This issue of Malaria Matters - Featuring Netting News was funded by PermaNet. They can be reached at: Vestergaard Frandsen A/S, Disease Control Textiles, Haderslevvej 36, DK-6000, Kolding, Denmark. Tel. +45 75 50 30 50, Fax: +45 75 50 30 44, email: sales@vestergaard-frandsen.dk, www.permanet.dk.

Update on Long Lasting Insecticidal Nets

By Dr. Pierre Guillet

Why Do We Need LLINs?

The treatment and retreatment rates of nets achieved so far in most ITN programmes, especially in Africa, have been very low. Three main approaches are now considered to ensure proper treatment and re-treatment of nets: 1) bundling of one insecticide treatment kit with one untreated net, 2) free re-treatment services and 3) introduction of long lasting insecticidal nets (LLINs). LLINs are ready-to-use factory pre-treated nets, which do not require further treatment during their expected life span (average 4 to 5 years).

How Are LLINs Treated?

Insecticide is either bound to netting fibres (Type 1) or is incorporated into polymers before fibre extrusion (Type 2). Insecticide bound around fibres is generally more exposed to degradation or physical removal than insecticide incorporated within fibres.

Generally in Type 1 LLINs, insecticide is mixed in a resin which coats the netting fibres. These nets can be washed many times, and will remain effective until insecticide concentrations fall below a critical threshold. Performances of Type 1 LLINs are expressed by the minimum number of standard washings the treatment can resist.

In Type 2 LLINs, insecticide, which is incorporated into polymers, has to migrate to the surface of the fibre to be active against mosquitoes. These nets, if repeatedly washed, may temporarily loose their efficacy until enough insecticide has re-migrated to the surface. In practice, insecticide concentration remains high enough since nets are not repeatedly washed within short intervals. Performances of Type 2 LLINs may be expressed in terms of wash resistance but specifications are based on the rate of insecticide migration.

In both types, enough insecticide has to be available at any time at the surface of the fibres to provide the expected biological efficacy during the entire life span of the nets.

How Are LLINs Tested?

LLINs are tested through the WHO Pesticide Evaluation Scheme (WHOPES). The testing, carried out by WHO Collaborating Centres, consists of investigations on the dynamics of the insecticide and accelerated wash resistance laboratory and field-testing. Since detergents and washing conditions are extremely variable, wash resistance of LLINs can only be assessed through fully standardized washings and testing procedures. In the absence of such procedures, different laboratories testing the same product have obtained variable results in the past. WHOPES evaluation usually requires between 1 and 2 years before provisional recommendations are made. These recommendations are revisited after 4 to 5 years once enough evidence has been gathered on the effective life duration of LLINs under programme conditions, following which final recommendations are proposed. In this way, WHO can only make recommendations for products which have been submitted to WHOPES and independently tested.

Which LLIN is Currently Recommended by WHO?

At the moment, only Olyset® has been recommended by WHO (report available on WHOPES website )

Olyset is wide mesh netting made of high-density polyethylene monofilament yarn with 2% w/w permethrin incorporated. Biological efficacy of Olyset is maintained for at least 4 to 5 years under field situations. It is available in rectangular shape, blue or white in colour. Green will soon be available. (Please see page 8 for WHO interim specifications for Olyset permethrin incorporated mosquito net.)

Which Product is Currently Being Tested by WHO?

Only one product, PermaNet®, is currently being tested by WHO. It was first submitted to WHOPES in 2001. PermaNet is a Type 1 polyester net treated with 50 mg/m2 deltamethrin (in contrast with 25 mg/m2 for conventional dipping). From several laboratory and field trials, variable results were obtained with a wide range of initial insecticide concentrations. The company claimed to have improved the manufacturing processes, and has recently submitted a new "generation" (PermaNet2) in early 2003 to WHOPES. Detailed specifications for PermaNet2 (including insecticide content and wash resistance) as well as standard operating procedures have been developed by the company for quality control. It is expected that PermaNet2 results will be reviewed in December 2003 and WHO recommendations made accordingly.

A number of other products and processes are currently under development, including incorporation of insecticide into polyester fibres. However, little is known about these products and none has yet been submitted to WHOPES for testing.

Practical Advice on Procurement and Use of LLINs

When purchasing nets, national programmes should systematically select LLINs already recommended by WHO. Olyset availability has so far been limited but production capacity has recently been increased to 132,000 nets/month. Olyset will soon be produced in Tanzania (35,000/month in August 2003 to 125,000/month in 2004), increasing the overall production capacity. It is anticipated that in the very near future, all LLINs including Olyset would cost not more than $US5 per net.

It is expected that LLINs will rapidly penetrate the market. However, national programmes or NGOs which are not able to access Olyset are advised for the time being, to order untreated nets with insecticide bundled and to provide free re-treatment services. Programmes which have already purchased products other than Olyset and do not have the capacity to monitor efficacy or insecticide content of these nets, are advised to ensure regular retreatment as for conventionally treated nets.

The situation will soon improve when large quantities of LLINs recommended by WHO will be available on the market. A private public partnership and a business plan are being developed to facilitate the transfer of LLIN technologies to net manufacturers in Africa. WHO provides technical information and regular updating on LLINs through the RBM website (technical strategies, vector control, insecticide treated materials), as well as specific advice on procurement and use of LLINs (contact: rbm@who.int).

Dr. Pierre Guillet, Parasitic Diseases & Vector Control, Communicable Diseases Control, Prevention & Eradication, WHO, 20 Avenue Appia, CH-1211 Geneva 27, Switzerland

Malaria Control in Emergencies: IRS, ITNs and LLITNs

By Richard Allan, Matthew Burns, Caroline Lynch, Mikkel Vestergaard Frandsen

Background

Over 180 million people in Africa alone are living in countries affected by conflict, where infrastructure breakdown, destitution, poor access to effective health care and basic food supplies have become the norm and where ongoing insecurity prevents economic recovery or meaningful development. These crisis-affected populations are amongst the most vulnerable in the world. In these situations disease and malnutrition thrive, usually killing more people than war injuries^_1.

The five most important causes of death normally associated with emergencies are in fact the same as in non-emergency situations in most developing countries; malaria, pneumonia, diarrhoeal diseases, measles and malnutrition. However, in emergencies mortality and morbidity rates due to these diseases often rise significantly. Often malaria causes death and suffering long after the initial crisis is over. Over 30% of the worlds malaria deaths occur in areas of long term crisis. Ready to use, available and context specific effective malaria control tools are essential to improving humanitarian response capacity and reaching the RBM partnership goal of halving malaria amongst the world´s most vulnerable populations.

Insecticide Treated Nets - a reality check

Many man made emergencies last several years, even decades in some cases. Where security allows access and community relations to be built up effectively insecticide treated materials such as nets are considered more suitable and can be more cost effective than repeated insecticide residual spraying (IRS). ITNs have been widely evaluated by international groups and there is no doubt that used correctly, these can be highly effective in providing personal protection from malaria. However, despite the efficacy of ITNs for malaria protection, plus increasing commercial availability of ITNs, coverage remains below 5% in many malaria endemic countries. In most crisis-affected countries ITN coverage is lower still.

Washing removes the insecticide of nets that have been treated by a simple dipping process. The insecticidal residual efficacy of conventionally dipped nets varies according to the insecticide used, the netting materials, the number of washes and use of soap and abrasives. In real life situations this may be as little as three months, or as much as 6-10 months, but rarely longer. Retreatment of ITNs with insecticide every three to ten months is required to remain effective, however retreatment rates for ITNs rarely exceed 25% on a regular basis. Untreated nets are approximately 75% less protective against malaria. In emergencies, insecurity often severely restricts access to (or for) affected communities. With communities fleeing conflict there may be only one point of contact before they flee again. This can make this tool an expensive short-term option.

Long Lasting Insecticidal Nets

At least two new technical approaches to treating polyester (PermaNet) and polyethylene (Olyset) with insecticide at an early stage of net production have been developed by commercial partners and both offer longer insecticide residual life than standard dipped nets^_2, and development is ongoing to extend the effective life span. Long lasting ITNs that remove the need for insecticide retreatment every few months in the field is the clear objective for responsible manufacturers, emergency programme managers and the end users. Long lasting ITNs (LLITNs) that achieve an effective residual insecticide life of several years will clearly make this important tool far more acceptable and effective in both relevant emergency and stable situations.

Fresh ideas and hope for displaced communities

ITNs have clear applications and clear limitations within emergency and stable situations. For example, mass population displacement into temporary camps presents major logistical and cost challenges that are particular to this emergency setting. ITN programmes in these circumstances often suffer low retention, very high ITN resale problems, and very low retreatment rates (where conventional nets are distributed). Both these settings need new solutions.

New innovative RBM partnerships formed in recent years between responsible public sector agencies involved in emergencies and private sector groups aim to jointly develop context specific tools designed to meet some of these needs. The first of these significant new tools development partnerships is focused on the fast track development of insecticide treated plastic sheeting (ITPS) for provision of refugee shelters combined with effective malaria control in complex emergencies.

Vestergaard Frandsen, a key commercial partner, has built the first of these tools. Danish and French WHO laboratory partners conducted phase I tests and the London School of Tropical Hygiene and Medicine conducted the Phase II experimental evaluation. Today the Johns Hopkins MENTOR Initiative with UNHCR is conducting the full scale Phase III real life evaluation in emergency settings with field partners in West Africa to inform policy development for shelter and health emergency agencies.

This important new tool is likely to address the key shelter and malaria control constraints faced by emergency partners supporting displaced populations. By making a dual purpose tool that is context specific and meets both technical and operational requirements (protection from weather and malaria) significant time and cost savings should be realised.

Conclusion

These are exciting times. The opportunity for rolling back malaria amongst the most severely affected populations in the world today has never been greater, despite the enormous constraints that partners face in complex emergencies. Political commitment and support for country level action is essential but these country partnerships must be supported with effective tools, funding and field level practical technical support if the RBM Partnership are to turn rhetoric into lives saved.

Richard Allan is the Director of the new RBM MENTOR Initiative launched in October 2002, as part of the Johns Hopkins School of Public Health, Centre for International Emergency, Disaster, and Refugee Studies. Richard was the RBM Secretariat complex emergencies co-ordinator from April 200 - October 2002.

Matthew Burns is the Operational Research Manager - MENTOR Initiative Sierra Leone.

Caroline Lynch is the Country Manager - MENTOR Initiative Liberia.

Mikkel Vestergaard Frandsen is the Chief Executive Officer of the Vestergaard Frandsen Group, a company specialised in disease control textiles.

Country report - Malaria and insecticide treated nets in Cambodia

By Sean Hewitt

Cambodia is renowned as one of the world´s malaria hotspots. Multi-drug resistant parasites, inaccessible communities and mosquitoes adept at avoiding insecticides come together to produce a very complex malaria situation. In addition there are numerous different ethnic groups living in forest and forest fringe areas of the country and this remarkable diversity adds considerably to the problem of malaria control as customs relating to living, farming and health practices often vary markedly from one village to the next.

Cambodia´s malaria profile

Cambodia has a total area of 180,000 km2 and a population of 11.8 million. Forest and jungle cover sixty-two per cent of its landmass and these areas provide ideal breeding sites for Anopheles dirus and Anopheles minimus, the principal vector mosquitoes in the region.

An estimated 2,000,000 people are at risk of malaria and 500,000 of these live in the high transmission forest areas. These areas are sparsely populated with an average of just 5 inhabitants per square kilometer (compared to 132 inhabitants per square kilometer in non-malarious central areas of the country). Malaria is a leading cause of mortality and morbidity in Cambodia. It is currently the third most common cause of outpatient attendance (accounting for 4.6% of patients), the principal cause of hospitalization (accounting for 13.7% of inpatients) and the leading cause of hospital mortality (accounting for 23.1% of deaths). It is also a key contributor to anaemia, complications during pregnancy, low-birth weight and poor child growth. Multi-drug resistant strains of falciparum are widespread.

Cambodia: at high risk of malaria

There are four main categories of people affected by malaria; the epidemiology of the disease varies between groups.

Ethnic minority groups. These traditional forest inhabitants live mainly in the northeastern part of Cambodia, concentrated in the provinces of Ratanakiri and Mondulkiri. All age groups are exposed seasonally to long periods of intense transmission. Adults are usually partially immune but children and pregnant women are extremely vulnerable. Malaria mortality data do not exist but the numbers of malaria related deaths in these communities are undoubtedly high. In some villages one in four children do not reach their fifth birthday, and about 50% of these deaths are likely malaria related.

Forest fringe inhabitants. Rice growing communities are situated close to the forest. Villagers (predominantly young men) make frequent overnight visits to the forest to hunt and to collect construction wood and other products, frequently getting infected with malaria. Returning to the village with malaria can spread malaria to anopheles mosquitoes breeding in and around the rice fields. Although these species are less efficient vectors of malaria than the forest mosquito, limited local transmission can occur. All age groups are therefore at risk but the majority of cases are found in adult males.

Temporary migrants.People working in the forest for extended periods such as gem miners, loggers, sandal wood collectors and soldiers are at high risk of contracting malaria. Most are adult males. Some come from villages near the forest and have previous malaria exposure, but many come seeking seasonal work from far away, from non-malarious regions, and have little or no immunity to malaria. Most attend health facilities close to the forest where they work but many also seek treatment when they return to their homes.

New forest settlers. Families who, for economic or political reasons, relocate to forested areas to establish farms are initially at high risk of contracting malaria. Their immunity is usually low. Malaria transmission diminishes with continued development and deforestation of the settled area.

These four different situations require different malaria control strategies, adapted to risk group behavior, local health infrastructure and environmental conditions. The aim is to increase the cost-effectiveness of malaria control activities without significantly increasing the demand for resources.

The current situation

The capacity of the National Malaria Centre (CNM) and the effectiveness of the National Malaria Control Programme have grown remarkably in recent years. There has been a steady reduction in the severe case fatality rate, reflecting improvements in patient care in public health facilities. There has also been a steady decline in the number of cases reported since the 1995 peak. Improved malaria prevention and control activities (based on Artemisinin-based combination therapy and distribution of heavily subsidized ITNs) have undoubtedly played a major part. CNM started to distribute ITNs in the late 1990's with WHO and WB funds and in collaboration with NGOs. Between 1998 and 2001 the CNM distributed 795,000 ITNs and 64,400 litres of K-Othrine. The average cost per unit was US$2.03 (based on US$2.10 for family sized net and US$1.70 for a single). Other positive developments include a number of social and political changes that have reduced human exposure to mosquitoes. Increased political stability resulting in a reduction in military activities in forested areas, a government enforced ban on illegal logging greatly reducing the numbers of people venturing into forests to collect timber, and major population displacements and resettlement in forested areas have all but ceased.

Nevertheless, morbidity and mortality remain unacceptably high with approximately 400,000 cases and 1,000 to 2,000 deaths each year, and efforts are continuing to bring the disease under tighter control, including increased use of ITNs.

Sean Hewitt. MSc, PhD, is a freelance vector borne disease control specialist. He has had extensive project management experience, working on dengue control in the Caribbean, leishmaniasis control in Afghanistan and malaria control in Pakistan, Afghanistan, Vietnam and Cambodia. His special interests are appropriate technology for vector borne disease control, operational research & development, and improved targeting of control activities.

Country report - Pyrethroid Impregnated Mosquito Nets for Malaria Control in North-Eastern India: a Success Story

By Vas Dev

Malaria has emerged as a major public health problem in the northeastern states of India and continues to impair the socio-economic development of the region. Over 70% of malaria infections are due to P. falciparum, and the remaining are P. vivax cases. Malaria outbreaks are frequent, especially in forest fringe areas along Inter-State and Inter-country borders under the influence of An. Minimus, a highly anthropophagic species, and thus an efficient transmitter of the malaria parasite. Despite anti-malaria measures taken under the National Anti-Malaria Programme (NAMP) of the Government of India, it is increasingly evident that malaria control requires a more skilled and integrated approach, based on local understanding of disease epidemiology, with community-based and self-sustaining intervention strategies.

In this context, insecticide treated nets (ITNs) were field evaluated against An. minimus transmitted malaria in endemic villages of Kamrup district (Dimoria Block) in the Brahmputra valley of Assam. There was over 70% decline in number of P. falciparum cases over a 2-year study period with concomitant decline in man/vector contact. The success of this project led the Government of India to launch a pilot project in all seven sister states of the north-east to test its operational feasibility, acceptability and sustainability as a strategy for malaria control. One hundred thousand mosquito nets treated with synthetic pyrethroid were freely distributed in different ethnic groups in all seven states of the region through The Primary Health Care system. In concordance with our earlier findings, there was a drastic reduction in malaria episodes as recorded by respective State Health Directorate along with collateral benefits, namely, freedom from head lice, bedbugs, and decreased nuisance due to other household pests. Community response was overwhelmingly positive, and additional demands are being generated by the respective State Health Directorate to cover additional vulnerable population groups under ITNs (now popularly know as medicated nets).

In keeping with the popular demand, one million additional medicated mosquito nets are proposed to be distributed under The World Bank assisted Enhanced Malaria Control Project in malaria outbreak prone areas of northeastern states, and more are in the offing. Thus, the use of Insecticide Treated Nets is being viewed as the main intervention strategy against malaria in the region in lieu of DDT residual house spraying. The treated nets are markedly better than the plain nets (untreated nets) as they ensure protection even if the net is torn or not properly tucked in. Further, these even confer mass effect in reducing vector populations and infectivity when used by the community as a whole, thus providing some protection even to those who do not sleep under nets.

The insecticides used for treating nets are synthetic pyrethroids - Cyfluthrin (Solfac 5% EW), Deltamethrin (2.5% flow), duly approved by the World Health Organization Pesticide Evaluation Scheme (WHOPES) for use in public health. These are colorless, odorless, less flammable, and are easy to transport and store. They are easily found on the public market and cost of treatment per net may vary between Rs. 20 to 25 ($US0.42 to 0.53) at the prevailing market prices.

The treatment procedure is simple and can be done with the aid of step-wise illustrated instructions available with the supplier or provided with a do-it-yourself kit.

There is a further scope of promoting this alternate strategy as it is simple, cost-effective, appropriate, sustainable and involves communities. The role of voluntary organizations is of paramount importance to reach the "unreachable" (isolated population groups), for increasing awareness of malaria and its prevention, and for enhanced coverage and compliance. It is projected that ITNs will be the main means for vector control, and to check the spread of multi-drug resistant malaria.

Vas Dev is the Officer-in-Charge of Malaria Research Centre (MRC) at Sonapur, Assam, India. MRC conducts research on malaria to support epidemiological and operational activities under the National Anti-Malaria Programme of the Governmentt of India

Permethrin-Incorporated Mosquito Net (NI) Interim Specification WHO/IS/NI/331/2002

1	Description
	The material shall consist of netting, formed from high density polyethylene mono-filament fibres, incorporating technical permethrin complying with WHO specification WHO/SIT/28, together with any necessary stabilizers, plasticizers and other formulants. The material shall be suitable for use as a long lasting insecticidal mosquito net.
2	Active Ingredient
	2.1	Identity tests (Note 1) The active ingredient shall comply with an identity test and, where the identity remains in doubt, shall comply at least one additional test.
	2.2	Total permethrin content The permethrin content shall be 20g/kg and, when determined by the method described in Note 1, the average content shall not differ by more than 3g/kg.
	2.3	1RS,3RS (cis) isomer percentage The 1RS/3RS (cis-) isomer percentage, when determined by the method described in Note 1, shall be in the range 35% to 45%.
	2.4	Permethrin initial surface concentration The initial surface amount of permethrin on the yarn, determined by the method described in Note 2, shall be not less than 500 µg/g of netting.
	2.5	Permethrin release index (bleeding speed index) The permethrin release index from the yarn, when determined by the method described in Note 2, shall be within the range 0.1 to 0.3.
3	Physical properties
	3.1	Fibre characteristics The fibres shall be of high density polyethylene mono-filament (Note 3) with a melt index of 0.9-1.1 g/10 min (ISO 1833-1997).
	3.2	Netting mesh size The netting shall have a minimum of 56 complete holes/inch2.
	3.3	Dimensional stability of netting to washing Dimensional stability (length and width): 10% of initial dimension (ISO 5077-1984).
	3.4	Mass per m2 of net Mass/m2: 50 5 g/m2 (ISO3801-1977).
	3.5	Bursting strength Minimum bursting strength: 350 Kpa (ISO 13938-1-1999).
4	Storage stability
	4.1	Stability at elevated temperature (MT 46.3, CIPAC J, pp. 128-130) After storage at 54 2 oC for 2 weeks, the total permethrin content (Note 1) shall not be lower than 95% relative to the determined average content found before storage (Note 5) and the netting must continue to comply with the clauses for isomer ratio (2.3), dimensional stability (3.3), and bursting strength (3.5). The initial surface concentration of permethrin (2.4) shall be not more than 2.5 times the value found before storage, whereas the permethrin release index (2.5) shall be not less than half the value found before storage (Note 2).
For the complete specification including notes, go to the WHOPES website.

Footnotes

1. International Rescue Committee & Centers for Disease Control (Atlanta); Mortality Survey - EDRC, May 2000.

2. WHOPES 2002 update on LL-ITNs.