Summarization of new Aedes aegypti mosquito control strategies.
The mosquito Aedes aegypti (Diptera: Culicidae), is adapted to different environments, mainly urban ones. They have a high degree of vectorial competence for viral diseases, especially Dengue, the arbovirus with the highest number of cases in the world. The adaptive ability of this insect and the abundance of breeding sites have undermined attempts at population’s control, resulting in a high degree of infestation in many regions of the world, resulting in a Dengue endemic. It is important to understand the different nuances of the insect in order to understand the adaptive capacity of this vector, through the knowledge of his behavior, to propose new strategies and engagement of population in proactive actions that allow the population control of this vector, especially in periods of greater proliferation. This chapter discusses population control strategies, in different scenarios and carried out by different researchers, mainly in Brazil.
- Aedes population control
- epidemiological surveillance
- mosquitoes control
- public health policies
The dissemination of this vector throughout the Brazilian territory was facilitated by the rapid displacement of the rural population to the urban environment without compatible sanitary conditions for the provision of essential services such as sewage and treated water, which contributes to the transmission of diseases, especially those of vector transmission [3, 4, 5]. In this context,
In Brazil, the first reports of dengue occurred in the late 19th century, in São Paulo (SP), and in the early 20th century, in Niterói (RJ), without laboratory diagnosis. However, in this period, the mosquito was already a problem, but not because of dengue, due to the transmission of yellow fever - which caused numerous outbreaks with a high mortality rate. In 1955, Brazil eradicated
At the end of the 1960s, the relaxation of the measures adopted led to the reintroduction of the vector into national territory. This period coincided with a period of intense and disorganized urbanization in several Brazilian cities. The industrialization has attracted the rural population to urban areas, leading to an exaggerated urban vegetative growth in a disorganized way and without adequate infrastructure, and many people living in conditions of poverty. The result was the resurgence of the mosquito and the occurrence of epidemic outbreaks of dengue, with the four serotypes, in addition to the proliferation of hemorrhagic dengue (the most serious manifestation of the disease) in all Brazilian states [3, 4, 7, 8].
In 1982 there was a new outbreak of Dengue in Roraima/RR, it was quickly controlled, and considered an epidemic. However, the first time that an epidemic was characterized in Brazil was in 1986–1987 from Nova Iguaçu/RJ, affecting several municipalities and with the largest number of cases in the northeast region. In 1990–1991 a second epidemic occurred, now with more than double the number of cases per 100,000 inhabitants [3, 4, 9, 10]. The Dengue virus was detected with a small outbreak of the disease in Mato Grosso do Sul during the year of 1987. Since then, the epidemics that occur in Brazil are also observed in our state, but especially in the most populous cities, where a moderate increase of cases is visible annually in the months of November and December, the first with the higher number of cases. January to July, coinciding with the increase in temperature, relative humidity and monthly precipitation [11, 12, 13].
Due to the growing number of cases, in different cities and regions of the country, the Ministry of Health started to organize itself in national actions and in 1996 launched the
In 2001, it was recognized that the mosquito eradication plan was not viable and a new activity plan was launched (called the Dengue Control Action Intensification Plan - DCAIP), with priority for the municipalities that transmit Dengue the most. In order to improve the DCAIP, in 2002, the National Dengue Control Program (NDCP) was launched, with an important change focusing on community mobilization [3, 14].
The implementation of the NDCP has an additional challenge in municipalities on the international frontier due to the movement of people between countries, making it a potential for the occurrence of epidemics; in this sense, dengue is the second most expressive disease in border municipalities. For example, in the municipalities of Corumbá and Ponta Porã (border with Bolivia and Paraguay respectively), the implementation of the NDCP was evaluated and considered partial. There was a demand for improvement
, with regard to the training of human resources. It was made like an answer to the inexistence or malfunction of the Municipal Committee for Mobilization, Monitoring and Evaluation of dengue control measures .
After a new Dengue epidemic in 2001–2002, the fight against the vector gained the participation of community health agents, who started to carry out preventive and control actions against dengue, according to the Ministry of Health Ordinance No. 44/GM. This initiative was important both for the optimization of resources and the greater involvement of the community in the fight against the mosquito [16, 17, 18].
Today, the four Dengue serotypes circulate throughout the country and it is not necessary to introduce a new serotype for new epidemics to occur, since we will always have susceptible people due to births, migration, and time interval between the occurrence of an epidemic with the same serotype [19, 20]. In addition to the number of cases that scare, the economic impact is also impressive and growing .
Besides that, the Dengue epidemic with thousands of cases annually across the country, in 2014 the first cases of Chikungunya in Brazil were reported and 8 months later in 2015 the first indigenous cases of Zika virus were also reported, both associated and transmitted by the vector
Some characteristics of epidemics in Brazil are important to highlight, among them the greatest number of cases occur in the first semester and it is important that measures to combat breeding sites and the application of adulticides are carried out as soon as the first cases are detected and not during the period. The epidemic, as transmission between people, occurs quickly and from cases concentrated in a city the number of cases increases rapidly and spreads throughout the city and what is interesting, despite the risk of dengue infection increases with the increase in the population of the mosquito; because infected mosquitoes live less and need to live at least ten more days infected before they are able to transmit the virus [24, 25, 26], epidemics are not always related to the size of the mosquito population, but with the susceptibility of the population to the serotypes prevalent in the period .
In an attempt to control these important diseases, not only in Brazil but in the world, global strategies have been proposed by WHO. WHO efforts were directed at obtaining reactive responses and intense proactivity for early disease warning systems, use of preventive measures, intense entomological and epidemiological surveillance, search for vaccines and strategies/products for vector control, and reduction of morbidity and mortality. In this context, measures for the population control of the vector through the evaluation of new control agents, mapping of risk zones, storage and logistics, surveillance and early diagnosis capacity, social, educational, and environmental interventions and effective communication between the responsible sectors, can provide efficient ways to control these arboviruses [27, 28, 29, 30]. However, despite all efforts made in the last decades, the results were not satisfactory, without being able to effectively control the mosquito population or reduce the incidence of these arboviruses.
We know that viral diseases are complex and require multifaceted responses that involve governments’ integrated and global strategy to promote coordinated action between different multisectoral partners with an integrated approach to vector management, sustained control, and measures at all hierarchical levels. The guiding principle should harmonize prevention, entomological and epidemiological surveillance, and efficient case management with existing health systems. The effort must ensure that all strategies be coherent, economically sustainable, and that provide for a reduction in environmental impacts [27, 28, 29, 30].
In Brazil, the efforts of the public authorities, especially in relation to the joint action of the federal, state and municipal powers, have been improved, in an attempt to cover all this thinking and strategy guided by WHO, as well as the training of trained human resources different areas, from the rapid diagnosis of the disease, vector control, and determination of risk areas . However, it is still essential to evaluate and create more control measures applied with a robust methodology in order to point out the most efficient practices, worthy of replication and allocation of more resources, within these alternatives.
In this context, our main objective will be to present some alternatives and strategies proposed by researchers, in Brazil and worldwide, to control the vector
2. Strategies of
Despite efforts to control the population of the mosquito
It was proposed  like a cyclical model of continuous improvement for vector control and, consequently, related viral diseases, with the proposal of an interactive process aiming to improve control programs through the regular and continuous evaluation of methods and techniques used and replacement by better and operationally valid alternatives. The authors propose that proactive control measures should be guided in time and space by epidemiological and entomological data. It is like if the proposed model serves as a catalyst for integrating data on mosquitoes and related arboviruses, filling a gap between control programs, the medical community, and the local government by developing a database that can also supply other activities public health and city planning.
Proactive or prophylactic population control measures for the vector
Within that mode, it is very important to encourage community participation, which tends to decrease their concern with these diseases in periods of lower incidence, requiring constant campaigns since the culture and the habit of the population to discard packaging in inappropriate places, in other words, involving the society in campaigns to fight mosquitoes. Thus, the population needs to be informed about the reproductive characteristics of the vector and its biological behavior, in order for the community to be proactively involved, which is an essential condition for success in controlling the vector [32, 33].
Countless campaigns have been carried out, in the most different media to achieve the proactive participation of the population and always targeting the adult population. However, as seen in other awareness campaigns, teaching and understanding the duties of the population, when inculcated in children, has a better effect, by charging children to their parents as well as creating a population more aware of their long-term duties. In this context, it was suggested , through the production of informative and interactive booklets, because the education of children generates greater collective awareness in the long run.
On the other hand, there was an interesting study  to understand the participation of users in the coproduction of vector control of dengue in Campo Grande - MS, Brazil. It was found that users when included in the relationship with professionals, are able to produce public policy results and benefit from these results. However, the authors still consider that the actions still follow a top-down direction, in the sense that the plan arrives “ready” from the municipality’s Health Secretariat, already indicating the actions to be carried out by each member (competencies of agents and actions expected by residents). The autonomy, emancipation, and involvement of managers and authors in the direction of public policy actions have not yet been sufficiently characterized, mainly due to the more effective participation of health agents and users (residents) regarding their responsibility in population control of the vector and reducing the incidence of viral diseases. In this epidemiological scenario, the importance of communication and their effective participation or role can be highlighted, in joint participation in the elaboration of the control plan and its effective application in a continuous and intensive way. In general, experiences show that
The epidemiological surveillance system is another sector of strategic importance in the control of vectors, which houses the surveillance of cases of arboviruses (mainly Dengue) and entomological, among others. It is the responsibility of the federal, state, and municipal public authorities that should act in collaborative and synchronous ways. The focus should be on data collection, processing and analysis actions, recommendations for prevention and control measures, as well as the promotion of data collection actions; the processing of collected data; analysis and interpretation of processed data; recommendation of appropriate prevention and control measures. It can promote of the indicated prevention and control actions; evaluation of the effectiveness of the measures adopted and dissemination of relevant information [36, 37].
Incomplete data collection makes it impossible to estimate population risks and allows new epidemics to occur, in addition to reducing the effect of contingency plans and the response capacity of the government to respond satisfactorily in epidemic periods. It is important to carry out periodic assessments of the health surveillance system in general, in order to monitor it efficiently and effectively .
It is worth mentioning that the surveillance of cases of dengue and other arboviruses are important to monitor the number of suspected cases to know the time, magnitude and locations of the transmission cases. However, many asymptomatic cases result in silent transmission, so the extent of cases is underestimated. In addition, clinical detection is imprecise and laboratory diagnosis can be time-consuming, which compromises the effectiveness of vector control actions, therefore, interventions to interrupt transmission are impaired . Although, it should be noted that investments in monitoring and case monitoring techniques, as well as the availability of rapid diagnostic tests in health centers, combined with an accurate reporting of each patient’s data, can greatly assist in understanding the dynamics of the disease in a municipality, allowing decision-making and effective control methodologies aimed at that specific population.
There is a need for the continuous training of health surveillance professionals, in addition to the constant evaluation of the surveillance system, as well as the carrying out of epidemiological studies that can contribute to interventions in dengue control not only in the state of the study, but across the country . One hundred and thirty-four professionals were interviewed, 70% of whom said they were unaware of the existence of a contingency plan for coping with the dengue epidemic, 59% argued that all suspected dengue cases should be confirmed in the laboratory. Still, one-third of the participants reported difficulty in closing serious cases of dengue . In this context, there is a need for the continuous training of health surveillance professionals, in addition to the constant evaluation of the surveillance system, as well as the carrying out of epidemiological studies that can contribute to interventions in dengue control not only in the state of the study, but across the country.
O vector control must be carried out in response to information from epidemiological surveillance allowing to reduce the transmission force of these viruses, which contributes to better care for people who need treatment. For this, interventions need to be carried out at the beginning of the epidemic peak, at the risk of it being impossible to contain the increase in cases. These interventions require a large amount of human and material resources, intense work, and even the application of insecticides from house to house .
Entomological surveillance for the purpose of monitoring to detect the presence and abundance of
Still, vector control in response to epidemiological data has some important problems, among which we highlight 1) the silent cases that make it difficult to monitor viruses at their onset, especially with new serotypes. 2) interventions often begin with confirmation of laboratory cases, and if this confirmation takes longer, control actions are delayed to prevent an epidemic. 3) the expansion of dengue cases occurs quickly, which makes it difficult to prevent epidemics 4) people move intensely within cities, transporting viruses throughout the city in a short time, making it difficult to monitor and isolate outbreaks of the disease .
About the population control of vectors, the most effective methods for the control of mosquitoes that was included a variety of insecticides aimed at controlling adult or immature insects. The implementation of effective control consists of impacting the largest proportion of the vector population. It can be demonstrated that the control strategy must be effective for the high coverage of aquatic mosquito habitats and the reach of winged forms. Among these, it is possible to use methods that use adult mosquitoes to transmit insecticides and other biological products using the behavior for the transfer and dissemination of products between resting and oviposition places in a controlled way to leave residual quantities for extension of population control as a technique of control .
In this regard, it is important that
An important indicator of the mosquito infestation index in a given area or region is RISAa (Rapid Index Survey of
The traditional method of dividing the city into blocks does not allow the visualization of the city in continuity precisely by dividing the method, which obviously the mosquito is not limited to these blocks in its locomotion in the environment. Thus, methods that can evaluate the blocks in greater detail, detecting points of greater infestation that were not possible for observation by RISAa are possible by using the Gaussian Kernel method. This method, although it has a certain subjectivity which requires knowledge from the researcher, allows a quick and easy view of the risk sites without the barriers imposed by the administrative political organization [45, 46].
It was performed an excellent non-systematic literature review  regarding
, such as selective monitoring of infestation, social measures, dispersion of insecticides, new biological control agents, and molecular techniques. The authors considered the integrated use of different compatible and effective techniques according to the region to be possible for the possible reduction of the vector and the related arboviruses. The authors also consider that in the case of technologies in development, they still require evaluation as to their effectiveness, feasibility, and costs for their use in conjunction with other techniques already recommended by the National Program for Dengue Control (NPDC).
However, new strategies have been proposed to control the mosquito population and reduce the incidence of diseases . Among these new techniques, we have the genetic modification of mosquitoes in the laboratory, which, when released to the environment, spread the modified genes to the native population, leading to a decrease in this population or its extermination.
The use of insects inoculated with
In the same vein, the use of
Despite the different strategies mentioned here, summarized in Table 1 and Figure 1, with their potential effectiveness, it is necessary to continue the search for methodologies to control arboviruses and their vector mosquitoes, requiring the development of diversified research involving both ecological aspects, behavior, and population biology. It was a way to increase the success of the control methods used, as well as, promoting conditions for the implementation of new control tools, including knowledge, education, and cultural habits of the population.
|Educational and social approach||Involvement and awareness of the population in home control of mosquito breeding sites.||It depends on the involvement of the population and the various sectors of society. Decrease in engagement during the period with the least number of cases.|
|Epidemiological analysis and risk mapping||It allows the precise analysis of risk regions allowing the correct targeting of resources.||Despite showing the critical regions, it is necessary to be allied with other technologies to be satisfactory.|
|Intra and extra-home nebulization.||It has spatial coverage and reduces disease transmission at the time of the outbreak.||Can promote selection of resistant populations insecticide; demand application agents trained; little adulticide availability.|
|Natural/synthetic compounds to larvicidal function||Alternative and safer products when compared to chemical insecticides. Synergistic compounds can increase the larvicidal function of natural or synthetic compounds.||Need of cost-effectiveness studies compared to chemical insecticide.|
|Transgenic mosquitoes||It leads to a reduction in the life span of mosquitoes; decreases infestation of mosquitoes; and dispenses with the use of radiation.||There is a need to use mosquito sexing technologies; depends on the protocol of release; requires constant production and release mosquitoes.|
|Wolbachia reduction of arbovirus transmission||Use of microorganism that causes a natural, self-sustaining infection, does not use insecticides and radiation.||Climatic differences, mosquito release protocols, level of urbanization and human density can limit the potential functions.|
|Mosquitoes insecticide dispersing||Use of larvicide already available and attested agents familiar with the type of trap used; mosquitoes take larvicides for breeding, eliminating them.||Promotes selection of resistant mosquito populations, requires insecticides with ideal concentration in small particles.|
The authors consider that partnerships between research centers (universities and institutes) and the government are important parts for the elaboration of strategies that are more appropriate to the location with resources that can be made available for the implementation of these strategies in a pilot plan like a way to evaluate the results by epidemiological and entomological criteria  on a continuous basis and with reassessments of the effect achieved in the programs and strategies employed. In Brazil, municipal and state committees have been organized with the presence of members from universities and research institutes, education departments, the legislature, the armed forces, as well as others leaders of organized civil society to better articulate the actions to combat this vector. These partnerships allow articulated actions in large-scale and the solution of problems related to mosquito control in a holistic way, involving different public and private sectors for intelligent decision making.
Finally, the authors conclude that the erradication of
Despite the proposal for different integrated population control strategies, such as breeding elimination, combined chemical control, genetic modification of mosquito populations, chemical control is still one of the most used tools for containing the insect and reducing impacts on public health. However, population control is still unsatisfactory due to the behavior, resistance to insecticides and survival strategies and adaptability, besides high fertility rate of the insect, which despite an apparent fragility, has overcome the restrictions and conditions imposed on its population control. Integrated preventive control is appropriate as long as it considers aspects of the behavior and habits of the target insect, residual and comprehensive activity, and that it can reduce the viability of breeding sites and eliminate, preferably, the egg banks present in the breeding sites. In addition, the voluntary service of the population in the control of the vector in homes and public spaces is essential, there is adequate sanitation infrastructure, health education for the community, stimulating the community’s adherence to the vector’s domestic control due to its anthropophilic habit. The reports show that immediate successes are not lasting and that all population control strategies, in isolation, present inefficiencies in the medium and long term or even that they present inconclusive results from the analysis of reduction of
This chapter discusses new products, strategies and proposals for the population control of
4. Future perspectives
Based on the contents, reports and data presented, it is proposed that new perspectives of population control should consider an integration between preventive and corrective forms, if necessary, based on the combination of different products and\or techniques that are compatible and synergistic in the application, due to the acquired resistance of the insect and\or the use of control strategies and\or applications of these products that are available in the regions. Still, it is important that applications of a single type of product or techniques are never carried out in isolation, which result in inefficient and non-lasting treatments, especially in conditions of high insect infestation mainly without considering environmental, climatic factors or local control peculiarities.
In this perspective, the need for a multidisciplinary approach is reinforced with the use of new technologies and products and\or combinations of different potentialized products in the form of smart devices with slow release for lasting (residual) control of the insect population, especially in breeding grounds. We can highlight as highly promising the strategies as follow: 1) an eco-bio-social approach, by focusing on social participation in insect control, in addition to compatibility with other strategies, in addition to dispensing with the use of insecticides, 2) risk mapping, by increased control accuracy, 3)