**4.4. Use of repellents**

Application of repellents such as DEET, DIMP, and of like is of paramount importance in reducing or controlling human to vector contact. The application should be done during active hours of the day.

#### **4.5. Surveillance**

Surveillance is important detect mosquito species in a certain area and changes in populations. By having valuable data, we are capable of more successfully time larvicide applications and more correctly target the adulticide activities. The WHO recommends of regular household surveys of *Aedes* spp. collecting evidence on the ecological and epidemiological indices to guide prevention and control strategies. This involves determining the habitat productivity, preference of the breeding sites, containers for the presence of egg, larvae and pupae as well as the collection of adult mosquitoes for further identification. Larval surveys involve identifying the presence of immature mosquitoes in breeding sites such as discarded tyres, containers, and water storage vases in the defined targeted area. Through this assessment, it is possible to identify most containers that are positive for *Aedes* spp. and parameters such Container Index (CI) and Breteau Index (BI) [6]. On the other hand, pupal survey is performed in houses and other breeding sites to identify the productivity in the breeding habitat [7]. In addition, surveys to determine the prevalence and circulating serotypes of DENV, ZIKV, CHIKV, and YFV as a part of regular surveillance are required to inform strategies to prevent transmission and provide early warning signal of outbreaks of clinical infections.

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

Ecology of *Aedes* Mosquitoes, the Major Vectors of Arboviruses in Human Population

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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.

*Aedes aegypti* is the most important vector in outbreak and transmission of arboviral infections. The environmental factors favor mosquitoes and risk of disease transmission. The diseases are expanding particularly in (sub-)urban settings with frequent water shortage, high human population, poor planning, and poor waste disposal systems. Primary prevention and control measures are to reduce the vector exposure, but current vector control tools are unsustainable and there is increasing threat due to insecticide resistance. Integration of *Aedes* spp. vector control with other ongoing program and coordination of insecticide resistance monitoring and management is crucial to increase the impact of interventions. Future interventions will require deployment of effective vaccines against arboviral infections combined

**6. Conclusion**

with integrated vector management.

surveillance and control at regional, national, and program levels.
