Mosquito-borne diseases in India over the past 50 years and their Global Public Health Implications: A Systematic Review.

Mosquito-borne diseases (MBDs) pose a significant public health concern globally, and India, with its unique eco-sociodemographic characteristics, is particularly vulnerable to these diseases. This comprehensive review aims to provide an in-depth overview of MBDs in India, emphasizing their impact and potential implications for global health. The article explores distribution, epidemiology, control or elimination, and economic burden of the prevalent diseases such as malaria, dengue, chikungunya, Japanese encephalitis, and lymphatic filariasis, which collectively contribute to millions of cases annually. It sheds light on their profound effects on morbidity, mortality, and socioeconomic burdens and the potential for international transmission through travel and trade. The challenges and perspectives associated with controlling mosquito populations are highlighted, underscoring the importance of effective public health communication for prevention and early detection. The potential for these diseases to spread beyond national borders is recognized, necessitating a holistic approach to address the challenge. A comprehensive literature search was conducted, covering the past five decades (1972-2022), utilizing databases such as Web of Science, PubMed, and Google Scholar, in addition to in-person library consultations. The literature review analyzed 4,082 articles initially identified through various databases. After screening and eligibility assessment, 252 articles were included for analysis. The review focused on malaria, dengue, chikungunya, Japanese encephalitis, and lymphatic filariasis. The included studies focused on MBDs occurrence in India, while those conducted outside India, lacking statistical analysis, or published before 1970 were excluded. This review provides valuable insights into the status of MBDs in India and underscores the need for concerted efforts to combat these diseases on both national and global scales through consilience.

Understanding the mechanism of Chikungunya virus vector competence in three species of mosquitoes.

Chikungunya virus (CHIKV) is primarily transmitted by Aedes spp. mosquitoes. The present study investigated vector competence for CHIKV in Aedes aegypti and Aedes albopictus mosquitoes found in Madurai, South India. The role of receptor proteins on midguts contributing to permissiveness of CHIKV to Aedes spp. mosquitoes was also undertaken. Mosquitoes were orally infected with CHIKV DRDE-06. Infection of midguts and dissemination to heads was confirmed by immunofluorescence assay at different time points. A plaque assay was performed from mosquito homogenates at different time points to study CHIKV replication. Presence of putative CHIKV receptor proteins on mosquito midgut epithelial cells was detected by virus overlay protein binding assay (VOPBA). The identity of these proteins was established using mass spectrometry. CHIKV infection of Ae. aegypti and Ae. albopictus midguts and dissemination to heads was observed to be similar. A plaque assay performed with infected mosquito homogenates revealed that CHIKV replication dynamics was similar in Aedes sp. mosquitoes until 28 days post infection. VOPBA performed with mosquito midgut membrane proteins revealed that prohibitin could serve as a putative CHIKV receptor on Aedes mosquito midguts, whereas an absence of CHIKV binding protein/s on Culex quinquefasciatus midguts can partially explain the non-permissiveness of these mosquitoes to infection.

Stability of nano-sized permethrin in its colloidal state and its effect on the physiological and biochemical profile of Culex tritaeniorhynchus larvae.

The occurrence of pesticidal pollution in the environment and the resistance in the mosquito species makes an urge for the safer and an effective pesticide. Permethrin, a poorly water-soluble pyrethroid pesticide, was formulated into a hydrodispersible nanopowder through rapid solvent evaporation of pesticide-loaded oil in water microemulsion. Stability studies confirmed that the nanopermethrin dispersion was stable in paddy field water for 5 days with the mean particle sizes of 175.3 ± 0.75 nm and zeta potential of -30.6 ± 0.62 mV. The instability rate of the nanopermethrin particles was greater in alkaline (pH 10) medium when compared with the neutral (pH 7) and acidic (pH 4) dispersion medium. The colloidal dispersion at 45°C was found to be less stable compared with the dispersions at 25 and 5°C. The 12- and 24-h lethal indices (LC50) for nanopermethrin were found to be 0.057 and 0.014 mg l-1, respectively. These results were corroborative with the severity of damages observed in the mosquito larvae manifested in epithelial cells and the evacuation of the midgut contents. Further, the results were substantiated by the decrease in cellular biomolecules and biomarker enzyme activity in nanopermethrin treated larvae when compared to bulk and control treatment.

Stability assessment of hydro dispersive nanometric permethrin and its biosafety study towards the beneficial bacterial isolate from paddy rhizome.

Nanopesticides such as nanopermethrin can serve as an alternative to conventional pesticides causing eco-toxicity. The nanoformulation of this pyrethroid pesticide was carried out by solvent evaporation of pesticide-loaded microemulsion. The Z average for the nanopermethrin dispersion in paddy field water was found to be 169.2 ± 0.75 nm with a polydispersity index of 0.371 that exhibits uniform dispersion. Further, the nanopermethrin (NP) dispersion exhibited an effective stability in the paddy field water for a duration of 48 h with a Z average of 177.3 ± 1.2 nm and a zeta potential of -30.7 ± 0.9 mV. The LC50 of the nanopermethrin against Culex tritaeniorhynchus in the field condition was found to be 0.051 µg/mL. In addition to the stability assessment, the biosafety of the nanopermethrin was commenced on the beneficial bacterial isolate Enterobacter ludwigii (VITSPR1) considered as plant growth-promoting rhizobacteria. The toxic effect of nanopesticide was compared to its bulk counterpart, i.e. bulk permethrin (BP) at a concentration of 100 µg/mL, and the nanopesticide was found to be potentially safe. The results of biomarker enzymatic assays (lipid peroxidase, glutathione reductase, lactate dehydrogenase) displayed insignificant (p < 0.05) toxicity of NP towards the bacterial cells compared to BP. The live-dead cell staining and SEM analysis illustrated negligible toxicity of NP towards the bacteria. The non-toxic behaviour of the NP towards the non-target species was studied which displayed the eco-safe property of NP.

Can community-based integrated vector control hasten the process of LF elimination?

Community-based integrated vector control (IVC) using polystyrene beads (EPS) and pyrethroid impregnated curtains (PIC) as an adjunct to mass drug administration (MDA) was implemented for lymphatic filariasis elimination, in the filaria endemic villages of Tirukoilur, south India. In all the villages, MDA was carried out by the state health machinery, as part of the national filariasis elimination programme. Thirty-six difficult-to-control villages were grouped as, viz, MDA alone, MDA + EPS and MDA + EPS + PIC arms. Implementation and monitoring of IVC was carried out by the community. After 3 years of IVC, higher reductions in filariometric indices were observed in both the community and vector population. Decline in antigenaemia prevalence was higher in MDA + IVC as compared to MDA alone arm. Vector density dropped significantly (P < 0.05) in both the IVC arms, and nil transmission was observed during post-IVC period. Almost 53.8 and 75.8 % of the cesspits in MDA + EPS and MDA + EPS + PIC arms were closed by the householders, due to the enhanced awareness on vector breeding. The paper presents the key elements of IVC implementation through social mobilization in a LF prevalent area. Thus, community-based IVC strategy can hasten LF elimination, as it reduced the transmission and filariometric indices significantly. Indices were maintained at low level with nil transmission, by the community through IVC tools.

Impact on prevalence of intestinal helminth infection in school children administered with seven annual rounds of diethyl carbamazine (DEC) with albendazole.

BACKGROUND & OBJECTIVES: One third of the world's population is infected with one or more of the most common soil-transmitted helminths (STH). Albendazole (ALB) is being administered with diethyl carbamazine (DEC) in filariasis endemic areas to eliminate lymphatic filariasis (LF) and helminth infections. In this study, the cumulative impact of seven annual rounds of mass drug administrations (MDA) of DEC and ALB on STH infection in school children in selected villages in southern India was determined. METHODS: During 2001-2010, seven MDAs were implemented by the Tamil Nadu s0 tate h0 ealth d0 epartment, India. LF and STH infections were monitored in school children from 18 villages of the two treatment arms (viz, DEC alone and DEC+ALB). Kato-Katz cellophane quantitative thick smear technique was employed to estimate STH infections at three weeks, six months and one year post MDA. RESULTS: Prior to treatment, an overall STH prevalence was 60 per cent. After each MDA, infection markedly reduced at three weeks post-treatment in both the arms. The prevalence increased at six months period, which was maintained up to one year. After seven rounds of MDA, the infection reduced from 60.44 to 12.48 per cent in DEC+ALB arm; while the reduction was negligible in DEC alone arm (58.77 to 52.70%). INTERPRETATION & CONCLUSIONS: Seven rounds of MDA with DEC+ALB reduced the infection load significantly, and further sustained low level of infection for 10 years. However, complete parasite elimination could not be achieved. To curtail STH infection in the community, MDA should be regularized and environmental sanitation measures need to be improved by effective community-based campaigns.

Seasonal abundance & role of predominant Japanese encephalitis vectors Culex tritaeniorhynchus & Cx. gelidus Theobald in Cuddalore district, Tamil Nadu.

BACKGROUND & OBJECTIVES: Japanese encephalitis (JE) is the leading cause of viral encephalitis in Asia. The first major JE outbreak occurred in 1978 and since 1981 several outbreaks had been reported in the Cuddalore district (erstwhile South Arcot), Tamil Nadu, India. Entomological monitoring was carried out during January 2010 - March 2013, to determine the seasonal abundance and transmission dynamics of the vectors of JE virus, with emphasis on the role of Culex tritaeniorhynchus and Cx. gelidus. METHODS: Mosquito collections were carried out fortnightly during dusk hours in three villages viz. Soundara Solapuram, Pennadam, Erappavur of Cuddalore district. Mosquitoes were collected during dusk for a period of one hour in and around the cattle sheds using oral aspirator and torch light. The collected mosquitoes were later identified and pooled to detect JE virus (JEV) infection by enzyme linked immunosorbent assay (ELISA). RESULTS: A total of 46,343 mosquitoes comprising of 25 species and six genera were collected. Species composition included viz, Cx. tritaeniorhynchus (46.26%), Cx. gelidus (43.12%) and other species (10.62%). A total of 17,678 specimens (403 pools) of Cx. gelidus and 14,358 specimens (309 pools) of Cx. tritaeniorhynchus were tested, of which 12 pools of Cx. gelidus and 14 pools of Cx. tritaeniorhynchus were positive for JE virus antigen. The climatic factors were negatively correlated with minimum infection rate (MIR) for both the species, except mean temperature (P<0.05) for Cx. gelidus. INTERPRETATION & CONCLUSIONS: High abundance of Cx. tritaeniorhynchus and Cx. gelidus was observed compared to other mosquito species in the study area. Detection of JEV antigen in the two species confirmed the maintenance of virus. Appropriate vector control measures need to be taken to reduce the vector abundance.

Decline in lymphatic filariasis transmission with annual mass drug administration using DEC with and without albendazole over a 10year period in India.

The National Programme for the Elimination of Lymphatic Filariasis is underway in the endemic districts of Tamil Nadu State, South India, since 2001. Annual mass drug administration (MDA) was carried out by the state health department to all eligible individuals. The impact of MDAs on transmission parameters was evaluated in 2 revenue blocks, viz, one with DEC alone and the other with a combination of albendazole. After 10 years with 6 annual MDAs, the transmission indices reached low levels in both treatment arms, but still persisted. However, the DEC alone arm showed higher transmission rates, compared to the DEC+ALB arm. Few villages which demonstrated persistent transmission need to be targeted with an additional control measure viz, vector control, to achieve LF elimination. It is evident from the 10 year period of the study that inclusion of albendazole along with DEC has significantly reduced the transmission indices to almost nil level, as compared to DEC alone.

Dengue vectors prevalence and the related risk factors involved in the transmission of dengue in Thiruvananthapuram district, Kerala, South India.

BACKGROUND & OBJECTIVES: A longitudinal, entomological and virological study was conducted from 2007 to 2010 in four dengue fever affected areas of Thiruvananthapuram district, Kerala to understand the risk factors involved in the dengue transmission. METHODS: Aedes surveys were carried out seasonally in the selected localities both indoors and peridomestic sites. Water holding containers were sampled for the presence of immature. Outdoor and indoor resting/landing mosquitoes were collected. Blood meal identification was performed by gel diffusion test and viral assay using the ELISA test. RESULTS: The species found were Aedes (Stegomyia) aegypti (Linn.), Ae. (Stegomyia) albopictus (Skuse) and Ae. (Stegomyia) vittatus (Bigot). Aedes aegypti and Ae. albopictus immature stages were also found during the study period. Aedes aegypti was the only prevalent species in the water-starved Vizhinjam, a rural coastal area with breteau index (BI) ranging from 40 to 271. Aedes albopictus was recorded in rest of the three surveyed localities­two urban and one rural ghat areas of Thiruvananthapuram district. INTERPRETATION & CONCLUSION: The vector control measures should be focused mainly on source reduction of water storage containers present in both outdoor (Ae. albopictus and Ae. vittatus) and indoor (Ae. aegypti). To achieve effective vector management, a public health response beyond routine larviciding or focal spraying is essential throughout the year.

Entomological investigations into an epidemic of Japanese encephalitis (JE) in northern districts of West Bengal, India (2011-2012).

BACKGROUND & OBJECTIVES: Japanese encephalitis (JE) is one of the most important arboviral diseases of human beings with outbreaks in many parts of Southeast Asia including India. We present the entomological findings of an outbreak occurred in northern part of West Bengal during 2011-2012 with special emphasis on the role of JE vectors in different seasons. METHODS: Adult mosquito collections were made with the help of mouth aspirators, aided by flash lights during day time resting inside human and animal habitations as indoor, and resting outside field grasses, bushes, underneath of culverts and bridges as outdoor, and in and around the pig enclosures and cattle sheds during dusk period in JE affected villages from Cooch Behar, Dakshin Dinajpur, Darjeeling and Jalpaiguri districts in North West Bengal. In all study villages, a long handled with enamel bowl dipper was used to obtain immature stages of mosquitoes from various breeding habitats. RESULTS: A total of 19 different types of mosquito breeding habitats were examined for vectors of JE. From these habitats, 23.7 per cent were positive for breeding during the study period. Overall, nine different species were recorded through emergence, but none was positive for JE virus when subjected for detection of virus. Adult mosquitoes of more than 50 per cent of the potential JE vector species obtained through dusk and the rest through indoor and outdoor collections in all seasons. Altogether, 27 different species were recorded. Most of these were JE vectors. INTERPRETATION & CONCLUSIONS: Our results showed that in addition to Cx. vishnui subgroup, detection of JE virus antigen in Cx. quinquefasciatus indicated the possible maintenance of JE virus in nature through poor vector mosquitoes throughout the year. Since, all potential vector species reported elsewhere in India were also found in this region and fluctuated in density in different seasons, a proper integrated vector control programme needs to be implemented to control JE transmission.

Dengue NS1 and prM antibodies increase the sensitivity of acute dengue diagnosis test and differentiate from Japanese encephalitis infection.

Accurate and early diagnosis of dengue infection is essential for dengue case management. In outbreak conditions, it is essential to include two different tests to diagnose dengue and the choice depends on the number of days after the onset of illness in which the sample is collected. During the laboratory diagnosis of dengue in late acute and convalescent phase by MAC-ELISA, it is necessary to rule out possible cross reactions of closely related flavivirus, such as Japanese encephalitis virus which is commonly co-circulating. In the present investigation, the usefulness of dengue virus NS1 and prM antibodies in diagnosing and differentiating dengue from Japanese encephalitis infection was assessed using samples collected during out-breaks. It was shown here that, detection of antibodies against dengue NS1 and prM proteins increases the sensitivity of dengue diagnosis until 15days. Moreover, detection of antibodies against both proteins was able to differentiate dengue from Japanese encephalitis infection.

Nanoemulsion of eucalyptus oil and its larvicidal activity against Culex quinquefasciatus.

Filariasis is a mosquito-borne disease that causes lymphedema and the main vector is Culex quinquefasciatus. A simple measure was taken to eradicate the vector using nanoemulsion. Eucalyptus oil nanoemulsion was formulated in various ratios comprising of eucalyptus oil, tween 80 and water by ultrasonication. The stability of nanoemulsion was observed over a period of time and 1:2 ratios of eucalyptus oil (6%) and surfactant (12%) was found to be stable. The formulated eucalyptus oil nanoemulsion was characterized by transmission electron microscopy and dynamic light scattering. The nanoemulsion droplets were found to have a Z-average diameter of 9.4 nm and were spherical in shape. The larvicidal activity of eucalyptus oil nanoemulsion and bulk emulsion was tested and compared. Our nanoemulsion showed higher activity when compared to bulk emulsion. The histopathology of larvae-treated and untreated nanoemulsion was analyzed. Furthermore, biochemical assays were carried out to examine the effect of nanoemulsion on biochemical characteristics of larvae. The treated larval homogenate showed decrease in total protein content and a significant reduction in the levels of acetylcholinesterase. The levels of acid and alkaline phosphatase also showed reduction as compared to control larval homogenate.

Persistence of lymphatic filarial infection in the paediatric population of rural community, after six rounds of annual mass drug administrations.

Under the Global Programme to Eliminate Lymphatic Filariasis (LF), mass drug administration (MDA) is being implemented in Tamil Nadu, south India, by the State health machinery. The impact of six annual rounds of MDA using diethylcarbamazine (DEC) with and without albendazole (ALB) on filarial infection (microfilaraemia prevalence-MFP; antigenaemia prevalence-AGP) in paediatric population of 2-9 years was determined in two revenue blocks, with a population of 321 000. After each MDA, 300-400 children were screened for filarial infection. After six MDAs, an overall MFP reduction of 84.67% and 57.95% was observed in DEC+ALB and DEC alone arms, respectively. Corresponding AGP reductions were 72.88% (p < 0.001) and 41.51% (p = 0.023). Observation of microfilaraemic children after six MDAs (0.32% in DEC+ALB; 0.75% in DEC alone), necessitates the need for supplementary control strategies (viz., vector control), in order to achieve the goal of LF elimination.

High-level expression of functionally active dengue-2 non-structural antigen 1 production in Escherichia coli.

Detection of nonstructural protein (NS1) is an important diagnostic marker during acute phase of dengue infection. Not only for diagnostic purpose, the protein had important role in vaccine design as well, as a candidate for studying virus assembly and maturation. Various researchers employed different expression systems and strategies for recombinant NS1 protein production. Attempts to express NS1 protein in prokaryotic and yeast expression system result in formation of insoluble protein which needs to undergo refolding to attain native structural and functional forms. Here, we report the production of soluble NS1 protein in E. coli by using appropriate vector and employing suitable culture conditions to maximize protein production. Proteins were purified using metal affinity chromatography. SDS-PAGE and western blot analysis reveal the native structure of NS1 protein. Solid phase ELISA using the recombinantly expressed antigen with positive and negative dengue samples showed that the expressed protein retains its antigenic and immunological properties. To our knowledge, this is the first report on the successful production of functionally active recombinant dengue-2 NS1 protein production without undergoing any in vitro posttranslational modification process.

Identification of structural motifs in the E2 glycoprotein of Chikungunya involved in virus-host interaction.

Chikungunya fever is one of the reemerging vector-borne diseases. It has become a major global health problem especially in the developing countries. There are no vaccines or specific antiviral drugs available to date. This study reports small molecule inhibitors of envelope glycoprotein 2 (E2 glycoprotein) which are predicted based on Chikungunya virus-host interactions. E2 glycoprotein of Chikungunya virus interacts at 216 residue of the host receptor protein which plays a vital role in initiating infection. Understanding the structural aspects of E2 glycoprotein is crucial to develop specific inhibitors to prevent the virus binding from host receptors. In silico method was adopted to predict the sequence motifs of envelope protein, as the method like yeast two hybrid system is laborious, time consuming, and costly. The E2 glycoprotein structure of the Indian isolate was modeled using two templates (2XFC and 3JOC) and then validated. The class III PDZ domain binding motif was found to be identified at 213-216 amino acids. The corresponding peptide structures which recognize the PDZ domain binding motif were identified by the literature search and were used for generating five point pharmacophore model (ADDDR) containing acceptor, donor and aromatic ring features. Databases such as Asinex, TosLab and Maybridge were searched for the matches for the predicted pharmacophore model. Two compounds were identified as lead molecules as their glide score is > 5 kcal/mol. Since the pharmacophore model is developed based on Chikungunya virus-host interaction, it can be used for designing promising antiviral lead compounds for the treatment of Chikungunya fever.An animated Interactive 3D Complement (I3DC) is available in Proteopedia at http://proteopedia.org/w/Journal:JBSD:21.