Olyset Net

Sumitomo Chemical’s Olyset Net has revolutionized the global fight against malaria. Protecting nearly 800 million people since it received WHO recommendation in 2002; the highly durable and award-winning LLIN (long lasting insecticidal net) uses hybrid polymer and controlled insecticide release technology to repel, kill and prevent mosquitos from biting for up to five years.

The pyrethroid insecticide permethrin was chosen after decades of successful use in public health applications, including everyday medically-approved hair and skin-care products such as head lice lotion and shampoo. As safe as it is powerful, Olyset Net poses minimal toxic risk to adults and young children. It is a long-lasting and wash-proof; surviving challenging conditions throughout the world thanks to its tough polyethylene fibres.


Malaria and Dengue Transmission 2013

Malaria and Dengue Transmission 2013

Data Source: This map is reproduced with acknowledgment to World Health Organization. Dengue, countries or areas at risk, 2011 by World Health Organization ©WHO 2012. All Rights Reserved.

Field Data/Biological

Wash Proof Tests on Olyset Nets

Olyset Nets have passed the >20 washes test required by the World Health Organisation (WHO) to be designated an LLIN:

Ref : Jeyalakshmi .J. & Rhanmugasundaram R., International Institute of Biotechnology and Toxicology, Tamilnadu, India

Wash Proof Tests on Olyset Nets

Biological Tests on Olyset Nets

Field tests have estimated that Olyset Nets are guaranteed for at least five years. Nets in Tanzania were tested after seven years of normal use in the field and still contained significant levels of permethrin, with contact tests causing an average of 92% mosquito knockdown.

Ref : Tami et al., Malaria Journal 2004, 3:19

Biological Tests on Olyset Nets

Impact of Olyset Nets on Vectors

Human bait catches of mosquitoes over five months in two villages that had Olyset Nets showed dramatic reductions in the numbers of mosquitoes caught.

Ref :Chheang & Sandy., National Malaria Centre, Cambodia, 1994

Impact of Olyset Nets on Vectors

Impact of Olyset Net on Disease

Olyset Net is proven to significantly reduce the cases of malaria and other insect-born diseases. A trial in Cambodia showed enormous reductions in all three measures of malaria between July-December 1993 and July-December 1994.

In Tanzania, a trial comparing one year pre-intervention and one year post-intervention using Olyset Nets in three villages reduced malaria parasite rates (APR) by ~80% and parasite densities (MPD) by ~40% in blood samples taken from children aged 0-9 years.

Ref : Chheang & Sandy., National Malaria Centre, Cambodia, 1994

Impact of Olyset Net on Disease

Research & Reports

M. Soleimani-Ahmadia, H. Vatandoosta, M. Shaeghia, A. Raeisic, F. Abedib, M.R. Eshraghiana, A. Madanib, R. Safari, M.A. Oshaghia, M. Abtahia, H. Hajjarane

Acta Tropica 123 (2012) 146– 153

In the Olyset net study area, there was a significant reduction of 41.1%, 54.4%, 59.39% and 64.1% in the indoor-resting density of A. culicifacies, A. stephensi, A. dthali and A. superpictus, respectively, with an overall reduction of 39.3% in total mosquitoes in comparison with untreated net area. A significant reduction was also observed in human blood index of vector species in the Olyset net villages. Bioefficacy test results of Olyset nets showed that the median knockdown time was 1.48 and 3.25 min, while the average mortality rate was 100% and 72.3% ± 7.07 in baseline and after 1 year of intervention, respec-tively. The average permethrin content reached to 68.31% (683.1 mg/m2) of the initial insecticide dose of 937 ± 21.69 mg/m2 (nearly 1000 mg/m2) at the end of intervention.

Malaria incidence was reduced by 96.6% and 64.8% in the village with Olyset nets and in the villages with untreated nets, respectively. During intervention period, there was a reduction of 93.2% in malaria incidence in Olyset net area as compared to the untreated area.

Field evaluation of permethrin long-lasting insecticide treated nets (Olyset™) for malaria control in an endemic area, southeast of Iran

Invest, John

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.

Olyset LLIN contribution towards malaria control, Invest 2008

Robert C Malima1, Stephen M Magesa1, Patrick K Tungu1, Victor Mwingira11, Frank S Magogo1, Wema Sudi1, Frank W Mosha2, Christopher F Curtis3, Caroline Maxwell1,3 and Mark Rowland3

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.

  1. National Institute for Medical Research, Amani Medical Research Centre, P.O. Box 81, Muheza, Tanzania
  2. Kilimanjaro Christian Medical Centre, P.O. Box 2228, Moshi, Tanzania
  3. London School of Hygiene and Tropical Medicine, WC1E 7HT, London, UK

An experimental hut evaluation of Olyset® nets against anopheline after seven years use in Tanzanian villages

Sreehari, et al., Olyset nets for Malaria Control 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.

Study of Olyset® Nets on malaria transmission in India, 2007

Ansari, M.A. et al., 2006

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.

Olyset Bio-efficacy Study-India 2006

Jeyalakshmi, T., et al., 2006

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.

Olyset vs conventional nets_2006

Tami, A., et al. 2004

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.

Olyset Efficacy after 7 years – Tanzania 2004

Erlanger, T.E. et al., 2004

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.

ITN Field Issues_200

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.

Uganda doubleblind study_2001

O.Faye, L.Konate, O.Gaye, D.Fontenille, N.Sy, A.Diop, M.Diagne, J-F. Molez.

Med.Top. 1998. 58, 355-360


The efficacy of permethrin treated bednets was evaluated in Wassadou, a hyper endemic village located in the Sudanese grasslands of Southeast Senegal. Pre-treatment data were collected between 1992 and 1993. Bed nets were distributed to the whole population in June 1995 and impact of their use on vector populations and malaria transmission was evaluated until November 1995.This period corresponds to the rainy season during which malaria transmission is highest. Data were compared with a control village in which bed nets were not distributed. Findings showed that use of bednets lead to a sharp decrease in the density of vector population and malaria transmission. The number of bites by Anopheles gambiae S.L. decreased 69%. The density of blood fed and pregnant females inside dwellings decreased 91 and 96% respectively. The sporozoite index of females captured on the skin decreased 76% and the daily rate of entomological inoculation decreased 88%. This impact was not great enough to eliminate the risk of infection. Prolonged study over a period of 4 to 5 years is needed to evaluate the impact of long-term use of insecticide treated bednets on vector populations and malaria transmission.

Impact of the use of permethrin-impregnated mosquito nets on malaria transmission in a hyper-endemic village in Senegal.

Vythilingam, I., et al., 1996

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.

Assessment Study

Yeang Chheang & Lek Sandy, 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
  • Odourless
  • 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.

Cambodia Paper

Malaria National Program of Ecuador (SNEM).

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.

Ecuador Paper

Thesis submitted for award of MSC.
London School of Hygiene and Tropical Medicine London UK.

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.

Magoma Thesis

Motovalli Emami, M et al., 2005

World Health Organization, Eastern Mediterranean Region, Final Technical Report, Project SGS04-76

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.

WHO Sandfly Study – Iran

Hougard, J-M, et al.

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.

Hougard-Impregnated Hammocks

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.

Cochrane Review_2006

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.

Kenya study

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.


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.


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