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Mosquito nets save lives
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The Story
Malaria is one of last three major epidemic diseases, killing well over a million people a year. Only AIDS and tuberculosis claim more victims. Malaria is caused by tiny single-celled organisms called plasmodia transmitted by mosquitoes of the Anopheles genus. Ninety percent of these cases are concentrated in Africa, with young children being most affected. Every 30 seconds a child dies of malaria in Africa and almost every second victim is under five.
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| The use and handling of the mosquito net Interceptor® are explained in personal discussions. This ensures that it will remain fully effective for many years. |
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For decades, BASF has been committed to the fight against malaria and other tropical diseases. The company's latest contribution is Interceptor®, a mosquito net coated with the insecticide Fendona®. The net remains effective against mosquitoes for several years. It thus meets the World Health Organization (WHO) requirements for a "Long lasting insecticide impregnated net" (LLIN). According to the WHO, the protection provided by these nets against the mainly night-active vector mosquitoes is the most effective means of preventing malaria infections. Simple, uncoated mosquito nets suspended over sleeping quarters keep the insects physically at bay, but cannot keep them from biting the sleeping person through the meshes of the net. Only treating the net with an insecticide that is safe for humans really puts the insects out of action. In Kenya, this solution reduced infant mortality in high-risk areas by 44 percent. But the extensive use of LLINs protects not only their users: the nets can kill so many mosquitoes that the infection rates also decrease for village neighbors who do not have their own mosquito protection.
Conventionally insecticide treated nets have the disadvantage of losing their insecticidal activity after just a few months. "The WHO therefore asked the chemical industry a few years ago to develop nets that would retain their insecticidal action even after several years and many washes," is how Dr. Ulrich Karl, development scientist in BASF's Performance Chemicals division, explains how Interceptor came to be developed. BASF already had access to the ideal active ingredient: alphacypermethrin. As the active ingredient in the insecticide Fendona, it already has a long history of use in BASF crop protection and global health products. Alphacypermethrin is modeled on the natural defensive compound produced by chrysanthemums and kills insects even in the smallest doses. For vertebrates, and thus for humans, the amount used on the nets is not toxic. "The main challenge was to incorporate Fendona in a polymer so that it would migrate to the surface at a steady rate over several years," explains Dr. Ulrich Karl. The factor found to be decisive for producing these characteristics was the degree of cross-linking of the performance polymer. This is what determines the three-dimensional structure and thus the permeability to the active ingredient molecules. The result was Fendozin®, the odorless coating of the Interceptor nets. Its polyester yarn feels soft and is skin-friendly despite the coating. This is important to ensure that the nets are used.
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The new product was tested for effectiveness at the London School of Hygiene & Tropical Medicine. The researchers found that in most cases even brief contact with the net is sufficient to seal a mosquito's fate. Within as little as five minutes after contact, the insect drops paralyzed to the floor, an effect known as knockdown. Almost all mosquitoes die. Thanks to Fendozin, Interceptor easily satisfies all the WHO requirements for an officially time limited interim recommendation as a LLIN. And the WHO sets very high standards. Even after 20 washes, the knockdown must still be at least 95 percent and the mortality rate 80 percent. Senior investigator Dr. Vincent Corbel of the Institut de recherche pour le développement in Montpellier - officially commissioned by the WHO to test the net – reached the conclusion: "Interceptor exceeds 95 percent knockdown even after 25 washes. And the net is fully ready for use again the very next day after washing."
Just as important as the effectiveness is the safety of the Interceptor net. "Our worst-case scenario is an infant sucking on the net throughout the night," says Dr. Thomas Maurer who is responsible at BASF for insecticide safety. "Our tests showed, however, that the quantity ingested in this scenario would still be a hundred times below the toxicological threshold limit." The test results also convinced the WHO: at the end of 2006, Interceptor received an official recommendation, opening the way to approval in many major tropical countries around the globe. But research is still ongoing: large-scale three-year field trials are currently being launched in Tanzania and India. While medical researchers around the world continue their intensive search for an effective anti-malaria vaccine and new drug treatments, the disease could already lose some of its fear factor through the widespread introduction of nets like Interceptor.
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