Mapping the Insecticide Resistance Landscape of Malaria Vectors in Odisha, India (1993–2024): A Scoping Review

Microarrays

Insecticide resistance threatens malaria control in Africa

BackgroundUnderstanding of malaria vector density, distribution, insecticide resistance, vector incrimination, infection status, and identification of sibling species are some of the essential components of vector control measures for achieving malaria elimination goals.MethodsAs part of the malaria elimination demonstration project, entomological surveillance was carried out from October 2017 to October 2019 by collecting indoor resting mosquitoes using hand catch method. Susceptibility test was done for determining the insecticide resistance status of vector mosquito Anopheles culicifacies using standard protocols by the World Health Organization. The cone bioassay method was used for determining the efficacy and quality of insecticide sprayed. Mosquitoes collected from different ecotypes were identified and processed for parasite identification, vector incrimination and sibling species determination.ResultsThe two known malaria vector species (Anopheles culicifacies and Anopheles fluviatilis) were found in the study area, which have been previously reported in this and adjoining areas of the State of Madhya Pradesh. The prevalence of An. culicifacies was significantly higher in all study villages with peak in July while lowest number was recorded in May. Proportion of vector density was observed to be low in foothill terrains. The other anopheline species viz, Anopheles subpictus, Anopheles annularis, Anopheles vagus, Anopheles splendidus, Anopheles pallidus, Anopheles nigerrimus and Anopheles barbirostris were also recorded in the study area, although their prevalence was significantly less compared to the An. culicifacies. In 2017, An. culicifacies was found to be resistant to dichloro-diphenyl-trichloroethane (DDT) and malathion, with possible resistance to alphacypermethrin and susceptible to deltamethrin. However, in 2019, the species was found to be resistant to alphacypermethrin, DDT, malathion, with possible resistance to deltamethrin. The bioassays revealed 82 to > 98% corrected % mortality of An. culicifacies on day-one post-spraying and 35 to 62% on follow-up day-30. Anopheles culicifacies sibling species C was most prevalent (38.5%) followed by A/D and E while B was least pre-dominant (11.9%). Anopheles fluviatilis sibling species T was most prevalent (74.6%) followed by U (25.4%) while species S was not recorded. One An.culicifacies (sibling species C) was found positive for Plasmodium falciparum by PCR tests in the mosquitoes sampled from the test areas.ConclusionBased on the nine entomologic investigations conducted between 2017–2019, it was concluded that An. culicifacies was present throughout the year while An. fluviatilis had seasonal presence in the study areas. Anopheles culicifacies was resistant to alphacypermethrin and emerging resistance to deltamethrin was observed in this area. Anopheles culicifacies was confirmed as the malaria vector. This type of information on indigenous malaria vectors and insecticide resistance is important in implementation of vector control through indoor residual spraying (IRS) and use of insecticide-impregnated bed nets for achieving the malaria elimination goals.

Monitoring of synthetic insecticides resistance and mechanisms among malaria vector mosquitoes in Iran: A systematic review

BackgroundMalaria vector control relies principally on the use of insecticides, especially pyrethroids. Because of the increasing occurrence of insecticide resistance in target vector populations, the development of new insecticides, particularly those with novel modes of action, is particularly important, especially in terms of managing insecticide resistance. The C8910 formulation is a patented mixture of compounds comprising straight-chain octanoic, nonanoic and decanoic saturated fatty acids. This compound has demonstrated toxic and repellent effects against several arthropod species. The aims of this study were to measure the insecticidal effects of C8910 against an insecticide susceptible (FANG) and a pyrethroid resistant (FUMOZ-R) laboratory strain of An. funestus as well as against wild-caught An. funestus material from Zambia (ZamF), and to investigate the repellent effects of two formulations of C8910 against these strains.MethodsToxicity against adult females was assessed using a range of concentrations based on the CDC bottle bioassay method and repellence of three different C8910 formulations was assessed using standard choice-chamber bioassays.ResultsC8910 proved equally toxic to adult females of the FUMOZ-R and FANG laboratory strains, as well as to adult females of the wild-caught (ZamF) sample. None of the C8910 formulations tested gave any conclusive indication of repellence against any of the strains.ConclusionC8910 is equally effective as an adulticide against pyrethroid resistant and insecticide susceptible An. funestus. However, the formulations tested did not show any consistent repellence against laboratory reared and wild-caught female samples of this species. Nevertheless, C8910 shows potential as an adulticide that can be used for malaria vector control, particularly in those instances where insecticide resistance management is required.

Malaria is a major contributor to the global disease burden and a significant impediment to socio-economic development in resource-poor countries. In contrast to improved trends of malaria morbidity and mortality in some parts of the world, malaria has remained a life threatening disease in many other regions including East Africa because of factors such as weak health systems, growing drug and insecticide resistance, ecological change, climate anomalies, socio-economic factors and changes in land use patterns. Ongoing malaria vector control strategies rely mainly on the use of indoor residual spraying (IRS) and insecticide treated nets (ITNs) which are the primary intervention strategies to reduce malaria burden. The current success in reducing malaria related morbidity and mortality has led to the optimism that elimination of the disease as a public health problem may be a realistic objective. Efforts during the last decades enabled access to ITNs in sub-Saharan Africa protecting millions of people at risk of malaria. The number of countries that employed IRS as a vector control strategy increased almost by two fold and the percentage of households owing at least one ITN in sub-Saharan Africa is estimated to increase from time to time. Currently, all ITNs are treated with pyrethroids while IRS depends on pyrethroids, DDT and recently on carbamates. Despite IRS and ITNs are known in reducing malaria incidence, insecticide resistance in malaria vectors threatens the success of malaria control program. Resistance to insecticides has occurred in most arthropod vectors with different mechanisms. If the current trends of increased insecticide resistance continue, it may jeopardise the efficacy of current vector control tools. Given the limited choice of available insecticides, i.e., only 12 insecticides belonging to 4 classes of insecticides (organochlorines, organophosphates, pyrethroids and carbamates), resistance to these insecticides has become a limiting factor for current efforts to sustain control. Currently, no other insecticide class with similar efficacy has been approved by WHOPES. The development of insecticide resistance in malaria vectors has been attributed to the prolonged use of insecticides for IRS and high coverage of ITNs/LLINs. The recent use of pyrethroids for indoor residual spraying is likely to have enhanced the selection pressure for insecticide resistance alleles among East African vector populations. Moreover, mosquitoes breeding in agricultural habitats are exposed to sub lethal doses of pesticides used in agriculture. Since currently recommended insecticides for IRS or ITNs were developed with similar active ingredients of pesticides used for agricultural pest control, their extensive and widespread use to boost agricultural productivity is believed to foster insecticide resistance in mosquito populations. There is strong evidence on the emergence of resistance to DDT and pyrethroids in the major malaria vectors in East Africa however, current information on resistance status of the malaria vectors in different areas of the sub-region is scarce. Genes conferring resistance to malaria vectors, including kdr, super kdr and acetylcholinesterase mutations and metabolic resistance are not mapped. The frequency and spatial distribution of East and West African kdr mutations and their association with the phenotypic resistance in East Africa is less understood. The bioassay results after WHO diagnostic tests in different East African malaria vector populations against insecticides used in public health is not well documented. In conclusion, planning and implementing insecticide resistance monitoring and management strategy should be part of the vector control program either for pre-emptive action without waiting for the development of resistance or to slowdown the spread of resistance in malaria vectors in the sub-region.

Insecticide resistance in malaria vectors threatens the effectiveness of long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) in Tanzania. Understanding the evolution of insecticide resistance is essential for guiding vector control policy in Tanzania. This review synthesises evidence on resistance patterns, surveillance and management strategies to inform programmatic decisions. To synthesise evidence on insecticide resistance patterns, mechanisms and management strategies in Tanzanian malaria vectors (2015-2024), and to highlight research and surveillance gaps. A scoping review was conducted using the PRISMA-ScR framework. Articles were retrieved from multiple databases based on predetermined eligibility criteria. Data on resistance patterns, mechanisms, surveillance approaches and management strategies were extracted and synthesised. Of 910 identified records, ten met inclusion criteria. All studies applied WHO susceptibility bioassays, and several incorporated molecular or biochemical assays. Pyrethroid resistance was consistently reported, largely driven by knockdown resistance (kdr) mutations and metabolic mechanisms. DDT resistance was common, while moderate resistance to carbamates appeared in about half of the studies. Organophosphates, particularly pirimiphos-methyl, remained effective and new insecticides such as clothianidin and chlorfenapyr showed high efficacy with no resistance detected. Reported management strategies included pyrethroid-PBO LLINs and integrated vector management, although surveillance coverage and mechanistic profiling were inconsistent across sites. Insecticide resistance is widespread in Tanzanian malaria vectors, with pyrethroids most affected. While new insecticides and management strategies show promise, gaps in surveillance and operational evidence limit effectiveness. Strengthened research capacity, sustained funding and cross-sectoral collaboration are essential to support evidence-based resistance management and protect malaria control gains.

BackgroundMyanmar is one of the six countries in the Greater Mekong Subregion (GMS) of Southeast Asia. Malaria vectors comprise many Anopheles species, which vary in abundance and importance in malaria transmission among different geographical locations in the GMS. Information about the species composition, abundance, and insecticide resistance status of vectorial systems in Myanmar is scarce, hindering our efforts to effectively control malaria vectors in this region.MethodsDuring October and November 2019, larvae and adult females of Anopheles mosquitoes were collected in three sentinel villages of Banmauk township in northern Myanmar. Adult female mosquitoes collected by cow-baited tent collection (CBTC) and adults reared from field-collected larvae (RFCL) were used to determine mortality rates and knockdown resistance (kdr) against deltamethrin using the standard WHO susceptibility test. Molecular species identification was performed by multiplex PCR and ITS2 PCR, followed by DNA sequencing. The kdr mutation at position 1014 of the voltage-gated sodium channel gene was genotyped by DNA sequencing for all Anopheles species tested.ResultsA total of 1596 Anopheles mosquitoes from seven morphologically identified species groups were bioassayed. Confirmed resistance to deltamethrin was detected in the populations of An. barbirostris (s.l.), An. hyrcanus (s.l.), and An. vagus, while possible resistance was detected in An. annularis (s.l.), An. minimus, and An. tessellatus. Anopheles kochi was found susceptible to deltamethrin. Compared to adults collected by CBTC, female adults from RFCL had significantly lower mortality rates in the four species complexes. A total of 1638 individuals from 22 Anopheles species were molecularly identified, with the four most common species being An. dissidens (20.5%) of the Barbirostris group, An. peditaeniatus (19.4%) of the Hyrcanus group, An. aconitus (13.4%) of the Funestus group, and An. nivipes (11.5%) of the Annularis group. The kdr mutation L1014F was only detected in the homozygous state in two An. subpictus (s.l.) specimens and in a heterozygous state in one An. culicifacies (s.l.) specimen.ConclusionsThis study provides updated information about malaria vector species composition and insecticide resistance status in northern Myanmar. The confirmed deltamethrin resistance in multiple species groups constitutes a significant threat to malaria vector control. The lack or low frequency of target-site resistance mutations suggests that other mechanisms are involved in resistance. Continual monitoring of the insecticide resistance of malaria vectors is required for effective vector control and insecticide resistance management.Graphical

Background: The application of insecticides for malaria vector control has led to a global problem, which is the current trend of increased resistance against these chemicals. This study aimed to review the insecticide resistance status was previously determined in Asia and how to implement the necessary interventions. Moreover, the implications of resistance in malaria vector control in this region were studied. Methods: This systematic review was conducted using a predefined protocol based on PRISMA-retrieved articles from four science databases, namely ProQuest, Science Direct, EBSCO, and PubMed in the last ten years (2009 to 2019). The searching process utilized four main combinations of the following keywords: malaria, vector control, insecticide, and Asia. In ProQuest, malaria control, as well as an insecticide, were used as keywords. The following criteria were included in the filter, namely full text, the source of each article, scholarly journal, Asia, and publication date as in the last ten years. Results: There were 1408 articles retrieved during the initial search (ProQuest=722, Science Direct=267, EBSCO=50, PubMed=285, and Scopus=84). During the screening, 27 articles were excluded because of duplication, 1361 based on title and abstract incompatibility with the inclusion criteria, and 20 due to content differences. In the final screening process, 15 articles were chosen to be analyzed. From the 15 articles, it is known that there was organochlorine (DDT), organophosphate (malathion), and pyrethroids resistance in several Anopheles species with a less than 80% mortality rate. Conclusion: This review found multiple resistance in several Anopheles includes resistance to pyrethroid. The reports of pyrethroid resistance were quite challenging because it is considered effective in the malaria vector control. Several countries in Asia are implementing an insecticide resistance management (IRM) strategy against malaria vectors following the Global Plan for IRM.

Background: The application of insecticides for malaria vector control has led to a global problem, which is the current trend of increased resistance against these chemicals. This study aimed to review the insecticide resistance status was previously determined in Asia and how to implement the necessary interventions. Moreover, the implications of resistance in malaria vector control in this region were studied. Methods: This systematic review was conducted using a predefined protocol based on PRISMA-retrieved articles from four science databases, namely ProQuest, Science Direct, EBSCO, and PubMed in the last ten years (2009 to 2019). The searching process utilized four main combinations of the following keywords: malaria, vector control, insecticide, and Asia. In ProQuest, malaria control, as well as an insecticide, were used as keywords. The following criteria were included in the filter, namely full text, the source of each article, scholarly journal, Asia, and publication date as in the last ten years. Results: There were 1408 articles retrieved during the initial search (ProQuest=722, Science Direct=267, EBSCO=50, PubMed=285, and Scopus=84). During the screening, 27 articles were excluded because of duplication, 1361 based on title and abstract incompatibility with the inclusion criteria, and 20 due to content differences. In the final screening process, 15 articles were chosen to be analyzed. From the 15 articles, it is known that there wasorganochlorine (DDT), organophosphate (malathion), and pyrethroids resistance in several Anopheles species with a less than 80% mortality rate. Conclusion:This review found multiple resistance in several Anopheles includes resistance to pyrethroid.The reports of pyrethroid resistance were quite challenging because it is considered effective in the malaria vector control. Several countries in Asia are implementing an insecticide resistance management (IRM) strategy against malaria vectors following the Global Plan for IRM.

BackgroundAfrica is still home to the highest number of malaria cases and deaths. To reduce the burden of malaria in Africa, different classes of insecticides have been used since the eradication era. However, the effectiveness of insecticides is reduced periodically. This study aimed to assess the susceptibility status of major African malaria vectors to different insecticides commonly used for public health.MethodsTo conduct this review, we used open-access global databases, i.e., PubMed, Google Scholar, Scopus, Web of Sciences, and Pro-Quest, to extract relevant articles published between January 2002 and 28 December 2023. Primary articles were searched using keywords such as “insecticide susceptibility status”, ‘insecticide resistance”,” malaria vectors”, “Africa”, and “Anopheles”. Articles published in English that met the inclusion criteria were included in this review. Data were extracted from the included article texts, tables, figures, and supplementary information. The validity of all included articles was checked before inclusion by critical evaluation using standardized methods. Finally, the results of the original articles are presented in tables, graphs, and maps.ResultsIn total, 61 relevant articles were retrieved and extracted from 1,794 accessed articles. Of these, most articles documented resistance in Anopheles gambiae s.l. and An. funestus to organochlorines, i.e., DDT (4%); cyclodins, i.e., dieldrin (4%); pyrethroids, including lambda-cyhalothrin (0.05%), cyfluthrin (0.15%), permethrin (0.75%), and deltamethrin (0.05%); and carbamate, i.e., propoxur (0.1%), across Africa. These mosquito species have also developed knockdown resistance to different insecticide classes (pyrethroids and organochlorines) in Africa. However, the resistance of these malaria vectors varied in different areas of the continent and in different localities within the same country. The highest levels of insecticide resistance in Anopheles mosquitoes across Africa were recorded between 2011 and 2015. However, currently, mosquito populations are susceptible to candidate insecticides such as chlothianidin (neoncotinoid), chlorfenapyr (pyrole), and brofanilide (meta-diamide), which are newly introduced insecticides for vector control interventions.ConclusionThis review revealed that the major African malaria vectors have developed resistance to most insecticides used for public health. However, they were susceptible to a few existing insecticides (pirimiphos-methyl) and new candidate insecticides such as clothianidin, chlorfenapyr, and brofanilide. This warrants the development and implementation of insecticide resistance monitoring and management strategies for malaria control and elimination programs in malaria endemic countries of Africa to extend the effective lifespan of insecticides to which populations of the major African malaria vectors are susceptible and to reduce the resistance frequency. We also recommend the use of integrated vector management to complement the chemical insecticide vector control interventions in the containment of major African malaria vectors.

BackgroundThe resurgence of Anopheles funestus, a dominant vector of human malaria in western Kenya was partly attributed to insecticide resistance. However, evidence on the molecular basis of pyrethroid resistance in western Kenya is limited. Here, we reported metabolic resistance mechanisms and demonstrated that multiple non-coding Ribonucleic Acids (ncRNAs) could play a potential role in An. funestus resistance to pyrethroid in western Kenya. Anopheles funestus mosquitoes were sampled using aspiration methods in Bungoma, Teso, Siaya, Port Victoria and Kombewa in western Kenya. The F1 progenies were exposed to deltamethrin (0.05%), permethrin (0.75%), DDT (4%) and pirimiphos-methyl (0.25%) following WHO test guidelines. A synergist assay using piperonyl butoxide (PBO) (4%) was conducted to determine cytochrome P450s’ role in pyrethroid resistance. RNA-seq was conducted on a combined pool of specimens that were resistant and unexposed, and the results were compared with those of the FANG susceptible reference strain. This approach aimed to uncover the molecular mechanisms underlying the observed phenotypic pyrethroid resistance.ResultsPyrethroid resistance was observed in all sites with an average mortality rate (MR) of 57.6%. Port Victoria had the highest level of pyrethroid resistance to permethrin (MR = 53%) and deltamethrin (MR = 11%. Teso had the lowest level of resistance to permethrin (MR = 70%) and deltamethrin (MR = 87%). Resistance to DDT was observed only in Kombewa (MR = 89%) and Port Victoria (MR = 85%). A full susceptibility to P-methyl (0.25%) was observed in all sites. PBO synergist assay revealed high susceptibility (> 98%) to pyrethroids in all the sites except for Port Victoria (MR = 96%). Whole transcriptomic analysis showed that most gene families associated with pyrethroid resistance comprised non-coding RNAs (67%), followed by immunity proteins (10%), cytochrome P450s (6%), cuticular proteins (5%), olfactory proteins (4%), glutathione S-transferases (3%), UDP-glycosyltransferases (2%), ATP-binding cassettes (2%) and carboxylesterases (1%).ConclusionThis study unveils the molecular basis of insecticide resistance in An. funestus in western Kenya, highlighting for the first time the potential role of non-coding RNAs alongside metabolic detoxification in pyrethroid resistance. Targeting non-coding RNAs for intervention development could help in insecticide resistance management.

Recombinant expression and characterization of GSTd3 from a resistant population of Anopheles arabiensis and comparison of DDTase activity with GSTe2

Objective: To collate and summarize phenotypic insecticide susceptibility data of Indian malaria vectors from 2017 to 2024, focusing on insecticides used in adult vector control, dichloro diphenyl trichloroethane, malathion, deltamethrin, alpha-cypermethrin, and permethrin to identify resistance patterns to different classes of insecticides. Methods: The data included information on vector species, location of the study (state/district), insecticide tested, mortality percentage, and susceptibility classification based on the World Health Organization interpretation criteria. Retrospective data were collected from peer-reviewed publications (2017-2024) and up to June 2025. The data were collated for five major malaria vector species, namely Anopheles (An.) culicifacies, An. fluviatilis, An. stephensi, An. baimaii, and An. minimus. Results: Insecticide susceptibility data were available from 86 districts across 16 Indian states for 40615 mosquitoes. The majority of the data was on An. culicifacies (n=28308), followed by An. stephensi (n=5 611), An. fluviatilis (n=5967), An. baimaii (n=365), and An. minimus (n=364). Intensity bioassays revealed low to moderate resistance levels in An. culicifacies populations from selected districts in 3 states, Odisha, Madhya Pradesh, and Chhattisgarh against deltamethrin and alpha-cypermethrin. Conclusions: This review highlights spatial and species-level variations in insecticide susceptibility among Indian malaria vectors. The low to moderate intensity suggested that it may not yet be severe enough to cause operational failure with current vector control interventions. Continued monitoring of insecticide resistance, as well as the use of new-generation insecticides and interventions, is suggested to sustain vector control efficacy and manage insecticide resistance in malaria vectors to support India’s malaria elimination.

The number of reported malaria cases transmitted by Anopheles mosquitoes in the Republic of Korea (ROK) increased from 420 in 2022 to 746 in 2023, a 77.6% increase. Eight Anopheles species are currently reported in the ROK, including six species belonging to the Anopheles Hyrcanus Group and one species each belonging to the Barbirostris Group and Lindesayi Group. However, studies on insecticide resistance in the ROK has predominantly concentrated on Anopheles sinensis or more broadly, members of the Hyrcanus Group. Reported differences in vector competence and ecological characteristics of mosquito species in the ROK highlight the importance for conducting accurate evaluations of insecticide resistance for each of the Anopheles species for informing the potential efficacy of vector control to reduce malaria transmission. All eight species of Anopheles mosquitoes were collected in/near the demilitarized zone (DMZ), a malaria high-risk region in the ROK. Additional specimens were collected in Seoul [Yongsan US Army Garrison (USAG)] and Pyeongtaek (Humphreys USAG) where malaria risks are much lower. Anopheles mosquitoes were identified to species using a multiplex PCR method and then evaluated for the presence of acetylcholinesterase-1 (ace-1) and voltage-gated sodium channel (vgsc) regions to identify mutations linked to insecticide resistance. Analysis of the ace-1 region identified insecticide resistance alleles in four species of the Hyrcanus Group (An. sinensis, An. kleini, An. belenrae, and An. pullus), while ace-1 resistance alleles were not observed in the other four species. The screening of the vgsc gene fragment confirmed the presence of resistant alleles only in An. sinensis (considered a poor malaria vector) and An. kleini (a primary malaria vector) in the ROK. This study represents a preliminary investigation of insecticide resistance mutations across all Anopheles species in the ROK. These findings are crucial in advancing mosquito control strategies to mitigate future malaria infections.