Insecticide-treated bed nets can end third world's scourge of filariasis

Researchers have found that insecticide-treated bed nets reduce transmission of lymphatic filariasis to undetectable levels - even in the absence of additional medication.

The World Health Organization reports that more than 120 million people suffer from lymphatic filariasis, commonly known as elephantiasis.

About a third of that number are disfigured or disabled by the disease, a parasitic-worm infection spread by mosquitoes.

"Our study quantifies the effect of the most widely implemented vector control measure - insecticide-treated bed nets - and highlights the importance of integrating this type of intervention as a part of the global strategy to eliminate lymphatic filariasis," senior author and Case Western Reserve University School of Medicine professor James Kazura, said.

"With a little bit of effort and not much money, we don't have to live with this painful, disfiguring disease," he said.

This study follows research that Kazura published in 2002 The New England Journal of Medicine. In that work, he and his colleagues evaluated the safety and efficacy of administered annual antifilarial drugs over five years to residents of five villages in Papua New Guinea.

The team demonstrated that the mass drug strategy nearly eliminated the parasite from humans but did not stop its transmission by mosquitoes.

The success of a strategy utilizing medication requires at least 80 percent of the population to receive treatment annually for at least five years. The initial results of mass treatment showed promising results, but transmission still took place in subsequent years, albeit at lower rates. Testing showed that parasite levels remained high in mosquitoes around the villages as much as decade later.

Ten years after villagers took their last medication round, they received free bed nets as part of Papua New Guinea's national malaria control effort.

In the 36 months that followed, Kazura and team saw a dramatic decrease in the number of infected mosquito bites per person.

In fact, rates fell annually from as many as 325 to zero.

Kazura and his colleagues ultimately concluded that transmission has stopped completely; they could find no mosquitoes harboring parasites capable of transmitting the disease.

The study is published in The New England Journal of Medicine.