Atypical Dengue Outbreak in Odisha: Insights from the Entomological Investigations.

An outbreak of dengue fever struck Tikarapada village, Rayagada district (April 2020). Among 117 fever cases, 49 tested positive for the dengue NS1 antigen. To identify mosquito-related factors in the outbreak, a survey of 101 houses found Aedes breeding sites in 11.6% of containers. Aedes aegypti (79%) and Aedes albopictus (21%) emerged from collected pupae. The village exhibited high (house index = 24.8), (container index = 11.6), (pupal index = 32.7), and (Breteau index = 40.6) indices. The findings confirmed the presence of Aedes and ample breeding sites, suggesting their role in the outbreak. A report recommending integrated vector control measures was submitted to district and state health authorities.

Current status of malaria elimination in Koraput district of Odisha, India.

BACKGROUND & OBJECTIVES: After launching of NFME and NSP with wide scale implementation of effective intervention tools during 2017, Odisha State of India observed a drastic reduction of malaria cases (81%) in 2018 and 88.6% in 2019, compared to 2017. The current study analysed the different factors causative for malaria reduction in Koraput district of Odisha State, India. METHODS: The vector density and malaria incidences were assessed from January 2016 to December 2019 and human blood index, bio-efficacy and use rate of LLINs were assessed after distribution of long-lasting insecticidal nets. RESULTS: The use rate of LLINs by the villagers ranged from 93.8% to 100% throughout the year. The mortality of Anopheles jeyporiensis remained 100.0% in both DuraNet and PermaNet LNs. The density of An. fluviatilis after distribution of LLINs reduced from 4.7 to 0.0 whereas, the density of An. culicifacies reduced from 12.2 to 9.3. The HBI of An. fluviatilis and An. culicifacies was 0.006 and 0.005, respectively after distribution of LLINs. The malaria incidences also drop from 14.2 to zero after distribution. INTERPRETATION & CONCLUSION: A significant reduction in malaria incidences was validated and the possible reasons for the reduction are discussed.

Evaluation of long-lasting indoor residual spraying of deltamethrin 62.5 SC-PE against malaria vectors in India.

BACKGROUND: Deltamethrin 62.5 polymer-enhanced suspension concentrate (SC-PE) is one of the World Health Organization-approved insecticides for indoor residual spraying and was recommended to evaluate its residual activity for determination of appropriate spray cycles in different eco-epidemiologic settings. In the current study, efficacy of deltamethrin 62.5 SC-PE was evaluated against vectors of malaria and its impact on malaria incidence in a Plasmodium falciparum hyper-endemic area in Koraput district, Odisha State, India. METHODS: The trial had two comparable arms, arm 1 with residual spraying of deltamethrin 62.5 SC-PE and arm 2 with deltamethrin 2.5% WP (positive control). Comparative assessment of the impact of each intervention arm on entomological (density, parity, infection and human blood index), epidemiological (malaria incidence) parameters, residual efficacy and adverse effects were evaluated. RESULTS: Both the arms were comparable in terms of entomological and epidemiological parameters. While, deltamethrin 62.5 SC-PE was found to be effective for 150 days in mud and wood surfaces and 157 days in cement surfaces; deltamethrin 2.5% was effective only for 105 days on mud surfaces and 113 days on cement and wood surfaces. CONCLUSIONS: Deltamethrin 62.5 SC-PE had prolonged killing effectiveness up to 5 months. Hence, one round of IRS with deltamethrin 62.5 SC-PE would be sufficient to cover two existing malaria peak transmission seasons (July-August and October-November) in many parts of India.

Evaluation of DawaPlus 3.0 and DawaPlus 4.0, deltamethrin-PBO combination nets against pyrethroid-resistant Anopheles culicifacies in experimental huts in India.

BACKGROUND: The development of resistance in vectors is one of the major impediments for malaria control. Adding synergists to insecticides has proven to be an alternative choice for controlling resistant mosquitoes. DawaPlus 3.0 and DawaPlus 4.0 are new long-lasting insecticidal nets (LLINs) in which deltamethrin and a synergist, piperonyl butoxide (PBO) are added into filaments and their efficacy was tested against resistant malaria vector, Anopheles culicifacies in experimental huts in India. METHODS: The performance of two trial nets in terms of deterrence induced exiting, blood-feeding inhibition and mortality of An. culicifacies was compared with DawaPlus 2.0 and untreated net. RESULTS: There was a significant reduction in entry, blood feeding and mortality (p < 0.05) and increase in exit rates of An. culicifacies in the treatment arms compared to untreated arm. But, both candidate LNs washed 20 times could not perform better than the washed reference net (DawaPlus 2.0). Cone bioassay results showed that all the treatment arms (both washed and unwashed) produced < 80% mortality of An. culicifacies before and after hut evaluation. CONCLUSIONS: DawaPlus 3.0 and DawaPlus 4.0 with their current specification may not be as effective as required to control the resistant vector, An. culicifacies, in east-central India.

Efficacy evaluation of Veeralin LN, a PBO-incorporated alpha-cypermethrin long-lasting insecticidal net against Anopheles culicifacies in experimental huts in Odisha State.

BACKGROUND: The success of malaria control using long-lasting insecticidal nets (LLINs) is threatened by pyrethroid resistance developed by the malaria vectors, worldwide. To combat the resistance, synergist piperonyl butoxide (PBO) incorporated LLINs is one of the available options. In the current phase II hut trial, the efficacy of Veeralin®LN (an alpha-cypermethrin and PBO-incorporated net) was evaluated against Anopheles culicifacies, a pyrethroid resistant malaria vector. METHODS: The performance of Veeralin®LN was compared with MAGNet®LN and untreated net in reducing the entry, induced exit, mortality and blood feeding inhibition of target vector species. RESULTS: The performance of Veeralin was equal to MAGNet in terms of reducing hut entry, inhibiting blood feeding and inducing exophily, and with regard to causing mortality Veeralin was better than MAGNet. When compared to untreated net, a significant reduction in hut entry and blood feeding and an increase in exophily and mortality were observed with Veeralin. In cone bioassays, unwashed Veeralin caused > 80% mortality of An. culicifacies. CONCLUSIONS: Veeralin performed equal to (entry, exit, feeding) or better than (mortality in huts and cone bioassays) MAGNet and could be an effective tool against pyrethroid resistant malaria vectors.

Evaluation of bio-efficacy and durability of long-lasting insecticidal nets distributed by malaria elimination programme in Eastern India.

BACKGROUND: Long-lasting insecticidal nets (LLINs) are the most favoured vector control tools worldwide. Timely monitoring and evaluation of LLINs is important to sustain the impact of this promising vector control method and for replacement of worn-out and those rendered ineffective. During the mid-2017, LLINs were distributed by the National Vector Borne Disease Control Programme (NVBDCP) in high malaria endemic districts of the eastern coastal state of Odisha. The study was carried out to assess the field performance of the LLINs post 30 months of distribution in Koraput district of Odisha state. METHODS: A total of 130 households were randomly selected from three villages of Laxmipur CHC in Koraput district, Odisha, India; one each from hilltop, foothill and plain terrain. The net users were interviewed to elicit information on usage, washing practices, physical integrity, bio-efficacy and survivorship of LLINs to confirm the claimed three-year life of the LLINs. RESULTS: 74.8% of the LLINs were physically present after 30 months of distribution. The numbers (%) of LLINs used previous night varied from 30 to 61% between study villages. 74% respondents were using the LLINs throughout the year and 26% only seasonally. Of the total, 85% of the nets were reported to be washed and 95% nets were dried under shade as recommended. Altogether, 58% of the surveyed nets were found torn with holes. Of these, 74 (57%) nets were in good condition, 10 (8%) nets were in serviceable and 45 (35%) nets were badly torn and needed replacement. A total of 45 (93.75%), 68 (80%) and 71 (63.8%) LLINs were physically present in hilltop, foothill and plain villages, respectively. The LLINs did meet the efficacy criteria, given the 100% mortality to the exposed Anopheles jeyporiensis mosquitoes post 30 months distribution. CONCLUSIONS: The findings of this study were communicated to the programme officials of the state and LLINs were replenished soon after 31st month post-distribution of LLINs.

Evaluation of MAGNet, a long-lasting insecticidal mosquito net against Anopheles fluviatilis in experimental huts in India.

BACKGROUND: MAGNet LN is a wash resistant long-lasting insecticidal (polyethylene) net (LLIN) in which the alpha-cypermethrin insecticide is incorporated within the 150 denier high density polyethylene monofilaments of the nets. The bio-efficacy of MAGNet LN was reported to be high even after 25 washes. The LN met the WHO criteria of Phase I evaluation and obtained recommendation from the World Health Organization Pesticide Evaluation Scheme (WHOPES) for Phase II trial. For registration of the LN in India, the current study was conducted to evaluate its efficacy after 20 or 25 washes compared to negative control (untreated net) and positive control (Duranet LN) in experimental huts against a wild, free flying pyrethroid susceptible population of Anopheles fluviatilis in terms of deterrence, blood-feeding inhibition, mortality and induced exophily. METHODS: The evaluation was carried out in six experimental huts located at Kandhaguda village in Malkangiri district, Odisha state following the WHO guidelines. RESULTS: The study showed that 25 times washed MAGNet LN produced 100% mortality in cone bioassays before and after hut evaluation. MAGNet washed 25 times did not differ significantly from all other treated nets in terms of deterring hut entry, induced exophily, blood feeding inhibition and causing mortality of An. fluviatilis. CONCLUSIONS: MAGNet LN showed extended wash resistance retaining its bio-efficacy up to 25 washes and met the WHOPES requirement of passing Phase II evaluation.

Entomological investigation of Japanese encephalitis outbreak in Malkangiri district of Odisha state, India.

BACKGROUND: A severe outbreak of Japanese encephalitis (JE) and acute encephalitis syndrome (AES) with high case fatality was reported from Malkangiri district of Odisha state, India during September to November 2016 affecting 336 children with 103 deaths. OBJECTIVES: The purpose of this study was to investigate the outbreak in the light of entomological determinants. METHODS: Entomological investigation was carried out in 48 villages from four mostly affected Community Health Centres (CHCs) of Malkangiri district. Dusk collections of resting adults was done in villages from indoor and outdoor sites to record the density of mosquito species, including the known JE vectors, feeding behaviour, parity, dusk index and infection status with JE virus (JEV). FINDINGS: The per man hour density and dusk index of JE vector species varied from 2.5 to 24.0 and 0.81 to 7.62, respectively in study villages. A total of 1136 mosquitoes belonging to six vector species were subjected to PCR and one pool of Culex vishnui was found to be positive for JEV. CONCLUSION: The JE transmission in Malkangiri district was confirmed. Thorough screening of human blood samples of JE/AES suspected cases and JE vector mosquitoes for the presence of JEV during rainy season every year is recommended.

Bio-efficacy, physical integrity, community usage and washing practices of mosquito nets treated with ICON MAXX long-lasting insecticidal treatment in India.

BACKGROUND: New brands of potential long lasting insecticide nets (LLINs) and LLIN treatment kits require field evaluation before they are used in a vector control programme. OBJECTIVES: The aim of this study was to evaluate the bio-efficacy, usage, washing practice and physical integrity of nets treated with LLIN treatment kit, ICON MAXX in a phase III field trial in Odisha state, India. METHODS: A total of 300 polyester nets treated with ICON MAXX and 140 polyester nets treated conventionally with lambda-cyhalothrin CS 2.5% ITNs were distributed. The bio-efficacy was evaluated with WHO cone bioassay. The chemical analysis of netting pieces was done at the beginning, after 12 and 36 months of the trial. FINDINGS: After one year of distribution of nets, the bioassay showed 100% mortality on both ITNs and ICON MAXX treated nets. At 36 months, the overall pass rate was 58.8% and the mean lambda-cyhalothrin content of LLINs was 34.5 mg ai/m2, showing a loss of 44.4% of the original concentration. CONCLUSION: ICON MAXX treated LLIN was found to retain bio-efficacy causing 97% knockdown of Anopheles stephensi up to 30 months and met the WHOPES criteria. However, the desired bio-efficacy was not sustained up to 36 months.

An experimental hut evaluation of Olyset Plus, a long-lasting insecticidal net treated with a mixture of permethrin and piperonyl butoxide, against Anopheles fluviatilis in Odisha State, India.

BACKGROUND: Fast development of pyrethroid resistance in malaria vectors prompted the development of new vector control tools including combination of insecticides with different modes of action as part of resistance management strategies. Olyset Plus® is a new long-lasting insecticidal net, in which, permethrin and a synergist, piperonyl butoxide (PBO), are incorporated into filaments. Mixture nets such as this may have application against resistant mosquitoes, particularly those whose resistance is based on oxidative metabolism. There may also be enhanced activity against susceptible mosquitoes since mixed function oxidases are involved in a many metabolic activities including activation to form bioactive compounds. METHODS: Bio-efficacy of Olyset Plus was evaluated against susceptible malaria vector, Anopheles fluviatilis in experimental huts. Deterrence, blood feeding inhibition, induced exophily and killing effect were measured to assess the bio-efficacy. The results were compared with Olyset Net®, a polyethylene permethrin-incorporated LLIN and a conventionally treated polyester net (with permethrin) washed to just before exhaustion. RESULTS: Results showed significant reduction in entry (treatment: 0.4-0.8; control: 4.2 per trap-night) and increase in exit (56.3-82.9 % and 44.2 %) rates of Anopheles fluviatilis in the treatment arms compared to control (P < 0.05). While blood feeding rates declined in treatment arms (18.8-30.6 %), it increased in control (77.6 %) (P < 0.05). This was further evident from the blood-feeding inhibition rates in treatment arms (60.6-90.6 %). Total mortality was significantly higher in all treatment arms (96.3-100 %) compared to control arm (2 %) (P < 0.05). Chemical analysis for active ingredient (AI) showed retention of 75 and 88 % in Olyset plus and Olyset net respectively after 20 washes. Performance of Olyset Plus washed 20 times was equal to the CTN and Olyset Net against the susceptible malaria vector An. fluviatilis, fulfilling the WHO efficacy criteria of Phase II evaluation for LLIN. However, the benefit of incorporating PBO and permethrin together in a long-lasting treatment could not be demonstrated in the current study as the target vector species was fully susceptible to pyrethroids. CONCLUSION: Olyset Plus, with its intrinsic bio-efficacy could be an effective vector control tool to prevent transmission of malaria by susceptible vectors like An. fluviatilis. However, the results of the current study need to be further supported by testing the net at village level (Phase III) for community acceptability. Before taking the net to village level, it needs to be verified whether the net is better than pyrethroid nets in terms of bio-efficacy against resistant An. culicifacies, another malaria vector that has developed resistance to synthetic pyrethroids in India.

Persistent foci of falciparum malaria among tribes over two decades in Koraput district of Odisha State, India.

BACKGROUND: Koraput, a predominantly tribe-inhabited and one of the highly endemic districts of Odisha State that contributes a substantial number of malaria cases to the India's total. Control of malaria in such districts would contribute to change the national scenario on malaria situation. Hence, a study was carried out to measure the magnitude of malaria prevalence in the district to strengthen the malaria control activities. METHODS: Prevalence of malaria was assessed through a sample blood survey (SBS) in seven randomly selected community health centres (CHCs). Individuals of all age groups in the villages selected (one in each subcentre) were screened for malaria infection. Both thick and thin smears were prepared from blood samples collected by finger prick, stained and examined for malaria parasites searching 100 fields in each smear. The results of a blood survey (n = 10,733) carried out, as a part of another study, during 1986-87 covering a population of 17,722 spread in 37 villages of Koraput district were compared with the current survey results. Software SPSS version 16.0 was used for data analysis. RESULT: During the current study, blood survey was done in 135 villages screening 12,045 individuals (16.1% of the total population) and among them, 1,983 (16.5%) were found positive for malaria parasites. Plasmodium falciparum was the major malaria parasite species accounted for 89.1% (1,767) of the total positives; Plasmodium vivax and Plasmodium malariae accounted for 9.3% (184) and 0.2% (5), respectively. Gametocytes were found in 7.7% (n = 152) of the positive cases. The majority of parasite carriers (78.9%) were afebrile. The 1986-87 blood survey showed that of 10,733 people screened, 833 (7.8%) were positive for malaria parasites, 714 (85.7%) with P. falciparum, 86 (10.3%) with P. vivax, 12 (1.4%) with P. malariae and 21 (2.5%) with mixed infections. CONCLUSION: The results of the current study indicated a rising trend in transmission of malaria in Koraput district compared to the situation during 1986-87 and indicated the necessity for a focused and reinforced approach for the control of the disease by improving people's access to diagnosis and treatment and ensuring implementation of the intervention measures with adequate coverage and compliance.

Analysis of entomological indices for transmission of Japanese encephalitis in Malkangiri district, Odisha State, east central India during 2015-2019.

There have been repeated episodes of the outbreak of Japanese encephalitis (JE) in Malkangiri district of Odisha State in the recent past. In the current study, we aimed to assess the entomological parameters of JE vectors in the district. Prevalence of JE vector species, their per man hour density (PMHD), dusk index (DI), human blood index (HBI), infection status and other factors responsible for transmission of JE were assessed over 5 years (2015-2019). Culex vishnui was the predominant JE vector species (32.0%) collected, followed by Cx. whitmorei (27.1%) and Cx. tritaeniorhynchus (18.0%). The PMHD was higher in cattle shed (CS) than human dwelling (HD) and outdoor resting collection (ODRC) sites for all the JE vector species, except An. barbirostris. In particular, the PMHD of Cx. vishnui (8.02), Cx. whitmorei (5.71) and Cx. tritaeniorhynchus (5.01) were significantly higher in CS than HD and ODRC. The DI of Cx. vishnui (2.47), Cx. whitmorei (1.66) and Cx. tritaeniorhynchus (1.59) was significantly higher in CS compared to HD and ODRC. The HBI of Cx. vishnui was 0.015, whereas the HBI of Cx. tritaeniorhynchus was 0.009 in the study area. Among the 829 pools of JE vector species subjected to PCR, JE virus was isolated from one pool of Cx. vishnui. Based on the abundance of JE vectors and JE virus isolation from Cx. vishnui, it is requisite to implement systematic and long-term control measures for effective control of JE vector species in Malkangiri district, Odisha State.

Preliminary study on susceptibility status of Anopheles minimus Theobald and An. fluviatilis James (Diptera: Culicidae) to DDT and deltamethrin in Keonjhar district of Odisha, India.

This study was carried out to determine the susceptibility levels of An. fluviatilis and An. minimus to DDT (4%) and deltamethrin (0.05%) and to select the insecticide to be used for routine national malaria vector control programme based on the results of the susceptibility test. Susceptibility test was done as per standard WHO susceptibility tests using DDT(4%) and deltamethrin (0.05%) in the villages of Keonjhar Districts during 2009. The results indicate that An. fluviatilis showed 100% mortality to DDT (4%) and deltamethrin (0.05%) and An. minimus showed 96.2 per cent mortality to DDT (4%) and 100 per cent to deltamethrin (0.05%). An. fluviatilis and An. minimus have been incriminated as the major malaria vectors of Keonjhar district. Successful application of DDT and deltamethrin could reduce the vector load from this area with consequent malaria control as these two species are found to be highly susceptible to DDT and deltamethrin. Another study as per WHO methodology is further recommended to substantiate the result of this study.

Intensity of pyrethroid resistance in Anopheles culicifacies s.l. (Diptera: Culicidae) in Odisha State, India.

ANOPHELES CULICIFACIES S.L: . is the principal malaria vector in India and has recently developed resistance to synthetic pyrethroids. For identifying the possible operational impact, quantitative measure of the intensity of this resistance is required. The purpose of this study was to measure the intensity of pyrethroid resistance in An. culicifacies s.l. The intensity bioassays with wild caught An. culicifacies s.l were carried out in 10 districts of east central India using 5x and 10x diagnostic concentrations of deltamethrin following WHO insecticides susceptibility guidelines. The results showed that the mortality of An. culicifacies s.l. ranged from 70% to 80% while exposed to 1x DC of deltamethrin (0.05%). Further bioassays conducted with 5x concentration of deltamethrin (0.25%) showed that the mortality of An. culicifacies s.l. in all the 10 districts varied from 92% to 97% indicating moderate resistance. While exposing to 10x concentration (0.5%) of this insecticide, 100% mortality was observed in all the districts; thereby confirmed moderate resistance intensity of this species. Since resistance was not confirmed at the 10x concentration, operational failure of this insecticide was unlikely. Hence, it is recommended to continue the use of LLINs for malaria vector control in these areas.

Bionomics of Anopheles minimus and An. fluviatilis (Diptera: Culicidae) in east-central India, endemic for falciparum malaria: human landing rates, host feeding, and parity.

The host feeding of Anopheles minimus Theobald and An. fluviatilis James was studied in the villages of east-central India by conducting human landing collections between 1800 and 0600 hours at monthly intervals from May 2006 to July 2007. Four species of anopheline mosquitoes, An. minimus, An. fluviatilis, An. maculatus Theobald, and An. subpictus Grassi, were collected, the former two known vector species of malaria being the most abundant (97.1%). The An. minimus complex has been identified as sibling species A and An. fluviatilis complex as species S (90.9%) and T (9.1%). Both the species were prevalent throughout the year and obtained from landing collections indoors and outdoors. The average human landing density (HLD) of An. minimus and An. fluviatilis was 1.76 and 1.78 indoors and 1.71 and 1.56 per human per night outdoors, respectively. The HLD was relatively higher during the rainy season, although not significant in the case of An. fluviatilis. The human landing activity of An. minimus and An. fluviatilis occurred between 2000 and 0400 hours and peaked during 2300-0200 hours both indoors and outdoors.

Entomological factors in relation to the occurrence of Japanese encephalitis in Malkangiri district, Odisha State, India.

Japanese encephalitis is a mosquito-borne arbo-viral disease with seasonal occurrence. Since 2009, AES/JE cases have been reported from Malkangiri district of Odisha State, India at an interval of one year.In the current study, the entomological parameters of known JE vector mosquito species were assessed for one year in Malkangiri district. Mosquito collections were done fortnightly in the index villages from August 2015 to July 2016 to record the density, their breeding habitats, feeding behaviour, parity, dusk index (DI) and infection status with JE virus. A total of 2347 JE vector mosquitoes belonging to nine species were collected from dusk collections. Culex vishnui (38.3%) was the predominant species followed by Cx. whitmorei (17.3%), Cx. fuscocephalus (13.6%), Cx. tritaeniorhynchus (11.1%), Cx. bitaeniorhynchus (6.1%), Anopheles subpictus (4.8%), An. barbirostris (4.4%), Cx. quinquefasciatus (2.3%) and Cx. gelidus (2.2%). The average DI of Cx. vishnui was 0.37 which was highest among all JE vector species and varied between 0.02 (April) and 0.9 (November). The human blood indexof Cx. vishnui was 0.026. A total of 1835 JE vector mosquitoes were screened for the isolation of JE virus, but none was found positive. Presence of paddy fields and ponds, abundance of JE vectors and their human feeding habit indicate the risk of JE transmission in the study area. Detection of JE virus in Cx. vishnui during 2016 outbreak in Malkangiri district further confirms that there would be a threat of JE transmission during the favourable period.

Multiple insecticide resistance in Anopheles culicifacies s.l. (Diptera: Culicidae) in east-central India.

Development of resistance among the vectors to different insecticides poses a potential threat to vector control programme. Regular monitoring of susceptibility status of vector species to commonly used insecticides is recommended for planning appropriate vector control measures. In this communication, we have determined the phenotypic resistance of Anopheles culicifacies s.l., the major malaria vector against commonly used various insecticides in ten highly malaria endemic districts of Odisha State in east-central India. Bioassays were conducted before and after mass distribution of long-lasting insecticidal nets (LLINs) on field caught female mosquitoes with dichlorodiphenyl-trichloroethane (DDT), malathion and deltamethrin following the standard World Health Organization (WHO) guidelines. From the bioassays using 1x diagnostic concentrations (DC) recommended by WHO, we confirmed a higher frequency of resistant phenotype in An. culicifacies s.l. against DDT (range: 72% to 90%; average: 82%) compared to that against malathion(range: 17% to 34%; average: 26.7%) and deltamethrin (range: 14% to 24%; average: 19.1%) during 2018. Since, resistance to pyrethroid is detected; it is recommended to carry out bioassays of An. culicifacies s.l. exposing to higher concentrations of deltamethrin which would yield relevant information on the intensity of resistance and be useful to select suitable insecticide for resistance management vector control interventions.