Vector Control Method Research Articles

Caregivers’ vector control methods and its effect on malaria infection in febrile children presenting in a Tertiary Hospital in Nigeria

Background: Malaria is a major public health problem in sub-Saharan Africa. Several efforts are being made to reduce its prevalence and morbidity in Nigerian children with emphasison vector control measures.Methods: This was acrosssectional descriptive study conducted on 382 febrile children seen at a tertiary hospital in Nigeria over an eight-month period. A structured questionnaire was used to collect information on sociodemographic, vector control measures and care given to the subjects. Investigations conducted included malaria microscopy and total leukocyte count.Results: Eighty percent (308/382) employed at least one vector controlmeasures to prevent malaria infection, and majority 232 (75.2%) use only one control measure. The commonest control measures used included always keeping doors and windows shut 298 (96.7%) and/or netted 280 (90.9%), use of conventional insecticide sprays 183 (59.4%), use of insecticide treated bed nets (ITNs) 178 (57.8%) and ensuring child sleeps at night with body adequately covered 77(25%). Approximately half (178/315) of households who owned ITN used it, and only 40.4% (72/178) used it daily. It was noted that children that slept under an insecticide treated bed net (RR 0.56, 95% CI 0.33-0.94; P=0.029) and those who slept well covered at night (RR 0.26, 95% CI 0.12-0.61; P=0.002) had less risk of malaria infection. The use insecticide treated bed net however lost significance following adjustment for other control measures used and socio-demographic factors of interest (RR 0.63, 95% CI 0.36-1.10;P=0.101).Conclusion: There is need to intensify education on appropriate malaria control measures especially proper use of insecticide-treated nets and suitable clothing during sleep at night.

The attitude control optimization of small rocket

In this article, an optimization method for attitude calculation and vector control of small rocket is proposed, which reduces the performance requirements and costs of gyroscopes. Dynamic model parameters such as engine thrust curve and rocket body moment of inertia are added to the traditional filtering and control algorithm, which can reduce the hardware performance requirements of sensors and the cost of rocket control system. This method has achieved good results in the test, and is of great significance for the promotion of small rockets.

Sensorless Control of Permanent Magnet Linear Synchronous Motor Based On Double Sliding Mode

Background & Objective: This document presents a dual sliding mode vector control method to estimate speed and position of Permanent Magnet Linear Synchronous Motor (PMLSM). Methods: Firstly, the motor simulation model is built based on the mathematical model of PMLSM. For the sake of solving the problems of the jitter and position angle deviation in the traditional SMO, the inverse hyperbolic tangent function is used and the software phase-locked loop algorithm is introduced, and the gain of exponential approach rate is improved to change the real-time, so as to eliminate the problems of high-frequency jitter and angle deviation. Secondly, global fractional order integral sliding mode control (GFOISMC) is used to replace PI control to eliminate jitter and improve the robustness to load disturbance. Finally, the dynamic performance of the system under constant speed no-load and constant speed sudden load is simulated. Results: The simulation result proves a proposed dual sliding mode control strategy combining the improved SMO and GFOISMC that can effectively reduce the jitter and improve robustness. Conclusion: In this paper, two sensorless control strategies are compared and their robust performance is studied. The two control scheme is simulated in the MATLAB/Simulink environment.

Plasmodial Prevalence with Respect to Gender in 6 Villages Around Balombo Town, Benguela Province, Angola, before Malaria Vector Control Implementation

Background: The different susceptibility of gender to infectious diseases is still a matter of concern and several studies were devoted to these issues; for malaria, recent studies reported a comparable “Force of Infection” in both gender while women could have a faster elimination of parasite than men.
 Study Area and duration Period of the Research: The study was done in villages around Balombo town, Benguela Municipality, Angola and initially scheduled for 5 years since year 2007 with 2 years before vector control implementation and 3 years after.
 Objectives of the research. The village scale malaria vector control program was planned and implemented to compare 4 methods of vector control with comprehensive entomological and parasitological evaluation, focusing on symptomless randomly selected patients, and noticing age and gender during each field survey for further analysis.
 Study Design: To check an eventual gender difference, we decided to analyze the parasitological data gained during the 56 cross sectional surveys (CSS) done during 2 consecutive years in the 6 villages used as “control” i.e. before implementation of vector control operations (VCO) considering the gender of symptomless patients (≤15 years old) surveyed. We considered 2 indicators: Plasmodial Prevalence (PP) and Parasite Load (PL).
 Main Results: 6727 thick blood smears (TBS) were prepared during these 56 CSS, and microscopically examined; the sex ratio of this total sample was well balanced with 3406 TBS (=50.6%) from men (“M”) and 3321 TBS (49.4%) from women (W”). The overall Plasmodial prevalence (all Plasmodium sp gathered because P. falciparum infections, as already noticed, are largely preponderant) were similar 41.02% for M and 40.1% for W.
 The overall plasmodial prevalence significantly decreased from Year 2007 to Year 2008: respectively 47.8% (n= 2686) and 35.7% (n= 4041); but the plasmodial prevalence were similar each year between gender: in year 2007: PP= 48.9% (n=1338) for M and 46.7% (n= 1348) for W and in year 2008: 35.9% (n=2068) for Men and 35.6% (n=1973) for Women.
 In Year 2007 the PP of Men and Women were similar in each village; in Year 2008 the PP were similar in 5 villages, but in Libata PP was significantly higher in Men than in Women.
 The trends of change from year to year appeared similar for gender excepted in Capango where the PP remained similar in W and significantly decreased for M.
 In term of Parasite Load the comparison of median of parasitaemia with the non-parametric Mann-Whitney test showed similar distribution between gender each year in each village and their evolution from year to year appeared also similar in each gender excepted for Men in Libata.
 Conclusion: These possibilities of changes of plasmodial infections according to gender with time and villages must be taken into consideration when planning, implementing and analyzing parasitological data of symptomless carriers before, and after, a vector control program which must be implemented on a long term basis. They show that an “only one” CSS could lead to wrong information and conclusion of malaria and gender and the recommendation to carry on longitudinal regular field studies for relevant conclusion on malaria infections among communities.
 The next step will be to analyze the plasmodial infection in both gender after vector control implementation.

A Deadbeat Current and Flux Vector Control for IPMSM Drive with High Dynamic Performance

In this paper, a new deadbeat stator current and flux linkage vector control (DB-CFVC) scheme for interior permanent magnet synchronous machines (IPMSM) is proposed. The control structure is simplified by implementing the proposed flux linkage vector control method in the α-β stationary coordinate. Unlike conventional deadbeat methods, the dynamic performance of the proposed DB-CFVC can be enhanced while voltage command saturation and over output current are avoided. This is achieved with a “reinforced” phase angle reference of stator flux linkage vector by considering rotor speed error and maximum voltage to properly enhance the quality of the calculated flux phase angle command. By predicting stator flux linkage and current in the stationary coordinate, the deadbeat direct flux linkage vector control based on the one-step delay compensation strategy becomes straightforward and exhibits low sensitivity to motor parameters compared to conventional methods performed in the rotating frame. Then, by developing a practical and robust hybrid flux linkage observer, the proposed DB-CFVC method can work more reliably and effectively than conventional methods. Simulations and experiments are conducted in a drive system for an IPMSM to evaluate the effectiveness and reliability of the proposed method.

Research on robust control method of permanent magnet synchronous motor

Abstract During the operation of permanent magnet synchronous motor, the traditional vector control method does not match the regulator parameters with the actual parameters due to the disturbance factors such as motor parameter perturbation and load change, resulting in the decline of control performance. The research object of robust control is uncertain system, which has natural advantages for improving the robustness of control system. Firstly, this paper introduces the basic principle and implementation process of robust control, simulates and analyzes the influence of motor parameters on control performance, investigates and summarizes the improvement methods of traditional vector control, and points out the advantages and disadvantages of each scheme; Secondly, the similarities and differences of the improved methods are analyzed and compared; Finally, the development trend of permanent magnet synchronous motor control technology based on robust control is prospected.

Genetic Stability and Fitness of Aedes aegypti Red-Eye Genetic Sexing Strains With Pakistani Genomic Background for Sterile Insect Technique Applications.

The mosquito species Aedes aegypti is the primary transmitter of viruses that cause endemic diseases like dengue in Pakistan. It is also a cause of other vector-borne diseases like yellow fever, Zika fever, and chikungunya, which significantly impact human health worldwide. In the absence of efficient vaccines (except for yellow fever) or drugs, vector control methods, such as the sterile insect technique (SIT), have been proposed as additional tools for the management of these diseases. Mosquito SIT programs are based on the release of sterile males and it is important female releases to be ideally zero or to be kept at a minimum, since females are the ones that bite, blood-feed and transmit pathogens. Recently, an Ae. aegypti genetic sexing strain (GSS), with and without a recombination-suppressing inversion (Inv35), was developed using the eye color as a selectable marker, with males having black eyes and females red eyes. In the present study, we introgressed the sexing features and the Inv35 of the Ae. aegypti red-eye GSS into the Pakistani genomic background aiming to their future use for SIT applications in the country. Both introgressed strains, the Red-eye GSS-PAK and the Red-eye GSS/Inv35-PAK, were evaluated in respect to their genetic stability and biological quality by assessing parameters like recombination rate, fecundity, fertility, pupal and adult recovery, time of development, pupal weight, survival, and flight ability in comparison with a wild Pakistani population (PAK). The results suggest that the sexing features and the recombination suppression properties of Inv35 were not affected after their introgression into the local genomic background; however, some biological traits of the two newly constructed strains were affected, positively or negatively, suggesting that a thorough quality control analysis should be performed after the introgression of a GSS into a new genomic background prior to its use in SIT field trials or applications. The importance of using GSS with local genomic background for SIT applications against Aedes aegypti is also discussed.

Long-term evolution of Plasmodium falciparum gametocytes index during a village scale malaria vector control program comparing durable lining, long-lasting treated net and indoor residual spraying in Angola

Rationale: Due to the serious side effect of some anti-gametocyte drugs on G6PG efficiency carriers, a special attention was given to the possible influence of vector control on the evolution of P. falciparum gametocyte index (GI) in the framework of the long-term village scale malaria vector control project implemented in 8 villages around the Balombo town (Angola). The aim of the project was to compare, in paired villages, the epidemiological efficacy of Long lasting deltamethrin Insecticide Treated Nets (δLLIN), lambdacyhalothrin Inside Residual Spraying (ʎIRS), and deltamethrin Insecticide Treated Plastic Sheeting (δITPS) applied on the indoor walls of houses, used alone, or associated with δLLIN or after the 2 rounds of λIRS. Methods: The program started in 2007 and full vector control (VC) implementation was done in December 2008 owing two years of baseline data collection in the 8 selected villages around Balombo city. Parasitological evaluation was based upon regular cross-sectional surveys (CSS) on randomized samples of population for each survey, focusing ≤ 15 years children, to compare GI before/after and here/there according to each VC method. Field made thick blood smears (TBS) were microscopically examined by the same team of the Medical Department of the Angolese Sonamet Company, which supported the trial, with 10% of randomized slides double-checked in OCEAC, Yaoundé (Cameroon). Results: 234 cross-sectional surveys were carried between 2007 and 2018. P. falciparum gametocytes were observed in 574 of the 23,822 thick blood smears examined for a GI of 2.41%. During the 3 years following the VC full implementation, the GI decreased by 71%, from 4.05% (n= 6,697) before VC to 1.17% (n= 7,667 after VC) with similar influence of each VC method. During the 5 following years GI remained at a very low level (0.23%; n=2,992). Due to the national malaria outbreak, an increase was noticed after 2015. The general CSS survey done in February 2018, 11 years after the first one (February 2007), showed in the same 5 villages a significant 80% decrease of GI, from 6.98% (n=773) to 1.42% (n=421). Conclusion: The trial showed that a long-term malaria village scale vector control program had a long lasting and significant impact on P. falciparum gametocytes and the influence of VC on GI could therefore be recommended as another relevant objective of the National Malaria Control Program.

Sand Flies (Diptera: Psychodidae): Fauna and Ecology in the Northeast of Algeria

Sand flies (Diptera: Psychodidae) transmit several Leishmania (Kinetoplastida: Trypanosomatidae) species, which cause leishmaniasis, a significant public health concern in Algeria. We compared sand fly species abundance and composition among different biotopes (urban, peri-urban, rural areas), bioclimatic zones (humid, sub-humid, semi-arid), and elevation ranges. We also used the additive partitioning of beta diversity to test whether the variation in sand fly composition among biotopes, bioclimatic zones, and elevation ranges is due to species turnover or community subsetting. In total, 7,478 specimens were captured; of which, 7,162 (51.5% males vs. 48.5% females) belong to eight species: Phlebotomus perniciosus Newstead, 1911 (77.4% of the total captured specimens), Phlebotomus perfiliewi Parrot, 1930 (14.6%), Phlebotomus longicuspis Nitzulescu, 1911 (5.9%), Phlebotomus papatasi Scopoli, 1786 (<1%), Phlebotomus sergenti Parrot, 1917 (<1%) and Phlebotomus chadlii Rioux, Juminer et Gibily 1966 (<1%), Sergentomyia minuta Adler et Theodor, 1927 (1%), and Sergentomyia fallax Parrot, 1921 (<1%). Sand fly total abundance showed negative correlations with altitude and was significantly higher in rural areas. Sandfly community composition was significantly different between rural and urban/peri-urban areas. The additive partitioning of beta diversity showed that 71.4% of the compositional dissimilarity among elevation ranges and bioclimates was due to sand fly species turnover, and 28.6% resulted from nestedness. However, the variation in sand fly composition among different biotopes was mainly due to community nestedness. Findings from this study help define the risk of Leishmania transmission and develop methods for vector control in Mila province and Algeria as a whole.

The ecdysone receptor regulates several key physiological factors in Anopheles funestus

BackgroundMalaria is a devastating disease, transmitted by female Anopheles mosquitoes infected with Plasmodium parasites. Current insecticide-based strategies exist to control the spread of malaria by targeting vectors. However, the increase in insecticide resistance in vector populations hinder the efficacy of these methods. It is, therefore, essential to develop novel vector control methods that efficiently target transmission reducing factors such as vector density and competence. A possible vector control candidate gene, the ecdysone receptor, regulates longevity, reproduction, immunity and other physiological processes in several insects, including malaria vectors. Anopheles funestus is a prominent vector in sub-Saharan Africa, however, the function of the ecdysone receptor in this mosquito has not previously been studied. This study aimed to determine if the ecdysone receptor depletion impacts An. funestus longevity, reproduction and susceptibility to Plasmodium falciparum infection.MethodsRNA interference was used to reduce ecdysone receptor expression levels in An. funestus females and investigate how the above-mentioned phenotypes are influenced. Additionally, the expression levels of the ecdysone receptor, and reproduction genes lipophorin and vitellogenin receptor as well as the immune gene, leucine rich immune molecule 9 were determined in ecdysone receptor-depleted mosquitoes using quantitative polymerase chain reaction.ResultsEcdysone receptor-depleted mosquitoes had a shorter lifespan, impaired oogenesis, were less fertile, and had reduced P. falciparum infection intensity.ConclusionsOverall, this study provides the first experimental evidence that supports ecdysone receptor as a potential target in the development of vector control measures targeting An. funestus.

EVITA Dengue: a cluster-randomized controlled trial to EValuate the efficacy of Wolbachia-InfecTed Aedes aegypti mosquitoes in reducing the incidence of Arboviral infection in Brazil

BackgroundArboviruses transmitted by Aedes aegypti including dengue, Zika, and chikungunya are a major global health problem, with over 2.5 billion at risk for dengue alone. There are no licensed antivirals for these infections, and safe and effective vaccines are not yet widely available. Thus, prevention of arbovirus transmission by vector modification is a novel approach being pursued by multiple researchers. However, the field needs high-quality evidence derived from randomized, controlled trials upon which to base the implementation and maintenance of vector control programs. Here, we report the EVITA Dengue trial design (DMID 17-0111), which assesses the efficacy in decreasing arbovirus transmission of an innovative approach developed by the World Mosquito Program for vector modification of Aedes mosquitoes by Wolbachia pipientis.MethodsDMID 17-0111 is a cluster-randomized trial in Belo Horizonte, Brazil, with clusters defined by primary school catchment areas. Clusters (n = 58) will be randomized 1:1 to intervention (release of Wolbachia-infected Aedes aegypti mosquitoes) vs. control (no release). Standard vector control activities (i.e., insecticides and education campaigns for reduction of mosquito breeding sites) will continue as per current practice in the municipality. Participants (n = 3480, 60 per cluster) are children aged 6–11 years enrolled in the cluster-defining school and living within the cluster boundaries who will undergo annual serologic surveillance for arboviral infection. The primary objective is to compare sero-incidence of arboviral infection between arms.DiscussionDMID 17-0111 aims to determine the efficacy of Wolbachia-infected mosquito releases in reducing human infections by arboviruses transmitted by Aedes aegypti and will complement the mounting evidence for this method from large-scale field releases and ongoing trials. The trial also represents a critical step towards robustness and rigor for how vector control methods are assessed, including the simultaneous measurement and correlation of entomologic and epidemiologic outcomes. Data from this trial will inform further the development of novel vector control methods.Trial registrationClinicalTrials.govNCT04514107. Registered on 17 August 2020Primary sponsor: National Institute of Health, National Institute of Allergy and Infectious Diseases

Behavioural alterations in female Aedes aegypti mosquito in response to entomopathogenic fungal infections.

Due to the rapid rise in arboviral disease cases, there is a need for alternative methods of vector control since fast growing insecticides resistance is a matter of great concern. Recent studies have shown the potential of entomopathogenic fungi in controlling mosquito vectors, but behavioural responses of the mosquitoes encountering with entomopathogenic fungi are still unclear. In this study, behavioural responses induced by the entomopathogenic fungus Metarhizium anisopliae (Metschnikoff) Sorokin in adult female Aedes aegypti mosquito were evaluated. The survival of female mosquitoes was significantly reduced after exposure to medium and high concentrations of fungal conidia. A significant increase in frequencies and durations of different self-grooming types was observed in mosquitoes exposed to medium or high concentrations of fungal conidia. Mosquitoes were able to differentiate between active and inactive fungal conidia as application of inactive conidia showed non-significant effect on survival and self-grooming parameters. A concentration-specific reduction in flight locomotor activity of the female mosquitoes was found after fungal treatments. Fungal-exposed mosquitoes showed significantly higher antifungal activity 72 h post-application. These findings provide greater understanding of behavioural responses of the mosquitoes to resist fungal infections and suggest that mosquitoes can remove the lower amounts of fungal conidia through self-grooming behaviour, which they encounter within natural field conditions.

Large-scale (Phase III) evaluation of broflanilide 50WP (VECTRON\u2122 T500) for indoor residual spraying for malaria vector control in Northeast Tanzania: study protocol for a two-arm, non-inferiority, cluster-randomised community trial

BackgroundIndoor residual spraying (IRS) is a major method of malaria vector control across sub-Saharan Africa. Effective control is being undermined by the rapid spread of insecticide resistance. There is major investment in development of new insecticides for IRS that possess novel modes of action, long residual activity, low mammalian toxicity and minimal cross-resistance. VECTRON™ T500, a new IRS product containing the active ingredient broflanilide as a 50% wettable powder (WP), has been shown to be efficacious against pyrethroid susceptible and resistant vector species on mud and concrete substrates in experimental hut (Phase II) trials.MethodsA two-arm non-inferiority cluster randomized controlled trial (Phase III) will be undertaken in Muheza District, Tanga Region, Tanzania. VECTRON™ T500 will be compared to the IRS product Fludora® Fusion (clothianidin 50% WP + deltamethrin 6.25% WP). The predominant malaria vectors in the study area are pyrethroid-resistant Anopheles gambiae s.s., An. arabiensis and An. funestus s.s. Sixteen village clusters will be pair-matched on baseline vector densities and allocated to reference and intervention arms. Consenting households in the intervention arm will be sprayed with VECTRON™ T500 and those in the reference arm will be sprayed with Fludora® Fusion. Each month, CDC light traps will collect mosquitoes to estimate changes in vector density, indoor biting, sporozoite and entomological inoculation rates (EIR). Susceptibility to IRS active ingredients will be assessed using World Health Organisation (WHO) bottle bioassays. Target site and metabolic resistance mechanisms will be characterised among Anopheles field populations from both trial arms. Residual efficacy of both IRS products will be monitored for 12 months post intervention. Questionnaire and focus group discussions will explore factors that influence adherence, adverse effects and benefits of IRS.DiscussionThis protocol describes a large-scale non-inferiority evaluation of a novel IRS product to reduce the density and EIR of pyrethroid-resistant Anopheles vectors. If VECTRON™ T500 proves non-inferior to Fludora® Fusion, it will be considered as an additional vector control product for malaria prevention and insecticide resistance management.Trial registration: ClinicalTrials.gov, NCT05150808, registered on 26 November 2021. Retrospectively registered.

The Impact of Malaria on Various Stages in Pregnancy in Rivers State

Malaria parasitaemia has remained an issue of public health concern. The coexistence of malaria and pregnancy is more burdensome with high mortality and other devastating effects on maternal and child health. This cross-sectional study carried out was focused on the impact of malaria among pregnant women attending antenatal clinics in General Hospital, Bori and Braithwaite Memorial Specialist Hospital, Port Harcourt. Four hundred women were involved in this study of which two hundred each from a facility. Pregnant women with pyrexia of unknown origin, HIV and those on anti-malarial drugs were excluded. Simple random sampling technique was used. Primary and secondary data sources were used including the use of a self-structured questionnaire comprising socio-demographic variables and items about gestation and pregnancy history. Statistical analysis involved the use of Statistical Package for Social Sciences version 25 for descriptive and inferential statistics – Chi Square at 0.05 level of significance. Laboratory investigation was according to the recommended standard analytical method for malaria parasite examination. Five milliliters (5mls) of blood was obtained from each subject by venepuncture into EDTA bottles. The samples were used to assay for malaria parasite determination using the Giemsa staining technique. Result revealed that pregnant women in the first trimester had the highest prevalence of malaria; BMSH (43.9%) and GHB (45.5%). Preventive safe practices are recommended including the use of insecticide treated nets, vector control methods and others. Diagnosis and treatment should be done timely especially in the first trimester.

Diurnal and nocturnal mosquitoes escape looming threats using distinct flight strategies

Flying insects have evolved the ability to evade looming objects, such as predators and swatting hands. This is particularly relevant for blood-feeding insects, such as mosquitoes that routinely need to evade the defensive actions of their blood hosts. To minimize the chance of being swatted, a mosquito can use two distinct strategies-continuously exhibiting an unpredictable flight path or maximizing its escape maneuverability. We studied how baseline flight unpredictability and escape maneuverability affect the escape performance of day-active and night-active mosquitoes (Aedes aegypti and Anopheles coluzzii, respectively). We used a multi-camera high-speed videography system to track how freely flying mosquitoes respond to an event-triggered rapidly approaching mechanical swatter, in four different light conditions ranging from pitch darkness to overcast daylight. Results show that both species exhibit enhanced escape performance in their natural blood-feeding light condition (daylight for Aedes and dark for Anopheles). To achieve this, they show strikingly different behaviors. The enhanced escape performance of Anopheles at night is explained by their increased baseline unpredictable erratic flight behavior, whereas the increased escape performance of Aedes in overcast daylight is due to their enhanced escape maneuvers. This shows that both day and night-active mosquitoes modify their flight behavior in response to light intensity such that their escape performance is maximum in their natural blood-feeding light conditions, when these defensive actions by their blood hosts occur most. Because Aedes and Anopheles mosquitoes are major vectors of several deadly human diseases, this knowledge can be used to optimize vector control methods for these specific species.

Chattering Reduction Using Boundary-SMC on Low-Speed Setting of 3-Phase Induction Motor with IFOC Method

Vector control has been widely used in induction motor speed settings due to its high performance and ability to be separately controlled as DC motors. Indirect Field Oriented Control (IFOC) is a vector control method applicable to induction motors due to the ease of design and implementation. However, its performance decreases due to changes in motor parameter variations and load disturbances, which led to the use of Sliding Mode Control (SMC), capable of resisting and stabilizing parameter changes and load disturbances. In the First Order Sliding Mode Control (FOSMC), a dangerous chattering phenomenon occurs and results in the stability of the control system. Therefore, this research designed a Boundary-SMC controller to control the speed of a 3-phase induction based on IFOC with a change in load disturbance to reduce the chattering phenomenon at low speeds, where the largest percentage occurs. Furthermore, this research used Lyapunov's stability theory to ensure stability with the performance of these controls monitored and analyzed in LabView. The results showed that FOSMC has better resilience and stability than PID, with a steady error rate of 0.001% and a chattering percentage of 0.12%. With Boundary-SMC, the chattering percentage and stiffness are reduced to 0.005% and 0.284%, respectively.

Single nucleotide polymorphism (SNP) in the doublesex (dsx) gene splice sites and relevance for its alternative splicing in the malaria vector Anopheles gambiae

Background: The malaria burden continues to be significant in tropical regions, and conventional vector control methods are faced with challenges such as insecticide resistance. To overcome these challenges, additional vector control interventions are vital and include modern genetic approaches as well as classical methods like the sterile insect technique (SIT). In the major human malaria vector Anopheles gambiae, a candidate gene favourable for sterility induction is the doublesex (dsx) gene, encoding somatic sexually dimorphic traits in mosquitoes. However, the mechanism that regulates the expression of this gene in anopheline mosquitoes is poorly understood. This study aimed to screen the An. gambiae dsx gene splice site sequences for single nucleotide polymorphisms (SNPs) that could be critical to its alternative splicing. Methods: Variant annotation data from Ag1000G project phase 2 was analysed, in order to identify splice-relevant SNPs within acceptor and donor splice sites of the An. gambiae dsx gene (Agdsx). Results: SNPs were found in both donor and acceptor sites of the Agdsx. No splice-relevant SNPs were identified in the female-specific intron 4 acceptor site and the corresponding region in males. Two SNPs (rs48712947, rs48712962) were found in the female-specific donor site of exon 5. They were not specific to either males or females as the rs48712947 was found in female mosquitoes from Cameroon, and in both males and females from Burkina Faso. In the other splice sites, the intron 3 acceptor site carried the greatest abundance of SNPs. Conclusions: There were no gender association between the identified SNPs and the random distribution of these SNPs in mosquito populations. The SNPs in Agdsx splice sites are not critical for the alternative splicing. Other molecular mechanisms should be considered and investigated.

Dynamics of a mosquito population suppression model with a saturated Wolbachia release rate

Releasing factory-reared Wolbachia-infected males to suppress wild females has been proven to be an effective method for mosquito vector control. We develop a delay differential equation model to study the interactive dynamics of released males and wild females under a saturated release strategy. Two thresholds on the release rate are found to offer a relatively complete description on the attraction basin of the origin, whose stability is necessary to suppression of wild females.

Situation of insecticide resistance in malaria vectors in the World Health Organization of Eastern Mediterranean region 1990-2020.

Malaria is the most important mosquito-borne disease, which is transmitted by Anopheles species. According to the recent report of World Health Organization, there were an estimated 229 million malaria cases in 2019 in 87 malaria endemic countries. There are several vector control method specially using pesticides. The aim of this study was to collect all the data about insecticide resistant of malaria vectors in the Eastern Mediterranean region countries. In this study, all the published papers related to insecticide resistance of malaria vectors in the region were collected and resistant status of vectors in the countries was mapped. Resistance to different insecticide classes such as pyrethroids, organophosphate, organochlorine and carbamates were evaluated using World Health Organization guidelines. Results showed a wide variety of susceptibility/resistance status to these chemicals according to the location, historical context of pesticide used, genetic background of vectors, age and abdominal conditions of adults may play a role in the susceptibility status of these species to different insecticides. The results of this study is providing a guideline for countries to manage their vector control activities against insecticide resistance of malaria vectors and provide novel approaches such as male sterility, using Wolbachia, using new insecticide with new mode of action.

A novel fuel-cell-driven system for rail transit vehicles based on dual-source motors

Currently, to alleviate environmental problems and energy crises, fuel cells are gradually being used in rail transit vehicle drive systems. In existing fuel-cell-driven systems, direct current (DC)/DC converters are widely used, but there are serious shortcomings in terms of cost, efficiency and market application. To solve these problems, a novel dual-source-driven system is innovatively presented in this study. In the dual-source-driven system, the multi-mode operating state of the dual-source motor was taken into consideration, and based on the independent vector control method, the dual-source-driven system was modelled and simulated to achieve the motor-independent control between power output and power generation as well as the energy exchange between fuel cell and secondary power battery under any working conditions. To verify the effectiveness of the proposed dual-source-driven system, the electric-driven performance test was carried out by the dual-source system experimental verification platform. The result for this drive system topology is further improved compared with the same level of DC/DC-driven system configuration used for this purpose.