Malaria Matters: Issue 8, August 2000

This issue of Malaria Matters - Featuring Netting News was partially funded by: Siamdutch Mosquito Netting Co., Ltd. They can be reached at:15 Sukhumvit Soi 33 Bangkok 10110 Thailand, Phone: +66-2-258-5621, Fax: +66-2-259-5084, info@siamdutch.com.

"Long Lasting" Impregnation of Mosquito Nets

By Mark Young

At the present time, mosquito nets must be retreated with pyrethroid insecticide approximately every six months (up to 12 months with Deltamethrin and Cyfluthrin), or after 2-3 washes, in order to maintain their effectiveness. When not treated properly with insecticide, the nets are not as effective in the reduction of mortality from malaria. There is even some suggestion that untreated nets may actually increase malaria morbidity by acting as a resting place, waiting for the unsuspecting subject to come out from behind the protective barrier during the nighttime feeding period.

The difficulties encountered in trying to maintain high retreatment levels among net users, particularly in poor, rural areas of malaria-endemic regions such as sub-Saharan Africa, are well known. Many reports have indicated retreatment rates lower than 10% in various ITN projects. More efforts are being made to improve these figures, often using innovative social marketing techniques. The cost to the consumer of 8 to 10 treatments over the 4-5 year life span of a net can be significant, and this cost concern, coupled with relative inaccessibility to regular retreatment, is the reason most often given for not retreating.

The benefits of "Long Lasting" treatment for nets are therefore obvious and this has been under investigation for some time. There are now some promising new products emerging. One of these, the "BILNET", is being marketed by Biotech International Ltd. in India (see article, page 4). The other, called PermaNet™, has been developed by The Vestergaard Frandsen Group and is currently being marketed by them (see picture on page 2). Their newly formulated and patented PermaNet™ impregnation is done on polyester bed nets which fully comply with the specifications and requirements of international aid and health organisations.

PermaNet™ has been tested by an International Reference Laboratory (previously known as Orstrom) according to WHO protocols. Test results show that even after 21 washes the net has a 100% "Knock Down" (KD), which is recognized by WHO as a criteria of good efficiency in terms of protection against malaria. Standardized washing tests have been performed for 20 min at 30°C using high a concentration of soap. See table below.)

Details of test results after 3 minutes exposure of malaria mosquitoes to PermaNet™:

21 WASHES
Total Mosquitoes	KD after 60 min.	% KD after 60 min.	Death Effective After 24 h	Death Functional after 24 h	% Mortality Effective after 24 h	% Mortality Functional after 24 h
20	20	100	18	18	90	90

KD = Knock Down

The results indicate that the PermaNet™ maintains a high level of effectiveness even after more than 20 washes, and therefore these nets can rightly be referred to as having "long lasting" or "lifetime" impregnation. Deltamethrin, a WHOPES (WHO Pesticide Evaluation Scheme) recommended insecticide, is currently being used in the manufacture of these nets.

Another beneficial property of the PermaNet™ is that a dirt-repellent product has been added, making them less adherent to dirt and dust and allowing more time between washings. According to Torben will remain the same as present market prices for pre-impregnated nets, despite having a 5-fold increase in lifetime as indicated in testing. The present testing will continue, and we have no reason to believe that our long life impregnation will not continue to reach even higher peaks of durability. We feel we have (now) passed the time of longevity that you can call "Life Time" Impregnation of Mosquito Bed Nets.

The PermaNet™ comes in various sizes and shapes (both rectangular and conical), with a mesh size of 156/inch2, and is available in deniers of 75 and 100.

For more information about The PermaNet™ contact: Mr. Torben Vestergaard Frandsen
Disease Control Textiles
Vestergaard Frandsen A/S
Akseltorv 4b 6000 Kolding, Denmark
Tel: +45-75-503-050
Fax: +45-75-503-044
Email: TVF@vestergaard-frandsen.dk
Web: www.vestergaard-frandsen.dk

African Summit on "Roll Back Malaria", April 25, 2000 - Abuja, Nigeria

A Major Roll but a Daunting Task for ITN Projects

By Mark Young

The African Summit on Roll Back Malaria was held in Abuja, Nigeria on the 25th of April 2000. It reflected a real convergence of political momentum, institutional synergy and technical consensus on malaria and was attended by senior officials from forty-four of the fifty malaria-affected countries in Africa as well as senior officials from WHO, World Bank, UNICEF, UNDP, UNESCO, USAID, DFID and CIDA. As can be seen here, ITNs played a major role in the discussion and follow-up action.

The African Leaders and Heads of State resolved to initiate appropriate and sustainable action to strengthen health systems to ensure that by the year 2005:

• at least 60% of those suffering from malaria have prompt access to, and are able to correctly use, affordable and appropriate treatment within 24 hours of the onset of symptoms,
• at least 60% of those at risk of malaria, particularly children under five years of age and pregnant women, can benefit from the most suitable combination of personal and community protective measures such as insecticide treated mosquito nets and other interventions which are accessible and affordable to prevent infection and suffering, and
• at least 60% of all pregnant women who are at risk of malaria, especially those in their first pregnancies, have access to chemoprophylaxis or presumptive intermittent treatment.

The Leaders also pledged to reduce or waive taxes and tariffs for mosquito nets and materials, insecticides, anti-malarial drugs and other recommended goods and services that are needed for malaria control strategies; to allocate the resources required for sustained implementation of planned Roll Back Malaria actions; and to commemorate this summit by declaring April 25th each year as African Malaria Day.

The main focus of the new control programme will be bed nets that have been treated with insecticide. A recent Cochrane review found that children who slept under treated bed nets were half as likely to develop malaria as controls.

Malaria accounts for nearly one million deaths each year in Africa, and research has found that the wider availability and use of insecticide treated bednets would result in 50% less malaria illness among children. At present, only about 2% of African children are protected at night with a treated net. The WHO wants a 30-fold increase in the availability of nets in the next five years. It also wants every family at risk of malaria to have immediate access to cheap and effective antimalarial combination therapy, and every pregnant woman in high risk areas to receive drug treatment.

"Roll Back Malaria aims to help African families create a mosquito-free zone in the home, through the use of nets, drapes, or bednets treated with insecticide," said Dr. Awash Teklehaimanot, acting project manager for Roll Back Malaria. "Our goal is to ensure that every person at risk of malaria in Africa is protected with an insecticide-treated bednet within the next five years."

This is indeed an awesome task and a tall order. In real numbers, the pledge of the African Heads of State to make protection available to at least 60% of those at risk means that, over the course of the next 5 years, more than 120 million nets will need to be distributed. Whether or not countries where health systems are already under serious economic burdens can rise to this challenge remains to be seen.

Ending the "Malaria Tax"

Following the declaration of the African Heads of State during the Abuja Summit, the country of Uganda, in their June budget, has completely scrapped taxes and tariffs on mosquito nets and insecticide used for malaria. Last year, Tanzania was the first African country to take action by reducing to 5% the taxes and duty on nets. These actions need to be applauded and encouraged. It is time for other countries to follow the lead of Uganda and Tanzania and take immediate action on the pledges made in Abuja!

High Density Polyethylene (HDPE) Net Use in India

By Shabnam Singhal

Bednet trails in India have shown significant reduction of mosquito bite and malaria incidence in the high malaria prone areas of Assam and Orissa. Although most accepted ITNs are made of polyester fabric, High Density Polyethylene (HDPE) nets are now very common and have high acceptance among low income groups and tribes, where they are the preferred method of protection from mosquitoes due to their low cost. Some of the properties of HDPE nets are:

• Very light in weight.
• Good tensile strength, medium life.
• Available in deniers of 100, 140 and 160.
• Monofilament.
• Dust does not stick to fibers, few washings are needed.
• Good ventilation.
• Low cost (US$ 1.80 to 2.00).

A recent major development in HDPE bednets is the "BILNET", where insecticides like K-Othrine are incorporated into the net, and which can then withstand washing for up to 2-3 years without requiring any further impregnation.

HDPE bednets are now widely used in India in both rural and urban settings. As India is the 2nd most populated country with a low per capita income, cost is of the essence. Teamed with various projects such as "The Orissa Health & Family Welfare Project" designed by Dr. R. Webber of the London School of Hygiene and Tropical Medicine (funded by DFID in collaboration with the Malaria Research Centre of ICMR, CARE India, The Malaria Consortium, and the Orissa State Departments of Health and Family Welfare and Social Welfare), a demand has been established for insecticide treated HDPE mosquito nets in an area of high P. falciparum incidence in rural Orissa. CARE India field staff have generated enthusiasm and interest with the help of Government staff, but their efforts need to be further supported by other NGOs.

A training package and starter kit for the Orissa project was developed by a British Council Project Team. In June 1994, poor predominantly tribal people in rural Orissa could not or would not buy mosquito nets. Within two years, 88.5% of the 5,822 households (total population 28,390) living in the trial area of Jhangira, Keonjhar district, purchased at least one net, at a 67% subsidized price, and treated it themselves. Many of these (1,762) also bought and treated a second net. Total population coverage was approximately 80% with 3-4 people sleeping under each net. Encouraged by the initial results in Orissa, DFID has agreed to formulate a large project that explores cost effective approaches to malaria control using ITNs in great detail, as a contribution to a new National Malaria Control Programme that will receive major funding from the World Bank.

As Roll Back Malaria has the aim of better access to insecticide treated materials, using public/private partnerships to bring down the cost of bednets and encouraging public/private donors to subsidize the provision of nets for those who can not afford them, the most cost effective nets made of HDPE can bring success to this important programme.

For more information contact:
Ms. Shabnam Singhal
Vice President, Marketing
Biotech International Ltd.
Vipps Centre, 2 LSC, Masjid Moth,
Greater Kailash-II, New Delhi-110 048
Tel: 00 91 11 6430 546 / 7
Fax: 00 91 11 6469166 / 6473089
E-mail: ssinghal@biotech-int.com

All the more reason why pregnant women should be using ITNs…!!!

Pregnant women are twice as attractive to malaria carrying mosquitoes as non-pregnant women, according to new research. This added attractiveness is thought to be linked to physiological and behavioural changes, and places pregnant women at greater risk of malaria, an important cause of stillbirths, low birth weight, and early infant mortality. The researchers, who report their findings in the Lancet (2000;355:1972), say that this increased attractiveness is likely to be linked to at least two physiological factors, a greater (21%) volume of exhaled air and warmer (0.7%C) skin surface.

Dr Steve Lindsay of Durham University, one of the study's authors, said: "This study underlines the importance of protection, particularly for women in their first pregnancy. Simple measures can help, such as using bed nets treated with insecticide and checking for lurking mosquitoes inside the net."

Suggested Reading

Risk Assessment of the Use of Deltamethrin on Bednets for the Prevention of Malaria

Report prepared for the Malaria Consortium
By Susan M Barlow and Frank M Sullivan, Consultants in Toxicology, Harrington House, 8 Harrington Road, Brighton, East Sussex BN1 6RE, UK

Risk assessments covering the use of the pyrethroid, deltamethrin, on bednets for the prevention of malaria were conducted and the toxicity of deltamethrin in humans and animals was reviewed, from which no-effect levels (NOELs) have been identified for systemic effects, following both dermal and oral exposure. From this, an Acceptable Exposure Level (AEL) of 10 mg/kg bodyweight/day has been derived for use in the risk assessments in relation to estimated dermal exposures. The NOEL for exposure via the oral route was 1 mg/kg bodyweight/day, with exposures above 1 mg/kg bodyweight/day causing neurotoxic effects in animals. This NOEL has been used to derive margins of safety (margins between predicted exposures and the NOEL). While direct skin contact does not seem to cause systemic toxicity in humans, it can cause burning, numbness and tingling of the skin, which is a local effect.

The risk assessments cover those treating bednets, by immersion in suspensions of deltamethrin, on an intermittent basis (adults and children) or on a regular basis (adults only), the washing of treated nets (adults and children), sleeping under treated nets (infants, children and adults) and the accidental swallowing of a deltamethrin tablet (infants and children). Worst case scenarios for each of these situations show that dermal exposures are low (one-tenth or less of the AEL) and the margins of safety for systemic exposure derived from oral data are acceptable, ranging from 10-3300. Skin sensations are however possible from contact with treated bednets during sleep, and this is borne out by reports of transient skin irritation in people using deltamethrin-treated bednets. Accidentally swallowing or chewing of a tablet of deltamethrin concentrate by an infant or child is regarded as an unlikely event, but if it did occur then toxicity, though not death, is likely.

It is concluded that the use of deltamethrin for the treatment of bednets is acceptable, with most risk scenarios giving large margins of safety. The benefits of the use of treated bednets in reducing morbidity and mortality from malaria are considerable and it can be concluded that the risk benefit ratio is very favourable.

(This Report was commissioned by Population Services International Tanzania, Social Marketing of Insecticide-treated Nets (SMITN) Project funded by the Department for International Development.)

A Literature Review of the Environmental Impact on Aquatic Animal Life of Pyrethroids Used for Mosquito Net Impregnation in Bolivia

Prepared by Jane Briggs for the Malaria Consortium, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
Report for Population Services International (PSI)- Bolivia. "Social Marketing of Insecticide treated materials in Bolivia"

Insecticide treated mosquito nets (ITNs) have been shown to be of benefit in malaria control and significantly reduce overall child morbidity and mortality, however it is known that when ITNs are washed, a certain amount of insecticide is lost from the net into the water. The amount of insecticide lost on washing varies but can be estimated at around 50% loss on first wash. Most bednet projects are in developing countries where domestic activities requiring water, such as washing and laundry, are carried out in local streams. The effect that the lost insecticide may have on the aquatic life could potentially be serious. This review focuses on two of the main pyrethroid insecticides used for net impregnation in the project area, Deltamethrin and Lambdacyhalothrin. The mode of action of pyrethroids as an insecticide is as a neuropoison. Pyrethroids have low mammalian toxicity, but are known to be toxic to fish. Fish are particularly sensitive due to their mode of respiration and the lipophilicity of pyrethroids. However, as pyrethroids are rapidly adsorbed by soil, their degradation to less toxic products by micro-organisms is rapid, so limiting exposure. Fish tend to have similar sensitivities across species to pyrethroids usually less than 10µg/l, although there is a variation in values, both inter and intra species, and the toxicity varies with formulation. Aquatic invertebrates are more sensitive to pyrethroids than fish and have a wider range of sensitivities, crustacea and insecta being the most sensitive.

All studies documenting the toxicity of pyrethroids to fish and other aquatic organisms have been carried out under laboratory conditions, but studies in a real natural aquatic environment are needed as many factors can alter the actual toxicity. Such factors include the rapid flow of water, which will dilute and remove the chemical quickly and the adsorption to soil and sediment. Both of these will limit the resultant exposure of organisms to only short periods and it is therefore unlikely that concentrations would reach the toxic values documented. In densely populated areas near to slower moving streams, if many nets were washed for the first time, it is possible that these concentrations could be high enough to cause toxic effects on the water life. However, it seems from the current evidence that the long term aquatic impact of pyrethroids resulting from bednet washing is negligible, as any possible effect is probably transient and the aquatic life likely to recover after cessation of exposure. In the absence of any conclusive studies on the effect of washing ITNs in small streams, ponds and rivers, further research is necessary.

The following recommendations for future activities are made:

• survey of users of insecticide-impregnated bednets and the effects seen on aquatic life following washing of ITNs,
• observational study at the project site on net washing practices and the effects on stream life,
• study of the effects on test fish, enclosed in, for example, a basket, in a natural stream exposed to the washing of several impregnated bednets,
• chemical analysis of the resulting concentrations of Deltamethrin and/or Lambdacyhalothrin in the streams in the project area,
• if there is clear evidence for the toxicity resulting from net washing, an effective IEC programme to advocate proper disposal, and monitor the progress of wash resistant long lasting nets.

Both of these reports, and further information concerning them, can be obtained from:
The Malaria Consortium
c/o London School of Hygiene and Tropical Medicine
Keppel Street London WC1E 7HT UK
E-mail: s.meek@lshtm.ac.uk