Mitigating the Public Health Issues Caused by the Filarial Vector, Culex quinquefasciatus (Diptera: Culicidae) Through Phytocontrol and Larval Source Marker Management.

Failure of conventional mosquito control strategies to curb the population of vectors have made the humans vulnerable to serious medical problems transmitted by them. This effect has been compounded by global climate change enabling the mosquitoes to cross geographical boundaries and cause trouble in regions where they were initially not found. As such, the scientific community has been compelled to devise alternative and innovative strategies of mosquito control that can be integrated with the conventional practices to implement multi-phasic approach of vector management. Culex quinquefasciatus is one such mosquito species that is reported to be one of the primary vectors of lymphatic filariasis and many other diseases of global health concern. However, not much is known about its breeding habitat ecology and microbial properties that have enabled the species to achieve reproductive success in urbanized habitats. The current investigation was carried out at Digha, West Bengal, India. The region, despite being endemic for lymphatic filariasis, has rarely been explored for its mosquito diversity and/or their breeding habitat characteristics. Therefore, these were attempted. For survey and sampling, seven villages were chosen, namely, Duttapur, Jatimati, Champabani, Padima, Gobindabasan, Bhagibaharampur and Palsandapur. The study showed that Cx. quinquefasciatus is the dominant mosquito species at the sampling sites with the highest density of their larvae being recorded from man-made structures like drains and pools close to human habitations and livestock. The study was, therefore, restricted to Cx. quinquefasciatus. Seasonal abundance showed that they were most prevalent in the monsoon followed by summer. The physicochemical characterization showed their larvae to prefer almost neutral pH (6.9 to 7.3), low chloride concentration (98 to 258 ppm) and turbidity. As far as other parameters are concerned, they were tolerant towards a wide range allowing them to adapt varied habitats in the study areas. The bacterial profiling of their natural habitat waters revealed the presence of Paenibacillus nanensis DGX1(OQ690670), Bacillus cereus DGX2(OQ690675), Bacillus sp. DGX3(OQ690700) and Escherichia coli DGX4(OQ690701). Bacillus cereus was found to have high oviposition attractant properties in oviposition assays. Bacillus cereus was also obtained from the midgut of third instar larvae indicating that they had entered from the surrounding medium and colonized the larval gut. Subsequent tests exhibited the roles of B. cereus in larval development. Numerous plant products have been reported either as insecticides for killing larvae or adult mosquitoes or as repellents for mosquito biting and the best alternatives for mosquito control. Larvicidal potential of emulsified neem oil formulation against the field collected 3rd instar larvae of Culex quinquefasciatus mosquito under laboratory conditions was also evaluated. The information thus obtained can be pooled to generate larval source markers and larval source management practices by altering their habitats that cannot be removed. Furthermore, the time of implementation of these strategies can also be planned.

Neem-based products as potential eco-friendly mosquito control agents over conventional eco-toxic chemical pesticides-A review.

Mosquitoes cause serious health hazards for millions of people across the globe by acting as vectors of deadly communicable diseases like malaria, filariasis, dengue and yellow fever. Use of conventional chemical insecticides to control mosquito vectors has led to the development of biological resistance in them along with adverse environmental consequences. In this light, the recent years have witnessed enormous efforts of researchers to develop eco-friendly and cost-effective alternatives with special emphasis on plant-derived mosquitocidal compounds. Neem oil, derived from neem seeds (Azadirachta indica A. Juss, Meliaceae), has been proved to be an excellent candidate against a wide range of vectors of medical and veterinary importance including mosquitoes. It is environment-friendly, and target-specific at the same time. The active ingredients of neem oil include limonoids like azadirachtin A, nimbin, salannin and numerous other substances that are still waiting to be discovered. Of these, azadirachtin has been shown to be very effective and is mainly responsible for its toxic effects. The quality of the neem oil depends on its azadirachtin content which, in turn, depends on its manufacturing process. Neem oil can be used directly or as nanoemulsions or nanoparticles or even in the form of effervescent tablets. When added to natural breeding habitat waters they exert their mosquitocidal effects by acting as ovicides, larvicides, pupicides and/or oviposition repellents. The effects are generated by impairing the physiological pathways of the immature stages of mosquitoes or directly by causing physical deformities that impede their development. Neem oil when used directly has certain disadvantages mainly related to its disintegration under atmospheric conditions rendering it ineffective. However, many of its formulations have been reported to remain stable under environmental conditions retaining its efficiency for a long time. Similarly, neem seed cake has also been found to be effective against the mosquito vectors. The greatest advantage is that the target species do not develop resistance against neem-based products mainly because of the innumerable number of chemicals present in neem and their combinations. This makes neem-based products highly potential yet unexplored candidates of mosquito control agents. The current review helps to elucidate the roles of neem oil and its various derivatives on mosquito vectors of public health concern.

Phylogenetic study based on 28S rRNA gene sequencing of Wuchereria bancrofti isolated from the filaria endemic areas of Bankura district, West Bengal, India.

Lymphatic filariasis is one of the major public health concern in India, and Bankura district of West Bengal is one of the main filaria prone area of the country. Wuchereria bancrofti is the causative organism and Culex quinquefasciatus is the main vector of lymphatic filariasis in India. In the present study, infection and infectivity rate of filarial vector C. quinquefasciatus were determined. The molecular characterization, DNA fingerprinting and phylogenetic analysis of W. bancrofti was done. In the study area, overall vector infection and infectivity rates were 4.83 and 0.97%, respectively. The infection and infectivity rate were found to be higher in rainy season and lower in summer season. The AT and GC content of W. bancrofti SNC Bankura (Accession No. JF930705) were 55.59 and 44.41%, respectively. The phylogenetic tree was prepared following neighbour joining, maximum parsimony, minimum evolutionary and UPGMA methods. The study revealed that W. bancrofti SNC Bankura (JF930705) showed 100% similarity with W. bancrofti (Accession No. EU370161). The cluster containing, W. bancrofti SNC Bankura (JF930705) and W. bancrofti (EU370161) branched with Brugia pahangi (M15309) with 62% bootstrap value. W. bancrofti SNC Bankura (JF930705), W. bancrofti (EU370161) and B. pahangi (M15309) branched with Dirofilaria immitis (AF188120) with 78% bootstrap value.

Molecular characterization and phylogenetic analysis of Plasmodium vivax, Plasmodium falciparum, Plasmodium ovale, Plasmodium malariae and Plasmodium cynomolgi.

18S ribosomal RNA gene sequences of different species of Plasmodium were aligned and analyzed to determine the molecular diversity among different species of Plasmodium. AT content of P. cynomolgi, P. ovale, P. falciparum, P. vivax and P. malariae ranged from 62.30 to 63.15, 63.90 to 65.29, 66.67 to 68.40, 61.66 to 63.25 and 64.09 to 76.36 in case respectively. GC content of P. cynomolgi, P. ovale, P. falciparum, P. vivaxand P. malariae ranged from 36.85 to 37.70, 34.71 to 36.43, 31.60 to 33.27, 23.64 to 35.91 and 36.75 to 38.34 respectively. Molecular weight (Da) of P. cynomolgi, P. ovale, P. falciparum, P. vivax and P. malariae ranged from 1,160,127.00 to 1,400,332.00, 437,273.00 to 481,438.00, 668,021.00 to 685,243.00, 540,378.00 to 1,176,962.00 and 132,788.00 to 305,211.00 respectively. Relative melting temperature (Tm) of P. cynomolgi and P. ovale varied from 0.36799 to 0.36837 and 0.36712 to 0.36814 respectively. In P. falciparum and P. vivax relative Tm ranged from 0.36545 to 0.36626 and 0.36802 to 0.36866 respectively. Relative Tm of P. malariae varied from 0.36174 to 0.36790.