*2.4.1 Mechanisms of resistance to chemical insecticides*

*Life Cycle and Development of Diptera*

pared to *Ae. albopictus* females.

indicators or breeding site microbiota.

and social responsibility by governments.

**control of vectors**

their population control.

cells mL<sup>−</sup><sup>1</sup>

cells mL<sup>−</sup><sup>1</sup>

Huang et al. [49], in a study with 14 isolates of bamboo leaf infusion bacteria,

. These studies showed a concentration range dependence of 106–109

for *Aedes* spp. attraction. *Ae. aegypti* and *Ae. albopictus* females are

14 bacterial isolates attracts *Ae. aegypti* and *Ae. albopictus* at densities of 107–108

attracted by an infusion of bamboo leaves and a mixture of 14 bacterial species [50–52]. The results indicate that volatile substances from plants or bacteria can be attractive to mosquitoes. Despite the differences in the responses of *Ae. aegypti* and *Ae. albopictus* to different bacterial concentrations and densities, *Ae. aegypti* females tend to be attracted to lower bacterial concentrations and densities com-

Other data available in the literature indicate that not all bacterial species produce the same semiochemicals (attractive or repellent) or sufficient amounts of attractants. These results suggest that there is a possible biological balance in the microbiota that controls, from the population density of the present species, the emission of volatile substances that can be perceived by the females in the process of attraction or repulsion to the breeding sites. Semiochemical composition variations from different bacterial species that stimulate the attraction or repulsion and oviposition of *Aedes* spp. explain the different species response. Further, other parameters, including variations in bacterial production time, can promote quantitative or qualitative differences for the chemical stimulus in the process of attraction or repulsion to the breeding sites and humans skins emanations [49, 53]. Thorn et al. [54] described significant differences in the type and concentration of volatiles produced by different bacteria grown in the laboratory and in nature for oviposition [6]. Ponnusamy et al. [50] showed the complexity of a microbiota balance and its importance in breeding sites for mosquito breeding. Their studies reinforce the hypothesis that the main stimulus for female ovipositors is the availability of food

**2.4 Perspectives of integrated pest management (IPM) applied to population** 

Diseases transmitted by *Ae. aegypti* are one of the major public health problems in many regions of the world; hence, their control is import. Thousands of years of natural selection increased vectoral competence and even species survival to the cultural habits of populations/communities. Additionally, lack of health education, high availability of breeding sites in domiciles and peri-domestic areas, and the absence in many places of sanitary infrastructure, among other factors, contribute to increase the survival and reproduction success of mosquito species and prevent

Despite of reports and dissemination of the polyvalent vaccine for dengue, chikungunya and zika that may be an option to reduce and control these diseases, this use can take up to 10 years for successful control, according to the Oswaldo Cruz Foundation (Fiocruz, RJ), due to the conditions required to guarantee efficiency and biosafety. There are four dengue serotypes and the number of serotypes for the other two viruses is still unknown, and must also be combated efficiently. For this reason, there is enormous dependence on chemical control and the need for eliminating *Ae. aegypti* breeding sites to reduce the mosquito population and consequently, the incidence of the diseases. The vaccine may be an important part for dengue control; however, other fronts should also be considered, such as health education, continuous epidemiological surveillance, infrastructure improvements

. The mixture of

showed that *Ae. aegypti* are repelled at densities of 109 cells mL<sup>−</sup><sup>1</sup>

**96**

Chemical methods are intensively used for adult insect vector population control. Non-implementation of preventive control strategies is in part, responsible for the occurrence and constant aggravation of epidemic outbreaks during hot periods in Brazil.

The difficulty for *Ae. aegypti* population control centers are on the adaptive process, species resilience and acquired resistance to conventional insecticides. The first report of resistance occurred with organophosphates followed by pyrethroids. Over time, other resistance records have been reported to organophosphates, pyrethroids and carbamates in regions with intense mosquito occurrence. Before the year 2000, resistance to the organophosphate insecticides Temephos used as a larvicide and Malathion used to combat adult mosquitoes, was detected in some Brazilian municipalities.

Reproductive capacity favors the emergence of insecticide-resistant individuals used for vector control, because resistance varies with the time of use and concentration of the products that act at specific sites of toxicity. Medeiros [55] presents four categories of enzymatic activity profiles: (1) greater activities in the adult stage; (2) greater activities in the larval stage (esterases "α-EST" and "β-EST"); (3) activities that increase during each stage evaluated (mixed function oxidase [MFO]); and (4) activities that tend to increase in the larval stage and decrease in the first days of adult life (DVA) [esterase "ρNPA" and glutathione S-transferase (GST)]. Biochemical assays with larvae and adults from field populations revealed alterations in acetylcholine esterase (AChE) and other esterases at the larval stage, changes in GST more restricted to the adult stage, and MFO alterations have been limited to the two vector stages.

The results from these experiments allow detailed evaluation of the resistance mechanisms in different vector populations and can be used for the development and choice of insecticides more suitable for *Aedes* spp. control. Guirado and Bicudo [56] showed some aspects of population control and resistance to insecticides in *Ae. aegypti* and concluded that mosquito population control, as long as no more modern vaccines or genetic techniques of epidemiological control are available, is exclusively dependent on chemical control and human population awareness for breeding site elimination.

The available insecticide resistance studies demonstrate that resistance is due to three main mechanisms: (a) reduction of insecticide penetration due to changes in the insect cuticle; (b) increased metabolism of the insecticide by the action of esterases, mono-oxygenases or glutathione-transferases that inactivate the molecule; and (c) modification of the insecticide's biological target. The literature also shows a behavioral resistance mechanism, where insects avoid contact with sites that contain the toxic substance used for control. The results of insecticide resistance and loss of control efficacy indicate the need for continuous monitoring of *Ae. aegypti* susceptibility to insecticides and the use of chemical control in more rational ways. These smarter considerations include analysis of insect populations and their resistance, use of integrated management techniques and different methodologies and/or control products, in addition to continuous monitoring during all periods of the year by endemic control programs.

#### **2.5 Attractiveness to breeding sites from water quality**

The availability of water by precipitation or accumulation at home and breeding grounds is an important factor for the reproductive process and establishment of

*Aedes* spp. [57, 58]. Additionally, food availability is the most important factor for larval survival and development. Researchers have analyzed breeding site physicochemical conditions and water parameters. The studies reveal species adaptations and tolerance to the physicochemical conditions of breeding sites, besides the presence of other species that share breeding site spaces and cooperate with each other. Gil et al. [29], through collection and analysis of breeding water, showed a close relationship between the conditions of drinking and non-potable water composition, temperature, availability of organic material, waste, and reproduction and development of *Ae. aegypti*. Beserra et al. [26] showed that *Ae. aegypti* develops in different environments with organic material availability. The temperature, pH and water composition (total solids, total nitrogen, ammoniacal nitrogen, total dissolved phosphate and DO) are important variables for *Ae. aegypti* reproduction at egg, larval and pupal stages.

Silva and Silva [59] studied the influence of egg quiescence (interruption in development induced by low humidity) period in the life cycle of *Ae. aegypti* under laboratory conditions, in search of information that could improve control actions. Notably, the egg is the most resistant form of the biological cycle, and this feature allows mosquito development and resistance to climatic adversities. The experiments have been performed in a biological chamber, maintained at 28 ± 1°C, with relative humidity of 80 ± 5% and a 12-hour photoperiod. Quiescence is highly significant for larval hatching. Eggs from the same quiescence period had statistically different incubation periods and the larvae hatched in groups (defined by incubation). Indeed, in 99.8% of the cycles, the variation was determined by incubation.

Quiescence is a very important adaptation in the passive dispersion of *Ae. aegypti* because it enables the transport of resistant (or quiescent) eggs into all kinds of artifacts, such as used tires. Its non-destruction can signal a feasible mechanism to increase *Ae. aegypti* dispersion, a factor that makes entomological and/or epidemiological surveillance essential. This context gains another dimension when one adds the highly significant effect of quiescence on larval hatching. Quiescence periods of up to 720 days can occur, but the literature demonstrated that eggs are still viable up to 492 days. In some studies, the highest hatching rate (97.2%) occurs after 121 days quiescence [59, 60]. In another study, high hatching occurs after 180 days [23]. Among these quiescence periods, the 121 days period is the most favorable to *Ae. aegypti*, with significantly higher hatching rate and number of cycles (groups) than for other periods.

Other authors [32, 34, 36] also observed the same phenomenon attributing to different factors these prolonged periods of viability that include resistant, durable, inactive and residual eggs. Whatever the factor is, quiescence provoked by climatic variables, such as the decrease of humidity and temperature, increases *Ae. aegypti* life expectancy by enabling re-growth of the species. This behavior is relevant to the control of this mosquito, since the eggs adhered to container walls resist desiccation and can hatch when the water level rises.

In dechlorinated water at 26°C, there is a 92% *Ae. aegypti* larvae survival rate [60]. The *Ae. aegypti* larvae grown in raw sewage water show shorter developmental periods, probably due to the high concentrations of organic materials that serve as nutrients, although the authors hypothesized that the surface tension and high viscosity of the water are responsible. Further, the formation of material on the surface may makes it difficult for the larvae to obtain atmospheric oxygen. Beserra et al. [60] showed that *Ae. aegypti* can develop in polluted environments such as domestic sewage, where there is a high concentration of organic material and practically zero DO (0.12 mg L<sup>−</sup><sup>1</sup> ), as well as in treated effluents, with carbonaceous material removed, as the post-treated effluent after anaerobic filter and in a polishing pond.

**99**

*The Yellow Fever Mosquito* Aedes aegypti *(Linnaeus): The Breeding Sites*

Notably, food availability is a decisive condition in the selection of the breeding site by the female, even in conditions considered unfavorable with regards to the available water quality, including high pollution levels. Beserra et al. [60] analyzed water quality and food availability for *Ae. aegypti* larvae. Water quality elongates the breeding period, with or without food and the medium turbidity decreases. Further, turbidity is an important parameter and low light penetrability in the aquatic environment is beneficial for the species, since *Ae. aegypti* larvae are photophobic. The *Ae. aegypti* is a competent vector for the transmission of flavivirus, which causes yellow fever and dengue fever. In this organism, there are at least 10 different rhodopsins. Mosquitoes have similar sets of rhodopsin and retinal organization, including the malaria vector *Anopheles gambiae* (Giles) (Diptera: Culicidae) that diverged from *Ae. aegypti* millions of years ago. Conservation of molecules within these visual systems implies that these species have visual processing

capabilities similar to those of the common ancestor. Thus, these capabilities remain important for the suitability of existing species and their adaptability to environmental conditions. In *Ae. aegypti*, several mechanisms contribute to the ability of a photoreceptor to adapt to ambient light conditions. The *Ae. aegypti* expresses long wavelength rhodopsin Aaop1 on all R1–6 photoreceptors and most R8 photoreceptors. These photoreceptors alter the cellular location of Aaop1 and rearrange their

The effects of temperature on *Ae. aegypti* larval behavior have been examined for different food availability conditions at breeding sites. With reduced food availability and low temperature, the larvae spend more time and energy to feed. At the temperature extremes, there are negative impacts on feeding behavior and larval

Increasing viscosity by elevating the concentration of dissolved solids imposes unfavorable conditions, including limiting movement of the organisms. However, females adapt, choosing to perform oviposition even under unfavorable conditions. This phenomenon shows that for *Ae. aegypti*, the water physicochemical quality is not the most important parameter, but rather the conditions that the breeding site presents for the development and survival of the immature individuals are crucial. Albeny-Simões et al. [63] showed that the choice of breeding grounds for oviposition and reproduction with aquatic larvae is influenced by the risk of offspring mortality and survival, and food availability. Studies revealed that *Ae. aegypti* is attracted to do the oviposition in breeding sites with predatory larvae (*Toxorhynchites* (Theobald) (Diptera: Culicidae)), as the density of dead larvae and metabolic products increase the bacterial abundance in the breeding location. Bacterial biomass and species composition are environmental determinants for the occurrence and

abundance of *Aedes* spp., breeding sites with competing species [64, 65].

Soares Pinheiro et al. [66] evaluated *Ae. aegypti* viability in the Amazon region that has high humidity. The *Ae. aegypti* eggs have been stored in plastic cups, paper envelopes or plastic bags and maintained in internal and external areas for different times. Overall, the storage form is important for egg viability. The authors concluded that *Ae. aegypti* viability in the Amazon region is maintained at high levels up to 4 months, at which time there are drastic reductions and hatchings up to 8 months occur at very low percentages. These results show that excess humidity and temperature can induce constant stimuli to hatching eggs and possibly due to water stress, reduce their viability. Comparatively, in dry environments this viability can be preserved for up to 492 days [59]. In this regard, the selection of suitable place for oviposition is fundamental for the distribution and establishment of *Ae. aegypti*. Studies indicate that *Ae. aegypti* females are not attracted to breeding grounds with clean water. This flexibility to choose breeding sites for posture,

*DOI: http://dx.doi.org/10.5772/intechopen.88852*

photosensitive rabdomeric membranes daily [61].

activity [62].

#### *The Yellow Fever Mosquito* Aedes aegypti *(Linnaeus): The Breeding Sites DOI: http://dx.doi.org/10.5772/intechopen.88852*

*Life Cycle and Development of Diptera*

at egg, larval and pupal stages.

for other periods.

zero DO (0.12 mg L<sup>−</sup><sup>1</sup>

and can hatch when the water level rises.

*Aedes* spp. [57, 58]. Additionally, food availability is the most important factor for larval survival and development. Researchers have analyzed breeding site physicochemical conditions and water parameters. The studies reveal species adaptations and tolerance to the physicochemical conditions of breeding sites, besides the presence of other species that share breeding site spaces and cooperate with each other. Gil et al. [29], through collection and analysis of breeding water, showed a close relationship between the conditions of drinking and non-potable water composition, temperature, availability of organic material, waste, and reproduction and development of *Ae. aegypti*. Beserra et al. [26] showed that *Ae. aegypti* develops in different environments with organic material availability. The temperature, pH and water composition (total solids, total nitrogen, ammoniacal nitrogen, total dissolved phosphate and DO) are important variables for *Ae. aegypti* reproduction

Silva and Silva [59] studied the influence of egg quiescence (interruption in development induced by low humidity) period in the life cycle of *Ae. aegypti* under laboratory conditions, in search of information that could improve control actions. Notably, the egg is the most resistant form of the biological cycle, and this feature allows mosquito development and resistance to climatic adversities. The experiments have been performed in a biological chamber, maintained at 28 ± 1°C, with relative humidity of 80 ± 5% and a 12-hour photoperiod. Quiescence is highly significant for larval hatching. Eggs from the same quiescence period had statistically different incubation periods and the larvae hatched in groups (defined by incubation). Indeed, in 99.8% of the cycles, the variation was determined by incubation. Quiescence is a very important adaptation in the passive dispersion of *Ae. aegypti*

because it enables the transport of resistant (or quiescent) eggs into all kinds of artifacts, such as used tires. Its non-destruction can signal a feasible mechanism to increase *Ae. aegypti* dispersion, a factor that makes entomological and/or epidemiological surveillance essential. This context gains another dimension when one adds the highly significant effect of quiescence on larval hatching. Quiescence periods of up to 720 days can occur, but the literature demonstrated that eggs are still viable up to 492 days. In some studies, the highest hatching rate (97.2%) occurs after 121 days quiescence [59, 60]. In another study, high hatching occurs after 180 days [23]. Among these quiescence periods, the 121 days period is the most favorable to *Ae. aegypti*, with significantly higher hatching rate and number of cycles (groups) than

Other authors [32, 34, 36] also observed the same phenomenon attributing to different factors these prolonged periods of viability that include resistant, durable, inactive and residual eggs. Whatever the factor is, quiescence provoked by climatic variables, such as the decrease of humidity and temperature, increases *Ae. aegypti* life expectancy by enabling re-growth of the species. This behavior is relevant to the control of this mosquito, since the eggs adhered to container walls resist desiccation

In dechlorinated water at 26°C, there is a 92% *Ae. aegypti* larvae survival rate [60]. The *Ae. aegypti* larvae grown in raw sewage water show shorter developmental periods, probably due to the high concentrations of organic materials that serve as nutrients, although the authors hypothesized that the surface tension and high viscosity of the water are responsible. Further, the formation of material on the surface may makes it difficult for the larvae to obtain atmospheric oxygen. Beserra et al. [60] showed that *Ae. aegypti* can develop in polluted environments such as domestic sewage, where there is a high concentration of organic material and practically

removed, as the post-treated effluent after anaerobic filter and in a polishing pond.

), as well as in treated effluents, with carbonaceous material

**98**

Notably, food availability is a decisive condition in the selection of the breeding site by the female, even in conditions considered unfavorable with regards to the available water quality, including high pollution levels. Beserra et al. [60] analyzed water quality and food availability for *Ae. aegypti* larvae. Water quality elongates the breeding period, with or without food and the medium turbidity decreases. Further, turbidity is an important parameter and low light penetrability in the aquatic environment is beneficial for the species, since *Ae. aegypti* larvae are photophobic. The *Ae. aegypti* is a competent vector for the transmission of flavivirus, which causes yellow fever and dengue fever. In this organism, there are at least 10 different rhodopsins. Mosquitoes have similar sets of rhodopsin and retinal organization, including the malaria vector *Anopheles gambiae* (Giles) (Diptera: Culicidae) that diverged from *Ae. aegypti* millions of years ago. Conservation of molecules within these visual systems implies that these species have visual processing capabilities similar to those of the common ancestor. Thus, these capabilities remain important for the suitability of existing species and their adaptability to environmental conditions. In *Ae. aegypti*, several mechanisms contribute to the ability of a photoreceptor to adapt to ambient light conditions. The *Ae. aegypti* expresses long wavelength rhodopsin Aaop1 on all R1–6 photoreceptors and most R8 photoreceptors. These photoreceptors alter the cellular location of Aaop1 and rearrange their photosensitive rabdomeric membranes daily [61].

The effects of temperature on *Ae. aegypti* larval behavior have been examined for different food availability conditions at breeding sites. With reduced food availability and low temperature, the larvae spend more time and energy to feed. At the temperature extremes, there are negative impacts on feeding behavior and larval activity [62].

Increasing viscosity by elevating the concentration of dissolved solids imposes unfavorable conditions, including limiting movement of the organisms. However, females adapt, choosing to perform oviposition even under unfavorable conditions. This phenomenon shows that for *Ae. aegypti*, the water physicochemical quality is not the most important parameter, but rather the conditions that the breeding site presents for the development and survival of the immature individuals are crucial.

Albeny-Simões et al. [63] showed that the choice of breeding grounds for oviposition and reproduction with aquatic larvae is influenced by the risk of offspring mortality and survival, and food availability. Studies revealed that *Ae. aegypti* is attracted to do the oviposition in breeding sites with predatory larvae (*Toxorhynchites* (Theobald) (Diptera: Culicidae)), as the density of dead larvae and metabolic products increase the bacterial abundance in the breeding location. Bacterial biomass and species composition are environmental determinants for the occurrence and abundance of *Aedes* spp., breeding sites with competing species [64, 65].

Soares Pinheiro et al. [66] evaluated *Ae. aegypti* viability in the Amazon region that has high humidity. The *Ae. aegypti* eggs have been stored in plastic cups, paper envelopes or plastic bags and maintained in internal and external areas for different times. Overall, the storage form is important for egg viability. The authors concluded that *Ae. aegypti* viability in the Amazon region is maintained at high levels up to 4 months, at which time there are drastic reductions and hatchings up to 8 months occur at very low percentages. These results show that excess humidity and temperature can induce constant stimuli to hatching eggs and possibly due to water stress, reduce their viability. Comparatively, in dry environments this viability can be preserved for up to 492 days [59]. In this regard, the selection of suitable place for oviposition is fundamental for the distribution and establishment of *Ae. aegypti*. Studies indicate that *Ae. aegypti* females are not attracted to breeding grounds with clean water. This flexibility to choose breeding sites for posture,

despite the apparent risks to reproduction, is an important fact. This posture behavior demonstrates the adaptability of the insect to the different environmental situations, even though they appear to represent unfavorable conditions [61, 62].

Additionally, breeding sites of principal dengue virus spreader *Ae. aegypti* [67] and secondary vector *Ae. albopictus* [68] or both [69] can be stopped through biological control [70]; with environmental modifications [71]; utilizing copepods (H. Milne-Edwards) (Copepoda: Cyclopidae) [72]; and using ecological services by frogs, toads and tadpoles (Anura) [73].
