Search Results (16)

In Brazil, public health programs have relied predominantly on chemical insecticides to control Aedes aegypti, Anopheles spp., Culex quinquefasciatus, triatomines, and phlebotomines. Rising vector-borne disease incidence and insecticide resistance (IR) call for a critical appraisal of historical and current control practices. This literature review compiles secondary data produced from 1901 to 2024 obtained from Medline/PubMed, Google Scholar, and governmental notes and reports. Brazil’s vector control progressed from organochlorines (e.g., DDT) to organophosphates, carbamates, pyrethroids, insect growth regulators, microbial larvicides (Bti and Lsp), spinosad, and recently formulations with dual active-ingredient. Ae. aegypti showed widespread resistance to temephos and pyrethroids, decreased susceptibility to pyriproxyfen, and no documented Bti resistance. Anopheles spp. exhibited low to moderate resistance to pyrethroids. Cx. quinquefasciatus resistance is likely influenced by collateral exposure from Aedes control and domestic use. Regarding triatomines and phlebotomines, there was a predominant reliance on pyrethroids; most studies indicate their susceptibility to these compounds. In short, Brazil’s century-long, insecticide-centric strategy has delivered episodic gains but fostered Aedes aegypti resistance. For other species, for which there is no dedicated program for a long period, data on resistance are scarce or nonexistent. Sustainable progress requires strengthened, nationwide IR surveillance and entomological mapping to coordinate cross-program actions. Full article

The increase in the world population and consequent rise in food demand have led to the extensive use of chemical pesticides, causing environmental and health concerns. In response, biological control methods, particularly those involving microbial agents, have emerged as sustainable alternatives within integrated pest management. This study highlights the potential of Lysinibacillus fusiformis as a biocontrol agent against the dipteran Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), a pest responsible for damaging soft-skinned fruits. Experimental treatments using vegetative cells, spores, and secondary metabolites of L. fusiformis on D. suzukii larvae demonstrated significant larvicidal effects, accompanied by observable changes in gut morphology under microscopy. Moreover, preliminary immunological assays showed the interference of this bacterium with the host immune system. All the results indicate the suitability of L. fusiformis for its possible integration into sustainable agricultural practices, although additional research is required to understand its applicability in the field. Full article

Bacillus thuringiensis (Bt) is widely recognized as the most important microbial pesticide controlling various insect pests and diseases due to its insecticidal crystal proteins (ICPs) and antimicrobial metabolites. The current study investigates the biocontrol potential of B. thuringiensis GBAC46 against the fungal pathogen Fusarium verticillioides and the insect pest Spodoptera frugiperda through multiple mechanisms. Phenotypic experiments revealed that GBAC46 effectively inhibited F. verticillioides growth by inducing reactive oxygen species (ROS) accumulation and showed enhanced larvicidal activity against second instar S. frugiperda larvae. Pot experiments showed that feeding by S. frugiperda enhanced F. verticillioides infection in maize. The Bt strain GBAC46 effectively controlled both pests and diseases in greenhouse maize seedlings. Applying the Bt strain GBAC46 reduced feeding damage from S. frugiperda, decreased leaf yellowing and wilting caused by F. verticillioides, and improved growth indicators such as plant height, fresh weight, and dry weight. RT-qPCR results revealed that the Bt strain GBAC46 induced key defense genes in maize involved in activating salicylic acid, jasmonic acid, and ethylene pathways. The overall study demonstrated and confirmed the GBAC46 strain as a promising microbial agent for disease and pest management. Full article

Rhamnolipids, biosurfactants synthesized from natural resources, demonstrate significant applications, including notable insecticidal efficacy against Aedes aegypti L., the primary vector for numerous arboviruses. The global spread of A. aegypti poses substantial public health challenges, requiring innovative and sustainable control strategies. This research investigates the use of andiroba (Carapa guianensis Aubl.) biomass waste as a substrate for synthesizing a rhamnolipid biosurfactant (BSAW) produced by Pseudomonas aeruginosa and evaluates its insecticidal activity against A. aegypti. The findings indicate a biosurfactant yield of 4.42 mg mL⁻¹, alongside an emulsification index approaching 60%. BSAW successfully reduced both surface and interfacial tensions to below 30 mN/m and 4 mN/m, respectively. Characterization revealed that BSAW is a di-rhamnolipid, consisting of two rhamnose units covalently linked to a saturated C₁₀ fatty acid chain. At a concentration of 1.0 mg mL⁻¹, BSAW exhibited notable larvicidal activity, leading to structural impairments and cellular dysfunctions in A. aegypti larvae while also disrupting their associated bacterial microbiota. Moreover, BSAW effectively deterred oviposition in adult mosquitoes. These findings underscore BSAW’s potential to compromise various developmental stages of A. aegypti, supporting integrated arbovirus management approaches. Furthermore, this research emphasizes the feasibility of utilizing agro-industrial waste as substrates for microbial rhamnolipid production. Full article

Culex quinquefasciatus resistance to the binary (Bin) toxin, the major larvicidal component from Lysinibacillus sphaericus, is associated with mutations in the cqm1 gene, encoding the Bin-toxin receptor. Downregulation of the cqm1 transcript was found in the transcriptome of larvae resistant to the L. sphaericus IAB59 strain, which produces both the Bin toxin and a second binary toxin, Cry48Aa/Cry49Aa. Here, we investigated the transcription profiles of two other mosquito colonies having Bin resistance only. These confirmed the cqm1 downregulation and identified transcripts encoding the enzyme pantetheinase as the most downregulated mRNAs in both resistant colonies. Further quantification of these transcripts reinforced their strong downregulation in Bin-resistant larvae. Multiple genes were found encoding this enzyme in Cx. quinquefasciatus and a recombinant pantetheinase was then expressed in Escherichia coli and Sf9 cells, with its presence assessed in the midgut brush border membrane of susceptible larvae. The pantetheinase was expressed as a ~70 kDa protein, potentially membrane-bound, which does not seem to be significantly targeted by glycosylation. This is the first pantetheinase characterization in mosquitoes, and its remarkable downregulation might reflect features impacted by co-selection with the Bin-resistant phenotype or potential roles in the Bin-toxin mode of action that deserve to be investigated. Full article

Culicoides are small biting midges with the capacity to transmit important livestock pathogens around much of the world, and their impacts on animal welfare are likely to expand. Hemorrhagic diseases resulting from Culicoides-vectored viruses, for example, can lead to millions of dollars in economic damages for producers. Chemical insecticides can reduce Culicoides abundance but may not suppress population numbers enough to prevent pathogen transmission. These insecticides can also cause negative effects on non-target organisms and ecosystems. RNA interference (RNAi) is a cellular regulatory mechanism that degrades mRNA and suppresses gene expression. Studies have examined the utility of this mechanism for insect pest control, and with it, have described the hurdles towards producing, optimizing, and applying these RNAi-based products. These methods hold promise for being highly specific and environmentally benign when compared to chemical insecticides and are more transient than engineering transgenic insects. Given the lack of available control options for Culicoides, RNAi-based products could be an option to treat large areas with minimal environmental impact. In this study, we describe the state of current Culicoides control methods, successes and hurdles towards using RNAi for pest control, and the necessary research required to bring an RNAi-based control method to fruition for Culicoides midges. Full article

Using essential oils to control vectors, intermediate hosts, and disease-causing microorganisms is a promising approach. The genus Croton in the family Euphorbiaceae is a large genus, with many species containing large amounts of essential oils, however, essential oil studies are limited in terms of the number of Croton species investigated. In this work, the aerial parts of C. hirtus growing wild in Vietnam were collected and analyzed by gas chromatography/mass spectrometry (GC/MS). A total of 141 compounds were identified in C. hirtus essential oil, in which sesquiterpenoids dominated, comprising 95.4%, including the main components β-caryophyllene (32.8%), germacrene D (11.6%), β-elemene (9.1%), α-humulene (8.5%), and caryophyllene oxide (5.0%). The essential oil of C. hirtus showed very strong biological activities against the larvae of four mosquito species with 24 h LC₅₀ values in the range of 15.38–78.27 μg/mL, against Physella acuta adults with a 48 h LC₅₀ value of 10.09 μg/mL, and against ATCC microorganisms with MIC values in the range of 8–16 μg/mL. In order to provide a comparison with previous works, a literature survey on the chemical composition, mosquito larvicidal, molluscicidal, antiparasitic, and antimicrobial activities of essential oils of Croton species was conducted. Seventy-two references (seventy articles and one book) out of a total of two hundred and forty-four references related to the chemical composition and bioactivity of essential oils of Croton species were used for this paper. The essential oils of some Croton species were characterized by their phenylpropanoid compounds. The experimental results of this research and the survey of the literature showed that Croton essential oils have the potential to be used to control mosquito-borne and mollusk-borne diseases, as well as microbial infections. Research on unstudied Croton species is needed to search for species with high essential oil contents and excellent biological activities. Full article

Chemical compounds from plants have been used as a medicinal source for various diseases. Aromachology is a unique field that studies the olfactory effects after inhaling aromatic compounds. Aromatherapy is a complementary treatment methodology involving the use of essential oils containing phytoncides and other volatile organic compounds for various physical and mental illnesses. Phytoncides possess an inherent medicinal property. Their health benefits range from treating stress, immunosuppression, blood pressure, respiratory diseases, anxiety, and pain to anti-microbial, anti-larvicidal, anti-septic, anti-cancer effects, etc. Recent advancements in aromatherapy include forest bathing or forest therapy. The inhalation of phytoncide-rich forest air has been proven to reduce stress-induced immunosuppression, normalize immune function and neuroendocrine hormone levels, and, thus, restore physiological and psychological health. The intricate mechanisms related to how aroma converts into olfactory signals and how the olfactory signals relieve physical and mental illness still pose enormous questions and are the subject of ongoing research. Aromatherapy using the aroma of essential oils/phytoncides could be more innovative and attractive to patients. Moreover, with fewer side effects, this field might be recognized as a new field of complementary medicine in alleviating some forms of physical and mental distress. Essential oils are important assets in aromatherapy, cosmetics, and food preservatives. The use of essential oils as an aromatherapeutic agent is widespread. Detailed reports on the effects of EOs in aromatherapy and their pharmacological effects are required to uncover its complete biological mechanism. This review is about the evolution of research related to phytoncides containing EOs in treating various ailments and provides comprehensive details from complementary medicine. Full article

Aedes albopictus is the sole vector for various mosquito-borne viruses, including dengue, chikungunya, and Zika. Ecofriendly biological agents are required to reduce the spread of these mosquito-borne infections. Mosquito densoviruses (MDVs) are entomopathogenic mosquito-specific viruses, which can reduce the capacity of isolated vectors and decrease mosquito-borne viral disease transmission. However, their variable pathogenicity restricts their commercial use. In the present study, we developed a series of novel larvicide oil suspensions (denoted Bacillus thuringiensis (Bti) oil, Ae. albopictus densovirus (AalDV-5) oil, and a mixture of AalDV-5+Bti oil), which were tested against Ae. albopictus larvae under experimental semi-field and open-field conditions. The effect of AalDV-5 on non-target species was also evaluated. The combined effect of AalDV-5+Bti was greater than that of individual toxins and was longer lasting and more persistent compared with the laboratory AalDV-5 virus strain. The virus was quantified on a weekly basis by quantitative polymerase chain reaction (qPCR) and was persistently detected in rearing water as well as in dead larvae. Wildtype densovirus is not pathogenic to non-target organisms. The present findings confirm the improved effect of a mixed microbial suspension (AalDV-5+Bti oil) larvicide against Ae. albopictus. The development and testing of these products will enable better control of the vector mosquitoes. Full article

Infectious diseases and their vectors have remained a concern for human population from their historical origin. Microbial pathogens have also emerged as a potent threat to the healthcare systems even in developed countries. Essential oils remain a less explored method for infectious disease control; besides, the ultrasound-assisted extraction (UAE) of essential oil production has emerged as promising source of bioactive volatiles over conventional methods. This study analyzed the possible use of UAE- Essential oils (EOs) from different species of Ocimum plants (Ocimum basilicum (OB), O. gratissimum (OG), O. tenuiflorum (OT), and O. canum (OC)) in the management of microbial pathogens and mosquito larval control. The antibacterial activity was estimated in terms of a disc diffusion assay and minimum inhibitory concentrations against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Salmonella enteritidis. The larvicidal property was found using three important mosquito vectors and the LC₅₀ value was determined. Furthermore, antioxidant and anti-inflammatory properties were estimated in terms of radical scavenging activities and the inhibition of lipoxygenase enzyme activity. The EOs exhibited significant DPPH radical scavenging (high in OG), hydrogen-peroxide scavenging (OB) and lipoxygenase inhibition (OB). The antibacterial activity was high in OB and OG (p < 0.05) and the larvicidal activity was of higher sensitivity against Aedis and Culex, whereas Armigeres was more resistant. However, no sign of toxicity in the Allium cepa model or non-targeted organism Guppy fishes was observed. Overall, the UAE extracted Ocimum essential oils were found to be effective against various human pathogenic microbial organisms, with OB and OG being highly active. Likewise, the EOs was also able to induce mortality in the larval forms of various mosquito vectors. Full article

Microbial larviciding can be an effective component of integrated vector management malaria control schemes, although it is not commonly implemented. Moreover, quality control and evaluation of intervention activities are essential to evaluate the potential of community-based larviciding interventions. We conducted a process evaluation of a larval source management intervention in rural Tanzania where local staff were employed to apply microbial larvicide to mosquito breeding habitats with the aim of long-term reductions in malaria transmission. We developed a logic model to guide the process evaluation and then established quantitative indicators to measure intervention success. Quantitative analysis of intervention reach, exposure, and fidelity was performed to assess larvicide application, and interviews with larviciding staff were reviewed to provide context to quantitative results. Results indicate that the intervention was successful in terms of reach, as staff applied microbial larvicide at 80% of identified mosquito breeding habitats. However, the dosage of larvicide applied was sufficient to ensure larval elimination at only 26% of sites, which does not meet the standard set for intervention fidelity. We propose that insufficient training and protocol adaptation, environment and resource issues, and human error contributed to low larvicide application rates. This demonstrates how several small, context-specific details in sum can result in meaningful differences between intervention blueprint and execution. These findings may serve the design of other larval source management interventions by demonstrating the value of additional training, supervision, and measurement and evaluation of protocol adherence. Full article

Bacillus thuringiensis ser. israelensis (Bti) has been widely used as microbial larvicide for the control of many species of mosquitoes and blackflies. The larvicidal activity of Bti resides in Cry and Cyt δ-endotoxins present in the parasporal crystal of this pathogen. The insecticidal activity of the crystal is higher than the activities of the individual toxins, which is likely due to synergistic interactions among the crystal component proteins, particularly those involving Cyt1Aa. In the present study, Cry10Aa and Cyt2Ba were cloned from the commercial larvicide VectoBac-12AS^® and expressed in the acrystalliferous Bt strain BMB171 under the cyt1Aa strong promoter of the pSTAB vector. The LC₅₀ values for Aedes aegypti second instar larvae estimated at 24 hpi for these two recombinant proteins (Cry10Aa and Cyt2Ba) were 299.62 and 279.37 ng/mL, respectively. Remarkable synergistic mosquitocidal activity was observed between Cry10Aa and Cyt2Ba (synergistic potentiation of 68.6-fold) when spore + crystal preparations, comprising a mixture of both recombinant strains in equal relative concentrations, were ingested by A. aegypti larvae. This synergistic activity is among the most powerful described so far with Bt toxins and is comparable to that reported for Cyt1A when interacting with Cry4Aa, Cry4Ba or Cry11Aa. Synergistic mosquitocidal activity was also observed between the recombinant proteins Cyt2Ba and Cry4Aa, but in this case, the synergistic potentiation was 4.6-fold. In conclusion, although Cry10Aa and Cyt2Ba are rarely detectable or appear as minor components in the crystals of Bti strains, they represent toxicity factors with a high potential for the control of mosquito populations. Full article

The Lauraceae is a family rich in aromatic and medicinal plants. Likewise, essential oils derived from members of this family have demonstrated a myriad of biological activities. It is hypothesized that members of the Lauraceae from Vietnam will yield essential oils that may be useful in controlling mosquito populations and treating microbial infections. In this work, the leaf essential oils of eleven species of Lauraceae (Beilschmiedia erythrophloia, B. robusta, B. yunnanensis, Cryptocarya concinna, C. impressa, C. infectoria, Litsea viridis, Machilus balansa, M. grandifolia, Neolitsea ellipsoidea, and Phoebe angustifolia) have been obtained by hydrodistillation and the chemical compositions analyzed by gas chromatography – mass spectrometry (GC-MS) and gas chromatography with flame ionization detection (GC-FID). The essential oils were screened for larvicidal activity against Aedes aegypti, Ae. albopictus, and Culex quinquefasciatus, and for antimicrobial activity against Enterococcus faecalis, Staphylococcus aureus, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica, and Candida albicans. The leaf essential oil of N. ellipsoidea, rich in (E)-β-ocimene (87.6%), showed excellent larvicidal activity against Ae. aegypti with a 24 h LC₅₀ of 6.59 μg/mL. The leaf essential oil of C. infectoria, dominated by germacrene D (55.5%) and bicyclogermacrene (11.4%), exhibited remarkable larvicidal activity against Cx. quinquefasciatus (48 h LC₅₀ = 0.40 μg/mL). N. ellipsoidea leaf essential oil also demonstrated notable antibacterial activity against E. faecalis and B. cereus with minimum inhibitory concentration (MIC) values of 16 μg/mL, while the leaf essential oil of C. impressa showed excellent anticandidal with an MIC of 16 μg/mL. Leaf essential oils from the Lauraceae should be considered for utilization as alternative agents for controlling mosquito populations and as antimicrobial agents. Full article

Mosquitoes are important vectors of several diseases, and control of these insects is imperative for human health. Insecticides have proven useful in controlling mosquito populations, but insecticide resistance and environmental concerns are increasing. Additionally, emerging and re-emerging microbial infections are problematic. Essential oils have been shown to be promising mosquito larvicidal agents as well as antimicrobial agents. In this work, the essential oils from four species of Myrtaceae (Baeckea frutescens, Callistemon citrinus, Melaleuca leucadendra, and Syzygium nervosum) growing wild in central Vietnam have been obtained by hydrodistillation and analyzed by gas chromatographic techniques. The essential oils have been screened for mosquito larvicidal activity against Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus, and for antimicrobial activity against Enterococcus faecalis, Staphylococcus aureus, and Candida albicans. Callistemon citrinus fruit essential oil, rich in α-pinene (35.1%), 1,8-cineole (32.4%), limonene (8.2%), and α-terpineol (5.8%) showed good larvicidal activity with 24-h LC₅₀ = 17.3 μg/mL against both Ae. aegypti and Cx. quinquefasciatus, and good antibacterial activity against E. faecalis (minimum inhibitory concentration (MIC) = 16 μg/mL) The 48-h larvicidal activities of M. leucadendra leaf essential oil, rich in α-eudesmol (17.6%), guaiol (10.9%), linalool (5.1%), (E)-caryophyllene (7.0%), and bulnesol (3.6%) were particularly notable, with LC₅₀ of 1.4 and 1.8 μg/mL on Ae. aegypti and Cx. quinquefasciatus. Similarly, M. leucadendra bark essential oil, with α-eudesmol (24.1%) and guaiol (11.3%), showed good antibacterial activity against. E. faecalis. Both B. frutescens and C. citrinus leaf essential oils demonstrated anti-Candida activities with MIC values of 16 μg/mL. The results of this investigation suggest that essential oils derived from the Myrtaceae may serve as “green” alternatives for the control of mosquitoes and/or complementary antimicrobial agents. Full article

The health challenges associated with pathogens and ectoparasites highlight the need for effective control approaches. Metal nanoparticles have been proposed as highly effective tools towards combatting different microbial organisms and parasites. The present work reports the antimicrobial and larvicidal potential of biosynthesized Ag/Ag₂O nanoparticles using aqueous leaf extract of Eupatorium odoratum (EO). The constituents of the leaf extract act as both reducing and stabilizing agents. The UV-VIS spectra of the nanoparticles showed surface plasmon resonance. The particle size and shape of the nanoparticles was analysed by transmission electron microscopy (TEM). The larvicidal study was carried out using third and fourth instar Culex quinquefasciatus larvae. The mosquito larvae were exposed to varying concentrations of plant extract (EO) and the synthesized nanoparticles, and their percentage of mortality was accounted for at different time intervals of 12 h and 24 h periods of exposure. The nanoparticles were more lethal against third and fourth instars of Culex quinquefasciatus larvae at the 24 h period of exposure with lower lethal concentration values (LC50 = 95.9 ppm; LC90 = 337.5 ppm) and (LC50 = 166.4 ppm; LC90 = 438.7 ppm) compared to the plant extract (LC50 = 396.8 ppm; LC90 = 716.8 ppm and LC50 = 448.3 ppm; LC90 = 803.9 ppm, respectively). The antimicrobial properties of the nanoparticles were established against different clinically-isolated microbial strains and compared to that of the plant extract (EO) and standard antimicrobial drugs. The nanoparticles were generally more active than the plant extract against the selected microbial organisms. The Gram-negative bacterial strains Escheerichua coli and Salmonella typhi were more susceptible towards the nanoparticles compared to the Gram-positive strains and the fungal organism. Full article