Insecticide Sprays Research Articles

Optimal Control of Microcephaly Under Vertical Transmission of Zika

The Zika virus, known for its potential to induce neurological conditions such as microcephaly when transmitted vertically from infected mothers to infants, has sparked widespread concerns globally. Motivated by this, we propose an optimal control problem for the prevention of vertical Zika transmission. The novelty of this study lies in its consideration of time-dependent control functions, namely, insecticide spraying and personal protective measures taken to safeguard pregnant women from infected mosquitoes. New results provide a way to minimize the number of infected pregnant women through the implementation of control strategies while simultaneously reducing both the associated costs of control measures and the mosquito population, resulting in a decline in microcephaly cases.

Mathematical Exploration of Malaria Transmission Dynamics: Insights from Fractional Models and Numerical Simulation

AbstractThis study presents an innovative mathematical model denoted as the fractional SIP(H)–SI(M) model, which aims to analyze and understand the dynamics of malaria transmission and spread. This model is distinguished by incorporating memory effects through fractional differential equations, allowing for a more accurate and realistic analysis of disease spread compared to traditional models. The proposed model is applied to Algeria by estimating its parameters using recent health data (from 2000). The results revealed that the disease‐free equilibrium is stable only when the basic reproduction number is less than one, indicating that controlling the spread of malaria and possibly eradicating it can be achieved by implementing appropriate preventive measures. Simulations also demonstrated a direct correlation between the rate of infection transmission and an increase in the number of infected individuals, highlighting the need for swift action when signs of an outbreak emerge. Based on these findings, a set of preventive measures is recommended, including insecticide spraying programs, widespread distribution of insecticide‐treated bed nets, and implementation of effective treatment protocols for infected individuals. This study also emphasizes the importance of continuous monitoring of health data and updating model parameters to ensure the effectiveness and sustainability of preventive measures.

Multi-year evaluation of an attract-and-kill strategy for apple maggot fly (Diptera: Tephritidae) in New England commercial apple orchards.

Previously developed behavioral approaches for controlling the apple maggot fly, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), include attract-and-kill (AK) systems such as perimeter trapping using either, odor-baited red sticky spheres or odor-baited, sticky-free attracticidal spheres with contoured tops that ensure the sustained release of both insecticide and feeding stimulant. Here, over a 3-year span in 26 commercial apple orchards across Massachusetts, New Hampshire, and Maine, we evaluated the effectiveness of a novel AK strategy for R. pomonella management. Synthetic apple blend lures were deployed on perimeter-row trees to attract the pest, while perimeter-row insecticide sprays blended with 2% sugar, a known phagostimulant, served as the lethal component. Comparatively, grower standard (GS) blocks received full-block insecticide sprays devoid of sugar and lures. Monitoring revealed that red sticky spheres in AK blocks captured significantly more R. pomonella adults than unbaited monitoring spheres in GS blocks. Penetration of R. pomonella into block interiors remained consistently low and statistically similar for both AK and GS blocks. Whole-block infestation levels showed no significant difference between the 2 management approaches. Notably, insecticide application in AK blocks was reduced by 75%, 64.7%, and 64.2% in 2019, 2020, and 2021, respectively, compared with GS blocks. This grower-friendly AK approach could be integral to a reduced insecticide spray-based strategy for apple cultivation in the northeastern United States.

Insecticide Resistance and Target-Site Mutations kdr, N1575Y, and Ace-1 in Anopheles gambiae s.l. Populations in a Low-Malaria-Transmission Zone in the Sudanian Region of Senegal.

Background/Objectives: Significant progress in malaria control has been achieved through long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS), raising hopes for malaria elimination. However, emerging insecticide resistance threatens these gains. This study assessed the susceptibility of Anopheles gambiae s.l. populations to public health insecticides, examined the frequencies of kdr, Ace-1, and N1575Y mutations, and explored their associations with phenotypic resistance in Dielmo and Ndiop, Senegal. Methods: Anopheles larvae collected between September and December 2022 were reared to adulthood. Adult mosquitoes were exposed to discriminating concentrations of various insecticides following WHO guidelines. Knockdown times (KDT50 and KDT95) for pyrethroids were calculated using the Probit model. RT-qPCR detected target-site mutations (kdr: L1014F and L1014S, Ace-1, N1575Y) and assessed correlations with phenotypic resistance. Species-specific PCR identified species within the An. gambiae complex. Results/Conclusions: The populations of Dielmo and Ndiop showed susceptibility to pirimiphos-methyl and bendiocarb, with no Ace-1 mutation detected. Resistance to DDT and pyrethroids was observed. The knockdown times indicated that alphacypermethrin and lambdacyhalothrin were more effective than permethrin and deltamethrin. The L1014F allele was widespread, while L1014S was absent in Ndiop and low in Dielmo. The N1575Y mutation occurred only in populations with L1014F. The L1014S mutation was significantly associated with resistance to lambdacyhalothrin in both villages and to deltamethrin in Ndiop.

Future semiochemical control of codling moth, Cydia pomonella

Codling moth (CM), Cydia pomonella, is a significant pest of apple (Malus domestica) and other orchard crops worldwide, posing challenges due to the decrease in registered insecticides, rising resistance, and a changing climate. The pest exhibits a strong resistance capacity to both synthetic and natural insecticides, while shifting seasonal temperatures disrupt the reliability of phenology-temperature models for predicting targeted control strategies. Alternative control strategies are necessary to future-proof control of this pest. Current control methods primarily rely on chemical insecticide sprays or granulosis virus applications during egg hatching. This review focuses explicitly on semiochemical-based manipulation of CM adults and larvae for control in orchards. Topics covered include the role of semiochemicals in integrated pest management, area-wide control, mating disruption, female attractants, larval kairomones, and incorporation into monitoring and control strategies. The potential of CM repellents in a push–pull strategy is also discussed. Primary sources for identifying relevant literature included GoogleScholar and ResearchGate, with a focus on papers published since 2013 but also include relevant papers from 2003. Nine review papers and 119 papers were reviewed. The review emphasizes that effective control necessitates an area-wide approach targeting all life stages (eggs, larvae, pupae, and adults). Comprehensive monitoring is crucial for identifying CM “hot-spots” and enhancing targeted interventions. Growers must consider landscape context when designing control programs. Lastly, recommendations are provided for future research and CM management strategies. There are opportunities to explore and exploit female kairomone attractants and repellents in control strategies and modify monitoring traps to be more attractive and autonomous.

Assessing the multifaceted repercussions of chemical insecticides on vegetable yield and human population: A modeling study

Vegetables stand out as invaluable reservoirs of essential vitamins, minerals, antioxidants, and vital dietary elements, yet their production faces a considerable threat due to insects. To tackle this challenge, farmers spray chemical insecticides to enhance vegetable yields by controlling the insect population. Nevertheless, the presence of insecticide residues in vegetables stands as a primary contributor to acute illnesses and chronic health conditions in humans. In the present research work, we formulate a novel nonlinear mathematical model meticulously designed to scrutinize the multifaceted repercussions of chemical insecticides on vegetable yield and the human population. In our model formulation, we adopt a dynamic approach where insecticide application on vegetables in agricultural fields correlates with the insect population. However, we acknowledge the consequential impact of insecticide usage on human health, which in turn reduces the growth rate of the human population. This study determines the critical value of the spraying rate of insecticide at which the human population reaches its maximum, ensuring that human needs for vegetables are met while minimizing the adverse effects of insecticide. Since various species of insects attack vegetables in the field and different insect species have different natural mortality rates, therefore we also identify the range of natural mortality rates of insects for which vegetable yield is minimal and fluctuates with time. Further, our research reveals that if the natural mortality rate of insects in a certain crop field lies within this identified range, then farmers should increase the insecticide spraying rate to avoid this upheaval situation and stabilize vegetable yield at a higher level.

Molecular xenomonitoring reveals Anopheles funestus and An. rivulorum as the primary vectors of lymphatic filariasis in coastal Kenya

BackgroundLymphatic filariasis (LF) is an infectious neglected tropical disease caused by mosquito-borne nematodes such as Wuchereria bancrofti, Brugia malayi, and Brugia timori. Globally, LF affects 51 million people, with approximately 863 million at risk in 47 countries. In Kenya, filariasis is endemic along the entire coastal strip, and more recently, at the Kenya–Ugandan border. The World Health Organization (WHO) recommends mass drug administration to reduce disease transmission and morbidity. Monitoring the effectiveness of such interventions relies on robust surveillance, achieved through microscopic examination of microfilariae in nighttime blood, detection of circulating filarial antigens (CFA), and molecular xenomonitoring. We focused on molecular xenomonitoring along the Kenyan coast due to its noninvasive nature and the opportunity to identify new vectors.MethodsIn 2022, mosquitoes were collected from Kilifi, Kwale, and Taita-Taveta counties located within the LF endemic region in Kenya. Subsequently, genomic deoxyribonucleic acid (gDNA) was extracted from these mosquitoes for speciation and analysis of Wuchereria bancrofti infection rates. The impact of sociodemographic and household attributes on infection rates was assessed using generalized estimating equations.ResultsA total of 18,121 mosquitoes belonging to Culicinae (63.0%, n = 11,414) and Anophelinae (37.0%, n = 6707) subfamilies were collected. Morphological identification revealed that Anopheline mosquitoes were dominated by An. funestus (45.4%, n = 3045) and An. gambiae (42.8%, n = 2873). Wuchereria bancrofti infection rates were highest in Kilifi (35.4%; 95% CI 28.0–43.3%, n = 57/161) and lowest in Taita Taveta (5.3%; 95% CI 3.3–8.0%, n = 22/412). The major vectors incriminated are An. rivulorum, An. funestus sensu stricto, and An. arabiensis. Mosquitoes of the An. funestus complex were significantly associated with LF transmission (OR 18.0; 95% CI 1.80–180; p = 0.014). Additionally, a higher risk of transmission was observed outdoors (OR 1.74; 95% CI 1.08–2.82; p = 0.024) and in homesteads that owned livestock (OR 2.00; 95% CI 1.09–3.66; p = 0.025).ConclusionsIn this study, we identified An. funestus s.l. sibling species, An. rivulorum and An. funestus s.s., as the primary vectors of lymphatic filariasis along the Kenyan coast. These findings also highlight that a significant portion of disease transmission potentially occurs outdoors where indoor-based vector control tools, including long-lasting insecticidal nets and indoor residual spray, may not be effective. Therefore, control measures targeting outdoor resting mosquitoes such as zooprophylaxis, larval source management, and attractive sugar baits may have potential for LF transmission reduction.Graphical

Efficacy of selected insecticide sprays against Indian meal moth (Lepidoptera: Pyralidae) wandering larvae on various surfaces

The Indian meal moth, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae), is a worldwide pest found in food product warehouses. Presence of P. interpunctella wandering larvae causes customer complaints and product rejection from customers. Its prepupal stage is susceptible to insecticide treatment due to their wandering behavior. We evaluated the efficacy of three insecticide sprays, ExciteR (0.017% pyrethrins, 0.174% piperonyl butoxide), Suspend SC (0.053% deltamethrin), and Transport Mikron (0.047% acetamiprid, 0.056% bifenthrin) against P. interpunctella wandering larvae by forced exposure to porous (vinyl tile, unpainted pinewood, concrete, and paper) and non-porous (steel, glazed ceramic) surfaces, and exposure to treated harborages made of two pieces of vinyl tiles, unpainted pinewood, and concrete. Under continuous exposure conditions, both ExciteR and Suspend SC caused significantly higher mortality (90–96%) than Transport Mikron (73–75%) on non-porous surfaces after 4 days (P < 0.05). But on porous surfaces, the three insecticides caused ≤63% mortality with Suspend SC being the most effective. When using 2× amount of insecticides as that in the previous test (2.1 gallon/1000 ft2, which is 4.33, 1.20, and 2.33 mg a.i./m2 of ExciteR, Suspend SC, and Transport Mikron, respectively), Suspend SC was the only insecticide causing high mortality (≥99%) through both forced exposure to concrete surface and exposure to treated concrete harborage. Whereas other treatments caused <12% mortality. Among the porous surfaces, residual efficacy of Suspend SC on concrete was significantly higher than that on vinyl tiles. Application of an effective liquid insecticide (such as 0.053% deltamethrin) into harborages or directly to the possible pupation sites, such as corners, cracks, and crevices could be an effective strategy for managing P. interpunctella wandering larvae in warehouse environment.

Effect of the Localized Insecticides Spray Technique to Control Halyomorpha halys in Actinidia chinensis Orchards.

Kiwifruit (Actinidia chinensis) cultivation is expanding worldwide, with China, New Zealand, and Italy being the major producing countries. Halyomorpha halys, the brown marmorated stink bug, is raising serious concerns to kiwifruit cultivation both in China and Italy. This study aimed at improving the chemical control efficacy against this pest by comparing two insecticide spray techniques (a conventional ray atomizer and a trumpet-modified atomizer adapted for localized spray application) in kiwifruit. In fact, kiwifruit is often grown with a 'pergola' training system, which may reduce the effectiveness of insecticide penetration into the canopy. Experiments were performed in naturally infested orchards of both Actinidia chinensis var. chinensis 'Jintao' and A. chinensis var. deliciosa 'Hayward'. Furthermore, mesh cages containing H. halys adults were deployed within orchards to assess the insects' mortality at 1, 3, 7, and 10 days after an insecticide application with two spray techniques during two consecutive seasons. In the cultivar 'Jintao', the two systems performed similarly, while in the cultivar 'Hayward', an overall significantly higher insect mortality was recorded with the trumpet atomizer (94-100%) compared to the conventional atomizer (59-78%). Crop damage was also evaluated on both cultivars, simulating the grower insecticide applications with the two spray techniques. At harvest, no difference emerged between the spray techniques, which provided a significantly better protection compared to the untreated control (12-17% compared to 33-47% of injured fruits). Further investigations in this direction are needed also considering the restriction of insecticidal active substances ongoing in the European Union and the need to maximize the efficacy of the available tools.

Analyzing the dynamics and optimal control of a vector-borne model with dual vertical transmission and multiple serotypes

Abstract Transmission and contact patterns have an important influence on the intensity and trend of disease transmission. Taking into account two different serotypes and the vertical transmission of the disease in both humans and mosquitoes, this paper proposes a novel vector-borne disease model. In order to explore the evolution mechanisms of the model and the impacts of contact pattern on disease transmission. The basic regeneration number of the proposed model is obtained via the next-generation matrix approach. Subsequently, we analyze the conditions of the stabilities and existences of the equilibrium points. Further, the sensitivity of the parameters is studied using numerical simulations. It is observe that the increase of vertical transmission rate of mosquitoes leads to the increase of the basic reproduction number. In addition, we develop vaccination and insecticide control strategies and derive the existence and expression of the optimal solution. Our numerical results show that vaccination has a little effect on preventing the spread of disease among mosquitoes. However, insecticide spraying is effective in reducing the spread of disease between humans and mosquitoes.&amp;#xD;

Development of bait station to complement attract-and-kill agents of Zeugodacus tau (Diptera: Tephritidae).

Zeugodacus tau (Walker) (Diptera: Tephritidae) is an important agricultural pest currently managed primarily through the application of insecticides due to limited control strategies. Bait station devices are target specific and have emerged as a behaviorally based alternative to traditional insecticide sprays for managing Z. tau. In this study, we designed a bait station by integrating female-biased olfactory, visual, and gustatory elements, and a killing agent in a wax-matrix. Our results showed that the wax-matrix integrated with spinetoram showed the highest toxicity to immature and mature Z. tau females. Furthermore, the color and shape of the spinetoram bait station significantly influenced its attractiveness and toxicity to female Z. tau. Green sausage-shaped exteriors were the most effective color and shape examined. Subsequent experiments showed a length-dependent effect on mortality and visiting frequencies of Z. tau females when the bait stations were 9-13 cm long. The addition of the olfactory stimulus of 5% ammonium acetate to the bait station attracted a higher number of mature Z. tau females than the control. The killing efficacy of the weathered bait station was similar to that of the fresh station within an 8-week period (over 794 mm of rainfall). The bait station developed herein would provide new insight into the attract-and-kill strategy for Z. tau and alleviate the pressure of the actual management program for this pest.

Seasonal activity of plum curculio (Coleoptera: Curculionidae) in small Southeastern peach orchards.

Plum curculio, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), is a key pest in Southeastern peach production by infesting fruit and decreasing yield. In Northeastern apples, plum curculio was found to have an "edge effect," where more plum curculio are present next to a forested border than in the center of an orchard, and their propensity to fly or walk depended on air temperature. We conducted field studies over 3 seasons (2019-2021) to investigate whether plum curculio in small Southeastern peach plots exhibits the edge effect and to determine its primary mode of movement (flying or walking). Our results revealed that plum curculio did not exhibit the edge effect in Southeastern peaches. Thus, unlike Northeastern apples where plum curculio exhibits the edge effect, the reduced-input application program where insecticide sprays mainly target a few perimeter-row trees instead of the whole orchard for plum curculio management is not recommended for Southeastern peaches. Additionally, we observed that plum curculio in Southeastern peaches did not exhibit a primary mode of movement, and in most of the sampling weeks, the numbers of flying and walking plum curculio were not significantly correlated in the field. These results emphasize that using plum curculio sampling tools that only capture flying or walking plum curculio is not ideal for monitoring plum curculio activity in the Southeast. Overall, our findings indicate that plum curculio in Southeastern small peach plots and Northeastern apples does not exhibit the same behavior (i.e., edge effect and propensity to fly or walk).

Influence of deployment method and maintenance on efficacy of sticky card traps for Halyomorpha halys (Hemiptera: Pentatomidae).

Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) is an invasive pest which feeds on numerous economically significant crops. Many integrated pest management strategies for this species rely on effective season-long monitoring for H. halys populations, including attract-and-kill and threshold-based insecticide sprays. Previous studies have shown that a black pyramid trap effectively captures all mobile life stages of H. halys, however, these bulky, ground-deployed traps can be impractical in active orchard rows. Clear sticky cards have been used as a more practical tool for monitoring when paired with the H. halys aggregation pheromone and synergist. Here, the efficacy of deploying single- or double-sided sticky cards hanging in trees or deployed on wooden stakes was compared to standard black pyramid traps over 2 years. The efficacy of single-sided sticky cards deployed on wooden stakes was also evaluated after occlusion of 25%, 50%, or 75% of the surface area by 2D inert materials and 3D organic matter. Single-sided sticky cards were also exposed to simulated sunlight and rainfall for 0, 4, 8, and 12 wk before deployment on wooden stakes. Captures of H. halys adults using sticky cards deployed on wooden stakes were comparable to pyramid traps. Occlusion of cards by 25% or more of any material type led to a decrease in H. halys captures, however, weathering did not influence capture. These data show that clear sticky cards deployed on wooden stakes are effective for season-long monitoring of H. halys in apple orchards, and card replacement should be driven by maintenance of cleanliness.

Studies on the Response of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) to Multicolour Light System

Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) commonly known as rust red flour beetle was a universal pest of stored produce with an extensive feeding diversity. The management of T. castaneum in field conditions was through fumigation and spraying of suitable insecticides. Even though many plant products were found effective against pests in invitro conditions, they could not be mixed with the stored produce for fear of losing the table quality. Physical forces seemed to be good alternatives to chemical treatment as far as stored grain pests were concerned. The use of gamma and UV radiations, microwaves and ultrasonic sound waves against T. castaneum and other stored grain pests had been tried by many authors. The objectives of this study were to check the adult beetles and final instar grubs of T. castaneum to different colours of light and it showedpreference for clear tungsten (white) light, while they were averse to red coloured light. This trend was explicit even after the entrainment of beetles to red colour light for further generations. Based on these results it could be presumed that T. castaneum adults preferred to move away from red coloured light. By changing the colour of bright light to dark lighting in warehouses, it could be possible to manage T. castaneum in small measure. Total eradication of stored product pests like T. castaneum was at least possibility and the selection of a proper management system could help to solve the stored produce pest problem to a greater magnitude.

Field Evaluation of Integrated Pest Management Strategies against Chilli Black Thrips Thrips parvispinus (Karny), in the Srikakulam District

Chilli (Capsicum annum L) is an important spice crop grown extensively in India for both domestic and export markets. Invasive black thrips Thrips parvispinus has been causing destructive damage to chilli crop in India leading to indiscriminate use of insecticidal sprays. On-farm trials were conducted during Kharif and Rabi 2022-23 &amp; 2023-24 to evaluate Integrated Pest Management practices against black thrips with emphasis on minimal pesticidal sprays with different mode of actions so that pests may not develop resistance which will reduce the residues on the produce in the farmer’s fields of Srikakulam district of Andhra Pradesh. IPM adopted fields i.e. seed treatment, marigold as trap crop, erection of blue sticky traps, Beauveria bassiana spray and Neem oil and Fipronil 5 SC spray at 30 DAT; Imidacloprid+Fipronil 40%WG spray at 50 DAT; have shown 40 to 85 per cent reduction in black thrips infestation over farmers practice during all the seasons of both the years. This resulted in a higher average mean yield of 57 q/ha, average net returns of Rs. 4,96,000 per hectare with cost benefit ratio of 3.29 in IPM fields over farmer’s practice depicting that the adoption of IPM practices helped in reducing the pest incidence and increase in yield, net returns.

Wind-mediated Dispersal of Beet Leafhoppers and Pine Pollen in Southern Idaho

The management of beet leafhoppers (BLHs) is important for disease control since BLHs can vector important plant pathogens such as curly top viruses and phytoplasmas in southern Idaho. Historical data for southern Idaho suggests that BLH need approximately 130 growing degree days (GDDs; 12.8°C base) to initiate dispersal and around 382 GDDs until they reach peak dispersal. A recent study in southern Idaho identified large peak dispersal events of BLHs on May 19, 2020 and June 2, 2021 in Elmore Co. near Mt. Home, ID. Historically, BLH have been thought to originate from local areas. However, based on GDDs and dispersal numbers under optimal conditions for Mt. Home, the BLHs likely did not originate from local areas. Data for wind and pine pollen dispersal combined with GDDs for areas known to contain BLH suggest that the BLH could have originated outside the local area and possibly up to 142 to 515 km away. At least five conditions appear to be necessary for observation of BLH dispersal into southern Idaho: a wind event must occur (35 km/h avg. hourly wind speed), dispersal temperature threshold (16 to 18°C) must be met, &gt;130 GDDs must be accumulated to initiate dispersal, daily peak temperatures should reach 24°C, and attractive BLH vegetation such as Russian thistle must be present. Combining wind event forecasts with temperature parameters in the future may make it possible to provide targeted timely insecticide sprays for BLH control.

Optimizing the production of dsRNA biocontrols in microbial systems using multiple transcriptional terminators.

Crop pests and pathogens annually cause over $220 billion in global crop damage, with insects consuming 5%-20%of major grain crops. Current crop pest and disease control strategies rely on insecticidal and fungicidal sprays, plant genetic resistance, transgenes, and agricultural practices. Double-stranded RNA(dsRNA) is emerging as a novel sustainable method of plant protection as an alternative to traditional chemical pesticides. Successful commercialization of dsRNA-based biocontrols requires the economical production of large quantities of dsRNA combined with suitable delivery methods to ensure RNAi efficacy against the target pest. In this study, we have optimized the design of plasmid DNA constructs to produce dsRNA biocontrols in Escherichia coli, by employing a wide range of alternative synthetic transcriptional terminators before measurement of dsRNA yield. We demonstrate that a 7.8-fold increase of dsRNA was achieved using triple synthetic transcriptional terminators within a dual T7 dsRNA production system compared to the absence of transcriptional terminators. Moreover, our data demonstratethat batch fermentation production dsRNA using multiple transcriptional terminators is scalable and generates significantly higher yields of dsRNA generated in the absence of transcriptional terminators at both small-scale batch culture and large-scale fermentation. In addition, we show that application of these dsRNA biocontrols expressed in E. coli cells results in increased insect mortality. Finally, novel mass spectrometry analysis was performed to determine the precise sites of transcriptional termination at the different transcriptional terminators providing important further mechanistic insight.

Historical review of surveillance methods, insecticide spray, and epidemiology of malaria in Bannu zone, Khyber Pakhtunkhwa, Pakistan

Historical review of surveillance methods, insecticide spray, and epidemiology of malaria in Bannu zone, Khyber Pakhtunkhwa, Pakistan

In silico Screening of Plectranthus amboinicus and Hyptis suaveolens Phyto-chemicals: Novel Repellents Targeting Odorant Binding Proteins of Aedes aegypti and Aedes albopictus

Background and Aim: Mosquitoes significantly threaten public health, transmitting dangerous diseases to humans and animals. Conventional insecticide spraying, while common, has limitations in effectively controlling vector-borne diseases. Many chemical pesticides harm humans and animals, and some persist in the environment and cause toxic effects. Recently, there has been renewed interest in plant-based products due to concerns about insecticide re-sistance, cross-resistance, potential toxicity associated with synthetic options, and rising costs. Therefore, this study aimed to screen the Plectranthus amboinicus and Hyptis suaveolens phy-tochemicals targeting the odorant binding proteins (OBPs) of Aedes aegypti and Aedes albopic-tus. Methods: In this study, we conducted molecular docking analyses using specific plant-derived compounds from H. suaveolens and P. amboinicus. Results: We focused on the interaction of these compounds with OBPs from dengue and chikungunya vectors (Aedes aegypti and Aedes albopictus). The selected phytochemical com-pounds exhibited strong binding with the OBP of both Ae. aegypti and Ae. albopictus. Tetrahy-drofuran-2-carboxylic acid, Carvacryl acetate, and Brallobarbital showed high binding affinity and significant interaction with Ae. aegypti. Tetrahydrofuran-2-carboxylic acid and 3-Methyl-4-isopropylphenol also demonstrated substantial binding affinity and effective interaction with Ae. albopictus OBP. Conclusion: These findings suggest that the identified compounds can potentially disrupt the attraction of mosquitoes to humans, thus reducing human-vector contact. They may offer a promising alternative for developing natural and efficient mosquito repellents, surpassing cur-rently used synthetic options like N, N-diethyl-meta-toluamide, and other conventional repel-lents.

Nuances of Cohort Studies and Risk Ratio.

Post-graduate students and faculty usually conduct case-control studies. However, sometimes they conduct cohort studies that are short-duration. Most investigators enroll the participants in two groups according to the exposure. Then, follow the participants for some duration. At the end of the study, relative risk is calculated, and the work is published in some journal. The exposure may be one time, which may or may not be quantified. The follow-up duration may not be participant-specific, and differential follow-up does not exist. The author has given three examples: the first example of consanguineous marriages and congenital disabilities, the second example of the ABO blood group system and childhood asthma, and the third example of insecticide spraying and stillbirth. In the given examples, cumulative or density incidence cannot be calculated in a true sense and, therefore, risk ratio. Even estimating the incidence of outcome variables in some studies is not appropriate. Risk ratio calculation in such scenarios is questionable because exposure quantification, follow-up period, and combination are the limiting factors. In case-control studies, the prevalence ratio is calculated, which is analogous to relative risk. The author suggests that, in such circumstances, prevalence ratio calculation will be more appropriate.