Malaria Matters: Issue 13, September 2004

This issue of Malaria Matters - Featuring Netting News was funded by Bayer Environmental Science. They can be reached at: Bayer Environmental Science S.A., 16 rue Jean-Marie Leclair, CP 106, 69266 Lyon (Cedex 09) France. Tel: 33 (0) 4 72 85 46 86, Fax : 33 (0) 4 72 85 46 32, email gerhard.hesse@bayercropscience.com, www.bayercropscience.com.

Considerations for the use of insecticide-treated mosquito nets in complex emergencies

By Jan Kolaczinski, PhD and Kate Graham, MSc

Insecticide-treated nets (ITNs) have become the favoured vector control tool for malaria and other vector-borne diseases, such as leishmaniasis. Present ITN implementation ranges from humanitarian emergency relief to use as a component of national malaria control programmes in stable situations. Data on effectiveness, i.e. reduction of malaria morbidity and mortality, under emergency field conditions are limited. Where it has been studied, for example in eastern Afghanistan, ITN users are at significantly lower risk of being infected with malaria, when compared to non-users.

Whether ITNs are a suitable tool for implementation during a complex emergency is determined by various factors. Differentiation between the different emergency phases is necessary. A complex emergency has an early, acute phase that may quickly be followed by a transitional phase towards development (e.g. East Timor). In some cases, the acute phase is followed by some stabilisation, but continuation of conflict and absence of clear development initiatives (e.g. Afghanistan before 2001), is referred to as a chronic phase (Box 1). Changes between phases can be rapid, with the situation either improving or deteriorating.

Generalised characteristics of the main phases of complex emergencies

Acute phase

• Crude mortality > 1 death per 10,000 per day
• Flimsy and temporary shelters with high concentrations of people
• Attention focused on emergency healthcare, delivery of food, blankets and shelter materials
• Inadequate health care facilities and high patient case loads
• Unpredictable security
• Limited inter-agency co-ordination
• Relatively large amounts of short-term funding (6-12 months)
• Short-term vision of implementation
• Strong presence of NGOs with expertise in emergency situations

Chronic phase

• Crude mortality < 1 death per 10,000 per day
• Some areas of a country may remain in the acute phase, others move towards post-emergency
• More stable and permanent housing structures
• Improved security
• Improved inter-agency co-ordination
• Improved healthcare provision
• Increasing presence of NGOs with development expertise

The inherent advantages and disadvantages of ITNs (Box 2) also need to be considered, to decide if ITNs are appropriate in the given context and what strategy should be used for implementation.

Box 2: Some operational considerations for deployment of ITNs
Advantage	Disadvantage
Physical barrier of net protects from host-seeking blood-sucking insects, as well as other insects, snakes, etc.	Physical barrier breaks down if net has holes or is not properly tucked-in. People not sleeping under nets are not protected. People need to be taught how best to use the nets.
Pyrethroid insecticide impregnation provides additional, chemical barrier, due to repellent and killing effect	Conventionally treated nets need to be re-treated at least once per year. Health education is required to create awareness for re-treatment need. Some expertise is required to ensure safe handling of insecticides and correct impregnation. [WHO endorsed long-lasting insecticide treated nets (LLIN) do not have this disadvantage, as they are pre-treated during manufacture].
Nets are "flexible", i.e. can be moved with the owner (e.g. returning refugees), or used as curtains / door hangings when not hung over bed (e.g. cool winter months)	Due to "flexibility" net can be easily sold, if owner is not aware of the health benefit and/or is in urgent need of money, and can be easily stolen if security is poor.
	Might require behavioural change if people are not used to them.
	Net and insecticide need to be ordered and delivered, which may take several months. Alternatively they need to be stock-piled.

 

Delivery of ITNs during the acute phase

The acute phase requires rapid delivery of emergency relief to people at risk that often have no housing, food, access to medical care or financial resources. To implement an ITN campaign the only feasible and acceptable strategy is rapid and free distribution of nets. The following problems may be encountered:

• Large quantities of nets (and insecticide if conventionally treated nets are used) are needed. Ordering and delivery of these can take months. If stockpiles are available, delivery of these to the people at risk can be problematic, due to lack of logistics and security.
• A population unfamiliar with ITNs may not use them effectively unless distribution is accompanied by basic health education.
• The skills and time to prepare and implement a health education campaign are not available.
• For people living in tents or under tarpaulins erection of nets is more problematic than for those living inside permanent structures. There may not be enough space or possibilities to support a net.

In view of the above limitations it is questionable whether ITNs will greatly contribute to malaria control during the acute phase. Resources are likely to be more effective when focused on rapid diagnosis of cases and adequate treatment.

If it is possible to obtain and distribute ITNs rapidly, limiting the distribution to biologically vulnerable groups (e.g. pregnant women and young children), and accompanying this with at least basic health education, can be an appropriate use of resources (in addition to diagnosis and treatment). Targeting of socio-economically vulnerable groups is generally not appropriate at this stage. Implementing partners should judge their operational success based on the coverage of target groups, rather than solely on the number of ITNs delivered.

Delivery of ITNs during the chronic phase

As an emergency is drawn out and becomes chronic, donor funding tends to decrease. This context requires longer-term malaria control strategies that should preferably be designed with the possibility of future contribution to a developmental approach and a national strategy. At the very least, strategies that would impact detrimentally on future national policy should not be entertained. At the same time, approaches need to remain flexible, as the chronic phase may deteriorate again into an acute one and as infrastructure and institutional capacity is limited. It is, therefore, vital to introduce locally adapted, sustainable interventions that encourage self-reliance and do not depend on vertical programmes.

In this more stable, chronic environment where people begin to build more permanent housing and return to methods of income generating, ITNs become more suitable. By this stage procurement of nets should have been possible and with the initial high mortality rate under control, it is realistic to start concentrating on the establishment of distribution mechanisms and the development and delivery of health education messages. Untargeted distribution of free nets at this stage is detrimental to the development of a national ITN programme, which must be able to survive the post-emergency period of donor fatigue and finally donor withdrawal. Cost-recovery for ITNs should be introduced and be combined with targeting of subsidies to biologically and economically vulnerable groups.

Implementing partners can start to judge their operational success more reliably. Collection of simple effectiveness data may be possible by recording case-control data of ITN use at treatment points.

Important contributions towards the implementation of ITNs in complex emergencies are: I) The ongoing development of long-lasting insecticide-treated nets Long Lasting Insecticidal Net (LLIN), to avoid the problem of annual re-treatment and the follow-up of a transient population for this purpose; and II) The soon to be finalised RBM Handbook for Malaria Control in Complex Emergencies (www.rbm.who.int/), providing practical advice to implementing partners with limited malaria specific expertise.

Selected Further Reading

• Howard N, Chandramohan D, Freeman T, Shafi A, Rafi M, Enayatullah S and Rowland M. 2003. Socio-economic factors associated with the purchasing of insecticide-treated nets in Afghanistan and their implications for social marketing. Tropical Medicine and International Health 8, 1043-1050.
• Meek S, Rowland M and Connolly M. 2000. Outline strategy for malaria control in complex emergencies (MS Word file). World Health Organisation, Geneva, WHO/CDS/RBM/2000.22
• Rowland M. 1999. Malaria Control: bednets or spraying? Transactions of the Royal Society of Tropical Medicine and Hygiene 93, 458-459
• Rowland M, Webster J, Saleh P, Chandramohan D, Freeman T, Pearcy B, Durrani N, Rab A and Mohammed N. 2002. Prevention of malaria through social-marketing of insecticide-treated nets: evaluation of coverage and effectiveness by cross sectional-survey and passive surveillance. Tropical Medicine and International Health 7, 813-822.
• Webster J, Lines J and Hill J. (2003) Insecticide-treated mosquito net interventions: A manual for national control programme managers. World Health 2002.45

Jan Kolaczinsk, PhD: Disease Control and Vector Biology Unit, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, United Kingdom, Phone: 44 (0)20 79272213, Fax: 44 (0)20 74679536 jan.kolaczinski@lshtm.ac.uk

Kate Graham, Msc: HealthNet International, 11-A Circular Lane, P.O. Box 889, University Town, Peshawar, Pakistan, Phone: 92 (0) 91 844474, Fax: 92 (0)91 840379 kate.graham@ishtm.ac.uk

Complex emergencies are situations where large civilian populations are involved in war or civil strife, food shortages and population displacement. Natural disasters may further complicate these man-made crises. Malaria is the most common cause of morbidity and mortality in many complex emergencies. Deaths due to malaria usually exceed deaths caused by conflict injuries. In complex emergencies the burden of malaria is often increased due to:

• Collapse of health services, malaria control programmes and poor coordination among multiple agencies providing health care
• Environmental deterioration that encourages vector breeding
• Weakened nutritional state of the displaced population
• Movement of non-immune people to endemic areas
• Supply and logistical problems

4TH MIM Pan-African Malaria Conference 2005: New Strategies Against an Ancient Scourge November 13 - 18, Yaound Cameroon

The MIM Pan-African Malaria Conferences are the largest meetings worldwide solely focusing on malaria. These meetings provide a unique opportunity for malaria scientists from all disciplines to meet, discuss and form new partnerships. The Conference is being organized by the MIM Secretariat, hosted by Stockholm University and Karolinska Institutet, Stockholm, Sweden on behalf of MIM partners and in close collaboration with the Biotechnology Centre of University of Yaoundé I, Yaoundé, Cameroon. For more information, click here.

PermaNet ®2.0, a new Long Lasting Insecticidal Net Recommended by WHO

The 7th WHOPES Working Group Meeting, held in WHO/HQ, Geneva, 2-4 December 2003, reviewed the results of laboratory and field studies of PermaNet and made the following conclusions and recommendations:

• PermaNet 2.0 is a long lasting insecticidal mosquito net where the insecticide (deltamethrin, 55 mg a.i./m2) is mixed in a resin coating the netting fibers so that the insecticide is progressively released from the resin and the net retains efficacy after repeated washings. Although PermaNet is treated at a higher concentration of deltamethrin, the transient side effects reported for 1st generation PermaNet were no more frequent than for mosquito nets conventionally treated with deltamethrin at a target concentration of 25 mg a.i./m2.
• The 1st generation PermaNet exhibited inconsistent results in terms of initial deltamethrin concentration and wash resistance. Some batches of PermaNet indicated wash resistance up to 20 WHO standard laboratory washes while others were not more wash resistant than conventionally treated nets with deltamethrin. Retreatment of exhausted PermaNet by conventional dipping restored insecticidal activity. PermaNet 2.0 has been consistent in terms of initial deltamethrin concentration and wash resistance. Unwashed PermaNet 2.0 was equally effective as conventionally treated deltamethrin nets against both susceptible and pyrethroid-resistant mosquitoes. Laboratory washing studies and experimental hut studies comparing washed and unwashed PermaNet 2.0 confirm that PermaNet 2.0 retains insecticidal activity up to 20 washes.
• When a WHO-recommended insecticide has been used in the manufacturing of long lasting insecticidal mosquito nets, interim recommendation may be given after specific requirements of laboratory and small scale field studies (experimental huts) have been met. This specific consideration is in response to the urgent need of the control programmes. Interim recommendations will be reviewed and full recommendations may be given, based on the data from large scale studies in different settings.

Recommendations

• Considering the safety, efficacy and wash-resistance of PermaNet 2.0, interim recommendation is given for its use in the prevention and control of malaria.
• WHO should support and facilitate large scale field studies of PermaNet 2.0 to confirm long lasting efficacy for malaria and other vector-borne disease prevention and control in different settings.

Note: PermaNet 2.0 and Olyset Net® are currently the only LLINs recommended by WHO for malaria prevention and control. No other LLIN is currently under evaluation by WHOPES. The full report of WHOPES testing/evaluation of PermaNet 2.0 will soon be available on WHOPES homepage. Geneva, 5/01/2004.