Determinants of transmission hotspots and filarial infection in households after eight rounds of mass drug administration in India.

OBJECTIVES: Lymphatic filariasis (LF) elimination through mass drug administration (MDA) of DEC and albendazole have resulted in very low levels of infection in most endemic districts in India. But small pockets with residual microfilaraemia in the community and antigeneamia in children ('hotspots') are a cause of concern. We aimed to identify the determinants of such transmission hotspots and filarial infection in households using data from 33 communities. METHODS: The filariasis vector Culex quinquefasciatus was collected from 627 randomly selected households using gravid traps. Parallel data on environmental, entomological, demographical, socio-economical and behavioural factors were analysed to identify the determinants of hotspots and household-level infection. RESULTS: Hotspots and non-hotspots did not differ significantly in terms of socio-economical and behavioural aspects, but did differ in terms of demographical and environmental factors. Logistic regression revealed that tiled and concrete houses increased the risk of an area being a hotspot by 2.0 and 2.9 times respectively. Presence of Culex breeding habitats was significantly associated with elevated risk of being a hotspot. Proximity of U-drains to a house increased the risk of filarial infection 5.8 times. CONCLUSIONS: An environment suitable to Culex breeding influences continued transmission despite eight rounds of MDA, particularly in hotspots. Proximity to U-drains increases the risk of infection in households. Implementing localised vector control measures may help interrupt low-level transmission, thereby reducing the risk of resurgence in the absence of MDA.

Prevalence and spatial distribution of Ixodid tick populations in the forest fringes of Western Ghats reported with human cases of Kyasanur forest disease and monkey deaths in South India.

Kyasanur forest disease (KFD) is a major tick-borne viral haemorrhagic fever caused by KFD virus (KFDV) (Flaviviridae). The disease was reported to be confined to five districts of Karnataka state India until 2011. During 2012-2016, emergence of KFD has been reported in newer areas of Karnataka and adjoining states. Therefore, survey of tick vectors was carried out in these new areas of Karnataka and adjoining states reported with monkey deaths and human cases of KFD. In all selected sites, ticks from the forest floor were collected by lint clothes using flagging method. Tick samples were tested for KFDV nucleic acid by real-time RT-PCR. A total of 4772 ticks, comprising eight species of genus Haemaphysalis and one species each of genus Amblyomma, Ixodes and Rhipicephalus was collected. Haemaphysalis spinigera, the principal vector of KFDV was the predominant tick species (59.5%) collected followed by H. turturis (8.6%). The abundance of H. spinigera ranged from 9.2 to 33.9 per man-hour in the six districts surveyed. Of 214 (4418 tick samples) pools screened by real-time RT-PCR, two pools of H. spinigera were positive for KFDV. High abundance of Haemaphysalis vectors in the six districts indicated that the districts are receptive for KFD outbreaks. KFDV was detected in the tick vectors in the new foci of the KFD. Data on tick distribution will be useful in creating KFD risk map for strengthening the ongoing preventive measures such as vaccination and supply of insect repellents to the high risk groups and intensive health education.

Efficacy of three formulations of diflubenzuron, an insect growth regulator, against Culex quinquefasciatus Say, the vector of Bancroftian filariasis in India.

BACKGROUND & OBJECTIVES: Insect growth regulators (IGRs) offer alternatives to conventional chemical larvicides that pose problem of resistance and environmental safety. However, only a limited number of IGRs have been approved for use in mosquito control. In the present study, two new formulations of the IGR diflubenzuron, 2 per cent granular (GR) and 2 per cent tablet (DT) were tested for its efficacy against Culex quinquefasciatus, in comparison to its 25 per cent wettable powder (WP) formulation. METHODS: The WP, GR and DT formulations were tested in cesspits, street drains and abandoned wells each at four dosages, 25, 50, 75 and 100 g ai/ha. Additionally, the DT formulation was tested at a higher dosage of 1 tablet/m² (equal to 400 g ai/ha). RESULTS: The WP and GR formulations yielded >80 per cent inhibition of adult emergence (IE) for 7-10 days in cesspits, 4-7 days in street drains and 7-21 days in abandoned wells at all dosages tested. The DT formulation was effective only at higher dosage 100 g ai/ha and or 1 tablet/m² for 7-15 days at all habitats. INTERPRETATION & CONCLUSIONS: The trial showed that the dosage 25 g ai/ha of 25 per cent WP could be the field dosage for cesspits and wells, and 50 g ai/ha for drains, to be applied at weekly intervals. The dosages 25, 50 and 100 g ai/ha of 2 per cent GR could be the field dosages for application in cesspits at weekly intervals, in abandoned wells every three weeks and in drains at weekly intervals, respectively. Diflubenzuron 25 per cent WP and 2 per cent GR could be used for larval control of Cx. quinquefasciatus under integrated vector management programme.

Invasion of toxic marine cyanobacteria in to the tsunami affected coastal villages of southern India.

This documentation explores the facts about the invasion of marine cyanobacteria in to the tsunami affected coastal villages of Nagapattinam district of Tamilnadu and Karaikkal district of Pondicherry Union Territory (UT) in southern India. Water samples were collected from eight tsunami-hit coastal villages in different open water sources. The collected samples were processed for detecting marine cyanobacterial growth. Totally 110 water samples were processed, three samples were positive for the toxic cyanobacteria, Lyngbya sp., and nine for nontoxic species such as Epithemia sp.,, Johannesbaptistia pellucida, Oscillatoria princeps, Phormidium fragile, Synechocystis sp. Besides posing a public health risk because of the toxic cyanobacteria, the bloom formation by the cyanobacterial species such as Anabaena, Microcystis, Lyngbya, Plectonema, Phormidium contaminated the water bodies and deteriorated the water quality in the tsunami affected villages. The study revealed that another kind of public health risk from the invasion of toxic cyanobacteria to the costal ecosystem during the tsunami. It is necessary, in this context, that the surveillance mechanism, which is geared up during or after natural disasters, should have a provision to monitor the transportation of toxic elements/organisms from marine system to coastal/inland ecosystems and to control such organisms.

Efficacy of two formulations of the bioinsecticide spinosad against Culex quinquefasciatus in India.

Spinosad 12% suspension concentrate (SC) and 0.5% granular (G) formulations were tested against Culex quinquefasciatus immatures at 3 dosages--50, 100, and 150 mg active ingredient (AI)/m2--in cesspits, street drains, and disused wells in comparison with temephos 1% G at 1 part per million. The 2 formulations reduced the density of pupae of Cx. quinquefasciatus by 80-100% for 7-14 days in cesspits, 7-18 days in drains, and 33-69 days in disused wells at the 3 dosages tested. The 12% SC and 0.5% G formulations were equally effective in suppressing the larval and pupal populations of Cx. quinquefasciatus in all the habitats treated. At 100 mg AI/m2 in drains and cesspits, the efficacy of spinosad 0.5% G was greater than that of temephos (1% G) and that of spinosad 12% SC was comparable to that of temephos (1% G) applied to the 2 habitats. In disused wells, both the formulations lasted longer than temephos. Based on the small-scale trial, the rate of 150 mg AI/m2 of spinosad was selected for field application to cesspits and drains and 50 mg AI/m2 for application to disused wells. The efficacy observed in medium-scale trials was in agreement with that of small-scale trials. The trial showed that the 2 formulations of spinosad can be used for larval control of Cx. quinquefasciatus, at 50 mg AI/m2, applied at weekly intervals to cesspits and street drains and at monthly intervals to disused wells. At the higher dose of 150 mg AI/m2, the 2 formulations were effective in suppressing the pupal population for 2 wk in cesspits and street drains and for 2 months in disused wells.

Efficacy of novaluron against Culex quinquefasciatus in small- and medium-scale trials, India.

Novaluron 10% emulsifiable concentrate (EC), an insect growth regulator (IGR), was tested against Culex quinquefasciatus immatures at 1, 5, and 10 mg active ingredient (AI)/m2 applied to cesspits, drains, and abandoned wells. The IGR produced 80-100% inhibition of adult emergence (IE) for > 1 week (10-14 days) in cesspits, 1-2 weeks in street drains, and 5-10 weeks in abandoned wells at the 3 application rates. The efficacy increased with the increasing dose in street drains and abandoned wells. The residual activity of the IGR was longer in abandoned wells compared to drains and cesspits. Based on the small-scale trial, doses of 1, 5, and 10 mg AI/m2 were used in the medium-scale trial for cesspits, abandoned wells, and street drains, respectively. The efficacy observed in medium-scale trial was similar to that in the small-scale trial. The results indicate that novaluron 10% EC can be used for larval control against Cx. quinquefisciatus at the application rate of 1 mg AI/m2 at 10-day intervals in cesspits, at 5 mg AI/m2 at 2-month intervals in abandoned wells, and at 10 mg AI/m2 applied at fortnightly intervals to drains. Even at the lowest rate of 1 mg AI/m2, the IGR prevented adult emergence for at least a week in cesspits and street drains and for a month in abandoned wells. Novaluron 10% EC could be one of the options for larval control operations in integrated vector management.

Field evaluation of an insect growth regulator, pyriproxyfen 0.5% GR against Culex quinquefasciatus, the vector of Bancroftian filariasis in Pondicherry, India.

Pyriproxyfen, 0.5% granular formulation (GR), an insect growth regulator (IGR) was tested against Culex quinquefasciatus larvae and pupae in disused wells, cesspits and drains at the dosages of 0.1, 0.25, and 0.5kg(ai)/ha to determine the most appropriate field dosage. The IGR was found to be effective against C. quinquefasciatus larvae and pupae in all the larval habitats tested. In drains with slow moving water, application of pyriproxyfen 0.5% GR at 0.5kg(ai)/ha resulted in >80% emergence inhibition (EI) of adults for 4 weeks. At 0.1 and 0.25kg(ai)/ha, the EI was always less than 80%. In stagnant drains, the IGR yielded >80% EI for 1-week period at 0.1kg(ai)/ha. At 0.25 and 0.5kg(ai)/ha, the efficacy was 5-10 times higher. In cesspits, the EI was >80% for 6 weeks when pyriproxyfen 0.5% GR was applied at 0.1kg(ai)/ha, for 11 weeks at 0.25kg(ai)/ha and 9 weeks at 0.5kg(ai)/ha. In disused wells treated at the dosage 0.1kg(ai)/ha, there was >80% EI for 15 weeks and at 0.25 and 0.5kg(ai)/ha, the effective duration was about 1.6-1.8 times longer (24-28 weeks). Considering the quantum of IGR required and the cost and also for safety reasons, the low dosage 0.1kg(ai)/ha is recommended as the field dosage to be applied at weekly interval in stagnant drains, 6 weeks interval in cesspits and 15 weeks interval in disused wells. Since pyriproxyfen 0.5% GR has a relatively longer residual effect than the other IGRs the operational cost could be minimized. Pyriproxyfen 0.5% GR could be one of the choices in the chemical control strategy in Integrated Vector Control Programmes.

rDNA-ITS2-PCR assay for grouping the cryptic species of Anopheles culicifacies complex (Diptera: Culicidae).

Anopheles culicifacies, a predominant vector of malaria in India exists as a complex of five sibling species A, B, C, D and E, of which, except species B, all the rest are vectors with varying vectorial capacities. With a combination of PCR assays, it is possible to identify all the five members of this species complex. These assays include amplification of the rDNA-ITS2 region followed by digestion of the ITS2 amplicon using restriction enzyme, Rsa I which groups the five members of the An. culicifacies complex into two categories: species A and D forming one category and species B, C and E forming another. The samples grouped thus are then subjected to two allele-specific PCR assays (AD-PCR and BCE-PCR), which has been designed using sequence differences in the mitochondrial cytochrome oxidase II (CO II) subunit. The AD-PCR assay distinguishes species A and D, whereas the BCE-PCR assay distinguishes species B, C and E. In the present study, the differences in the ITS2 region of the five species was used to design a PCR assay which groups the five members into the same two categories as obtained after digestion of the ITS2-PCR product. This assay uses a common forward primer based on the 5.8S region and two reverse primers, which is specific for the two categories. Amplification of a PCR product of size 253bp indicates the presence of species A/D, while a product of size 409bp indicates the presence of species B/C/E. By using this ITS2 PCR assay, the three-step procedure is reduced to two cutting down the time and cost involved. The ITS2 PCR assay has been validated on specimens collected from different regions of India and the results confirm to the earlier reports on the distribution of the members of the An. culicifacies complex.

Delivery strategy of mass annual single dose DEC administration to eliminate lymphatic filariasis in the urban areas of Pondicherry, South India: 5 years of experience.

BACKGROUND: The recommended strategy for elimination of Lymphatic filariasis is single-dose, once-yearly mass treatment with anti-filarial drugs and the program is in operation on a national level in India. Rate of coverage and consumption is the most crucial factor in the success of Mass Drug Administration (MDA) program. In spite of massive efforts, the program demonstrated sub-optimal coverage and consumption in urban areas than rural. The involvement of Anganwadi workers (AWWs) of the Integrated Child Development Scheme (ICDS) as communicators and drug distributors was attempted to enhance the coverage and consumption in urban areas and the results presented here. METHODS: An annual single dose MDA program was launched under the auspices of Freedom From Filariasis (FFF) program in Pondicherry, India, in the year 1997 and continued for five years. A questionnaire survey was carried out following all the treatment rounds (TRs) for assessing coverage of distribution and consumption Five percent of randomly selected households constituted the sample. All the members available in the selected household at the time of interview formed the respondent of the study. RESULTS: The coverage of drug distribution during the TRs varied from 74.3 to 95.4 percent and consumption rate from 52.9 to 78.8. Among the respondents, 71% were aware of the MDA program and the source of information for 62.8% of them was through personal communication by the AWW. It was observed that 33.2% of the respondents who accepted the drug did so based on the trust on the AWW as a government representative. The main reason for non-consumption in all TRs was fear of side reaction (25.4 - 42.2%). CONCLUSION: The delivery-strategy of health information and Diethylcarbamazine (DEC) drug to the urban community using the AWWs could achieve relatively higher coverage and consumption than reported in other urban areas. In order to achieve the optimum level, it is imperative to equip the AWWs with current knowledge and skills, and design innovative Information, Education and Communication (IEC) campaign to target the less compliant groups. The beneficial effect of this delivery strategy may be used in similar urban settings to achieve the elimination of LF.

An outbreak of Kyasanur forest disease in the Wayanad and Malappuram districts of Kerala, India.

Kyasanur forest disease (KFD) is a zoonotic viral haemorrhagic fever and has been endemic to Karnataka State, India. Outbreaks of KFD were reported in new areas of Wayanad and Malappuram districts of Kerala, India during 2014-2015. Investigation of the outbreaks was carried out in these districts during May 2015. The line-list data of KFD cases available with District Medical Office, Wayanad were analysed. Case investigation was carried out to determine the risk factors associated with the outbreak and possible site of contraction infections. Ticks from the forest floor were collected in areas associated with monkey deaths by flagging method to estimate species abundance. Of 102 confirmed cases of KFD reported in Wayanad, 91% were adults aged >15years. About 43% of the cases were from the areas of Poothady Primary Health Centre (PHC) followed by Chethalayam PHC (22%). Most of the affected individuals belong to Kattunayakan tribe, dependent on forest for their livelihood. Those tribes are engaged in trench digging and fire line works in summer months and hence are at a higher risk. In Malappuram, the Cholanaickan tribe, are under high risk of exposure to infected ticks as they live deep in the forest and trap monkeys for game meat. High abundance of Haemaphysalis spinigera and H. turturis, the established vectors of KFD virus was recorded in all affected areas. Incidence of KFD cases/monkey deaths and high abundance of Haemaphysalis vectors in the forest ranges of Wayanad and Malappuram districts indicate that the area has become receptive for KFD outbreaks. Preventive measures (vaccination of high risk groups) coupled with intensive health education should be carried out prior to transmission season.

A simple and rapid DNA extraction method for the detection of Wuchereria bancrofti infection in the vector mosquito, Culex quinquefasciatus by Ssp I PCR assay.

A simple, rapid and inexpensive method for the extraction of DNA from filarial vector, Culex quinquefasciatus, useful in Ssp I PCR assay for xenomonitoring of infection with Wuchereria bancrofti is presented. The DNA extracted by this method was found suitable for PCR detection of W. bancrofti infection in pools of 10-30 mosquitoes. The PCR assay employing the simplified DNA extraction method was evaluated for its sensitivity on field caught Cx. quinquefasciatus, in comparison with the conventional dissection and microscopy technique. When assayed on dissection washings of vector mosquitoes the PCR assay detected 45 pools out of 49 dissection positive pools as positive for infection and hence found to be less sensitive than the conventional technique. The reason for detecting four dissection positive pools as negatives by the PCR assay may be due to the loss of a few numbers of parasites (1-3) present in these pools during the transfer of washings of dissected mosquitoes. The PCR assay detected ten out of 72 dissection negative pools as positives, while it did not detect any of the 62 known negative (laboratory reared, uninfected) mosquito pools as positives. When 38 pools (10 mosquitoes/pool) of intact mosquitoes were assessed for infection by each method, the infection rates obtained by the two methods were almost similar (3.35 and 3.01%, respectively, for conventional method and PCR assay). The results thus show that the DNA extraction method, which is simple, rapid, safe and inexpensive, is efficient to generate DNA from vector mosquitoes useful in PCR assay and hence has potential application in xenomonitoring.

Field evaluation of a formulation of Pseudomonas fluorescens against Culex quinquefasciatus larvae and pupae.

VCRC B426, 0.09% emulsifiable concentrate (EC) formulation developed from a metabolite of Pseudomonas fluorescens was tested for efficacy against Culex quinquefasciatus larvae and pupae. At application rates of 100, 200, 300 ml/m2, the formulation caused 100% elimination of larvae and pupae at day 1 after treatments and >80% reduction in pupal density for periods of 7, 12 and 11 days in cesspits and 5, 9 and 10 days in U-shaped drains. In both the habitats, the efficacy of the formulation against pupae was 1.7 times more at 200 ml/m2 than at 100 ml/m2. An increase in dosage to 300 ml/m2 did not improve the efficacy in cesspits but a marginal increase was observed in drains.

Reliability of light trap sampling for Anopheles fluviatilis, a vector of malaria.

The utility of light traps for sampling Anopheles fluviatilis, the major malaria vector in the hill tracts of Koraput district, Orissa, was assessed. A modified version of the CDC miniature light trap was used in the study. The data generated from light trap collections were analysed and compared with daytime resting, man-biting and night resting collections carried out in parallel. The number per trap recorded in cattle sheds was significantly higher than that recorded in human dwellings. A similar pattern was observed in hand catches of indoor resting population though the difference was not significant. The density recorded from light traps over time was found to have a significant positive linear association with corresponding indoor (r = 0.625; p = 0.0019) as well as outdoor (r = 0.603; p = 0.0029) diurnal resting densities. The proportion with different gonotrophic stages varied significantly between different types of collections. The age structure of A. fluviatilis did not differ significantly with the types of collection. As the light trap catches reflect seasonal fluctuations in the diurnal resting collections, they can justifiably be used in monitoring the relative density of A. fluviatilis in the place of cumbersome hand catch methods. Other uses of light traps are also discussed.

Laboratory & field evaluation of controlled release formulation of the insect repellents N,N-diethyl-m-toluamide (DEET) & N,N-diethyl phenylacetamide (DEPA) against mosquito vectors.

BACKGROUND & OBJECTIVES: Repellents can play a useful role in reducing the man-vector contact and help in interrupting disease transmission. Newer formulations are necessary to improve the efficacy of the repellent on the treated sites for enhanced protection. METHODS: To determine the comparative efficacy, 20 per cent liposphere lotion formulation and 20 per cent alcohol solution of two insect repellents DEET and DEPA were evaluated for the extent of protection on rabbits against Aedes aegypti during the day in the laboratory and on human volunteers during the night against Culex quinquefasciatus in the urban areas of Pondicherry, India. RESULTS: In the laboratory, the lotion formulations of DEPA and DEET were found to enhance the repellency by 1.5 (4.00 to 6.00 h) and 1.25 (4.00 to 5.00 h) times respectively compared to the alcohol solution of the repellents against Ae. aegypti at the application rate of 0.5 mg/cm2. In the field, the lotion formulation of DEPA at 0.3 mg/cm2 could increase the protection time from 6.30 to 8.36 h (1.3 times) whereas the lotion formulation of DEET at 0.3 mg/cm2 could increase the protection time from 6.54 to 8.42 h (1.2 times). INTERPRETATION & CONCLUSION: In laboratory and field tests, the lotion formulations of both repellents were found to give a higher protection compared to alcohol solution. The lotion formulations of DEET and DEPA were found to be equally effective.

Anopheline fauna of Koraput district, Orissa state, with particular reference to transmission of malaria.

The anopheline fauna was surveyed in Koraput district of Orissa, which is highly malarious. A total of 62,086 anophelines belonging to 22 species and two varieties were collected, including eight species of anophelines which are recognized malarial vectors in India. Anopheles sergenti, A. pulcherrimus, A. jeyporiensis var candidiensis and A. annularis var adiei was recorded for the first time in this area. A total of 24154 mosquitoes were dissected and 18 mosquitoes belonging to four species, A. fluviatilis. A. annularis, A. culicifacies and A. aconitus were found with the gut/gland infection.

Prevalence of bancroftian filariasis & its control by single course of diethyl carbamazine in a rural area in Tamil Nadu.

The prevalence of microfilaraemia, clinical spectrum of bancroftian filariasis and vector potential were studied in Vettavalam village in North Arcot district of Tamil Nadu. The effectiveness of selective therapy with diethyl carbamazine (DEC) in controlling filariasis in rural areas was also evaluated. The prevalence of microfilaraemia (mf rate) and disease (disease rate) was found to be 11.7 and 11.09 per cent respectively. Hydrocele was the dominant clinical sign in males and lymphoedema in females. The density of the vector Culex quinquefasciatus was 25.44 females/man-hour, and the infection and infectivity rates were 18.16 and 1.09 per cent respectively. All mf carriers detected after the mass blood survey were given a single course of DEC at the dosage of 6 mg/kg of body wt/day for 12 days. Only 61.6 per cent of them took the full course of DEC treatment. DEC therapy brought down the mf rate from 11.7 to 5.84 per cent after one month. In the absence of further treatment, there was no significant change in mf prevalence after one year.

Studies on dispersal of malaria vectors in a hilly tract of Koraput District, Orissa State, India.

Dispersal of malaria vectors was studied in a hilltop village in Koraput, a highly malarious district of Orissa. Immatures from terraced stream beds and day-time resting adults from artificially dug pit shelters, distributed centrifugally at different distances from the village were sampled. Breeding of Anopheles fluviatilis, An. annularis and An. culicifacies was found up to a distance of 1,700 m. Immature density of An. fluviatilis and An. culicifacies showed a negative correlation with the distance, but they were not statistically significant. The maximum distance at which An. fluviatilis adult females collected was 1,500 m. A significantly negative correlation was observed between An. fluviatilis resting females and distance. An. culicifacies adults were collected in low numbers even in the nearest pit shelters. No An. annularis was recorded from the pit shelters. The present record on the dispersal range of An. fluviatilis is estimated to be higher than that reported elswhere in India.

Observations on nocturnal activity and man biting habits of malaria vectors, Anopheles fluviatilis, An. annularis and An. culicifacies in the hill tracts of Koraput District, Orissa, India.

Biting and feeding behavior of malaria vectors were studied in nine villages (5 from Jeypore zone and 4 from Malkangiri zone) of Koraput District. Man biting catches comprised of 16 anopheline species including the incriminated vectors of this area: An. fluviatilis, An. annularis and An. culicifacies. An. fluviatilis was predominant and biting of this species recorded indoors throughout the year in both the zones. The period, during which the biting activity peaked, was different between the two zones and consequently the time of peak transmission was also different between the zones. The biting activity was at its peak between 21.00 and 03.00 hours in both the zones. However, in cold season the biting activity peaked in the first quarter of the night in Jeypore zone. The anthropophilic index (AI) of An. fluviatilis was 26.2% in Jeypore and 83.7% in Malkangiri and of An. culicifacies the AI was 0.4% in Jeypore and 7% in Malkangiri. Analysis of gonotrophic stages of night resting females indicated that in Jeypore zone, the majority of An. fluviatilis female left indoors for outdoor resting before the completion of gonotrophic cycle, but in Malkangiri, the females remained indoors till the end of the gonotrophic cycle. The presence of full-fed females in night resting catches in Jeypore village further suggested that the females do not leave the house immediately after taking blood meal but rest for some time.

A note on the impact of mud plastering on the efficacy of DDT residual spraying in tribal villages of Koraput District, Orissa State.

A field trial was undertaken to study the impact of mud plastering on the efficacy of DDT spraying in two villages in Koraput district. In Maliguda village, where 95 per cent spray coverage was achieved and the spray surfaces were retained without mud plastering up to 29 and 60 days in first and second round of the spray respectively, malaria cases reduced by 72 per cent after spray for a period of two months. In Dandabedha village with 85 per cent coverage and immediate mud plastering, the malaria cases reduced by 49 per cent. It is concluded that even though mud plastering reduces the effectiveness of the residual spraying to a certain extent, timely spray and better coverage with correct dosage can still effectively reduce the malaria incidence.