitoes because they are an effective way to eliminate larvae and prevent an increase in mosquito numbers, while simultaneously not polluting the environment or damaging health. This investigation was designed to study the potential toxicity of three species of algae, Caulerpa racemosa (Weber-van Bosse, 1909), Padina boryana (Thivy, 1966), and Turbinaria ornata (Turner J. Agardh, 1848), on the larvae of Aedes aegypti mosquito, the vector of dengue and Zika viruses. Among the studied species, Caulerpa racemosa showed the greatest effectiveness in eradicating A. aegypti larvae with an LC₅₀ = 43.5 ppm, followed by Padina boryana with an LC₅₀ = 51.93 ppm. Both species proved to be excellent candidates as a source of larvicidal agents and could be used commercially in mosquito control programs as eco-friendly biopesticides. The combined activity of different mixtures against mosquito larvae was expressed as the coeffective factor (C.F.). C.F. values showed that the joint activity of insect growth regulator Dudim in combination with Caulerpa racemosa and Padina boryana extracts produced degrees of potentiation effects and degrees of additive effects were obtained with Dudim in combination with Turbinaria ornata extract.     

Larvicidal effects of fungal Meroterpenoids in the control of Aedes aegypti L., the main vector of dengue and Yellow fever

The mosquito Aedes aegypti is an increasing problem of public health, being the vector responsible for dengue and Yellow Fever in tropical and subtropical regions. The aim of this work was to determine the potential larvicidal activity of a series of meroterpenoids, compounds 1-7, previously obtained fungal secondary metabolites from Penicillium sp., against the third-instar larvae of A. aegypti. The lethal concentrations (LC(50) and LC(90)) of 1-7 were evaluated 24 h after exposure. Dehydroaustin (4) was the most active meroterpenoid in the series, with an LC(50) value of 2.9 ppm, making it an attractive natural insecticide.     

Comparative larvicidal activity of essential oils from three medicinal plants against Aedes aegypti L

This work aimed at comparing larvicidal activity of essential oils extracted from the dried leaves of Alpinia speciosa, Cymbopogon citratus, and Rosmarinus officinalis against Ae. aegypti larvae. The larvae were observed for 4 h and at 24 h according to a completely randomized design with three replications and the following concentrations [μl/ml]: 0.25, 0.5, 1.0, 1.5, 2.0, 2.5, and controls were distilled water, and commercial standard citral, camphor, eucalyptol, α‐pinene, and β‐myrcene. The essential oil of C. citratus had the lowest LC₅₀ (0.28) and LC₉₀ (0.56) values, followed by that of A. speciosa (0.94 and 1.2, resp.) and of R. officinalis (1.18 and 1.67, resp.), and only the commercial standards citral and α‐pinene were larvicidal.     

Distribution and mitochondrial CO1-based genetic diversity of Aedes aegypti L (Culicidae: Diptera) in Saudi Arabia

Mosquitoes (Diptera: Culicidae) act as vectors for various pathogens and parasites that affect millions of people worldwide. Aedes aegypti (Linnaeus, 1762) is one of the devastating pests of humans, acting as a key vector of dengue viruses. Therefore, correct identification of this serious pest to determine its distribution is paramount in its management. Morphological identification is usually based on the maturity and quality of the specimens. This can still yield ambiguous results in distinguishing Ae. aegypti species due to limited taxonomic expertise and the presence of cryptic species. In this research, mitochondrial CO1 gene-based identification was adopted to analyze 7 samples, each containing 7 specimens of Ae. aegypti from various localities of Saudi Arabia: Jeddah (A1), Makkah (A2), Al Madinah Al Munawwarah (A4), Jazan (A5), Qunfudah (A6), Yanbu (A8), and Najran (A10). DNA barcoding and maximum likelihood (ML) tree analysis revealed that all 49 species belong to Ae. aegypti and showed high similarity with specimens of this species worldwide.     

Prevalence of dengue fever in Saudi Arabia: Jeddah as a case study

Dengue fever is widespread in tropical and subtropical regions, including Saudi Arabia. Aedes aegypti (Diptera: Culicidae) transmits dengue and many other diseases, including chikungunya and Zika. This study provides an overview of dengue fever in Saudi Arabia since the first case was recorded in the early 1990s. In addition, it focuses on the epidemiological situation in Jeddah as a case study to study the spatial distribution of dengue cases using Geographic Information Systems (GIS) techniques over 5 years, from 2019 to 2023. The first recorded case in Saudi Arabia was in October 1993; however, daily data indicates that 2023 is a major epidemic year. The number of infections has reached 4099 so far during the first half of the year, which indicates a significant increase compared to previous years. GIS analysis has unveiled the locations of high infection rates across multiple municipalities, commonly called hotspots, and identified areas where dengue cases remain relatively low. The Inverse Distance Weighted (IDW) tool was used to determine the severity of infection in different areas of Jeddah. The study concluded that factors such as temperature, rainfall, and septic tanks in areas that lack a proper sanitation network are the most contributing factors to the spread of disease vectors and, thus, dengue. Winter rainfall creates conducive breeding environments for dengue mosquito vectors, increasing transmission rates. On the other hand, summer heat accelerates the mosquito life cycle and enhances viral replication, heightening the risk of dengue transmission.     

Resistance development to bioinsecticides in Aedes aegypti (Culicidae: Diptera), the vector of dengue fever in Saudi Arabia

A laboratory strain of Aedes aegypti (L) was subjected repeatedly to larval selection pressure with two bacterial insecticides, spinosad (Saccharopolyspora spinosa) and bacilod (Bacillus thuringiensis israelensis). The results indicated that the mosquito Ae. aegypti acquired low resistance to spinosad and bacilod by about 3.1 and 2.4-fold, respectively, due to selection pressure for fifteen successive generations. The slope values of the selected strains were increased gradually from one generation to the next, indicating moderate homogeneity between individuals in their response to the test bio-insecticide. Moreover, larval selection with current bacterial bioinsecticides prolonged the time required to digest a blood meal. It showed an evident decrease in the reproductive potential of adult mosquitoes surviving selected larvae.     

The 2000 epidemic of Rift Valley fever in Saudi Arabia: mosquito vector studies

In mid-September 2000, Rift Valley fever (RVF) virus was diagnosed as the cause of infection in humans and livestock in Jizan Region, Saudi Arabia. This is the first time that this arbovirus has been found outside Africa and Madagascar. Collections of mosquitoes (Diptera: Culicidae) were therefore undertaken (from 25 September to 10 October) at eight sites during the epidemic to obtain mosquitoes for attempted RVF virus isolation. Among 23 699 mosquito females tested, six isolations of RVF virus were made from 15 428 Culex (Culex) tritaeniorhynchus Giles and seven from 8091 Aedes (Aedimorphus) vexans arabiensis Patton [corrected]. Minimum mosquito infection rates per 1000 at sites with infected mosquitoes were 0.3-13.8 Cx. tritaeniorhynchus and 1.94-9.03 Ae. v. arabiensis. Viral activity moved northwards as collecting was in progress and collectors 'caught up' with the virus at the two most northerly sites on the last two trapping evenings. Other species occurred in small numbers and were identified but not tested. Both Cx. tritaeniorhynchus and Ae. v. arabiensis were susceptible to RVF virus and transmitted between hamsters, and an additional quantitative test with Cx. tritaeniorhynchus showed that 71-73% of mosquitoes became infected after ingesting 6.9-7.9 log10 FFU/mL of virus; transmission rates were 10% (post-infection day 14) and 26% (post-infection day 20). It was concluded that both species were vectors on grounds of abundance, distribution, preference for humans and sheep, the virus isolations and vector competence tests.     

Chrysanthemum extract and extract prepared silver nanoparticles as biocides to control Aedes aegypti (L.), the vector of dengue fever

Mosquitoes play a key role in the transmission of some important diseases. The need for controlling these insects is critical to reduce their risks to human and domesticated animals. Recently the trend to explore effective chemical compounds from local plants has begun as a safe means of control. The present study aimed to evaluate the anti-larval activity of Chrysanthemum extract and the prepared silver nanoparticle (AgNPs) against the Aedes aegypti mosquito, the dengue vector in Saudi Arabia. A series of different concentrations of ethanol extract and extract prepared AgNPs against the fourth-life larvae was tested. The effective concentrations of crude extract and AgNPs ranged from 50 to 250 and 10 to 30 ppm respectively, and the death percentages corresponding to these concentrations ranged from 18 to 92 and 36 to 96% respectively. According to the LC₅₀ values of treated larvae, AgNPs (12.754 ppm) is more effective against A. aegypti mosquito larvae than the crude extract (228.345 ppm) at about 17.9 times. The mixing of the plant extract with the silver nitrate has led to potentiation. This is due to the synergy that occurs between the extract and the silver particles during the reduction process. The compounds in the extract are related to the surface of the particles, increasing the strength of their effects. It is recommend to separate the active elements in the Chrysanthemum plant and its preparation in the form of nanoparticles as a promising compound in mosquito control programs with least damage to human kind and the environment.     

Evaluation of the composition and in vitro antimicrobial,antioxidant, and anti-inflammatory activities of Cilantro (Coriandrum sativum L. leaves) cultivated in Saudi Arabia (Al-Kharj)

BackgroundIn the present study, we explored the composition of Cilantro (Coriandrum sativum L. leaves) essential oil (CEO) cultivated in Saudi Arabia (Al-Kharj) and explored its antioxidant, antimicrobial, and anti-inflammatory effects in vitro.MethodsGas chromatography-mass spectroscopy was used to detect the CEO composition. The 2, 2-diphenyl-1-picrylhydrazyl (DPPH)-induced free radical and ferric chloride scavenging methods were used to determine the antioxidant activity. Antimicrobial activity was investigated using the well diffusion method. Anti-inflammatory activity was evaluated using egg albumin and trypsin-induced inflammation methods.ResultsForty-six compounds representing 90.17% of the total aroma were identified in the CEO; the major constituents were found to be 1-decanol (17.85%), decanal (11.04%), trans-2-dodecen-1-ol (7.87%), menthone (6.71%), 2-decen-1-ol, trans- (5.44%), dodecanal (4.76%), trans-tetradec-2-enal (3.14%), sedanolide (3.02), and thymol (3.01%). DPPH-induced free radical and ferric chloride scavenging assays demonstrated low antioxidant effects of CEO, and the antioxidant activity was observed at a high CEO concentration. The antimicrobial activity of CEO was assessed against 5 microorganisms (bacteria and fungi) by using well diffusion methods; CEO was found to possess excellent antimicrobial activity against all microorganisms, except Escherichia coli. Moreover, CEO demonstrated strong anti-inflammatory activity against egg albumin- and trypsin-induced inflammation.ConclusionThe essential oil extracted from C. sativum chemotype grown in Al-Kharj region of Saudi Arabia possesses low antioxidant potential, superior antimicrobial activity, and outstanding anti-inflammatory effects.     

市售长叶松油和锡兰肉桂油对登革热媒蚊埃及伊蚊的灭幼效果(英文)

松油和桂皮油由于具有芳香性气味, 因而成为良好的成虫驱避剂, 但是关于它们对蚊虫的杀幼虫作用研究不多。为揭示市售的长叶松Pinus longifolia油和锡兰肉桂Cinnamomum zeylanicum油对来源于印度德里的埃及伊蚊Aedes aegypti 4龄幼虫的毒杀潜力, 我们进行了室内研究, 以幼虫死亡率及行为改变和形态改变等指标评估其杀幼虫潜力。结果表明： 两种油对埃及伊蚊4龄幼虫均具有毒杀作用, 且松油的灭幼效果优于桂皮油。松油的LC₅₀和LC₇₀ 值分别为0.33093 mg/L 和0.54476 mg/L, 而桂皮油的LC₅₀和LC₇₀ 值分别为0.63159 mg/L和0.77736。进一步观察发现, LC₉₀剂量下桂皮油的杀幼虫潜力强于松油, 其LC₉₀为1.11879 mg/L, 而松油的LC₉₀为 1.04915 mg/L。在处理的幼虫中观察到行为改变, 如兴奋、 坐立不安、 颤抖、 痉挛然后瘫痪, 说明这两种油可能对其神经肌肉系统产生了影响。显微观察处理幼虫的形态改变发现, 与对照相比, 大多数器官的外观正常, 只是肛鳃略为内收缩而引起结构畸形, 提示肛腮可能是这两种油的作用位点, 腮的功能异常引起了幼虫死亡。这两种油品可开发用作防治蚊虫的新型杀幼虫药剂。     

Synergistic repellent and irritant effect of combined essential oils on Aedes aegypti (L.) mosquitoes

This study was designed to compare the behavioral responses of Aedes aegypti to a single essential oil and to a mixture of two or three essential oils using an excito‐repellency test chamber. Mixtures were prepared from essential oils extracted from Litsea cubeba (LC), Litsea salicifolia (LS), and Melaleuca leucadendron (ML). In general, the mixture of essential oils produced a much stronger escape response by Ae. aegypti, regardless of the test conditions. No significant difference in escape responses was seen when the mixture of oils was compared with a standard commercial product containing DEET. Greater contact irritancy was seen from mixed oils of LC and LS than with other mixed oils. Mixtures of LC and LS at 0.075% showed the highest synergistic action (65.5% escaped) compared to that with unmixed oil alone at the same concentration (LC/20% and LS=32.2%). In addition, mixtures of LC and LS at 0.075% demonstrated the highest non‐contact repellency (62.7%) and showed a greater effect than the use of LC (20%) or LS (20.3%) alone. We conclude that mixtures of two essential oils show potential as active ingredients for mosquito repellents.     

Larvicidal activity of acetone extract and green synthesized silver nanoparticles from Allium sativum L. (Amaryllidaceae) against the dengue vector Aedes aegypti L. (Diptera: Culicidae)

Mosquito vectors of major human diseases are currently controlled using chemical and biological products. Extensive insecticide use has led to resistance development and human/environmental health risks, and alternative sustainable control options are needed; in this study, activity of an extract of garlic (Allium sativum; Amaryllidaceae), and silver nanoparticles (AgNPs) synthesized from the extract, were evaluated against 2nd and 3rd instar larvae of the yellow fever mosquito, Ae. aegypti (Diptera: Culicidae). Synthesis of AgNPs was confirmed using UV–Vis spectroscopy, and characterised using powdered X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Larvae were exposed to five concentrations (50, 100, 150, 200, 250 ppm) of garlic extract or synthesized AgNPs, with distilled water and silver nitrate solution (1 mM) as controls. The mortality of larvae was recorded after 6, 12, 24, 36, and 48 h following addition of the respective extracts.Dose- and time-dependent toxicity were recorded in both treatment groups with no mortality in control groups. Exposure to AgNPs at 250 ppm for 48 h yielded 100% mortality for both larval instars, with corresponding LC₅₀ values of 44.77 (2nd) and 62.82 ppm (3rd). Exposure to garlic extract resulted in similar 48-hour mortality (99 ± 0.77% (2nd) and 98 ± 1.10% (3rd), but consistently higher LC₅₀ values after all exposure times compared to AgNPs (e.g. 48-hour exposure: 108.42 ppm (2nd), 129.11 ppm (3rd), suggesting that AgNPs may potentially be used at lower concentrations for Ae. aegypti control.     

Genetic variation and subspecific status of the grey wolf (Canis lupus) in Saudi Arabia

This work represents the most extensive genetic study of the grey wolf (Canis lupus Linnaeus, 1758) in Arabia and the first considering genetic data from multiple locations within Saudi Arabia. Previous suggestion of the occurrence of two subspecies of wolves in Arabia is not supported by this study. The genetic evidence suggests that the wolves of Saudi Arabia are genetically variable and more closely related to the Eurasian wolf Canis lupus group (dog included) than to the Indian wolf C. l. pallipes. The genetic diversity observed for C. lupus in Saudi Arabia indicates that the subspecific status C. l. arabs should be retained for the Arabian wolf. What remains unclear is the degree to which genetic introgression from domestic dogs has influenced the composition and integrity of C. lupus in Saudi Arabia.     

Composition of the essential oils in various organs at different developmental stages of Ammi visnaga (L.) Lam. from Tunisia

The composition of the essential oils isolated by hydrodistillation from various organs at different development stages of Ammi visnaga (L.) Lam. growing in Tunisia was determined by GC/MS analysis. In particular, the oil profiles of the leaves, stems, flower buds, roots, umbels, and fruits have been examined during the whole life cycle. The oil from the flowering aerial parts was characterized by a high content of isoamyl 2-methylbutanoate. After flowering and during desiccation and fructification, the umbels and fruits expressed a high content of linalool. The oils, extracted from the roots collected in the vegetatif, buds floral, and floral stages, were rich in monoterpene aldehydes, oxygenated monoterpenes, and monoterpene hydrocarbons. The highest level of non-terpene hydrocarbons was found at the flower-bud stage, represented by 61.3% of nonane. Among the monoterpenes, sabinene (12.5%) and β-pinene (8.5%) were identified in the flower buds.     

Excito‐repellency of essential oils against an Aedes aegypti (L.) field population in Thailand

An investigation of the behavioral responses of Aedes aegypti (= Stegomyia aegypti) to various concentrations of essential oils (2.5, 5, and 10%) extracted from hairy basil (Ocimum americanum Linn), ginger (Zingiber officinale Roscoe), lemongrass (Cymbopogon citratus Stapf), citronella grass (Cymbopogon nardus Rendle), and plai (Zingiber cassumunar Roxb) were performed using an excito‐repellency test chamber. Results showed that Ae. aegypti exhibited varying levels of escape response in both the contact and noncontact chambers in response to different essential oils. The magnitude of the behaviors changed in a dose‐response fashion depending on the percent volume to volume concentration of oil used. A 2.5% concentration of hairy basil oil produced a significantly greater escape response compared to the other extracts at the same concentration (P< 0.05). Oils of ginger, lemongrass, and citronella produced stronger irritant and repellent responses at the median 5% concentration compared to the lowest and highest concentrations. There was marked suppression of escape for both contact and noncontact tests using 10% concentrations of hairy basil, lemongrass, and citronella, with high knockdown for all three oils after 30 min. Hairy basil and lemongrass had the highest insecticidal activity to Ae. aegypti, with LC₅₀ values of 6.3 and 6.7 percent, respectively. We conclude that the essential oils from native plants tested, and likely many other extracts found in plants, have inherent repellent and irritant qualities that should to be screened and optimized for their behavior‐modifying properties against Ae. aegypti and other biting arthropods of public health and pest importance.     

Genetic diversity among different species of the genus Leiurus (Scorpiones: Buthidae) in Saudi Arabia and the Middle East

The molecular phylogenetic relationship among two species of genus Leiurus, from Saudi Arabia with additional comparative sequence data available from Egypt, Oman and Turkey is presented. The molecular phylogeny was performed using maximum parsimony, neighbor joining and bayesian inference. Our results indicate a clear deep splitting between the Western clade, which represented by L. quinuestriatus sequences from Egypt and those from the Eastern clade which encompassing different Leiurus species from Saudi Arabia, Oman and Turkey was shown. Also, the phylogenetic relationship represents additional support for the taxonomic status of Arabian Leiurus species.     

Larvicidal and smoke repellency effect of Toddalia asiatica and Aegle marmelos against the dengue vector, Aedes aegypti (Insecta: Diptera: Culicidae)

Investigations were made to evaluate the larvicidal activity and smoke repellent potential of Toddalia asiatica (L.) and Aegle marmelos at different concentrations (20, 40, 60, 80 and 100 p.p.m.) against first to fourth instar larvae and pupae of Aedes aegypti (L.). The LC₅₀ of A. marmelos and T. asiatica against first instars was 50.960 and 47.893 p.p.m., respectively; against second instars, 52.979 and 50.922; third instars, 56.653 and 54.461; and fourth instars, 60.778 and 61.278. The LC₅₀ and LC₉₀ for A. marmelos and T. asiatica against pupae were 56.634 and 112.992, and 53.64 and 116.22 p.p.m., respectively. The smoke toxicity of T. asiatica against Ae. aegypti was greater than that of A. marmelos . Smoke-exposed gravid females oviposited fewer eggs when compared to those that were not exposed to smoke. Smoke-exposed females hatched a lower percentage of eggs compared to unexposed females.     

Chemical composition of the essential oils of ripe berries of Juniperus oxycedrus L., growing wild in Kosovo

The main objective of this work was to study the essential oil composition of ripe Juniperus oxycedrus L. berries and its natural variation among wild populations in Kosovo. Essential oil was analysed using GC-FID and GC–MS. Plant materials were collected from five locations in Kosovo in August and September of 2011. In total, twenty-seven compounds were identified in the essential oils. The main components were β-myrcene (45.5–56.9%), α-pinene (10.2–36.6%), dl-limonene (3.6–13.8%) and germacrene D (1.7–8.7%). Of the total identified compounds, monoterpenes constituted the highest percentage of all components (70.24–88.22%), followed by oxygenated sesquiterpenes (4.9–11.4%), sesquiterpenes (3.5–11.0%), oxygenated monoterpenes (0.2–2.7%) and oxygenated diterpenes (0.0–1.7). Hierarchical Cluster Analysis (HCA) and Principal Component Analyses (PCA) were used to identify any geographical variations in essential oil composition. Statistical analysis suggests that the clustering of populations is not related to their geographic location, but rather seemed to be linked to local selective forces acting on chemotype diversity.