A note on the insecticide susceptibility status of principal malaria vector Anopheles culicifacies in four states of India.

BACKGROUND & OBJECTIVES: The major malaria vector, Anopheles culicifacies Giles is reported to contribute ~ 65% of the malaria cases in India. This species developed resistance to DDT and later to HCH, malathion and also to pyrethroids in some states due to their use in the national malaria control programme. In the present study, insecticide susceptibility of this species was monitored in four states of India. METHODS: To determine insecticide susceptibility status of the major malaria vector An. culicifacies, adult mosquitoes were collected from different localities of 32 tribal districts in the states of Andhra Pradesh, Odisha, Jharkhand and West Bengal during October/November 2009-10. Mosquitoes were collected from stratified ecotypes comprising a group of districts in West Bengal and individual districts in three other states. Mosquitoes were exposed to papers treated with WHO diagnostic dose: 4% DDT, 5% malathion and 0.05% deltamethrin following the WHO tube method. RESULTS: RESULTS provided the susceptibility status of An. culicifacies to different insecticides used in the public health programme in 32 districts in four states. An. culicifacies was found resistant to DDT (mortality range 0-36%) in all the 32 districts; to malathion it was resistant in 14 districts, verification required in 10 districts and susceptible in eight districts (mortality range 32.2-100%). It was resistant to deltamethrin in four districts, verification required in 11 districts and susceptible in 17 districts (mortality range 43.3-100%). INTERPRETATION & CONCLUSION: Development of widespread resistance to insecticides used in public health sprays for vector control including to pyrethroids in An. culicifacies in the surveyed districts is of great concern for the malaria control programme as the major interventions for vector control are heavily reliant on chemical insecticides, mainly synthetic pyrethroids used both for indoor residual spraying and for long-lasting insecticidal nets. Thus, there is a need to periodically monitor and update the susceptibility status of malaria vector(s) to suggest alternative vector control strategies for effective disease management.

Evaluation of the pyrrole insecticide chlorfenapyr for the control of Culex quinquefasciatus Say.

Culex quinquefasciatus Say (Diptera: Culicidae) is a widely distributed mosquito vector species in India and also in other tropical regions of the world. This species is implicated in the transmission of lymphatic filariasis in many countries. This species is reported to be widely resistant to insecticides of different classes in current use. In the present study, bio-efficacy of chlorfenapyr, an insecticide of pyrrole class with a novel mode of action was tested for the control of Cx. quinquefasciatus. Studies were performed to determine the diagnostic dosage; residual efficacy on different artificially fabricated substrates, namely wood, mud, mud+lime, cement and cement+distemper; to assess cross-resistance with different insecticides; and synergism/antagonism using piperonyl butoxide (PBO). A dosage of 5.0% chlorfenapyr was determined as diagnostic dosage with 2 h exposure and 48 h holding period for assessing the susceptibility of mosquitoes. The residual efficacy was observed up to 34 weeks on wood and mud+lime substrates while on other substrates, it was about 15 weeks at a dosage of 400mg a.i./m(2). Laboratory-reared strains of Cx. quinquefasciatus showed cross-resistance, whereas field-collected mosquitoes showed absence of cross-resistance to chlorfenapyr. Potentiation bioassays showed antagonistic effect of PBO to chlorfenapyr toxicity owing to the involvement of oxidases in the initial step of a conversion of pro-insecticide chlorfenapyr to toxic form CL 303268. The present study results have shown that chlorfenapyr can be a potential insecticide for the control of multiple insecticide resistant strains of Cx. quinquefasciatus. However, in countries where indoor residual spray (IRS) is not targeted for the control of this species, like in India, chlorfenapyr used in IRS for the control of malaria vectors in rural and peri-urban areas can additionally provide control of Cx. quinquefasciatus also.

A review on Anopheles culicifacies: from bionomics to control with special reference to Indian subcontinent.

Anopheles culicifacies, is a complex of five isomorphic sibling species A, B, C, D and E and is considered to be the major malaria vector in the Indian subcontinent. Despite numerous studies, it is difficult to have a global view of the ecological and bionomical characteristics of the individual sibling species, as different identification methods have been used. Major biological and ecological trends such as the high plasticity of behaviour and the sympatry of species are addressed. In spite of the availability of rapid molecular identification tools, we still lack important information concerning the biological characteristics of each sibling species. Resistance to insecticide is alarming as it has developed quadruple resistance in two states of India. An intensified and appropriate intervention measure to interrupt transmission is the call of the day. The authors focus on (1) reviewing the vectorial aspects of An. culicifacies (2) discussing recently published data on bionomics of each sibling species, (3) identifying lacunae in the understanding of the Culicifacies complex, and (4) exploring the possibility of proper control measures. Our understanding of the bionomics of all the five sibling species would certainly help, keeping in mind the climatic changes we are to face in the next few years.

Nanosilica-from medicine to pest control.

Nanotechnology is a broad interdisciplinary area of research, development, and industrial activity that has been growing rapidly worldwide for the past decade. More ambitious uses of nanoparticles are bioremediation of contaminated environments, controlled release of fragrances, biocides, and antifungals on textiles. Silica nanocomposites have received much attention because of its thermal degradation behavior and applications in chromatography, medicine, optics, etc. Nanobiotech takes agriculture from the battleground of genetically modified organisms to the brave new world of atomically modified organisms where rice has been modified atomically. Silica has been widely applied in various industries. Application of gold-coated silica has been used in the treatment for benign and malignant tumor. Surface-modified hydrophobic as well as lipophilic nanosilica could be effectively used as novel drugs for treatment of chicken malaria and nuclear polyhedrosis virus (BmNPV), a scourge in silkworm industry. Here, the authors attempt to provide a review to explain the impact of nanosilica on basic biology, medicine, agro-nanoproducts, and use of amorphous nanosilica as biopesticide.