Mosquito Population Suppression Research Articles

Upscaling the production of sterile male mosquitoes with an automated pupa sex sorter.

Effective mosquito population suppression has been repeatedly demonstrated in field trials through the release of male mosquitoes to induce sterile mating with wild females using the incompatible insect technique (IIT), the sterile insect technique (SIT), or their combination. However, upscaling these techniques requires a highly efficient and scalable approach for the sex separation of mass-reared mosquitoes to minimize the unintentional release of females, which can lead to either population replacement or biting nuisance, a major bottleneck up to now. Here, we report the successful development of an automated mosquito pupa sex sorter that can effectively separate large numbers of males from females for population suppression of Aedes aegypti, A. albopictus, and Culex quinquefasciatus. The male production capacity of the automated sex sorter was increased by ~17-fold compared with manual sex separation with the Fay-Morlan sorter and enabled one person to separate 16 million males per week. With ~0.5% female contamination, the produced males exhibited high flight ability and mating performance. The field trial demonstrates that the quality of A. albopictus males produced using the automated sex sorter is suitable for inducing population suppression. These results indicate that the automated sex sorter offers the potential to upscale IIT and SIT against mosquito vectors for disease control.

Integrating pyriproxyfen into the incompatible insect technique enhances mosquito population suppression efficiency and eliminates the risk of population replacement.

The incompatible insect technique (IIT) has been used for Aedes mosquito population suppression to curb the transmission of dengue. However, its wide application is limited owing to the low output of male mosquitoes and the risk of population replacement from the release of fertile Wolbachia-infected females. This study aims to improve IIT efficiency for broader adoption. We assessed the impact of 10% pyriproxyfen (PPF) sticky powder exposure on Wolbachia (from Culex molestus)-transinfected Aedes albopictus Guangzhou line (GUA line) (GC) mosquitoes. We found that the exposure caused chronic toxicity in adult mosquitoes without affecting the cytoplasmic incompatibility (CI)-inducing capability of males. The PPF-contaminated GC females exhibited significant sterilization and the ability to disseminate lethal doses of PPF to breeding sites. Subsequently, we conducted a field trial combining PPF with IIT aiming to suppress the Ae. albopictus population. This combined approach, termed boosted IIT (BIIT), showed a notable enhancement in population suppression efficiency. The improved efficacy of BIIT was attributed to the dispersion of PPF particles in the field via the released PPF-contaminated male mosquitoes. During the BIIT field trial, no Wolbachia wPip-positive Ae. albopictus larvae were detected, indicating the effective elimination of the risk of Wolbachia-induced population replacement. Additionally, the field trial of BIIT against Ae. albopictus resulted in the suppression of the nontarget mosquito species Culex quinquefasciatus. Our results highlight the remarkable efficiency and feasibility of combining IIT with PPF in suppressing mosquito populations, facilitating the widespread implementation of IIT-based management of mosquito-borne diseases. © 2024 Society of Chemical Industry.

Impacts of diapause eggs on mosquito population suppression based on incompatible or sterile insect technique

Mosquito-borne diseases kill more than 700, 000 people a year, and the toll continues to rise. Controlling mosquito population is the key measure to prevent mosquito-borne diseases. Releasing sterile male mosquitoes to suppress wild mosquito population is an environmentally friendly and efficient method, which has been proven to successfully eliminate wild mosquitoes in laboratory, but it is difficult to achieve such effectiveness in the field. The diapause of mosquito eggs is considered an important factor hindering mosquito population suppression. In this paper, we formulate an ordinary differential equation model to discuss the impact of diapause eggs on mosquito population suppression. We prove that there exists at most one periodic solution in our model, and obtain sufficient and necessary conditions for the existence of an unique periodic solution. We give numerical simulations to confirm our theoretical results.

Modelling mosquito population suppression based on competition system with strong and weak Allee effect.

Mosquito-borne diseases are threatening half of the world's population. To prevent the spread of malaria, dengue fever, or other mosquito-borne diseases, a new disease control strategy is to reduce or eradicate the wild mosquito population by releasing sterile mosquitoes. To study the effects of sterile insect technique on mosquito populations, we developed a mathematical model of constant release of sterile Aedes aegypti mosquitoes with strong and weak Allee effect and considered interspecific competition with Anopheles mosquitoes. We calculated multiple release thresholds and investigated the dynamical behavior of this model. In order to get closer to reality, an impulsive differential equation model was also introduced to study mosquito suppression dynamics under the strategy of releasing $ c $ sterile male mosquitoes at each interval time $ T $. Finally, the relationship between the releasing amount or the waiting period and the number of days required to suppress mosquitoes was illustrated by numerical simulations.

Mirrored dynamics of a wild mosquito population suppression model with Ricker-type survival probability and time delay.

Here, we formulated a delayed mosquito population suppression model including two switching sub-equations, in which we assumed that the growth of the wild mosquito population obeys the Ricker-type density-dependent survival function and the release period of sterile males equals the maturation period of wild mosquitoes. For the time-switched delay model, to tackle with the difficulties brought by the non-monotonicity of its growth term to its dynamical analysis, we employed an essential transformation, derived an auxiliary function and obtained some expected analytical results. Finally, we proved that under certain conditions, the number of periodic solutions and their global attractivities for the delay model mirror that of the corresponding delay-free model. The findings can boost a better understanding of the impact of the time delay on the creation/suppression of oscillations harbored by the mosquito population dynamics and enhance the success of real-world mosquito control programs.

Finite-Time Contraction Stability and Optimal Control for Mosquito Population Suppression Model

Releasing Wolbachia-infected mosquitoes into the wild to suppress wild mosquito populations is an effective method for mosquito control. This paper investigates the finite-time contraction stability and optimal control problem of a mosquito population suppression model with different release strategies. By taking into account the average duration of one reproductive cycle and the influences of environmental fluctuations on mosquitoes, we consider two cases: one with a time delay and another perturbed by stochastic noises. By employing Lyapunov’s method and comparison theorem, the finite-time contraction stabilities of these two cases under a constant release strategy are analyzed. Sufficient conditions dependent on delay and noise for these two systems are provided, respectively. These conditions are related to the prespecified bounds in finite-time stability (FTS) and finite-time contraction stability (FTCS) of the system, and FTCS required stronger conditions than FTS. This also suggests that the specified bounds and the delay (or the noise intensity) play a critical role in the FTCS analysis. And finally, the optimal control for the stochastic mosquito population model under proportional releases is researched.

Dynamics of discrete Ricker models on mosquito population suppression

Dengue fever is currently one of the most serious mosquito‐borne infectious disease in the world. How to effectively prevent the outbreak of dengue fever has become a matter of significant public health concern. In this work, the cytoplasmic incompatibility induced by Wolbachia is assumed to be complete. Based on this assumption, we establish an extended discrete Ricker model with overlapping generations to investigate the suppression of mosquito population in the wild by adopting two different release strategies: the constant release strategy and the proportional release strategy. We prove the nonnegativity, boundedness, and stability of equilibrium points and finally find the release threshold, denoted as and , for the successful suppression in these two release strategies. In addition, we demonstrate that the model that adopts the constant release strategy, respectively, has a saddle node bifurcation when and a stable period‐doubling bifurcation when . While in the case of proportional release strategy, the model exhibits a transcritical bifurcation when and a stable period‐doubling bifurcation when . Finally, we substantiate the conclusions through numerical simulations.

Global dynamics of a mosquito population suppression model with seasonal switching

Global dynamics of a mosquito population suppression model with seasonal switching

Data-driven networking of global transcriptomics and male sexual development in the main malaria vector, Anopheles funestus

Deaths from malaria remain staggering despite global support that drives research into new territories. One major gap is our understanding of the sexual biological aspects of the male mosquito, which maintain the vector population solidity. Although Anopheles funestus s.s. is an extremely efficient African vector, little is known about the network between its sexual physiology and gene expression. The Culicidae male’s sexual maturity involves a suite of physiological changes, such as genitalia rotation that is necessary for successful mating to occur. We show that mating success is guided by genes and physiological plasticity. Transcriptome analysis between newly emerged males (immature) versus males with rotating genitalia (maturing) provides insight into possible molecular mechanisms regulating male sexual behaviour. Putative transcripts that were associated with male sexual maturation were identified and validated. The discovery of the functions of these transcripts could lead to identifying potential targets for innovative vector control interventions, and mosquito population suppression.

Modeling the Impact of Migration on Mosquito Population Suppression

Modeling the Impact of Migration on Mosquito Population Suppression

Estimating mosquito abundance and population suppression in an incompatible insect technique study

Abstract Aedes aegypti (L.) is an invasive mosquito responsible for vectoring diseases such as dengue, Zika and Chikungunya. Dengue affects a large proportion of the global population, with the World Health Organization estimating that half the global population is at risk, with 390 million infections occurring each year. Control of mosquito vector populations over large geographical scales can be improved and made economically viable by computer models with potential to aid decision support. We introduce a method for estimating mosquito abundance (population size) over time in biocontrol programmes that involve the release of sterilised insects. We employ Bayesian state‐space modelling to provide insight into population trajectories using data from an application of incompatible insect technique (IIT) biological control, in Far North Queensland, Australia. The general approach could be adapted to other insect species. We demonstrate how the modelling approach can estimate trajectories of abundance over time as an unmarked–release–recapture analysis. Additionally, it provides a means for quantifying population suppression in IIT programmes (a statistic that can be challenging to estimate in practice) using counterfactuals. Modelling results show that estimated population trajectories exhibit similar temporal patterns to raw trapping rate data collected in the field, for example, the presence of peaks (and troughs) associated with the timing of rainfall events. Additional confidence in our model was demonstrated through a cross‐validation study where we left out each of the six landscapes from our dataset, fit the model using the remaining five regions and assessed its predictive skill. Modelled counterfactuals allowed us to estimate that population suppression in treated landscapes was 95%–99%. Synthesis and applications. Our model can provide valuable insights that can shape decision support systems in sterile insect technique and incompatible insect technique programmes operating over large geographical scales. The model helps determine how many sterile/incompatible insects should be released over time and how population control is progressing (via use of counterfactual scenarios). These outcomes are achieved because the model provides estimates of wild‐type populations over time, even when there has been no differentiation between sterile/incompatible and wild‐type insects caught in traps.

DMKPs provide a generalizable strategy for studying genes required for reproduction or viability in nontraditional model organisms.

The advent of CRISPR/Cas9-mediated genome editing has expanded the range of animals amenable to targeted genetic analysis. This has accelerated research in animals not traditionally studied using molecular genetics. However, studying genes essential for reproduction or survival in such animals remains challenging, as they lack the tools that aid genetic analysis in traditional genetic model organisms. We recently introduced the use of distinguishably marked knock-in pairs (DMKPs) as a strategy for rapid and reliable genotyping in such species. Here we show that DMKPs also facilitate the maintenance and study of mutations that cannot be maintained in a homozygous state, a group which includes recessive lethal and sterile mutations. Using DMKPs, we disrupt the zero population growth locus in Drosophila melanogaster and in the dengue vector mosquito Aedes aegypti. In both species, DMKPs enable the maintenance of zero population growth mutant strains and the reliable recovery of zero population growth mutant animals. Male and female gonad development is disrupted in fly and mosquito zero population growth mutants, rendering both sexes sterile. In Ae. aegypti, zero population growth mutant males remain capable of inducing a mating refractory period in wild-type females and of competing with wild-type males for mates, properties compatible with zero population growth serving as a target in mosquito population suppression strategies. DMKP is readily generalizable to other species amenable to CRISPR/Cas9-mediated gene targeting, and should facilitate the study of sterile and lethal mutations in multiple organisms not traditionally studied using molecular genetics.

Global suppression and periodic change of the mosquito population in a sterile release model with delay

In this paper, we study a mosquito population suppression model with a time-delay effect, which includes explicitly the growth stage and sex structure of the mosquito population. According to the release function of sexually active sterile male mosquitoes in the field, we determine a release threshold and obtain sufficient conditions to successfully suppress the wild mosquito population. When these conditions are not satisfied, we use the fixed point theorem to obtain the existence of positive periodic solutions and determine their existence region for the common periodic release case in practice. Finally, we present a numerical example to support our theoretical results.

A mosquito population suppression model with a saturated Wolbachia release strategy in seasonal succession

Releasing Wolbachia-infected male mosquitoes to suppress wild female mosquitoes through cytoplasmic incompatibility has shown great promise in controlling and preventing mosquito-borne diseases. To make the release logistically and economically feasible, we propose a saturated release strategy, which is only implemented during the epidemic season of mosquito-borne diseases. Under this assumption, the model becomes a seasonally switching ordinary differential equation model. The seasonal switch brings rich dynamics, including the existence of a unique periodic solution or exactly two periodic solutions, which are proved by using the qualitative property of the Poincaré map. Sufficient conditions are also obtained for determining the stability of the periodic solutions.

Global dynamics of a mosquito population suppression model with stage and sex structure

<abstract><p>In this paper, we study a kind of mosquito population suppression model incorporating the growth stage as well as the sex structure of mosquitoes. For the general non-autonomous case, a threshold $ m^* $ for the number of sexually active sterile mosquitoes in the field is defined, and sufficient conditions for successful suppression and partial suppression of wild mosquito population are obtained. For the first special case when the release period of the sterile mosquito is equal to its sexual lifespan, we determined the initial population size under which the mosquito population can be suppressed finally for different release intensities. For the latter special case when sterile mosquitoes are released with a constant rate, we give a threshold $ u^* $ for the release rate, and investigate the dynamic behavior of the system based on this threshold. Finally, some numerical examples are presented to confirm the theoretical results.</p></abstract>

Rich and complex dynamics of a time-switched differential equation model for wild mosquito population suppression with Ricker-type density-dependent survival probability

<abstract><p>Dengue presents over 390 million cases worldwide yearly. Releasing <italic>Wolbachia</italic>-infected male mosquitoes to suppress wild mosquitoes via cytoplasmic incompatibility has proven to be a promising method for combating the disease. As cytoplasmic incompatibility causes early developmental arrest of the embryo during the larval stage, we introduce the Ricker-type survival probability to assess the resulting effects. For periodic and impulsive release strategies, our model switches between two ordinary differential equations. Owing to a Poincaré map and rigorous dynamical analyses, we give thresholds $ T^*, c^* $ and $ c^{**} (>c^*) $ for the release period $ T $ and the release amount $ c $. Then, we assume $ c > c^* $ and prove that our model admits a globally asymptotically stable periodic solution, provided $ T > T^* $, and it admits at most two periodic solutions when $ T < T^* $. Moreover, for the latter case, we assert that the origin is globally asymptotically stable if $ c\ge c^{**} $, and there exist two positive numbers such that whenever there is a periodic solution, it must initiate in an interval composed of the aforementioned two numbers, once $ c^* < c < c^{**} $. We also offer numerical examples to support the results. Finally, a brief discussion is given to evoke deeper insights into the Ricker-type model and to present our next research directions.</p></abstract>

Dynamical behavior of a mosquito population suppression model composed of two sub-models

In this paper, a new mosquito population suppression model with stage and sex structure is constructed, which is composed of two sub-models switching each other. Sterile mosquitoes are released with period [Formula: see text] and remain sexually active for time [Formula: see text]. For the case [Formula: see text], three thresholds [Formula: see text] [Formula: see text] and [Formula: see text] are determined for the release period [Formula: see text] and release amount [Formula: see text]. According to the values of [Formula: see text] and [Formula: see text] in different ranges determined by these thresholds, we study the dynamical behavior of the system for different release strategies, mainly including the existence and stability of the mosquito-extinction equilibrium and positive periodic solutions. Finally, some numerical simulations are performed to illustrate our results.

Modeling of periodic compensation policy for sterile mosquitoes incorporating sexual lifespan

In this paper, a delayed mosquito population suppression model with stage and sex structure is constructed incorporating periodic releases of the sterile mosquito and its sexual lifespan. Sterile mosquitoes are released periodically into the field to suppress the wild mosquito population, and only sexually active sterile mosquitoes are included in the interaction system of these two populations. According to the relationship between the release period and the sexual lifespan , we study the dynamic behaviors of the system, such as the existence of positive periodic solutions and the stability of extinction equilibrium in three cases. A series of numerical simulations are performed, which not only verify the reliability of the theoretical results but also make a numerical analysis of the open problems raised in the theoretical research.

The Effect of an Irradiation-Induced Recombination Suppressing Inversion on the Genetic Stability and Biological Quality of a White Eye-Based Aedes aegypti Genetic Sexing Strain.

Simple SummaryAedes aegypti is a vector of viruses transmitting diseases such as dengue, chikungunya, Zika, and yellow fever. Current vector population control methods, based mainly on insecticides, are ineffective and raise concerns due to their negative impact on the environment and human health. In this frame, the sterile insect technique (SIT), which relies on the mass production and release of sterile males to reduce fertile crosses in the natural population, has recently gained increased interest as an environment-friendly, species-specific method. Sterile males are the ‘active’ component of SIT, however, for SIT to be effectively applied in mosquitoes, the efficient elimination of females from the male release batch is a prerequisite, since they are blood-feeders and transmit pathogenic microorganisms. To this end, developing and utilizing genetic sexing strains (GSS) that facilitate sex separation are highly desirable. However, GSS must be stable during rearing and competitive in the field to be considered for operational release projects. Here, we present our findings regarding the genetic stability and biological quality of an Aedes aegypti GSS that is based on the white eye mutation. Moreover, we discuss the effects of the incorporation of a recombination-suppressing inversion on the strain’s biological quality and on important fitness parameters.Aedes aegypti is the primary vector of diseases such as dengue, chikungunya, Zika fever, and yellow fever. The sterile insect technique (SIT) has been proposed as a species-specific and environment-friendly tool for the suppression of mosquito vector populations as a major component of integrated vector management strategies. As female mosquitoes are blood-feeders and may transmit pathogenic microorganisms, mosquito SIT depends on the release of sterile males. Genetic sexing strains (GSS) can be used for the efficient and robust separation of males from females. Two Ae. aegypti GSS were recently developed by exploiting eye colour mutations, resulting in the Red-eye GSS (RGSS) and the White-eye GSS (WGSS). In this study, we compared two WGSS, with and without the chromosomal inversion 35 (Inv35), and evaluated their biological quality, including genetic stability. Our results suggest that the WGSS/Inv35 presents a low recombination rate and long-term genetic stability when recombinants are removed from the colony (filtering) and a slow accumulation of recombinants when they are not removed from the colony (non-filtering). The two strains were similar with respect to fecundity, pupal and adult recovery rates, pupation curve, and pupal weight. However, differences were detected in fertility, survival rate of females, and flight ability of males. The WGSS/Inv35 presented lower fertility, higher survival rate of females, and better flight ability of males compared to the WGSS.

Global Asymptotic Stability in a Delay Differential Equation Model for Mosquito Population Suppression

Global Asymptotic Stability in a Delay Differential Equation Model for Mosquito Population Suppression