Field evaluation of Icon®Life, a long-lasting insecticidal net (LLIN) against Anopheles culicifacies and transmission of malaria in District Gautam Budh Nagar (Uttar Pradesh), India.

Background & objectives: In the present study, Icon®Life net, a long-lasting polyethylene net, 100 denier and bursting strength of minimum 280 kpa incorporated with deltamethrin @ 65 mg/m2 was evaluated for its efficacy in reducing the density of malaria vector Anopheles culicifacies and impact on malaria prevalence in a malaria endemic area of District Gautam Budh Nagar, India. Methods: Wash resistance of Icon® Life LLIN was determined up to 20 serial washings using An. culicifacies in cone bioassays under field conditions. Efficacy of Icon®Life LLIN was determined in the field in three sets of villages in District Gautam Budh Nagar (Uttar Pradesh), India, selected randomly for the intervention with Icon®Life LLIN, untreated nets and a control without any intervention for the period of August 2008–July 2009. Entomological and malariometric indices in all the three villages were compared during pre- and post-intervention periods for one year against An. culicifacies. A survey was also conducted in the village provided with Icon® Life LLIN to assessing the perception of community regarding acceptance of these nets by the community. Results: In cone bioassays on Icon®Life LLIN with An. culicifacies, >95% knockdown within 1 h and 100% mortality after 24 h exposure were reported even after 20× serial washings under field conditions. Results of the field study revealed reduced entry rate, resting density and parity rate of An. culicifacies in the village with Icon®Life LLIN when compared to no net and untreated net villages. Number of malaria cases reported were less in the Icon®Life LLIN used villages when compared to other two villages. The community compliance and acceptance was high and no adverse health events were reported by the households using these nets. Conclusions: Icon® Life LLIN is an effective intervention for the control of An. culicifacies transmitted malaria in India. Long-term studies are indicated for the duration of effectiveness and to ascertain the epidemiological impact of the use of Icon® Life nets.

Resting behaviour of Anopheles stephensi type form to assess its amenability to control malaria through indoor residual spray.

Background & objectives: In the present study, an attempt was made to find reasons of ineffectiveness of indoor residual spray to interrupt malaria transmission by investigating the behaviour of two variants of Anopheles stepnesi, viz. type form and mysorensis in rural areas of Rajasthan, India. Methods: Both low malarious (DDT spray from 1958 to 1976) and high malarious (DDT spray from 1958 to April 2006) villages were selected for the study in Arid zone district Jodhpur, Rajasthan during March–April 2006. Resting behaviour of the species during all its movement rhythms covering 24 h period related to: (i) swarming/ mating; (ii) pre- and post-biting rest; (iii) after feed resting between hoping movements; (iv) night and day time resting and; (v) diel activity movements in response to temperature changes, were carried out. Results: The results showed that household objects like cupboards, furnitures, hanging clothes, goods stacked on loft, stored clothes, cobwebs and floor were the dominant resting sites both in sprayed and unsprayed villages. About 95 and 97% of An. stephensi preferred to rest on household objects of unsprayed and sprayed villages respectively. There was no significant difference in resting behaviour of the species in both groups of villages (p >0.05). The pre-biting resting time was recorded as 5 to 15 min whereas post-biting resting time lasted for 15 to 25 min. After biting outdoor (in courtyard – open to sky) species starts entering the rooms at around 2330 hrs. It was observed that during III quarter (0100 to 0400 hrs) maximum species entered into the room were 56% in unsprayed and 62% in sprayed villages. Statistically there was no significant difference in the entry of mosquitoes (p >0.05) in both the groups of villages. Conclusion: Before DDT era, An. stephensi was found resting at all heights of the walls inside the human dwellings. Present study revealed that An. stephensi is trying to avoid sprayable surfaces and tend to rest on unsprayable surfaces during all its movement rhythms starting from swarming, pre-/post-biting and during hopping movements in the courtyard and thereafter household objects inside the room as final day time resting. It was concluded that changed behaviour of resting of An. stephensi on unsprayable objects in sprayed rooms largely accounted for failure of malaria control. Control of An. stephensi, thus requires an integrated vector control strategy based upon interesectoral, environmental, larviciding with chemical/biolarvicide and use of larvivorous fish wherever feasible. Such a control strategy offers cost-effective and sustainable option than indoor residual spray.

In vitro assessment of drug resistance in Plasmodium falciparum in five States of India.

Background & objectives: In vitro assays are an important tool to assess baseline sensitivity and monitor the drug response of Plasmodium falciparum over time and place and, therefore, can provide background information for the development and evaluation of drug policies. This study was aimed at determining the in vitro sensitivity of P. falciparum isolates to antimalarials. Methods: The in vitro activity of 108 P. falciparum isolates obtained from five States of India was evaluated using WHO microtest (Mark III) to chloroquine, monodesethylamodiaquine, dihydroartesunate and mefloquine. Samples were collected from the States of Orissa, Jharkhand, Karnataka, Goa and Chhattisgarh from September 2007 to August 2009. In addition, representative samples from different States of India cryopreserved and culture adapted in the Malaria Parasite Bank of National Institute of Malaria Research, New Delhi, were also evaluated. Results: The proportion of isolates resistant to chloroquine and monodesethylamodiaquine was 44.4 and 25 per cent, respectively. Of the 27 isolates resistant to monodesethylamodiaquine, 16 (59.3%) were cross-resistant to chloroquine. No isolate showed resistance to dihydroartesunate and mefloquine. Isolates from Orissa showed the highest degree of resistance to chloroquine and amodiaquine followed by Jharkhand. Forty two isolates were genotyped for pfcrt T76K chloroquine resistant mutation; mutations were seen in 38 (90.47%) isolates. Interpretation & conclusions: The Indian P. falciparum isolates showed a high degree of resistance to chloroquine followed by monodesethylamodiaquine. No resistance was recorded to mefloquine and dihydroartesunate.

Evaluation of toxicity of plant extracts against vector of lymphatic filariasis, Culex quinquefasciatus.

Background & objectives: Conventional insecticides are generally used as larvicides to control Culex quinquefasciatus, vector of lymphatic filariasis. This study was undertaken to evaluate the larvicidal activity of some potential larvicidal plants leaf extracts against Cx. quinquefasciatus larvae. Methods: The toxic effects of petroleum ether leaf extracts of plants viz., Argemone mexicana (Mexican prickly poppy), Clausena dentata (Dentate), Cipadessa baccifera (Rana bili), Dodonaea angustifolia (Hop bush) and Melia dubia (Pride of India) were evaluated under laboratory conditions in individual and in combination against 3rd - 4th instar larvae of Cx. quinquefasciatus. Results: The results indicated that among the selected plants, A. mexicana showed maximum larvicidal activity with an LC50 value of 48.89 ppm. Its toxicity was enhanced when the extract was mixed (1:1) with that of C. dentata as the LC50 value became 28.60 ppm indicating synergistic action of A. mexicana. Interpretation & conclusions: Our results showed high larvicidal potential in A. mexicana leaf extract, and it also showed additive effect when mixed with C. dentata extract.

Retrospective study of chikungunya outbreak in urban areas of India.

Background & objectives: A retrospective study on chikungunya outbreak in India in five States viz. Delhi, Madhya Pradesh, Orissa, Maharashtra and Kerala was conducted in 2007-2008 to know the distribution and determinants of chikungunya fever outbreak in India. Methods: On the basis of high and low incidence of chikungunya fever, two districts from each State and two wards from the selected district were taken for random selection of 1000 households from 10 districts and 5 States. Semi-structured questionnaires were administered to individuals, patients, qualified health professionals and to stakeholders for collecting information. Results: The educational background and occupation of the respondents showed variations across the study States. Only in high incidence ward of Maharashtra, water storage period for 3-6 days and emptying, drying of water containers on weekly basis was noted. The study through knowledge, attitude, belief, practice (KABP) obtained individual's perception of chikungunya fever, its prevention and control. Patients’ expenditure on treatment was mainly recorded less than Rs 500 across study States. Health facility survey obtained an overview of the capacity of local health facilities. Stakeholders’ perception regarding chikungunya fever was also noted. Interpretation & Conclusions: The study revealed differences in awareness of chikungunya, cause of the disease, vector responsible, mode of transmission, biting time and elimination of breeding of mosquitoes statistically significant among high and low incidence wards of all the States. Expenditure on treatment was independent of economically active status and loss of man-days across all the States. Education and occupation did not have any relation with emptying/drying of water containers in high incidence wards. Strengthening of surveillance, information, education and communication (IEC) activities along with case management facilities may be provided by the State health department for prevention of chikungunya outbreaks in future. Stakeholders should be more involved in outbreak management and future planning.

Evaluation of the impact of ZeroFly®, an insecticide incorporated plastic sheeting on malaria incidence in two temporary labour shelters in India.

Background & objectives: Prevention of malaria is a major technical and operational problem in displaced and mobile populations such as refugee camps and temporary labour settlements. Insecticide incorporated plastic sheeting is a new technology to control mosquitoes in emergency shelters and also temporary habitations at different locations. In view of this, efficacy of ZeroFly®, an insecticide incorporated plastic sheeting (factory treated with deltamethrin 2.0 g/kg or 265 mg/m2) was evaluated for its efficacy against malaria vectors and its impact on malaria incidence in temporary labour settlements in two urban areas in India. Methods: This trial was conducted in two labour settlements in two urban areas, Delhi and Noida (U.P.), India with ~ 250 populations. In an area, two localities were selected for intervention with ZeroFly and untreated plastic sheets (control). Entomological and epidemiological data were collected using standard methods for one year. Results: Baseline studies on the susceptibility of mosquitoes in Delhi and Noida areas revealed 100% susceptibility of the malaria vector species Anopheles culicifacies and An. stephensi to deltamethrin. Cone bioassay tests performed against An. culicifacies and An. stephensi to determine the efficacy of ZeroFly sheets showed 100% mortality against An. culicifacies and An. stephensi with 3 min exposure and after 24 h recovery period. Against Culex quinquefasciatus and housefly 100% mortality was obtained after 30 min of exposure period. Intervention with the ZeroFly plastic sheets resulted in almost complete reduction in the resting density of An. culicifacies and An. stephensi, the two major malaria vectors and also in the reduction of malaria cases in ZeroFly camps as compared to control camps. The ZeroFly plastic sheeting was found to be safe for human. Barring some complaints of skin irritation and itching, which were temporary in nature, no adverse health effects were reported by the users. The community acceptance was high. Conclusion: Results of the present study revealed that ZeroFly® plastic sheeting is highly effective in reducing the indoor resting density of mosquitoes, man-vector contact and malaria incidences in labour populations living in temporary shelters.

Efficacy of Advanced Odomos repellent cream (N, N-diethyl-benzamide) against mosquito vectors.

Background & objectives: Repellents are commonly used personal protection measures to avoid mosquito bites. In the present study, Advanced Odomos cream (12% N, N-diethyl-benzamide) was tested for its efficacy against mosquitoes in comparison to DEET (N,N-diethyl-3-methyl benzamide). Methods: Bioassays were conducted to assess the repellency of Advanced Odomos and DEET creams against Anopheles stephensi and Aedes aegypti. Their efficacy was tested on human volunteers applied with different concentrations of test creams ranging from 1 to 12 mg/cm2 and by exposing them to mosquitoes at hourly intervals. Field evaluation was also carried out to test the duration of protection of the test creams against Anopheles and Aedes mosquitoes during whole night and day time collections, respectively on human volunteers. Mosquito collections were done using torch light and aspirator. Results: Complete (100%) protection was achieved at 10 mg/cm2 cream formulation of Advanced Odomos (1.2 mg a.i/cm2) dose against An. stephensi and 12 mg/cm2 (1.44 mg a.i./cm2) against Ae. aegypti on human baits. There was no statistically significant differences in per cent protection against mosquito bites between Advanced o0 domos and DEET cream (P>0.05) in respective doses. Complete protection up to 11 h was observed against Anopheles mosquitoes during whole night collections and up to 6 h against Ae. aegypti in day time collections. No adverse reactions such as itching, irritation, vomiting, nausea, etc. were reported by the volunteers. Interpretation & conclusions: Advanced odomos cream applied at 10 mg/cm2 concentration provided 100% protection from Anopheles mosquitoes up to 11 h whereas about 6 h protection was recorded against Ae. aegypti. The laboratory and field trials indicate that for longer protection against Anopheles mosquitoes 10 mg/cm2 will be appropriate and in case of Ae. aegypti more than 10 mg/cm2 application is required for complete protection. In conclusion, the Advanced Odomos cream was comparable to the known repellent cream DEET for prolonged protection against malaria and dengue vectors.

Field evaluation of lambda-cyhalothrin (ICON 10 CS) indoor residual spraying against Anopheles culicifacies in India.

Background & objectives: Field trials of lambda-cyhalothrin 10 CS (ICON 10 CS) in indoor residual spraying (IRS) with 25 mg a.i./m2 against Anopheles culicifacies was undertaken vs malathion IRS (25% WP–2 g a.i./ m2) in Tumkur district, Karnataka; vs deltamethrin IRS (2.5% WP–20 mg a.i./m2) in Dharmapuri district; and vs lambda-cyhalothrin (10 WP–25 mg a.i./m2) in Ramanathapuram district, Tamil Nadu, India. Methods: Spray operations in the experimental villages were done by the National Institute of Malaria Research (NIMR) and in the control villages by the respective State Health Department staff. Persistence of efficacy of insecticide sprayed in villages was assessed by contact bioassays against vector mosquitoes. Entomological indicators such as per structure density, parity rates of vector mosquitoes and sporozoite rates were measured in all the three study areas using standard procedures. Mass blood surveys and active fever case detections were carried out in experimental and control villages to study the impact of IRS on malaria transmission. Results: Persistence of effectiveness of ICON 10 CS was observed up to 2–3 months in all the three study areas. ICON 10 CS was found effective at par with or better than the insecticides used in the national programme in reducing the mosquito densities and in interrupting malaria transmission in the study villages. Vector density, parity rates and malaria cases considerably reduced in the ICON 10 CS-sprayed villages. Conclusion: Field trials at three sites have established that ICON 10 CS formulation was relatively more effective than malathion 25% WP, deltamethrin 2.5% WP and lambda-cyhalothrin 10% WP in some evaluation parameters like indoor resting mosquitoes, parity rates in vector mosquitoes and persistence of effectiveness. It can be used for IRS for malaria vector control with two rounds of spray at an interval of 3 months for curtailing the malaria transmission and an additional round is recommended in perennial malaria transmission areas.

Community awareness, perceptions, acceptability and preferences for using LLIN against malaria in villages of Uttar Pradesh, India.

Background & Objectives: Long-lasting insecticidal nets (LLINs) have been introduced in India recently into the vector control programme. A study was undertaken to assess the community perception regarding use of LLIN, their acceptability, collateral benefits, etc. in certain villages of District Gautam Budh Nagar, Uttar Pradesh, India where LLINs are in use by the community. Method: A randomized community-based survey was undertaken during April–May 2009 covering 596 respondents in LLIN villages where LLINs have been distributed along with 307 respondents in untreated net villages where untreated nets were distributed using structured questionnaire. Qualitative data were collected and the difference in proportion was calculated by z-test. Results: A substantial number of respondents had good knowledge of the symptoms of malaria. According to respondents, LLINs were very much effective in bringing down the malaria incidence in their families. About 98.3% of the respondents asserted the use of LLINs as their use not only reduced the number of mosquitoes as well as other non-target insects, but also reduced the malaria incidence. About 93.2% of the respondents were ready to purchase LLINs if available at nominal prices. All the respondents were satisfied about the performance of the LLINs in reducing the mosquito nuisance, safety of use and collateral benefits in LLIN villages. Conclusion: LLINs are safe, socially acceptable and should be promoted for vector control to reduce the disease burden in the communities.

Persistence of DDT, malathion & deltamethrin resistance in Anopheles culicifacies after their sequential withdrawal from indoor residual spraying in Surat district, India.

Background & objectives: Under the national antimalaria programme DDT was introduced in early 1950s for vector control and later hexachloro cyclohexane (HCH) followed by malathion and recently synthetic pyrethroids in 1990s to manage the insecticide resistance in Anopheles culicifacies. Subsequent replacement led to development of multiple resistances in An. culicifacies in Surat district in Gujarat State. Indoor residual spray (IRS) was completely withdrawn in southern villages in Surat in 2002. This study was undertaken in these areas to study the persistence of resistance to DDT, malathion and deltamethrin after sequential withdrawal of IRS with these insecticides at different times. Methods: Susceptibility tests on An. culicifacies were conducted using standard WHO methods and kits. Mortality, knockdown time and lethal times were calculated for An. culicifacies exposed to WHO prescribed diagnostic concentrations of different insecticide impregnated papers. Results: Persistence of DDT-resistance was observed even after 30 yr of its withdrawal from IRS. Similarly, persistence of malathion resistance was also observed after 9 yr of its withdrawal from IRS, while reversal of deltamethrin-resistance was observed very fast within 2-3 yr after its withdrawal from IRS in 2002. Interpretation & conclusion: Present data indicate that the quantum of reversion of insecticide resistance in a population is relative and depends on the genetic stability of the respective resistance genes in the mosquitoes. In the present study withdrawal of pyrethroid-IRS resulted in increased susceptibility against pyrethroids alone and was independent of existence of resistance to insecticides of other groups. This study emphasizes that appropriate rotation of different insecticides; including carbamates may prevent or delay the onset of resistance.

Spatio-temporal variations in adult density, abdominal status & indoor resting pattern of Culex quinquefasciatus Say in Panaji, Goa, India.

Background & objectives: Goa is one of the filariasis endemic states of India. However, information on density pattern and resting behavior of Culex quinquefasciatus Say, the principal vector of filariasis in Goa is lacking. Therefore, current longitudinal study was undertaken to investigate these aspects. Methods: Panaji was divided into six zones and a total of 240 man hours were spent in 60 fixed catching sites to collect the adult Cx. quinquefasciatus mosquitoes on fortnightly basis from indoor resting sites during 2005-06. The female mosquitoes were classified as unfed, fed, semi-gravid and gravid to ascertain the resting behavior of Cx. quinquefasciatus adults. The data were analysed to evaluate the spatio-temporal variations in adult density, abdominal status and indoor resting sites and linked to meteorological variables like temperature, relative humidity, rainfall and number of rainy days. Results: Cx. quinquefasciatus adults were prevalent perennially in Panaji with highest per man hour density of females (48.6) in February and the lowest density (6.6) in September. Monthly variations in the densities between different months was significant (F=15.3; P<0.05). Rainfall significantly influenced the population of Cx. quinquefasciatus (t=2.63; P<0.05). Fed group and semi-gravid group showed a strong correlation with the relative humidity (P<0.05), rain fall (P<0.05) and number of rainy days (P<0.05). 62.4 per cent of females and 65.1 per cent of males preferred to rest on hanging objects. Spatio-temporal variations in the number of Cx. quinquefasciatus females and males resting on different sites and also the variations in different sites (P<0.05) were significant. Interpretation & conclusion: The density of female Cx. quinquefasciatus encountered in all the months was higher than the estimated tolerated level of density of 34 per ten man hours up to which there is no risk of filariasis transmission. The strong correlation between the abdominal conditions and relative humidity, rainfall and number of rainy days imply that these meteorological variables significantly influenced the feeding and fecundity of the species. 85.3 per cent of the indoor resting population comprising of fed, semi-gravid and gravid females confirmed the endophilic nature of the species. The preferential resting behavior of both females and males on hanging objects suggest that use of insecticide treated long-lasting bed nets as personal protective measure can be exploited to reduce the density of the vector species.

Adulticidal activity of essential oil of Lantana camara leaves against mosquitoes.

Background & objectives: Development of insect resistance to synthetic pesticides, high operational cost and environmental pollution have created the need for developing alternative approaches to control vector-borne diseases. In the present study we have investigated the insecticidal activity of essential oil isolated from the leaves of Lantana camara against mosquito vectors. Methods: Essential oil was isolated from the leaves of L. camara using hydro-distillation method. Bioassay test was carried out by WHO method for determination of adulticidal activity against mosquitoes. Different compounds were identified by gas chromatography-mass spectrometry analysis. Results: LD50 values of the oil were 0.06, 0.05, 0.05, 0.05 and 0.06 mg/cm2 while LD90 values were 0.10, 0.10, 0.09, 0.09 and 0.10 mg/cm2 against Ae. aegypti, Cx. quinquefasciatus, An. culicifacies, An. fluvialitis and An. stephensi respectively. KDT50 of the oil were 20, 18, 15, 12, and 14 min and KDT90 values were 35, 28 25, 18, 23 min against Ae. aegypti, Cx. quinquefasciatus, An. culicifacies, An. fluviatilis and An. stephensi, respectively on 0.208 mg/cm2 impregnated paper. Studies on persistence of essential oil of L. camara on impregnated paper revealed that it has more adulticidal activity for longer period at low storage temperature. Gas chromatographic-mass spectrometric analysis of essential oil showed 45 peaks. Caryophyllene (16.37%), eucalyptol (10.75%), α-humelene (8.22%) and germacrene (7.41%) were present in major amounts and contributed 42.75 per cent of the total constituents. Interpretation &conclusion: Essential oil from the leaves of L. camara possesses adulticidal activity against different mosquito species that could be utilized for development of oil-based insecticide as supplementary to synthetic insecticides.

Role of CR1 Knops polymorphism in the pathophysiology of malaria: Indian scenario.

Background & objectives: Plasmodium falciparum is the leading cause of mortality and causes cerebral malaria associated with sequestration caused by cytoadherence of the trophozoite and schizont-infected erythrocytes to the endothelial cells of the deep vascular beds in the brain. Pathophysiology of malaria is complicated by rosetting. Rosetting is a process of binding of uninfected erythrocytes to the erythrocytes infected with mature asexual parasites and is controlled by expression of complement receptor 1 (CR1) on RBC surface. Various polymorphic forms of CR1 are known including molecular weight polymorphism, red blood cell expression levels/density polymorphism and Knops (KN) polymorphism. The Knops blood group includes several allelic pairs; Knops a and b (Kna and Knb), McCoy a and b (McCa, McCb), Swain-Langley (Sla), and Villien (Vil). Knops phenotype Sl (a–) has been found to rosette less effectively than Sl (a+) and hence suggested to be more protective. P. falciparum cases have not reduced much as compared to the reduction in the total number of malaria cases in the past few years. In addition, P. falciparum is the leading cause for all mortality and most of the morbidity in India. We, therefore, investigated the role of CR1 Knops polymorphism in the pathophysiology of malaria in Indian population. Methods: A case control approach was used for this study. CAPS (Cleaved amplified polymorphic sequence) methodology was adopted. A total of 100 normal individuals (free from any ailment) and 100 individuals suffering from P. falciparum infection (uncomplicated malaria) were recruited for this study. Results: We found that in Indian population (normal individuals and P. falciparum-infected individuals), only the wild type allele is present. Interpretation & conclusion: We concluded that the process of rosetting in the Indian context could be occurring independently of the effect of Knops polymorphism and in part could be controlled by other polymorphisms of the CR1 gene (density and structural polymorphism).

Field evaluation of ZeroFly® - an insecticide incorporated plastic sheeting against malaria vectors & its impact on malaria transmission in tribal area of northern Orissa.

Background & objectives: Insecticide incorporated plastic sheeting is a new technology to control mosquitoes in emergency shelter places and also temporary habitations in different locations. Therefore, field studies were conducted to assess the efficacy of ZeroFly® plastic sheeting treated with deltamethrin on prevailing disease vectors Anopheles culicifacies and An. fluviatilis and its impact on malaria transmission in one of the highly endemic areas of Orissa. Methods: The study was conducted in Birkera block of Sundargarh district, Orissa state. The study area comprised 3 villages, which were randomized as ZeroFly plastic sheet, untreated plastic sheet and no sheet area. ZeroFly plastic sheets and untreated plastic sheets were fixed in study and control villages respectively covering all the rooms in each household. Longitudinal studies were conducted on the bioefficacy with the help of cone bioassays, monitoring of the mosquito density through hand catch, floor sheet and exit trap collections and fortnightly domiciliary active surveillance in all the study villages. Results: In ZeroFly plastic sheeting area, there was a significant reduction of 84.7 per cent in the entry rate of total mosquitoes in comparison to pre-intervention phase. There was 56.2 per cent immediate mortality in total mosquitoes in houses with ZeroFly sheeting. The overall feeding success rate of mosquitoes in the trial village was only 12.5 per cent in comparison to 49.7 and 51.1 per cent in villages with untreated plastic sheet and no sheet respectively. There was a significant reduction of 65.0 and 70.5 per cent in malaria incidence in ZeroFly plastic sheeting area as compared to untreated plastic sheet and no sheet area respectively. Interpretation & conclusions: Our study showed that introduction of ZeroFly plastic sheets in a community-based intervention programme is operationally feasible to contain malaria especially in the high transmission difficult areas.

Application of spatial technology in malaria research & control: some new insights.

Geographical information System (GIS) has emerged as the core of the spatial technology which integrates wide range of dataset available from different sources including Remote Sensing (RS) and Global Positioning System (GPS). Literature published during the decade (1998-2007) has been compiled and grouped into six categories according to the usage of the technology in malaria epidemiology. Different GIS modules like spatial data sources, mapping and geo-processing tools, distance calculation, digital elevation model (DEM), buffer zone and geo-statistical analysis have been investigated in detail, illustrated with examples as per the derived results. These GIS tools have contributed immensely in understanding the epidemiological processes of malaria and examples drawn have shown that GIS is now widely used for research and decision making in malaria control. Statistical data analysis currently is the most consistent and established set of tools to analyze spatial datasets. The desired future development of GIS is in line with the utilization of geo-statistical tools which combined with high quality data has capability to provide new insight into malaria epidemiology and the complexity of its transmission potential in endemic areas.

Laboratory studies on mosquito larvicidal efficacy of aqueous & hexane extracts of dried fruit of Solanum nigrum Linn.

Background & objectives: Aqueous and organic solvent extracts of plants/plant parts were effective in killing the mosquito larvae. Comparative efficacy of the aqueous and hexane extracts of dried fruit of Solanum nigrum was tested against five laboratory colonized strains of mosquito species, namely Anopheles culicifacies species A, An. culicifacies species C, An. stephensi, Culex quinquefasciatus and Aedes aegypti to assess the possibility for use of these extracts for their control. Methods: Concentrations of aqueous extract of dried fruit in the range of 62.5 to 2000 ppm and hexane extract of dried fruit in the range of 0.781 to 150 ppm were used in bioassays. The mortality data were subjected to log probit regression analysis to detertmine the median lethal concentrations (LC50 and LC90) to kill 50 and 90 per cent of the treated larvae of the respective species. Results: All the five species registered 100 per cent mortality in larval bioassays at 1000 ppm with aqueous extract and at 100 ppm with hexane extract of dried fruit. In bioassays with aqueous extract An. culicifacies species A registered the lowest LC50 of 208.5 ppm (range-208.5-359 ppm for different mosquito species) while with hexane extract, An. stephensi registered the lowest LC50 of 6.25 ppm (6.25- 17.63 ppm for different mosquito species). The LC50 of aqueous extract was 13-39 fold higher than the values of hexane extract of dried fruit for different species. The calculated LC90 for hexane extract of dried fruit for different species was in the range of 43.38-95.28 ppm. Interpretation & conclusion: Hexane extract showed good mosquito larvicidal efficacy than that of the aqueous extract. The calculated LC 90 for the extract for different species was below 100 ppm and could be effective for comprehensive control of disease vectors.