Seasonal abundance and infection of Japanese encephalitis vectors from Gorakhpur district, Uttar Pradesh, India.

BACKGROUND & OBJECTIVES: Japanese encephalitis (JE) is a major public health problem in many states of India. Uttar Pradesh state contributes 75% of the total cases reported. A longitudinal study was undertaken to find out the seasonal abundance, infection in the JE vectors in Gorakhpur region of Uttar Pradesh, and intervention strategies like indoor residual spraying and long-lasting insecticidal nets were adopted. METHODS: The vector abundance was monitored from July 2013 to August 2016 at fortnightly intervals and identified using standard mosquito identification keys and screened for viral infection. Intervention measures like indoor residual spraying with lambda-cyhalothrin 10% WP at 25 mg/m2 in 58 gramasabha in Bhathat Block and long-lasting insecticidal nets were distributed @ 2 LLIN for each household with 5-6 members in 5 villages of Korabar block. RESULTS: A total of 5,36,609 mosquitoes constituting 34 species and 10 genera were collected during this study period. Among the JE vector, peak abundance of Culex tritaeniorhynchus was recorded just before the JE season from July to October in all the blocks. There was a marked reduction in the density of Cx. tritaeniorhynchus from July compared to baseline year 2014 in Bhathat Block where indoor residual spraying (IRS) was performed in June 2015. The vector density declined in 5 villages of Khorabar Block where long-lasting impregnated bed nets (LLINs) were distributed during July 2016. INTERPRETATION & CONCLUSION: The present study provided knowledge about the seasonal JE vector density and JE virus infection in mosquitoes during the monsoon season in Gorakhpur region of Uttar Pradesh. IRS and the personal protection measure like LLINs were distributed to interrupt the JE transmission in this area which gave encouraging results.

A Preliminary Study to Forecast Japanese Encephalitis Vector Abundance in Paddy Growing Area, with the Aid of Radar Satellite Images.

Vector mosquitoes of Japanese encephalitis (JE) breed mostly in rice fields, and human cases occur scattered over extended rural rice-growing areas. From this, one may surmise an ecological connection with the irrigation facilities and paddy cultivation. Furthermore, it has been hypothesized that a particular stage of paddy growth is a premonitory sign that can lead to a markedly increased population of the vector mosquitoes. The present study aimed to forecast the vector abundance by monitoring the paddy growth using remote sensing and geographical information systems. The abundance of the JE vector Culex tritaeniorhynchus peaked when the paddy crop was at its heading stage and dipped when the crop reached the maturing stage. A significant positive correlation was observed between paddy growth and adult density (r = 0.73, p < 0.008). The sigma naught values (σ0) derived from satellite images of paddy fields ranged from -18.3 (during transplantation stage) to approximately -10 (during the noncultivation period). A significant positive correlation was observed between σ0 and paddy growth stages (r = 0.87, p < 0.05) and adult vector density (r = 0.74, p = 0.04). The σ0 value observed during the vegetative and flowering stages of paddy growth ranged from -17.6 to -17.16, at which period the vector density started building up. This could be the spectral signature that denotes the "risk," following which a high vector abundance is expected during heading stage of the paddy.

Chikungunya virus isolated in Lakshadweep islands in the Indian Ocean: evidence of the Central/East African genotype.

Virological investigation was carried out to determine the etiology of suspected Chikungunya fever among humans reported in the Lakshadweep islands in the Indian Ocean. Three out of 23 acute sera samples showed cytopathological changes in Vero cell lines. Further, indirect immunofluorescence antibody test and reverse transcriptase-polymerase chain reaction studies demonstrated the Chikungunya virus etiology during the episode. E1 gene sequence analysis has confirmed the involvement of the Central/East African genotype of the Chikungunya virus.

Natural vertical transmission of dengue virus in Aedes albopictus (Diptera: Culicidae) in Kerala, a southern Indian state.

The natural occurrence of vertical transmission of dengue viruses in Aedes albopictus (Skuse) mosquitoes was examined in the state of Kerala in southern India. Adults and larvae of Ae. albopictus collected from Kerala were screened for dengue viruses by using enzyme-linked immunosorbent assay with dengue-specific monoclonal antibodies. The possibility of the vertical transmission of dengue virus in Ae. albopictus was further evidenced by the detection of the virus in field-collected adult males as well as females emerged from field-collected larvae. Two pools, one pool from the adult males and one pool from the emerged females derived from field-collected larvae, were collected in the relatively hot months of June and March, respectively, and found to be positive for dengue virus antigen. Dengue serotype 2 virus was isolated from field-collected male adults in Kerala. These findings suggest that dengue virus is maintained in Ae. albopictus mosquitoes during the dry season by vertical transmission in nature.

Prediction of 3-dimensional structure of salivary odorant-binding protein-2 of the mosquito Culex quinquefasciatus, the vector of human lymphatic filariasis.

Olfaction of insects is currently recognized as the major area of research for developing novel control strategies to prevent mosquito-borne infections. A 3-dimensional model (3D) was developed for the salivary gland odorant-binding protein-2 of the mosquito Culex quinquefasciatus, a major vector of human lymphatic filariasis. A homology modeling method was used for the prediction of the structure. For the modeling, two template proteins were obtained by mGenTHERADER, namely the high-resolution X-ray crystallography structure of a pheromone-binding protein (ASP1) of Apis mellifera L., [1R5R:A] and the aristolochene synthase from Penicillium roqueforti [1DI1:B]. By comparing the template protein a rough model was constructed for the target protein using MODELLER, a program for comparative modelling. The structure of OBP of the mosquito Culex quinquefasciatus resembles the structure of pheromone-binding protein ASP1 of Apis mellifera L., [1R5R:A]. From Ramachandran plot analysis it was found that the portion of residues falling into the most favoured regions was 86.0%. The predicted 3-D model may be further used in characterizing the protein in wet laboratory.