Recherche et rapports
Insecticide Treated Bed Nets: A Significant Contribution Towards Malaria Control
Outlooks on Pest Management - August 2008 pps. 160-163
Mosquito LLINs have revolutionized vector control today because of their simplicity. They do not require specialist spray teams or equipment, are easy to distribute, repel and kill mosquitoes, reduce malaria and cost about $5 and can last 5 years - which is only $1/year to protect a mother and her child. In addition, LLINs are generally well-received by the population, as recipients consequently get a good nights sleep free from mosquitoes. ImageOlyset LLIN contribution towards malaria control, Invest 2008
An experimental hut evaluation of Olyset® nets against anopheline after seven years use in Tanzanian villages
Malaria Journal 2008, 7:38
Examples of Olyset nets, which had been in use in Tanzanian villages for seven years, were tested in experimental huts against naturally entering Anopheles gambiae and Anopheles funestus mosquitoes. Performance was compared with new Olyset nets, conventionally treated ITNs (either newly treated with alphacypermethrin or taken from local villages after 1.5 years of use) and untreated nets.
After seven years of regular use, the LLIN Olyset remained highly insecticidal to mosquitoes that came into contact with it under field conditions.
- National Institute for Medical Research, Amani Medical Research Centre, P.O. Box 81, Muheza, Tanzania
- Kilimanjaro Christian Medical Centre, P.O. Box 2228, Moshi, Tanzania
- London School of Hygiene and Tropical Medicine, WC1E 7HT, London, UK
Impact of Olyset® Nets on malaria transmission in India
J Vect Borne Dis 44, June 2007, pp. 137–144
Background & objectives: Efficacy of Olyset 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 Plasmodium falciparum 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.
Bio-efficacy of Olyset nets against mosquitoes in India
Journal of the American Mosquito Control Association. 22(1):102-106, 2006
Finds that Olyset nets are highly effective in killing Anopheline mosquitoes after three-minute exposures. These nets also showed efficacy on other vector mosquitoes at higher exposure periods. Use of the nets inside the house also resulted in drastic reduction of daytime resting density of mosquitoes because of high repellency, excito-repellency, and killing action of the nets. The efficacy remained at ~90% even after 20 washings against Anopheles culicifacies and Culex quinquefasciatus. Olyset nets killed 100% of the mosquitoes which landed on them, and also killed the mosquitoes that entered the room having Olyset nets.
Comparative efficacy and persistency of permethrin in Olyset net and conventionally treated net against Aedes aegypti and Anopheles stephensi
Journal of the American Mosquito Control Association, 22(1):107-110.
The efficacy of the Olyset net was compared to a net treated conventionally with permethrin 10% emulsifiable concentrate at the World Health Organization recommended dose. Data were not collected for the conventionally treated (polyester) netting after five washings, because the treatment was no longer effective. The results of the study indicate permethrin persisted on Olyset net for at least 20 washings, confirming the regeneration of pesticide after each wash.
Evaluation of Olyset insecticide-treated nets distributed seven years previously in Tanzania
Malaria Journal 2004, 3:19
An assessment was carried out on the effectiveness of Olyset nets after seven years of use in rural Tanzania. The survey was conducted in two Tanzanian villages to examine insecticide dosage, efficacy and desirability compared with ordinary polyester nets. Of 103 randomly selected nets distributed in 1994 to 1995, 100 could be traced. Most nets were in a condition likely to offer protection against mosquito biting. The nets still gave high knock-down rates at 60 minutes (92%) and although functional mortality had fallen, it was still 50% after seven years. The study concluded that Olyset nets are popular, durable and with a much longer insecticide persistence than ordinary polyester nets. Hence, Olyset nets are one of the best choices for ITN programmes in rural malaria-endemic areas.
Field issues related to effectiveness of insecticide-treated nets in Tanzania
Medical and Veterinary Entomology (2004) 18, 153-160.
Trials were undertaken to provide some essential field information on polyester ITNs within the site of an extended ITN programme in the Morogoro region of Tanzania. It was found that 45% of all nets were in bad condition (defined as having more than seven large holes). It is concluded that an effective ‘life’ for polyester nets is 2–3 years. Further, two-thirds of the 20% of nets that were reported as having been re-treated within the last 12 months had less than 5 mg/m2 of insecticide. According to the World Health Organization, this is insufficient to be effective.
A double blind, randomized comparison performance of long-lasting and conventional insecticide treated mosquito nets in western Uganda -- Interim report after 12 months of follow-up
Lilian, AHD. et al. 2001
Finds that long lasting polyester nets after 12 months field use performed significantly better than conventionally treated nets after six months, but that polyester nets developed holes relatively quickly. After 12 months the proportion of nets with holes differed between the two types: 54.1% (44.0 – 64.1) of conventionally treated nets and 69.1% (64.5 – 73.7) of long lasting nets had at least one hole. These results suggest that in the examined rural setting, polyester nets are not likely to “survive” more than three years, particularly in poor households.
Assessment of a new type of permethrin impregnated mosquito net
Journal of Bioscience Vol. 7 Issue 1, 1996
Olyset net was tested and compared with polyethylene monofilament and nylon multifilament nets impregnated with permethrin. The longevity of the insecticidal effect of Olyset net against two other commonly used nets after repeated washing with water or with soap and water was tested. The penetrability of mosquitoes due to the large mesh used in Olyset was also measured. Two species of mosquitoes were used Anopheles maculatus and Aedes aegypti. The percentage mortality of An. maculatus exposed to Olyset, nylon multifilament and polyethylene nets after 15 washes with water was 95%, 83% and 26% respectively, while for Ae. aegypti mortality was 100%, 91.7% and 81.7% respectively. After the nets had been washed four times with soap and water the percentage mortality of An. maculatus exposed to Olyset, nylon and polyethylene nets was 86.7%, 80.3% and 3.3% respectively, while for Ae. aegypti the mortality was 90.3%, 50% and 5% respectively. In the penetrability study, although some mosquitoes were able to penetrate the large mesh, none were blood fed and all died within 12 hours.
Final report on a field trial of Olyset net for the control of malaria transmitted by Anopheles dirus and Anopheles minimus in RattanakKiri Province, Cambodia, 1994.
National Malaria Centre, Phnom Penh, Cambodia.
Olyset was well received by the local population with the following key points noted by them:
- Ready to use
- Good ventilation
- Good knockdown of mosquitoes
- No adverse side effects
The entomological data showed that Olyset was very effective in not only reducing the indoor biting, but also in decreasing the whole population of exophilic mosquito species of An. dirus by 71.4% and An. minimus by 72.2% and indoor parity rate of An. dirus by 62.4% and An.minimus by 63.4% in the study area. Bioassay tests on the nets gave 100% through the 7 months of the trial. The impact on malaria was good with the number of malaria cases being reduced by 91.1% and 100% reduction in deaths.
Effectiveness of permethrin incorporated Olyset bednet for malaria control in an endemic area of Esmeraldas Province, Republic of Ecuador July 1993 – June 1994
Olyset nets were tested in an area of high malaria transmission. The impact of the nets was compared with DDT spraying, Olyset and spray combination, and control area (no intervention). The best results were obtained from the Olyset-only area, where there was an 82% reduction of malaria cases. Where there was only DDT spraying, the reduction was only 16%. In the control area, malaria transmission remained high. The Olyset nets were well accepted by the population, who appreciated the wide mesh for better ventilation.
Bioassays on Olyset long lasting insecticidal nets
Bioassay were conducted using Anopheles stephensi to determine the ability of Olyset nets to retain their insecticidal power after several washes and to determine if heating is required to regenerate the insecticidal power lost through washing. The netting was either unwashed or washed five times, and in one series of tests the nets were heated. Very high and consistent knockdown and mortality was found in all replicates. There was no significant effect of five washes, although there was some loss after five vigorous hand washes. There was no statistically-significant evidence to support the need to heat the net to restore insecticidal power lost after several hand washes. This study indicates Olyset nets retain their insecticidal power after several washes and are a suitable and cost-effective option to control malaria in endemic areas of Africa.
Impact of Olyset nets against Sandflies, vectors of leishmaniasis Impact of Olyset long lasting nets to control transmission of anthroponotic cutaneous leishmaniasis in central Iran
Motovalli Emami, M et al., 2005
A large scale intervention field trial to control cutaneous leishmaniasis using Olyset nets was conducted in two cities. A total of 8620 individuals were involved in the study. Results showed significant reduction in cutaneous leishmaniasis incidence from 1.6% to 0% in one area and 3.5% to 0.099% in another area, compared to a 6% increase in untreated areas. It is concluded that Olyset nets could provide a high degree of personal protection against this disease; these results account for a 98% reduction in leishmaniasis.
Preliminary Field Testing of a Long-Lasting Insecticide-Treated Hammock Against Anopheles Gambia and Mansonia spp. (Diptera: Culicidae) in West Africa
Journal of Medical Entomology 40 (4), 651-655, 2007
Hammock nets made from Olyset netting were tested alongside traditional mosquito coils in experimental huts in Benin. One hut was used as a control with no treatments. Human volunteers slept in the huts to simulate actual conditions and were crotated to counteract any variations in attractiveness. Tests were conducted over 20 successive weeks. The control hut caught a mean of 27.8 mosquitoes per night. The repellent effect of both coils and Olyset significantly reduced the number of Anopheles mosquitoes entering the huts – 50% reduction with coils and 35% for Olyset. The figures for Mansonia repellency were 59.8% and 39.68% respectively. There was no significant difference between coils and the net for blood feeding inhibition 93-97% or in mortality 88-98%. The authors concluded that using the Olyset nets was much more cost effective and pleasant to use than coils.
Insecticide-treated nets for preventing malaria in pregnancy
In endemic areas, malaria in pregnancy is a major public health problem. It contributes to severe anaemia in the mother and low birth weight for babies, which are associated with poor infant health and early infant death. Also, the unborn child and the pregnant woman may die from malaria in pregnancy. Protection with insecticide-treated bednets (ITNs) during pregnancy is widely advocated, but evidence of their benefit has been inconsistent. This review found five trials of ITNs in pregnant women. The four trials in sub-Saharan Africa compared ITNs with no nets and showed a benefit from ITNs in terms of fewer malaria infections, fewer low birthweight babies, and fewer babies that died before delivery. ITNs have been shown to be beneficial, and should be included in strategies to try to reduce the adverse effects of malaria in pregnant women in endemic areas of the world.
Mosquito net coverage reaches 50% in Kenya
Nationwide distribution of up to 3.5 million insecticide treated nets (ITNs) per year has led to a rapid increase in coverage of vulnerable groups in the malaria endemic provinces of Kenya. By targeting heavily subsidized ITNs to vulnerable groups attending antenatal clinics (ANCs), as well as promoting sales through the commercial sector, coverage has reached 46% of children under five and 50% of pregnant women in three key malaria endemic provinces.
World Malaria Report 2005
This is the first comprehensive report by the Roll Back Malaria Partnership (RBM) on the burden of malaria in the 107 countries and territories at risk of malaria transmission, and on countries’ progress to control the disease.This report from WHO and UNICEF indicates that despite the tremendous challenges which remain, significant progress in the battle against malaria has been made in all malaria-affected regions.
Trends in International Funding for Malaria Control
The Roll Back Malaria (RBM) Partnership commissioned this study to review external resource flows earmarked for malaria and to explore the attitudes of key development agencies to supporting malaria. This work is intended to feed into efforts to mobilize resources. It found that international funding available for malaria increased over the period 1999 to 2004, with a dramatic rise in 2001 as the Global Fund appeared in the picture. The Global Fund made a vast and sudden difference. Given the growing importance of GFATM as a funding source, the uncertainty over its future level of funding brings considerable uncertainty to future malaria funding.