Water bug aids dengue fever fight

The battle against dengue fever is being won in Vietnam thanks to a tiny water predator, experts say.

Scientists, with the help of local children, have been placing the bug into water tanks where the mosquitoes which carry the disease breed. The scheme reduced the cases of dengue fever to zero in nine areas of north and central Vietnam over a five-year period, the Lancet said. The disease infects 50 million people a year, killing 12,000. It is most commonly found in tropical areas of Africa, South America, the east Mediterranean, south east Asia and countries in the western Pacific. It starts off as a flu-like illness but without the proper support it can develop into a deadly fever. At the moment there is no treatment and vaccination is often difficult because dengue fever can take a number of forms. The best form of protection is the use of insecticides but this is often costly. Scientists from the Queensland Institute of Research in Australia and Vietnam’s Ministry of Health believe their technique offers a low-cost, environmentally-friendly alternative. Mosquito Professor Brian Kay, from the Queensland Institute of Research, said the scheme is being extended to 37 areas of Vietnam but he wanted to see it used across the rest of the world. “As the global prognosis is poor, we predict that this model, or modification of it, will become increasingly important.” As well as placing the bug, a crustacean called Mesocyclops, in water tanks, the scientists encouraged children to place it in discarded containers where the mosquito, Aedes aegypti, is also known to thrive.At the start of the programme in 1998 there were 112 cases of dengue fever per 100,000 people. Professor Chris Curtis, of the London School of Hygiene and Tropical Medicine, who has visited the team in Vietnam, said: “I think it is an excellent scheme and has the potential to be used in other areas of the world where dengue fever is found. “However, I suppose one problem could be that not all countries have the community facilities to support the programme.” But Dr Simon Hales, of the Welling School of Medicine and Health Sciences in New Zealand, said he doubted whether it would prove as effective everywhere because of the strong emphasis on community participation. “It is not a universal answer, but has the potential to make an important difference in rural communities.” (Source: The Lancet, BBC Health, February 2005)