Mosquito nets save lives


WEBWIRE – Thursday, May 08, 2008

With Interceptor BASF is supporting the fight against malaria.

The Story

Mosquito nets protect against malaria
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.

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.

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.

The Prospects

The WHO’s medium term goal is to provide access to LLINs such as Interceptor for everyone living in endemic malaria regions – at present only about ten percent of the at-risk population of Africa sleep under mosquito nets. The total demand is likely to reach 50 to 60 million nets annually in the years ahead. BASF has established production capacities to supply a good portion of the demand. The main customers for the Interceptor net, which costs only a few dollars, are international aid organizations, national health agencies and nongovernmental organiziations, which usually purchase the nets in large public tenders or fund countries for local tenders.

Interceptor nets are also on sale in Latin America and Asia, but the main market is Africa. BASF also makes donations as part of its fight against malaria. Richard Allan, CEO of the international aid organization The Mentor Initiative, is grateful for the support being provided for his malaria program. “As well as the new, highly effective Interceptor nets we also use the conventional BASF products such as Fendona spray to treat indoor walls and the insecticide Abate® to kill mosquito larvae in stagnant waters. We are hoping to expand our joint project to combat malaria even further in 2008.”

The Info Box

Malaria – threat from single-celled organisms

The vectors of malaria are tiny single-celled organisms belonging to the genus Plasmodium, four of whose numerous species can attack humans. But only Plasmodium falciparum, the multifaceted pathogen of malaria tropica, became the fatal scourge of mankind.

Development in humans

Plasmodia are transmitted by the saliva of an infected mosquito vector of the genus Anopheles, enter the blood stream in the form of sporozoites, and then penetrate into the cells of liver tissue where they multiply by division. In this way, every single sporozoite produces up to 30,000 merozoites which finally cause the host cell to rupture. The pathogens thereby released now attack and penetrate other red blood cells in which they continue to multiply. The dying red blood cells release increasing numbers of pathogens which in turn attack other healthy cells. A small portion of the merozoites then develop into male and female gametocytes. The next time the mosquito bites a human, the gametocytes can enter the mosquito’s intestine where the parasites reproduce sexually. This results in the formation of up to 1,000 new sporozoites that penetrate into the insect’s salivary glands from where they are injected into a new victim with the next mosquito bite – the fatal

Effects of malaria

The destructive activity of the plasmodia in the red blood cells rapidly leads to anemia, violent attacks of fever and cramps. If left untreated, serious complications affecting the kidneys, spleen, lungs and brain often result in the death of the victim within a few days. Although malaria is regarded as curable under optimal medical conditions, the necessary expensive medications are often lacking, especially in the rural regions of Africa. Moreover, increasing numbers of Plasmodium strains are developing resistance towards the most commonly used drugs – which is why preventing new infections is seen as the best approach to combating malaria.



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