Efficacy of Agnique MMF monomolecular surface film against Anopheles stephensi breeding in urban habitats in India.

Efficacy of Agnique MMF, a monomolecular film formulation, was tested against immatures of Anopheles stephensi, an urban malaria vector in India, in simulated and natural habitats. Simulated field trials carried out in cement tanks showed 100% inhibition of adult emergence for up to 1 wk at 0.4 ml/m2 and up to 3 wk at 1 ml/m2. A small-scale field trial in tanks and wells at 1 and 2 ml/m2 produced more than 75% reduction of late instars and 100% reduction of pupae on day 1. The reduction in pupae at 1 and 2 ml/m2 lasted up to 2 wk in tanks and 5 wk in wells. These results suggest that Agnique MMF could be used as one of the choices in an urban malaria control program.

Effectiveness of mosquito nets treated with a tablet formulation of deltamethrin for malaria control in a hyperendemic tribal area of Sundargarh District, Orissa, India.

A village-scale trial on the efficacy of mosquito nets treated with a tablet formulation of deltamethrin (K-OTAB) against malaria in comparison to untreated nets or no net was conducted in Sundargarh District of Orissa, India, which is characterized by perennial transmission with Plasmodium falciparum accounting for more than 80% of malaria cases. Three villages with similar topographical and epidemiological situations were selected and randomly assigned to 3 arms of the study: treated net, untreated net, and no net. Distribution of nets, based on a sleeping pattern survey, was carried out to cover 100% of the population in treated-net and untreated-net villages. Longitudinal and cross-sectional surveys were conducted to measure malaria incidence, prevalence, and splenomegaly. Malaria incidence was reduced by 64.3% in the village with treated nets, 45.2% in the village with plain nets, and 21.4% in the control village without nets. Comparison of malaria incidence data after 1 year of intervention showed significant difference between villages with treated net vs. untreated net (P < 0.05) and treated net vs. no net (P < 0.005). The incidence of clinical attack rate due to P. falciparum was significantly lower in the population using treated nets than in those using untreated nets and no nets. However, no age-specific protective efficacy of treated nets or untreated nets was observed. A significant reduction occurred in spleen rate and parasite rate in children aged 2-9 years using treated nets or untreated nets. An overall significant reduction was found in parasite rate in the total population using treated and untreated nets as compared to nonusers.

Efficacy of IGR compound Starycide 480 SC (Triflumuron) against mosquito larvae in clear and polluted water.

BACKGROUND AND OBJECTIVES: An environmental friendly formulation Starycide 480 SC (Triflumuron-OMS-2015 ), a new insect growth regulator with chitin synthesis inhibitor type mode of action was evaluated against mosquito larvae in laboratory and small-scale field trials carried out in and around Delhi. METHODS: The formulation was tested in laboratory for its bio-efficacy against late III instar mosquito larvae of different species using WHO bioassay procedure. In the field formulation was sprayed at doses of 0.3, 0.5 and 1 ppm (g/m3) in the natural breeding habitats of Anopheles and Culex mosquitoes. The impact was assessed by monitoring densities of larvae by dipper and observing the reduction in larval density and inhibition of adult emergence. RESULTS: In the laboratory, formulation was more effective against larvae of Anopheles stephensi and Aedes aegypti than Culex quinquefasciatus, but it produced 100% inhibition of adult emergence for all mosquito species at a concentration of 0.02 ppm. In the field trials, formulation did not produce 100% reduction in the density of late stage larvae even at 1 ppm (g/m3), the highest dose tested, but it resulted in 100% inhibition of pupal formation of both Anopheles and Culex spp in different types of habitats for 3-7 weeks even at a lower dose of 0.5 ppm. INTERPRETATION AND CONCLUSION: Application of triflumuron in the natural breeding habitats in both clean and polluted water @ 0.5 ppm (g/m3) resulted in complete inhibition of adult emergence of both Anopheles and Culex spp for 3-7 weeks. This formulation may be tested in large-scale field trials for further use in the vector control programme.

Village-scale evaluation of mosquito nets treated with a tablet formulation of deltamethrin against malaria vectors.

A field trial was carried out in the Sundargarh district of Orissa, India on the efficacy of mosquito nets treated with a tablet formulation of deltamethrin (K-O TAB) against malaria vectors. Treated nets were used in one village, and in the two control villages, one used untreated nets and the other used indoor spraying with DDT, without nets. In this area the primary malaria vectors are Anopheles culicifacies Giles sensu lato (Diptera: Culicidae) and An. fluviatilis James s.l., which are both endophagic and endophilic, and fully susceptible to deltamethrin. Treatment of a 10-m(2) mosquito net with one of the tablets gave a deltamethrin deposit of 25 mg/m(2). Bioassays repeated on domestically used nets over 7 months showed persistence of almost 100% mortality of An. fluviatilis, whereas An. culicifacies showed a decline from 100% to 71% mortality over this period, after which the nets were re-treated and bioassays were not continued. The sum of collections of mosquitoes resting in village houses and those in exit traps and dead on floor sheets showed a reduction in the numbers of the two vector species due to the treated nets, compared with untreated or no nets, but no reduction in other anophelines or Culex species. Large proportions of the collections of the vector and non-vector anophelines were dead on the floor sheets, but among Culex, mortality was delayed. Treated and untreated nets reduced the proportion of anophelines that had blood-fed; the treated nets did so more effectively than the untreated in the case of An. culicifacies and of Culex mosquitoes. In rooms with treated nets a larger proportion of the total collections [dead + live] were in the exit traps, which can be attributed to the excito-repellent effect of deltamethrin. It is easier to pack and handle tablets of insecticide than liquid concentrate and the use of one tablet per net may be preferable to making up a large volume of diluted insecticide and dipping many nets at a time.

Evaluation of bifenthrin treated mosquito nets against anopheline and culicine mosquitoes.

BACKGROUND AND OBJECTIVES: The main rural malaria vector Anopheles culicifacies has developed resistance to dichloro diphenyl trichloroethane (DDT), hexachloro cyclo hexane (HCH) and malathion in the state of Haryana in northern India. An alternative synthetic pyrethroid insecticide bifenthrin was therefore evaluated on mosquito nets against anopheline and culicine mosquitoes, in two villages Jagdishpur and Garh Mirakpur of Community Health Center (CHC) Badhkhalsa in district Sonipat, Haryana state. METHODS: Two formulations of bifenthrin, suspension concentrate (SC) and micro-emulsion (ME) were compared with micro-capsule suspension (CS) of lambdacyhalothrin. The impact of three doses of bifenthrin (10, 25 and 50 mg/m(2)) impregnated on mosquito nets was compared with lambdacyhalothrin (25 mg/m(2)) and untreated control. Quality assessment of treatment on treated nets was carried out by residue analysis and the persistence of the insecticide on nets was determined by contact bioassays. Efficacy of treated nets on mosquito density was assessed by calculating mosquito entry rate, immediate mortality, delayed mortality and excito-repellency to the insecticides. RESULTS: In susceptibility tests An. culicifacies was susceptible to bifenthrin (0.1% test papers) and to lambdacyhalothrin (0.05% test papers). Bioassays on treated nets against A. culicifacies recorded 100 per cent mortality up to tenth fortnight for all the doses of impregnation with bifenthrin (SC and ME) and lambdacyhalothrin (CS). Ring-net bioassays against An. culicifacies showed median knock-down time between 3.1 to 11.4 min. Behavioural indices were also studied for anopheline and culicine mosquitoes. The reduction in entry rates of anopheline and culicine mosquitoes into the rooms with treated nets compared to control indicated good efficacy with all the formulations and doses of the insecticides. INTERPRETAION AND CONCLUSION: Indoor (immediate) mortality of mosquitoes with bifenthrin ME formulation was relatively lower compared to SC fomulation of bifenthrin and based on delayed mortility and continued susceptibility in bioassays, bifenthrin ME at the rate of 10 mg/m(2) dose was found suitable for the impregnation of mosquito nets for phase III trial.

Comparative toxicity of selected larvicidal formulations against Anopheles stephensi Liston and Aedes aegypti Linn.

Toxicity of selected larvicidal formulations of Bacillus sphaericus, Bacillus thuringiensis H-14 israelensis (Bti) and insect growth regulators was determined against Anopheles stephensi and Aedes aegypti, the two major urban mosquito vectors of malaria and dengue fever in India respectively. The study revealed that the formulations of Bacillus thuringiensis H-14 and IGR compounds were highly toxic against both the mosquito species but Bacillus sphaericus formulation was less toxic against Aedes aegypti and has a limited potential for use against Aedes aegypti. Of the two Bti formulations, 'Vectobac' formulation was more toxic against both the species than 'BMP-1442X' formulation. Bti formulations were more toxic against Aedes aegypti (LC50 = 0.06 and 0.14 mg/Litre) than against An. stephensi (LC50 = 0.14 and 0.81 mg/Litre), while B. sphaericus formulation was more toxic against An. stephensi LC50 = 0.031 mg/Litre than Aedes aegypti LC50 = 0.294 mg/Litre. Among different larvicidal formulations tested in this study, IGR compounds were found to be toxic against both the mosquito species at very low concentrations (EC50 values ranging between 0.0001 and 0.0004 ppm).

Impact of urbanization on bionomics of An. culicifacies and An. stephensi in Delhi.

Study on bionomics of malaria vectors was carried out in riverine and non-riverine areas, on account of tremendous ecological changes in the topography of Delhi. The densities of adult anophelines were estimated by two techniques, hand catch and total catch index. Percentage of An. stephensi (15.68) collected by both the techniques was more than An. culicifacies (3.16) in both the areas. Day-time resting preferences of vector species in human dwellings and cattlesheds did not differ significantly. Preferred larval habitats of An. culicifacies in riverine area shifted to large lakes, channels and ponds. In malaria transmission, An. culicifacies played a role only in the northern part of the riverine area where water pollution was at minimal level, while An. stephensi played an equal role in the malaria transmission in both the areas. High sporozoite rates were found in type form of An. stephensi in localities where its proportion was high, thus confirming its active role in malaria transmission. The overall sporozoite rate of vectors was 0.7 per cent and P. falciparum sporozoite infections of the vectors were detected in An. stephensi only. P. vivax and P. falciparum infections were found in the ratio of 68:32. The non-riverine area was more malarious than the riverine area.

Control of aedes aegypti breeding in desert coolers and tires by use of Bacillus thuringiensis var. Israelensis formulation.

Three different formulations of Bacillus thuringiensis var. israelensis (Bti) were evaluated for their efficacy against immature Aedes aegypti in desert coolers and tires. Three formulations, viz., VectoBac tablets, VectoBac granules, and Bacticide powder, at the application rate of 0.75, 2, and 1 g per cooler, respectively, and VectoBac tablets at 0.75 and 0.375 g per tire, were evaluated. In coolers and tires, 100% reduction in the abundance of late larval instars of Ae. aegypti was observed for a period of 2 and 3 wk, respectively. The possibility of using tablets and capsules filled with Bti granules and powder formulation by individuals or communities for control of Ae. aegypti breeding has been discussed in view of the increasing outbreaks of dengue and dengue hemorrhagic fever in India. Use of these formulations over conventional methods is better and more user-friendly.

Malaria investigation in District Jodhpur, Rajasthan, during the summer season.

Studies were carried out in District Jodhpur of the Thar region of Rajasthan. Epidemiological investigation revealed high slide positivity rate in the canal irrigated area (54.5 per cent), sand dunes area (67.54 per cent), stone quarry area (26.66 per cent) and in the desert plain area (41.5 per cent). Similarly, slide falciparum rates were 7.10, 4.38, 6.66 and 5.6 per cent respectively. Entomological studies showed An. stephensi and An. culicifacies as major species and their densities ranged between 2 to 14.58 and 0 to 0.9 pmh respectively. Resistance in malaria vectors to insecticides, poor surveillance and suppressive treatment of cases appear to be the factors for persistent transmission in the study area.

Efficacy of neem oil-water emulsion against mosquito immatures.

Neem oil-water emulsion was used in mosquito breeding habitats to find out its larvicidal effect on immatures of different mosquito species. Application of 5% neem oil-water emulsion @ 50 ml/sq m in pools and @ 100 ml/sq m in tanks resulted in 100% reduction of III and IV instar larvae of An. stephensi after 24 h while, against Cx. quinquefasciatus it was 51.6 and 91.2% reduction in the larval density after Day 1 and 14 respectively. Similarly, application of 10% emulsion in desert coolers against Aedes aegypti @ 40 to 80 ml per cooler resulted in complete inhibition of pupal production.

Residual efficacy of deltamethrin 2.5 wp (K-othrin) sprayed on different types of surfaces against malaria vector Anopheles culicifacies.

Residual efficacy of deltamethrin 2.5 wp on various types of surfaces was tested against Anopheles culicifacies under field conditions using WHO standard procedure. Deltamethrin was most effective on the thatched surface and produced 100% mortality of An. culicifacies adults up to 12 weeks, even when exposed at the lowest dose /12.5 mg/m2. It was least effective on brick surface and 100% mortality was observed only for three weeks. The efficacy was observed for 8 and 7 weeks on mud and cement surfaces, respectively. However, at the higher rate of application, i.e. 25 mg/m2, 100% mortality of this species was obtained for 12, 10, 9 and 12 weeks on mud, cement, brick and thatch surfaces, respectively.

Laboratory and field evaluation of Spherix, a formulation of Bacillus sphaericus (B-101), to control breeding of Anopheles stephensi and Culex quinquefasciatus.

Spherix, a powder formulation of Bacillus sphaericus strain B-101, serotype H5a 5b, was evaluated against larvae of Anopheles stephensi and Culex quinquefasciatus in both the laboratory and field. In laboratory tests the formulation @ 0.1 g/sq m produced 100% mortality against larvae of both mosquito species at room temperature (28-32 degrees C). The larvicidal activity of Spherix against An. stephensi @ 0.5 g/sq m persisted for over 12 weeks under laboratory conditions. Field evaluation of Spherix @ 0.25-2.0 g/sq m produced 95-100% reduction in the larval density of both An. stephensi and Culex quinquefasciatus within 48 h in different habitats, and the larvicidal activity persisted for 2-4 weeks in water habitats.

Genetic markers in refractory and susceptible malaria patients in village Bhanera, Distt. Ghaziabad, U.P.

Malaria 'susceptible' and 'refractory' subjects from village Bhanera in District Ghaziabad (Uttar Pradesh) were examined for various genetic markers, viz., ABO, haptoglobin, haemoglobin and glucose-6-phosphate dehydrogenase polymorphism. One hundred and nine susceptible and 36 refractory subjects were studied. No significant differences with respect to distribution patterns of the genetic markers were observed in the two groups except for AB blood group. In general, a high incidence of ahaptoglobinaemia was observed in this population and incidence increased with the increase in malaria attacks, suggesting that repeated malaria attacks cause ahaptoglobinaemia.

Evaluation of Bacillus sphaericus to control breeding of malaria vectors.

Bacillus sphaericus formulations (Solvay liquid 2362 and Abbott granules 2297) were tested in the laboratory and field for the control of mosquito breeding. Results of laboratory evaluation revealed that both formulations had good larvicidal activity against Culex quinquefasciatus, at 0.04 ml and 1 gm/sq m dosages respectively. Higher dosages at 5 ml liquid or 5 gm/sq m granules were required to control A. stephensi and A. subpictus. A. culicifacies required still higher dosages of Solvay (25 ml/sq m) to achieve same levels of control whereas Abbott granules were not effective even at 20 gm/sq m.