Kamaraju Raghavendra

Background: Vector‐borne diseases (VBDs) are a serious threat to public health, globally. Different genera of mosquitoes, acting as disease vectors, transmit diseases such as malaria, filariasis, dengue, chikungunya, Zika fever, and others. Malaria in humans is caused by Plasmodium species transmitted by Anopheles mosquitoes. Odisha is one of the malaria‐endemic states in the country contributing to about 25% of the total (1.5–2.0 million) reported malaria cases and 30% deaths annually. Chemical insecticides and interventions have been effective in controlling vectors, and their continued usage resulted in widespread insecticide resistance in mosquito disease vectors, limiting their efficacy. Methods: Insecticide resistance data in malaria vector species in Odisha were compiled from the published peer‐reviewed literature and other validated sources by search using keywords Anopheles, anopheles species, insecticide, susceptibility, mortality, survival, insecticide resistance, Odisha, Orissa, etc. The inclusion and exclusion criteria were followed to ensure the selection of quality data published between 1993 and 2024. Data from 28 published sources were collated for compilation and adapted for this scoping review. In adult susceptibility tests, mortality rates were categorized as susceptible/resistant to the specific insecticide following the World Health Organization (WHO) criterion: susceptible: > 98% mortality; possible resistance: between 90% and 97% mortality; and confirmed resistance: < 90% mortality. Intensity bioassay data from 10 southern districts were presented for the major vector Anopheles culicifacies . Results: Odisha with 30 administrative districts has five defined ecotypes, coastal plains, central plateaus, central mountainous and highlands region, and western rolling and main flood plains. An. culicifacies, a major malaria vector, is reportedly prevalent in all 30 districts of Odisha, An. fluviatilis in 24 districts, An. annularis in 22, and An . minimus in two districts. An. culicifacies was the most resistant species to DDT (dichlorodiphenyltrichloroethane) (26 districts), malathion (17), and deltamethrin (10 districts). Limited data were available for other Anopheles species. Analyzed data on the status of resistance to different insecticides in anopheles vector species are provided. Conclusion: The emergence of multiple insecticide resistance in An . culicifacies signifies the urgency for effective management strategies. Insecticide resistance management requires regular monitoring and implementation of innovative approaches for vector control, emphasizing the need for insecticides with a novel mode of action and integrated vector management methods. Gaps in the data and ways to address them and issues on insecticide resistance management are discussed.

Mosquito-borne diseases remain a significant global health burden, prompting continuous efforts to develop effective mosquito control strategies. Use of ch

Background: The development of insecticide resistance in malaria vectors has necessitated a need to evaluate new insecticide molecules with different modes of action. In the present study, Fludora Fusion 562.5 WP‐SB (clothianidin 50% + deltamethrin 6.25% AI/kg) was evaluated for its efficacy and residual action for the control of pyrethroid‐resistant malaria vector, Anopheles culicifacies (Diptera: Culicidae), during May 2017 to February 2018 in Gujarat state, India. Methods: Fludora Fusion at the dose of 225 mg AI/m ² and bendiocarb at a dose of 400 mg AI/m ² as a positive control were sprayed in 5 villages each in districts of Kheda, Vadodara, and Panchmahal. The persistence of their efficacy on different local surfaces was determined against An. culicifacies . Entomological indices such as indoor resting density, human landing collections, pyrethrum spray collections, and exit trap collections were monitored to assess the impact of spraying. Results: The observed residual action of Fludora Fusion on mud and cement surfaces was for 6 months and bendiocarb for 3–4 months on both surfaces. Indoor resting densities and parous rate of An. culicifacies were significantly lower in houses sprayed with Fludora Fusion compared to bendiocarb‐sprayed houses. Daily entomological inoculation rate (EIR) declined from 1.275 during prespray period to 0.5225 in the Fludora Fusion arm and 0.3802 in the Ficam arm in postspray period, indicating a reduction in the malaria transmission potential of An. culicifacies in both arms. Conclusion: Based on the residual action of the Fludora Fusion on most common sprayed surfaces and its effects on the elements of vectorial capacity, Fludora Fusion at 225 mg/m ² dose was found effective for more than 6 months and could be a potential option for the control of resistant mosquito vectors.

Background: The biological characteristics of mosquito vectors vary, impacting their response to control measures. Thus, having up-to-date information on vector bionomics is essential to maintain the effectiveness of existing control strategies and tools, particularly as India aims for malaria elimination by 2030. Objective: This study aims to assess the proportions of vector species resting indoors and outdoors, determine their preference for host biting/feeding, identify transmission sites, and evaluate the susceptibility of vectors to insecticides used in public health programs. Methods: Mosquito collections were conducted in 13 districts across 8 Indian states from 2017 to 2020 using various methods to estimate their densities. Following morphological identification in the field, sibling species of Anopheles mosquitoes were identified molecularly using polymerase chain reaction (PCR)–specific alleles. Plasmodium falciparum and Plasmodium vivax infections in the vectors were detected using enzyme-linked immunosorbent assay (ELISA) and PCR assays. In addition, we assessed the insecticide susceptibility status of primary malaria vectors following the World Health Organization (WHO) protocol. Results: Anopheles culicifacies, a primary malaria vector, was collected (with a man-hour density ranging from 3.1 to 15.9) from all states of India except those in the northeastern region. Anopheles fluviatilis, another primary vector, was collected from the states of Madhya Pradesh, Maharashtra, Karnataka, and Odisha. In Haryana and Karnataka, An. culicifacies sibling species A predominated, whereas species C and E were predominant in Madhya Pradesh and Maharashtra. An. culicifacies displayed mainly endophilic behavior across all states, except in Madhya Pradesh, where the proportion of semigravid and gravid mosquitoes was nearly half of that of unfed mosquitoes. The human blood index of An. culicifacies ranged from 0.001 to 0.220 across all study sites. The sporozoite rate of An. culicifacies ranged from 0.06 to 4.24, except in Madhya Pradesh, where none of the vector mosquitoes were found to be infected with the Plasmodium parasite. In the study area, An. culicifacies exhibited resistance to DDT (dichlorodiphenyltrichloroethane; with <39% mortality). Moreover, it showed resistance to malathion (with mortality rates ranging from 49% to 78%) in all districts except Angul in Odisha and Palwal in Haryana. In addition, resistance to deltamethrin was observed in districts of Maharashtra, Gujarat, Haryana, and Karnataka. Conclusions: Our study offers vital insights into the prevalence, resting behavior, and sibling species composition of malaria vectors in India. It is evident from our findings that resistance development in An. culicifacies, the primary vector, to synthetic pyrethroids is on the rise in the country. Furthermore, the results of our study suggest a potential change in the resting behavior of An. culicifacies in Madhya Pradesh, although further studies are required to confirm this shift definitively. These findings are essential for the development of effective vector control strategies in India, aligning with the goal of malaria elimination by 2030.

Background. The attractive toxic sugar bait (ATSB) is a promising strategy for controlling mosquitoes at the adult stage. The strategy is based on the use of a combination of fruit juice, sugar, and a toxin in order to attract and kill the adult mosquitoes. The selection of the components and optimization of their concentrations is significant for the formulation of an effective ATSB. Methods. The present study formulated nine ATSBs and evaluated their efficacy against two laboratory strains (AND-Aedes aegypti and AND-Aedes aegypti-DL10) and two wildcaught colonized strains of Aedes aegypti (GVD-Delhi and SHD-Delhi). Initially, nine attractive sugar baits (ASBs) were prepared using a mixture of 100 fermented guava juice (attractant) with 10 sucrose solution (w/v) in 1:1 ratio. ATSBs were formulated by mixing each ASB with different concentrations of deltamethrin in the ratio of 9:1 to obtain final deltamethrin concentration of 0.0031250.8mg/10mL ATSB. Cage bioassays were conducted with 50 mosquitoes for 24h in order to evaluate the efficacy of each ATSB against the four strains of Ae. aegypti. The data were statistically analyzed using PASW software 19.0 program and 2-way ANOVA. Results. The ATSB formulations registered 8.3397.44 mortality against AND-Aedes aegypti and 5.1596.91 mortality against AND-Aedes aegypti-DL10 strains of Ae. aegypti, while GVD-Delhi strain registered 2.0495.83 mortality and SHD-Delhi strain showed 5.1097.96 mortality. The administration of 0.8mg of deltamethrin within 10mL of attractive toxic sugar bait (ATSB) has led to the maximum mortality rate in adult mosquitoes. Conclusions. The ATSBs formulated with guava juice-ASB and deltamethrin (9:1) showed toxin dose-dependent toxicity by all the four strains of Ae. aegypti. Most effective dosage was found as 0.8mg deltamethrin/10mL ATSB which imparted 96 to 98 mortality in adult mosquitoes. The investigations demonstrated the efficacy of deltamethrin-laced ATSB formulations against Ae. aegypti and highlighted the need for conduct of structured field trials and investigating the impact on disease vectors and nontarget organisms.

A comprehensive entomological survey was undertaken in Alipurduar District, West Bengal, from 2018 to 2020 and in 2022. This study was prompted by reported malaria cases and conducted across nine villages, seven Sub-Centres, and three Primary Health Centres (PHCs). Mosquitoes were hand-collected with aspirators and flashlights from human dwellings and cattle sheds during the daytime. Both morphological and molecular techniques were used for species identification. Additionally, mosquitoes were tested for Plasmodium parasites and human blood presence. Mosquito species such as An. barbirostris s.l., An. hyrcanus s.l., An. splendidus, and An. vagus were morphologically identified. For species like An. annularis s.l., An. minimus s.s., An. culicifacies s.l., and An. maculatus s.s., a combination of morphological and molecular techniques was essential. The mitochondrial cytochrome c oxidase gene subunit 1 (CO1) was sequenced for An. annularis s.l., An. maculatus s.s., An. culicifacies s.l., An. vagus, and some damaged samples, revealing the presence of An. pseudowillmori and An. fluviatilis. The major Anopheles species were An. annularis s.l., An. culicifacies s.l., and An. maculatus s.s., especially in Kumargram and Turturi PHCs. Plasmodium positivity was notably high in An. annularis s.l. and An. maculatus s.s. with significant human blood meal positivity across most species. Morphological, molecular, and phylogenetic analyses are crucial, especially for archived samples, to accurately identify the mosquito fauna of a region. Notably, this study confirms the first occurrence of An. pseudowillmori and An. sawadwongporni in West Bengal and implicates An. maculatus s.s., An. culicifacies s.l., and An. annularis s.l. as significant vectors in the Alipurduar region.

Mosquitoes are the best‐known disease vectors for most vector‐borne diseases that significantly impact global health in terms of morbidity and mortality. In a geographical area, mosquito faunal diversity often alters with changing climatic factors and variable breeding habitats that differ across seasons. Using biodiversity indicators as tools, a study was conducted in rural, peri‐urban, and urban areas of district Ganjam, Odisha state, to determine mosquito faunal diversity as an approach to forecast the possible risk of disease transmission in the three representative topographies. A two‐year study was undertaken to assess the alpha diversity of mosquito species by the numerical strength of the species using various eco‐diversity indices. Species richness and abundance of mosquito species are significantly higher in peri‐urban areas compared to urban and rural areas. The species dominance ofCulex quinquefasciatuswas observed in all three topographies, whileAedes aegypti,Aedes albopictus, andAnopheles stephensiwere in urban areas. Species richness may dilute the risk of disease in an area, but increased species dominance, mostly vector species, in a new habitat often allows pathogens to infect newer communities at risk, leading to the emergence of new diseases. The current study indicates the possible risk of lymphatic filariasis (LF) infection in all three topographies. On the other hand, the risk of malaria and dengue/chikungunya transmission is higher in urban areas. With routine entomological monitoring, including vector incrimination, the biodiversity indicators will be the best tool to forecast the risk of vector‐borne diseases in an area; accordingly, judicious vector control strategies can be adopted.

Northeast region (NER) states of India remain highly malarious due to their geographical and ecotype diversity. Furthermore, rapid urbanization and change in climate are also affecting the vector biology and behavior of the existing species. Hence, a study is conducted in the states of Tripura and Meghalaya to generate data on the bionomics of the prevalent malaria vector species. The data from this study show that primary vectors of malaria An. minimus and An. baimaii were anthropophagic. However, An. baimaii showed a behavioral shift towards zoophagicity (14). Insecticide bioassays confirm that these two major vector species are reportedly susceptible to DDT, Malathion, and indicate that intervention by DDT-IRS is effective. Thus, the implementation of appropriate strategies based on this recent information on the bionomics of malaria vectors in NE region of India will provide an opportunity to achieve malaria elimination by date in these states.

Background: Mass distributions of long-lasting insecticidal nets (LLINs) have contributed to large reductions in the malaria burden. However, this success is in jeopardy due in part to the increasing pyrethroid-resistant mosquito population as well as low LLINs coverage in various areas because the lifespan of LLINs is often shorter than the interval between replenishment campaigns. New insecticide-treated nets (ITNs) containing pyrethroid and piperonyl-butoxide (PBO) have shown a greater reduction in the incidence of malaria than pyrethroid LLINs in areas with pyrethroid-resistant mosquitoes. However, the durability (attrition, bio-efficacy, physical integrity and chemical retainment) of pyrethroid-PBO ITNs under operational settings has not been fully characterized. This study will measure the durability of pyrethroid-PBO ITNs to assess whether they meet the World Health Organization (WHO) three years of operational performance criteria required to be categorized as “long-lasting”. Methods: A prospective household randomized controlled trial will be conducted simultaneously in Tanzania, India and Côte d’Ivoire to estimate the field durability of three pyrethroid-PBO ITNs (Veeralin®, Tsara® Boost, and Olyset® Plus) compared to a pyrethroid LLIN: MAGNet®. Durability monitoring will be conducted up to 36 months post-distribution and median survival in months will be calculated. The proportion of ITNs: (1) lost (attrition), (2) physical integrity, (3) resistance to damage score, (4) meeting WHO bio-efficacy (≥ 95% knockdown after 1 h or ≥ 80% mortality after 24 h for WHO cone bioassay, or ≥ 90% blood-feeding inhibition or ≥ 80% mortality after 24 h for WHO Tunnel tests) criteria against laboratory-reared resistant and susceptible mosquitoes, and insecticidal persistence over time will be estimated. The non-inferiority of Veeralin® and Tsara® Boost to the first-in-class, Olyset® Plus will additionally be assessed for mortality, and the equivalence of 20 times washed ITNs compared to field aged ITNs will be assessed for mortality and blood-feeding inhibition endpoints in the Ifakara Ambient Chamber Test, Tanzania. Conclusion: This will be the first large-scale prospective household randomized controlled trial of pyrethroid-PBO ITNs in three different countries in East Africa, West Africa and South Asia, simultaneously. The study will generate information on the replenishment intervals for PBO nets.

Background. The major malaria vector in India is Anopheles culicifacies, and indoor residual spraying (IRS) and distribution of long-lasting insecticidal nets (LLINs) are the two main vector control measures in the national program. This species has shown resistance to dichlorodiphenyltrichloroethane (DDT), malathion, and synthetic pyrethroids (SP). The study was carried out in three districts, that is, Dindori of Madhya Pradesh and Kanker and Bastar from Chhattisgarh state to know the range of resistance phenotypes and to assess the strength of resistance in An. culicifacies. Methods. An. culicifacies collected from the field was tested to determine the susceptibility status to the discriminating concentration (DC) of different insecticides, that is, DDT 4.0, malathion 5.0, alphacypermethrin 0.05, and deltamethrin 0.05 following the World Health Organization (WHO) procedures. Further, intensity bioassays of the resistant An. culicifacies to 1X discriminating concentration (DC) of alphacypermethrin and deltamethrin were conducted by exposing 5X and 10X concentrations of 1X DC. Results are interpreted as per the WHO criterion. Results. The overall result of susceptibility status in An. culicifacies in districts Dindori, Kanker, and Bastar revealed confirmed resistance to DDT, malathion, alphacypermethrin, and deltamethrin registering mortality of 15 (1020), 70 (6575), 78.6 (7782.5), and 87 (84.891.3), respectively. Further, in district Dindori and Baster, the intensity bioassay test at 5X DC of alphacypermethrin and deltamethrin revealed 99 and 100, respectively, while in district Kanker, the species registered moderate resistance with 92.5 and 95 mortality, respectively, in 5X DC of alphacypermethrin and deltamethrin. However, in 10X DC, the An. culicifacies was susceptible to both pyrethroids (100) in district Kanker. Conclusion. The results of the intensity bioassay tests with SP-resistant An. culicifacies suggested no change of insecticide is required in the ongoing intervention. However, regular monitoring of insecticide susceptibility and intensity bioassays in malaria vectors in view of continued use of these interventions may increase resistance and for implementing effective vector management strategies.