**5. Discussion**

*Ae. aegypti* remains a serious public health threat due to its importance in arboviral transmission, DENV, CHIKV, and ZIKV transmission. Globally, the incidence of DENV infections is on the rise, and recently, reemergence of CHIKV and ZIKV has been observed. Vaccine, prophylaxis, and therapeutics for most arboviral infections are still in development pipeline; hence, integrated vector management remains the cornerstone to stop outbreak transmission and sustainable control. Therefore, understanding of the ecology is important for outbreak prediction and effective planning of strategies to control transmission of arboviral infections.

Studies on the ecology of *Ae. aegypti* are important to better understand the preference of the vector in terms of the oviposition and colonization of mosquitoes [8]. The ecological factors play a role on influencing the population dynamics of larvae and pupae. The evidence is clear that both abiotic and biotic factors are important determinants of adulthood characteristics of life cycle such as longevity, fecundity, and body size [8, 9]. The factors are important to explain the vectorial capacity of *Ae. aegypti* on disease transmission. Furthermore, there is compelling evidence that *Ae. aegypti* is most productive in containers, which varies among regions, geographical settings, and seasonality [10]. In addition, it undoubtedly clears that water storage containers and discarded containers influence the vector density and risk of arboviral transmission particularly in poorly planned cities in (sub-)tropical regions [11]. Unless appropriate actions are taken, increasing urbanization, poor environmental management will continue to influence the stability of the *Ae. aegypti* populations. In addition, the vector density is influenced significantly by environment factors and urbanization [9, 11, 13]. *Ae. aegypti* feed exclusively on human and is increasingly a threat particularly in unplanned (peri-)urban areas. The recent data highlight the increasing *Aedes* spp*.* abundance and urbanization that could potentially escalate the risk of arboviral outbreaks [31]. Furthermore, the environment contributes to the breeding and ecological colonization of the vector. The presence of organic nutrients and microorganisms such as cyanobacteria seems to have influence on the productivity and development of *Ae. aegypti* [11, 15]. The presence of microalgae in the larval habitats, therefore, represents high adequacy of nutrients for immature stages of *Ae. aegypti* [11, 15]. Microalgae are associated with the presence and abundance of the vectors being the source of food for the larvae in breeding habitats. The evidence suggests that better understanding of these factors may be a useful indicator for mosquito population control. Measures to control microalgae to deprive nutrients to the vector could be explored for additional measures of the vector control. Importantly, approaches targeting immature stages of *Ae. aegypti* are highly recommended for effective and sustainable vector control. *Ae. aegypti* vector lays eggs in containers, buckets, care tyres and water storage vases; thus, the appropriate intervention such as proper disposal and management of containers and discarded tyres for source reduction could prove effective in reducing the vector population and mitigate the risk of arboviral transmission. Therefore, implementation of strategies to address the challenge of reemergence and expansion of arboviral infections will require a strong multisector commitment and integration for effective surveillance and control at regional, national, and program levels.

There is widespread resistance to the commonly widely used insecticide, pyrethroids and organophosphates in *Aedes* spp. control. Insecticide resistance is likely to impact disease outbreak and transmission measures and cost of the interventions [16, 17]. This is currently a major concern in South America where organophosphates, pyrethroids, and DDT have been widely used in vector control. However, there is also evidence on decreased susceptibility to pyrethroids in Sub-Saharan Africa and Asia [10, 13]. The origin and evolution of *Aedes* spp. resistance to insecticides remain unclear; however, it is assumed that the use of the insecticide in other vector interventions such as malaria control and agricultural may have exerted selective pressure on the *Aedes* spp. The mechanism of *Ae. aegypti* resistance to insecticides seems to be mediated by the nonsynonymous mutations *kdr* gene [18, 19]. Other studies suggest the role of enhanced enzymatic biodegradation or sequestration [20, 21]. Studies suggest the potential role of the metabolic enzymes including cytochrome P450s and GSTs in conferring resistance to pyrethroids and organophosphates in *Aedes* spp. Evidence on the possible behavioral resistance or avoidance is patchy, and more investigation is needed to understand how it may affect the current interventions. Despite the worsening *Ae. aegypti* resistance to pyrethroids and organophosphates, studies on susceptibility profile of *Bti* are reassuring that *Aedes* spp. retains considerable susceptibility to the biolarvicides [17]. Therefore, *Bti* remains a suitable alternative for prevention and control tool in regions where resistance to pyrethroids is widespread. To mitigate the risk of resistance and its public health consequences, it is crucial to strengthen monitoring and surveillance at all levels. Susceptibility testing of the commonly used insecticides and biolarvicides using the standardized WHO bioassay protocol should be integrated as part of the surveillance program and profiling of molecular markers of resistance may be considered as appropriate.
