Insecticide resistance of Dengue vectors in South East Asia: a systematic review

Resistance status of Aedes mosquitoes as dengue vectors and the potential of plant larvicides from Indonesia for biological control: A narrative review

Dengue fever remains a major public health threat in Indonesia, exacerbated by rising insecticide resistance in Aedes aegypti. Strategies relying on chemical insecticides, while initially effective, have led to widespread resistance in mosquito populations. This resistance is particularly pronounced in areas such as Java, where the extensive use of insecticides, including organophosphates and pyrethroids, has been documented. To address this challenge, one promising alternative is the utilization of biolarvicides derived from local Indonesian plant materials. Biolarvicides are environmentally friendly, safe, and have the potential to mitigate the adverse impacts associated with chemical insecticides. Numerous studies have explored the larvicidal properties of indigenous plants native to Indonesia, demonstrating their efficacy against A. aegypti. The aim of this study was to examine insecticide resistance in Aedes mosquitoes across Indonesia, highlighting geographical variations and underexplored regions, and exploring plant- based biolarvicides as sustainable alternatives. Biolarvicides derived from native Indonesian plants could be eco-friendly alternative for dengue vector management. Their integration into existing control strategies could significantly enhance efforts to control dengue while reducing the environmental and health risks posed by chemical insecticides.

Dengue: epidemiology, diagnosis methods, treatment options, and prevention strategies

Dengue is an arboviral disease caused by dengue virus, which is mostly found in tropical regions, and the number of human cases has increased dramatically since 2000, with 5.2 million cases reported in 2019, according to WHO reports, 70% of which were in Southeast Asia, the Western Pacific, and Asia. Dengue infection can result in a wide range of clinical manifestations, ranging from fever to severe dengue shock syndrome, which can be fatal, particularly in those with secondary dengue. This review of the aetiology of dengue fever examines the complex interactions between the virus and the immune system and the interaction between viral and host factors and also covers outbreaks, the severity of disease caused by different serotypes, and methods for diagnosis of dengue, such as serological tests, nucleic acid amplification tests, and ELISA assays for detecting the NS1 antigen. Current treatment options and prevention strategies, including vector control measures, environmental interventions, and insect repellents are also discussed. This review highlights the challenges involved in developing a dengue vaccine, which is complicated by the need for an efficient and balanced immune response against all genotypes of the four serotypes.

Consequences of insecticide overuse in Hungary: assessment of pyrethroid resistance in Culex pipiens and Aedes albopictus mosquitoes

BACKGROUND

Mosquitoes, as vectors of various pathogens, have been a public health risk for centuries. Human activities such as international travel and trade, along with climate change, have facilitated the spread of invasive mosquitoes and novel pathogens across Europe, increasing the risk of mosquito-borne disease introduction and their spread. Despite this threat, mosquito control in Hungary still relies predominantly on chemical treatments, which poses the risk of developing insecticide resistance in local populations. While pyrethroid resistance has been documented in several countries, there is no information on this issue from Hungary. This study aims to investigate the presence of resistance in Hungarian mosquito populations by analyzing a native, already known disease vector and a recently established invasive species with public health significance.

METHODS

We assessed the presence of knockdown resistance (kdr) mutations L1014F in Culex pipiens and V1016G and F1534C in Aedes albopictus mosquitoes, which are responsible for pyrethroid resistance. Mosquito specimens were investigated retrospectively, collected from previous years within the framework of local monitoring programs run in urban areas representing five regions of Hungary. The mutations in mosquitoes were detected individually by allele-specific polymerase chain reaction (PCR) and gel electrophoresis, following generally used protocols.

RESULTS

In Cx. pipiens, the kdr mutation was detected across all five collection sites, with resistance allele frequencies ranging from 18.1% to 36.3%. Resistance alleles were identified in homozygosity and heterozygosity with the susceptible allele, resulting in 53% of the investigated mosquitoes showing resistance to pyrethroids in the Hungarian populations. In contrast, for Ae. albopictus, the analyzed individuals were found to carry only the susceptible alleles, indicating a homozygous susceptible genotype across the investigated populations on the basis of V1016G and F1534C genes.

CONCLUSIONS

Our work highlights the consequences of the unilateral and long-term use of chemical treatments on mosquitoes. This indicates an urgent need for a change of concept in mosquito control strategy in Hungary, as well as in countries where mosquito control still relies dominantly on insecticides. The restricted use of chemical treatment is highly recommended to prevent the development of pyrethroid resistance in recently established populations of the invasive Ae. albopictus, and to decrease the public health risk of vector-borne diseases.

Beyond top-down: community co-creation approaches for sustainable dengue vector control

Dengue fever, a mosquito-borne viral illness transmitted by Aedes mosquitoes, continues to be a significant public health burden in tropical and subtropical regions. Traditional vector control methods, primarily reliant on insecticides and larvicides, face challenges because of emerging insecticide resistance and limited community engagement. This narrative review explores co-creation as a collaborative approach to dengue control, where communities actively participate in designing and implementing solutions. Through an examination of existing literature, we discuss the rationale for co-creation, the various methods employed, evidence for effectiveness, challenges, and other items. Findings from previous studies suggest that co-creation can empower communities by fostering a sense of ownership and responsibility for dengue control efforts. Using local knowledge and insights, co-creation approaches have also been shown to identify and address specific community needs and preferences, leading to more contextually relevant interventions. Additionally, co-creation initiatives have demonstrated success in promoting behavior change within communities, leading to increased uptakes of preventive measures such as proper waste management and use of personal protective measures. However, challenges such as building trust and collaboration, addressing power dynamics, and ensuring long-term sustainability remain critical factors that are essential to foster collaboration, empower communities, and develop sustainable strategies for dengue control in affected regions.

Review of dengue vectors in Cambodia: distribution, bionomics, vector competence, control and insecticide resistance

BACKGROUND

Dengue fever is one of the most prevalent mosquito-borne diseases in Cambodia. Until now, no specific vaccine nor antiviral treatment exists the virus causing Dengue fever. Consequently, its prevention relies only on vector control strategies. However, efficient vector control in turn relies on a good knowledge of the biology of the vector species. Therefore, this study aims to provide the first review of the distribution, ecology, meteorological impacts, trophic behavior, vector competence, vector control and insecticide resistance of dengue vector species in Cambodia.

METHODS

A systematic search of the Google Scholar and PubMed databases was conducted for relevant published articles. Of the 610 published articles originally identified, 70 articles were ultimately selected for inclusion in this review. We also included new data from unpublished research conducted in Cambodia between 2017 and 2023 related to dengue vector bionomics.

RESULTS

Eleven Aedes (Stegomyia) mosquito species have been recorded in Cambodia, including a new species described in 2024. Four species are associated with dengue virus transmission, among which Aedes aegypti and Ae. albopictus are the main vectors and Ae. malayensis and Ae. scutellaris are considered to be potential vectors. Aedes aegypti and Ae. albopictus are present in all provinces of Cambodia. Aedes albopictus shows a preference for forest, rural and suburban areas, while Ae. aegypti is mostly found in urban and suburban areas. The distribution of these two species is also influenced by meteorological factors, seasonality and the availability of breeding habitats and blood meals. Both species are predominant during the rainy season, and their respective density is impacted by precipitation and temperature. Aedes aegypti is characterized as anthropophilic, while Ae. albopictus exhibits zooanthropophilic behavior, and both species have been observed to be predominantly diurnal. In addition, they were found to be highly resistant to the insecticides used in Cambodia for their control, such as temephos for larvae and deltamethrin and permethrin for adult mosquitoes.

CONCLUSIONS

This review provides extensive and important knowledge on dengue vectors in Cambodia. This knowledge is derived not only from published research articles but also from many recent studies in Cambodia on the bionomics of dengue vector species. The review provides valuable information for use by public health authorities on dengue virus transmission and to develop better vector control strategies in the country.

Recent Dengue Infection in Bangladesh: A Seasonal Endemic Progressing to Year-long Serious Health Concern

Dengue represents one of the most dangerous mosquito-borne viral diseases. Although the disease has been prevalent around the globe over the centuries, recent outbreaks of dengue have devasted the healthcare delivery system of many countries. Being a global infection, dengue virus (DENV) is endemically present mainly in Latin America and Caribbean countries as well as countries in South Asia. The recent outbreak of DENV infection has indicated an exceptional outbreak of DENV in some countries in South Asia. There has been a serious endemic of DENV during 2019. After a heterogeneous pause, another severe outbreak of DENV was reported in some Asian countries in 2023. Among the Asian countries, Bangladesh has reported an acute upsurge of DENV infection in 2023 with record numbers of fatalities. However, this pattern of DENV has not been detected in neighbors of Bangladesh, such as India or other countries in Southeast Asia. This provides an emergent task of dissecting the present DENV infection in Bangladesh from different angles to get insights for future containment of the DENV infection, not only in Bangladesh but also in other DENV endemic areas or DENV-native areas.

How to cite this article

Akbar SMF, Khan S, Mahtab M, et al. Recent Dengue Infection in Bangladesh: A Seasonal Endemic Progressing to Year-long Serious Health Concern. Euroasian J Hepato-Gastroenterol 2023;13(2):145-151.

Susceptibility of Aedes albopictus Larvae to the Larvicidal Activity of Three Types of Derris elliptica Extract

<b>Background and Objective:</b> The methanol, ethyl acetate and n-hexane extracts of <i>D. elliptica</i> root have high larvicidal activity against <i>Aedes aegypti</i> larvae, the primary vector of dengue but have not been understood their potential against <i>Ae. albopictus</i> larvae, the secondary vector of dengue that also transmits Chikungunya and Zika viruses. This <i>in vitro</i> study aims to understand the larvicidal activity of the 3 extract types of <i>D. elliptica </i>root against <i>Ae. albopictus</i> larvae. <b>Materials and Methods:</b> The tuba root extract types were obtained from the sequential extraction process with 3 steps of liquid-liquid partition as described in the previous report. Six concentrations were occupied in this experiment ranging of 0.5, 1.0, 2.0, 4.0, 10.0 and 15.0 mg L<sup>1</sup> each concentration was 5 times replicated and placed in 250 mL plastic cups. As many as 20 of 3rd instar larvae of <i>Ae. albopictus</i> were subjected in each treatment cup and larval mortality was observed after 24 and 48 hrs of exposure. <b>Results:</b> Larval mortality rates based on concentration range of 13.75-97.00 and 43,75-100%, 14.00-44.00, 34.00-90.00%, 12.00-47.00 and 28.00-88.00%, with the LC<sub>50</sub> after 24 and 48 hrs of exposure were 2.925 and 0.414, 16.184, 2.900, 15.789 and 4.380 mg L<sup>1</sup>, respectively for methanol, ethyl acetate and n-hexane extracts. <b>Conclusion:</b> The methanol, ethyl acetate and n-hexane extract of tuba root have high larvicidal activity against <i>Ae. albopictus</i> larvae. Further study on prototype formulation of larvicide and elucidation of the specific phytochemical compounds of the extracts were necessarily conducted.