29 March 2004

Kenya: 'Rediscovering' Traditional Mosquito Repellents

Nairobi — Traditionally, many communities had developed the knowledge that hanging leaves of certain plants on doorways were effective deterrents to mosquitoes.

With the expected malaria outbreak in many parts of Kenya following the onset of the long rains, scientists at the International Centre of Insect Physiology & Ecology (Icipe) are "rediscovering" and improving on the traditional methods adopted by communities in East Africa and elsewhere to reduce the human-mosquito contact.

And having proved that most of these methods are effective, researchers at Icipe have been talking to a number of companies in Kenya to have them incorporate the plants into the manufacture of such products like candles, oil and mosquito coils, thereby make them readily available to the general population.

Icipe has also been holding discussions with a Chinese company, Kernel of Wuhan Province, with a view to lowering the cost of producing a bacterium called Bacillus thuringiensis israelensis (BTi). When sprayed into mosquito-breeding sites in a solution, the bacteria kill mosquitoes. In 2002, the Chinese Ministry of Science and Technology agreed to provide equipment valued at $1 million towards the establishment of the demonstration facility at Icipe headquarters in Nairobi.

Traditionally, and without the enlightened scientific approach, many communities had developed the knowledge that hanging leaves of certain plant on doorways, or burning certain plants and cow dung were effective deterrents against mosquitoes.

For instance, the Kamba, Swahili and Luo communities had identified such plants as mwenye, mukandu and kirumbasi as effective fumigants. By hanging branches from the trees on doorways and on windows, they were able to prevent mosquitoes from entering their dwellings. Today, the Swahili people still burn Kirumbasi in small jikos to produce mosquito-repelling incense.

Icipe's project started with a sociological survey conducted in Kenya's Suba District in Nyanza Province from which scientists tested the effectiveness of these plants by subjecting them to burning and to thermal fumigation. Dubbed Bio-prospecting for Mosquito Repellent & Larvicidal Botanicals, the project is a collaboration between Icipe, Kenyatta University, Jomo Kenyatta University of Agriculture and Technology, the University of Dar es Salaam, Makerere University, the Kenya Medical Research Institute (Kemri) and the Tanzanian Institute of Natural Malaria Research. It is administered by the World Health Organisation (WHO).

"The field tests have shown that some of the plants are effective as potted plants and/or thermal fumigants," said Prof Ahmed Hassanali, Icipe's head of behavioural & chemical ecology. Out of the 12 plants screened, 10 have been found to display a high degree of effective mosquito control.

In order to improve on these traditional methods, the scientists have identified and isolated chemicals and essential oils which they later used to produce mozigone, a mosquito repellent.

It is hoped that this will go along way in controlling malaria, the planet's most devastating disease that affects about 500 million people worldwide each year. In Africa, it is estimated that between 2 and 2.5 million succumb to the disease each year, thus severely limiting both social and economic development on the continent. Over the past decade, the disease seems to have established new beach heads, for besides being common in lowlands, there are now what are referred to as epidemics of "highland malaria" in high-altitude regions of Kenya.

This has had scientists, ordinary people, research organisations and East African governments worried.

But while the world still lacks an effective method of eradicating the disease, scientists are divided down the middle on what needs to be done to lessen the impact of malaria in the tropics. On the one hand, there are those who, with support from WHO, believe that the way forward is the development of a malaria vaccine; the alteration of genes essential to the survival and proliferation of the anopheles mosquito, and the use of bed nets impregnated with insecticides.

But an antagonistic group of scientists believe that malaria can never be eradicated and what needs to be done is to minimise its incidence by adopting the Integrated Vector Management (IVM) method, which combines a number of solutions.

WHO, which incidentally takes the position held by big pharmaceutical giants, has come under criticism for failing to embrace initiatives targeting the malaria-causing mosquito itself. "It is a conspiracy," ICIPE's director general, Dr Hans Herren said last week, expressing anger that, "as one child dies every 30 seconds from malaria in Africa, the WHO heads a lobby that has been campaigning against mosquito control saying it does not work."

Dr Herren believes that rather than spend millions of dollars on the search for a vaccine, the funds ought to be used to develop simple techniques of controlling the disease. Dr Herren added that everyone involved must use every method available. "With such a high rate of deaths, we cannot sit back and peg our hopes on the eventual development of a vaccine," he said.

In the attempt to control the mosquito itself and to break the cycle of malaria transmission, Icipe has been applying BTi on the mosquito and its larvae. Widely considered safer and more environmentally friendly than other chemical equivalents, BTi kills the mosquito by eating into its internal organs.

Dr Herren told The EastAfrican that the BTi can now be produced in Kenya at a factory completed at Icipe premises in Nairobi in December last year. Having been proved to be effective in Eritrea, Icipe has conducted similar field tests in Suba District and plans to extend them to Mwea Irrigation Scheme in Eastern Kenya and to Kisii District in Nyanza Province. "The aim is to have the Ministry of Health incorporate this additional tool to control mosquitoes at source."

He also takes issue with the practice of pharmaceutical companies of isolating a single active ingredient and using it to prepare anti-malaria drugs. He believes that as a dynamic organism, the plasmodium germ - which is implanted in humans with each mosquito bite - is easily able to develop resistance to such drugs. "To go around this problem, we are adopting a holistic approach by experimenting on whole plants that have traditionally been known to contain cures for malaria."

Icipe has also incorporated environmental clean ups in the malaria-control campaign. Scientists at the centre say that 90 per cent of mosquito-breeding sites are man-made.

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