Researchers say they have found the first successful treatment for advanced lymphatic filariasis, better known as elephantiasis*, which afflicts an estimated 120 million people in tropical and subtropical countries. 

Lymphatic filariasis is an extremely disabling disease, caused by a mosquito-borne parasite that resides in the lymph system, a network that's part of the circulatory system and helps protect the body against infection.

The worms burrow into the lymphatic system, often within the legs, causing limbs to swell many times their normal size. Another common feature of elephantiasis is the painful, massive swelling, or lymphedema, of male genitals.

In its larval and early stages, during the transmission phase, lymphatic filariasis is fairly easy to treat with an anti-worm medication and a particular antibiotic, Ivermectin. But until now, there has been no effective treatment for the adult stage of lymphatic filariasis.

Now, an international team of researchers has demonstrated the effectiveness of an inexpensive antibiotic, doxycycline, which they say cures most cases of advanced elephantiasis.

Mark Taylor of the Liverpool School of Tropical Medicine in England says the antibiotic kills the parasite through indirect means. It destroys a bacteria inside the filariasis worm, which the parasite relies on to survive.

"And so we've used both simple, cheap and available antibiotics to try and attack this bacteria, and found that we can clear the bacteria from the worm," Dr. Taylor says. "And in doing so, we can cause both the sterilization of the worm, which means it can no longer produce any offspring, and, most importantly though, the adult worms can't survive without the bacteria. So, they then die, and in that way, we can cure the adult stage of the disease."

The study with doxycycline, conducted by Dr. Taylor and colleagues in Germany and Tanzania, involved about 70 worm-infested individuals in Tanzania. Researchers found doxycycline almost completely eliminated the parasite, within eight to 14 months.

Dr. Taylor says researchers' goal is to find a way to reduce the treatment time.

Wilma Stolk of the Department of Public Health of Erasmus Medical Center in the Netherlands is an expert on elephantiasis.

"Doxycycline has never been used for the treatment of lymphatic filariasis before," she says. "So, it's a very new approach, actually, to use this already existing drug for lymphatic filariasis."

The study on doxycycline and lymphatic filariasis is published in the June 18th issue of the medical journal, The Lancet.

*Correction published 20 June 2005.