By Caroline Ryan
BBC News health reporter
Elephantiasis, a disfiguring tropical disease, can be prevented using a simple, cheap antibiotic, scientists have found.
Elephantiasis causes swelling in the limbs
The condition, also known as Lymphatic Filariasis, causes severe swelling in the limbs. In men, it often affects the genitals.
A study in the Lancet reveals that doxycycline, a widely available antibiotic, kills the worms that cause the disease.
The same antibiotic has been shown to sterilise the worms which cause river blindness.
Lymphatic Filariasis (LF) affects around 120m people worldwide. It is caused by a microscopic, parasitic worm that invades the body's lymphatic system - the network of vessels carrying infection-fighting cells.
The worm is spread by mosquitoes, who pass it on when they take blood from humans.
The worms lodge in the lymphatic system, producing millions of minute larvae which spread throughout the bloodstream.
People who are affected often cannot work or marry, and can be shunned by others in their village because of their disfigurement.
The current treatment programme for LF involves giving drugs which reduce the transmission of larvae. But the treatment has little or no effect on adult worms.
As the adults can live from five to 10 years, people have to take the medication every year in order to gradually kill off the worms.
However, it can be difficult to reach people who live in poor rural areas to ask them to come back for further treatment.
An additional problem with the current treatment is that killing the worms causes a sudden release of the Wolbachia bacteria which they carry, causing inflammation.
The Liverpool researchers say it appears the worms and the bacteria have a symbiotic relationship, where one cannot survive without the other.
They decided to investigate whether antibiotics could be used to kill the bacteria, thereby depriving the worms of their "life-support".
The current treatment method has no effect on the bacteria.
The researchers carried out a study in Kimanga, Tanzania. They selected 120 men in the village to either receive an eight-week course of the antibiotic or a dummy pill.
They then followed the men for 14 months before using ultrasonography to assess how many worms were present in the genital lymph glands.
Because the antibiotic killed the bacteria the adult worms need to survive, numbers were significantly reduced over the period the men were followed.
In addition, the treatment appeared to sterilise the adult worms, so larvae levels in the blood were completely eradicated. The researchers suggest new worm embryos cannot develop without the presence of the bacteria.
Dr Mark Taylor, of the Liverpool School of Tropical Medicine, who led the study, told the BBC News website: "The big challenge is getting rid of the adult worms, and what we found was a gradual reduction in numbers over 14 months.
"If you kill adult worms straight away, you release bacteria and get an unpleasant inflammatory response.
"Killing them slowly is a good thing because it doesn't appear to cause an inflammatory reaction."
He added: "One of the major outcomes was that, if you treat these worms with antibiotics, you will sterilise them. They are no longer able to make embryos.
"And after a much longer period of time - about a year - we see an effect on adult worms' viability."
The men who had the antibiotic treatment did not appear to develop the painful nodules which are seen around worms killed by the conventional treatment.
The researchers say an eight-week course of treatment is too long for community-based treatments, so they will be studying if a shorter course is as effective.
In addition, doxycycline is not recommended for pregnant women and young children. The team plan to see if other common antibiotics or other drugs can also kill the bacteria and therefore deprive the worms of their "lifeblood".
Writing in the Lancet, Dr Wilma Stolk from Erasmus University in Rotterdam, the Netherlands, said: "Research should now focus on identification of regimens, based on doxycycline or other antibiotics, that are practical for use in mass treatment."