Understanding Insecticide Resistance in Mosquitoes

Arthropod vectors, such as mosquitoes from the Culicidae family, transmit diseases between humans or from animals to humans. They are responsible for spreading vector-borne diseases including dengue fever, Zika virus, and West Nile Virus. The transmission cycle involves mosquitoes biting infected individuals and transferring the pathogens to other hosts through subsequent bites. Vector-borne diseases account for over 17% of all infectious diseases,¹ posing a threat to over half the global population.

Given the significant impact on global health, the implementation of effective prevention and control strategies is crucial. These measures include the use of mosquito repellents, protective netting, and the proactive elimination of mosquito breeding sites to mitigate disease transmission.

Insecticides are widely used to control mosquito populations and reduce disease transmission, with effective approaches targeting different stages of the mosquito life cycle, from larvae to adults. Indoor residual spraying, insecticide-treated bed nets, and fogging have demonstrated positive results in interrupting disease transmission cycles. However, the indiscriminate use of insecticides has led to the development of resistance in mosquitoes, posing significant challenges. Understanding mosquito insecticide resistance is vital in managing vector-borne diseases.

According to Causaly, approximately 100 mechanisms of action responsible for driving resistance to insecticides have been reported. Notably, almost 400 documents have implicated protein overexpression as a driver for insecticide resistance. Cytochrome P450s, for example, have been linked to insecticide resistance through overexpression and detoxification mechanisms in insect species.²

Several mosquito species have been implicated in insecticide resistance. Three main genera of mosquitoes which have been associated with insecticide resistance were identified using Causaly: Anopheles, Aedes and Culex (Figure 1). These genera encompass species that play crucial roles as vectors of significant diseases, including malaria, dengue fever, Zika virus, and West Nile virus.

Anopheles mosquitoes are vectors of the Plasmodium species, which is the causative agent of malaria. Over 2500 documents relating to insecticide resistance and anopheles mosquitoes were identified using Causaly.

Genetic variations, including the overexpression of P450 gene CYP6Z1, were observed in resistant Anopheles coluzzii mosquitoes following sublethal permethrin exposure.³ This study suggested that insecticide-treated nets (ITNs) with a P450 inhibitor could be more effective in controlling these mosquitoes.³ Similarly, in Anopheles gambiae, three genes, namely Cyp6m2, Cyp6p3, and Gste2, were overexpressed in at least one class of insecticide, providing cross-resistance to all four major classes of insecticides currently used in public health.⁴ These findings underscore the complexity of managing insecticide resistance in Anopheles mosquitoes, which is crucial for effective malaria control.

Aedes mosquitoes serve as carriers for a range of diseases, notably including dengue fever and the Zika virus. Utilizing Causaly, approximately 1500 documents relating to insecticide resistance and Aedes mosquitoes were uncovered.

A 2020 study reported a mutation of the voltage-gated sodium channel gene contributes to insecticide resistance of Aedes aegypti from Indonesia.⁵ Another study discovered that Aedes aegypti mosquitoes originating from Douala exhibited resistance to insecticides such as DDT, permethrin, and deltamethrin, a phenomenon potentially linked to a mutation identified at F1534C.⁶ Genetic mutations driving insecticide resistance in Aedes mosquitoes could intensify dengue and Zika spread, necessitating innovative control tactics.

Culex mosquitoes play a critical role as vectors for the transmission of the West Nile Virus. Over 1000 documents relating to insecticide resistance and Culex mosquitoes were identified using Causaly.

Recent research has revealed insights into insecticide resistance mechanisms and genetic mutations in Culex mosquitoes. A study found that NYD-OP7 regulates deltamethrin resistance in Culex pipiens pallens by influencing phospholipase C and certain P450 genes.⁷ Another study pinpointed resistance-linked mutations, specifically L1014F in voltage-gated sodium channels and G119S in acetylcholinesterase, in Belgium’s Culex pipiens and Culex modestus mosquitoes.⁸

Understanding mosquito insecticide resistance is vital in managing vector-borne diseases. Resistance can enhance disease transmission, alter mosquito behavior, and impact control programs. Research into genetic mutations driving resistance, as seen in Anopheles, Aedes, and Culex mosquitoes, is crucial for developing effective, innovative control strategies and mitigating global health impacts.

To find out more about Causaly, request a demo now!