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.

Malaria in seasonal migrant population in Southern Gujarat, India

Malaria in migrant workers is always a major problem to control due to their temporary stay in shelters, and other operational constraints. Hence, a study was undertaken in brick kilns in Bharuch district, Gujarat state, India to study the problem of malaria in the work force. Mass blood surveys were carried out in 15 brick kilns. Blood slides were collected from both febrile and afebrile cases. Positive cases were treated as per the national drug policy and were followed up. Mosquito collections were carried out by pyrethrum spray collection in early morning hours. Human blood index and sporozoite rates were determined as per standard procedures. All age groups were found affected with malaria at brick kilns. Prevalence of malaria was significantly higher in 50% in migrant population. In stable population in villages, overall decline in malaria cases was observed in 2008-2010. The sporozoite rate of 4.2% in Anopheles culicifacies indicates active malaria transmission at brick kilns. The investigation demonstrated that suitable microclimatic conditions for malaria transmission exist in these areas during hottest period. The district health department should consider these factors in planning malaria surveillance and control. As current magnitude and diversity of population movements in rural as well as in urban areas are unprecedented, this issue is worthy of attention.

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.

Impact of etofenprox (Vectron® 20 WP) indoor residual spray on malaria transmission.

Background & objectives: A longitudinal study was carried out to assess the impact of indoor residual spray with Vectron® 20 WP (etofenprox) against Anopheles culicifacies and on malaria transmission in a selected village of Dadri primary health centre (PHC), District Gautam Budh Nagar, Uttar Pradesh, India. Methods: Two villages, namely Patadi and Anandpur in District Gautam Budh Nagar, Uttar Pradesh, with similar malaria incidence and vector prevalence were selected for the present evaluation. In one village two rounds of indoor spraying of etofenprox (0.1 g/m2) were done at an interval of 12 wk and the other village was kept as control where no intervention except intensive active surveillance for early detection and prompt treatment (EDPT) was undertaken during the study period. Entomological and epidemiological data were collected using standard procedures. Results: Persistence of the effectiveness of etofenprox against An. culicifacies was observed up to 12 wk. Spraying of etofenprox signifi cantly reduced the density signififi (P<0.001) and proportion of parous An. culicifacies mosquitoes (P<0.05) in the experimental village. There was a signififi cant reduction in malaria cases in the experimental village during the post-spray period when compared to the control village (P<0.05). No adverse effect was reported by the spraymen and inhabitants during and after the spray. Interpretation & conclusion: Indoor residual spray of etofenprox (0.1 g/m2) with an interval of three months in between two rounds of spray produced the desired impact in reducing the indoor resting density of vector mosquitoes and also in curtailing malaria transmission in the sprayed village when compared with the control village without spray.

Impact of Olyset nets on malaria transmission in India.

BACKGROUND & OBJECTIVES: Efficacy of Olyset nets, long-lasting insecticidal nets were tested from August 2003 to August 2006 against Anopheles culicifacies, the vector which transmits 60% of all malaria cases in rural India. METHODS: Three villages in District Gautam Budh Nagar (Uttar Pradesh), India were selected for the trial and Olyset nets were distributed in one village, in another village untreated nets were distributed and the third village was kept as control where nets were not used. Entomological, and epidemiological data were collected using standard methods. RESULTS: The use of Olyset nets reduced the indoor resting density of An. culicifacies and also reduced mosquito entry into the structures where Olyset nets were used. No mosquitoes were caught landing on the Olyset nets. There was a reduction in the parity rate of An. culicifacies in the Olyset net village as compared with untreated net and no net villages. The impact of Olyset nets was observed on malaria incidence and only one case of Plasmodiumfalciparum malaria was reported in the Olyset net village but these continued to be found in the village with untreated nets and the control. CONCLUSION: Results of the present study confirmed that Olyset nets are highly effective in reducing the indoor resting density of mosquitoes, man-vector contact and malaria incidence.

Larvicidal and mosquito repellent activities of Pine (Pinus longifolia, family: Pinaceae) oil.

BACKGROUND AND OBJECTIVES: Various plant-based products are safe and biodegradable alternatives to synthetic chemicals for use against mosquitoes. Oil of Pinus longifolia is traditionally used for protection against mosquitoes in some rural areas but there is no documented report of its use against mosquitoes. The present study was undertaken to scientifically evaluate the activity of Pine oil against mosquitoes. METHODS: The oil was procured from the market and its contents were chemically analysed. Larvicidal activity of oil was tested in laboratory bioassays, while repellent action was studied during whole night bait collections in field by direct application on the skin and after its impregnation on mats. RESULTS: Results showed varying degree of larvicidal activity of Pine oil against mosquitoes with LC50 values ranging between 82 and 112 ppm. The Pine oil had strong repellent action against mosquitoes as it provided 100% protection against Anopheles culicifacies for 11 h and 97% protection against Culex quinquefasciatus for nine hours respectively. Electrically heated mats prepared from Pine oil provided, 94 and 88% protection against An. culicifacies and Cx. quinquefasciatus for 10 and seven hours respectively. INTERPRETAION AND CONCLUSION: Pine oil is effective against mosquito larvae at very higher doses which are not of any practical utility. However, Pine oil showed strong repellent action against An. culicifacies (malaria vector) and Cx. quinquefasciatus (pest mosquito). Thus its use could be popularised as mosquito repellent.