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[CHENNAI] Wild turmeric extract can offer a cheap, biological method to control the mosquito that spreads filariasis, a disease that threatens 1.3 billion people in tropical countries, according to Indian scientists.

Filariasis is a parasitic infectious tropical disease, caused by a worm that invades the human lymph system and, like malaria, is spread by blood-sucking mosquitoes. It results in thickening of skin and underlying tissues.

A team led by V. A. Vijayan, professor at the department of zoology at University of Mysore, isolated two substances from Curcuma aromatica — a wild variety of turmeric grown in several Indian states for its medicinal value — that were toxic to mosquito larvae.

"A teaspoon of C. aromatica powder in stored water — a flower vase, small water tank, even drinking water pot — prevents mosquitoes from breeding for over a month. As turmeric is locally available people can use it easily," Vijayan told SciDev.Net.

Vijayan's team used petroleum ether to isolate the compounds. "Our costs were low because we dissolved the turmeric powder in a small amount of acetone and then made the test solution in water. For every 100 grams of C. aromatica powder, nearly 12 grams of [wild turmeric] extract was obtained," said Vijayan.

The only way to reduce the incidence of filariasis is to control the vector, say the scientists, pointing out that there is no vaccine against the disease which, if left untreated, develops into elephantiasis, a crippling and chronic condition. 

Vijayan and his team highlighted the fact that mosquitoes rapidly develop resistance to synthetic insecticides. "Many of the currently available synthetic insecticides share more or less similar modes of action, which makes mosquitoes attain resistance and cross-resistance," they say.

"Because of its significant larvicidal [ability to kill mosquito larvae] properties and local availability, it might form a new arsenal for vector management, especially in areas where mosquitoes have developed resistance to conventional insecticides," they concluded.

In 2009, as many as 125 kinds of mosquitoes were reported to have developed immunity for different classes of insecticides and more than 500 species of arthropods may fall in this category, Vijayan said, citing entomological studies.

Currently available synthetic insecticides are also expensive and need to be applied with care to avoid irritation, allergic reactions and cancers.

There are no reports to date on vector resistance towards biocides. "Our attempt has been to find an effective, natural mosquito control agent which is highly economical and much safer," Vijayan's team reported.

The findings are published in January 2010 issue of Acta Tropica. 

Link to abstract in Acta Tropica

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