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LB2100

The performance of a new polypropylene multifilament long-lasting insecticidal mosquito net against malaria mosquitoes in laboratory and field evaluations. Karin Horn, Thomas Boecker, Guenther Nentwig, Rainer Sonneck, Ronald Stoecker - Bayer CropScience AG, Environmental Science Innovation, Monheim, Germany

ABSTRACT This poster presents the performance of a new polypropylene (PP) long-lasting Deltamethrin mosquito net (LN) against malaria mosquitoes in laboratory and field evaluations following the WHOPES laboratory testing guidelines and through WHOPES phase I and II evaluation.

The new polypropylene LN: • showed full control of susceptible malaria mosquitoes above WHO threshold beyond 35 washes; • had good efficacy against field populations of Anopheles and Culex spp. e.g. in South Africa, Benin, Tanzania, India;

• had good efficacy against Aedes spp. mosquitoes; • was fully recharged within a day after washing; • received the WHOPES Interim Recommendation in April 2011. The WHOPES field studies in India, Tanzania, and Benin, demonstrated the good efficacy of the Bayer polypropylene-LNs, washed 20 or 30 times, on mortality and blood feeding inhibition of prominent malaria vectors – thereby exceeding the WHOPES requirements of 20 washes.

INTRODUCTION

MATERIAL & METHODS

What is a long-lasting insecticidal net (LN)? *Definition by WHO: A long-lasting insecticidal net is • a factory-made mosquito net • treated with a WHO evaluated insecticide • that must retain its biological activity • without re-treatment • for at least 20 standard lab washes • and 3 years under field conditions.

MATERIAL The new Bayer polypropylene LN: Polypropylene - 0.85% Deltamethrin; Incorporation; Multifilament.

Existing long-lasting insecticidal nets made from: Polyester • are soft in handling but generally have limited mechanical strength to maintain physical integrity for as long as 2-3 years. Polyethylene • are generally stronger than polyester, but often need heat treatment for insecticide regeneration, effective lifespan limited if bioefficacy drops below effective levels. The new Bayer polypropylene multifilament long-lasting insecticidal mosquito net: • based on new polymer polypropylene • with inclusion of Deltamethrin • multifilament for soft handling • ready to use immediately after washing and drying • effective even after 35 washes • corresponding to more than 5 years of useful life (assuming that a net is washed 7 times per year on average). Energy Dispersive X-ray Spectroscopy (EDX) Polypropylene Multifilament with Deltamethrin crystals on the surface.

Other netting material: Polyester - 55mg/m2 Deltamethrin; Coating; Multifilament. Polyethylene - 2% Permethrin; Incorporation; Monofilament. METHODS Mosquitoes tested: Anopheles gambiae; Anopheles arabiensis; Anopheles fluviatilis; Culex Quinquefasciatus and other Culicidae. Lab testing sites: Bayer CropScience, Monheim, Germany; LIN Montpellier, France; BioGenius, Bergisch-Gladbach, Germany; SABS, Johannesburg, South Africa. WHOPES collaboration centers for WHOPES ph I and II trials LABORATORY METHODS ACCORDING TO WHO1 WHO washing procedure: • Net samples (25x25cm) in bottles • 0.5 L deionized water with 2 g/soap per liter • Bottles shaken at 30°C for 10 min at 155 movement/min • Rinsed twice for 10 min. WHO bioassays: • female Anopheles gambiae (susceptible) • 3 min exposure to the net • in WHO plastic cylinders or WHO cones (see below) • Knock down at 5, 10, 15, 20, 30, 40, 50, 60 min • Mortality at 24 hours.

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* Source: WHO LN Position Statement, Global Malaria Programme

Testing was carried out according to WHOPES guidelines, WHO/CDS/NTD/ WHOPES/GCDPP/2006.3

WHO CONES

CONCLUSION The Bayer polypropylene long-lasting insecticidal net showed: • full control of susceptible malaria mosquitoes above WHO threshold beyond 35 washes • good efficacy against field populations of Anopheles and Culex spp. e.g. in South Africa, Benin, Tanzania, India (*refer: 14th WHO WG report: http://whqlibdoc.who.int/publications/2011/9789241502160_eng.pdf)

• good efficacy against Aedes spp. mosquitoes • no regeneration delay – LifeNet is fully recharged within a day • good personal protection against prominent malaria vectors due to strong inhibition of blood feeding, as shown by WHOPES* Phase II experimental hut trials carried out in Tanzania, Benin and India.

CONTACT INFORMATION: Dr. Karin Horn, karin.horn@bayer.com, Justin McBeath, justin.mcbeath@bayer.com


ASTMH_LifeNet_Biology_summary_2011