By Fergus Walsh
BBC News, Medical correspondent
It is one of the world's most disfiguring diseases.
LF can cause grotesque swelling
Lymphatic filariasis (LF) - commonly known as elephantiasis - can cause grotesquely swollen limbs.
It affects 83 of the world's poorest countries, and 120 million people are infected.
Ghana is one of many countries now attempting to eliminate the disease using mass drug distribution.
LF is caused by parasitic thread-like worms which are carried by mosquitoes.
When the mosquito bites the larvae enter through the broken skin.
They migrate to the lymphatic vessels where they can live for several years.
During that time they produce young which enter the blood and are passed back to mosquitoes when they bite an infected person.
Unlike another mosquito borne infection - malaria - LF doesn't kill. But it does disfigure, and can wreck lives.
It does that via what the textbooks call the "clinical manifestations" of the disease.
The worms disrupt the balance of the lymphatic system which helps maintain the fluid balance between tissues and blood.
The result is that it can hugely swell body parts of patients - most commonly legs, breasts and scrotums.
A health team in Ghana took us to meet a patient with LF who they had discovered only a week before.
Ya was sitting on a bench outside her home - these days she is unable to walk very far.
Her left leg was swollen to several times its normal size and grotesquely misshapen.
Drugs are being distributed in Ghana
The swelling is known as elephantiasis and the skin on Ya's legs did resemble the hide of an elephant. Her toes had so many growths and lumps on them that they were unrecognisable.
Ya did not complain about her illness even though for her, there was little prospect of improvement.
Caught early enough the swelling can sometimes be reversed. But the nurses with me said Ya's condition was too advanced.
She lived with her mother and son and told me that she now relied on them to run the house.
Her family and the villagers seemed very supportive. But many sufferers are shunned by their community or made a figure of fun.
In men the disease commonly leads to swelling of the scrotum - known as a hydrocele.
Almost 25 million men are affected worldwide.
I met a tractor driver who had lived for many years with LF.
His scrotum had swollen to the size of a melon.
An operation can reduce the swelling - although this may be temporary.
We filmed him anonymously, but I wanted to be sure that he was willing to have his condition recorded and broadcast.
He said it was important that people knew what LF could do.
Even though he had told few people in his village beyond his wife, he was ready to show the effects of LF to the world.
Lack of support
The images we have shown will undoubtedly disturb some viewers.
But doctors who treat LF and parasitologists who research it say that they have struggled to get support for combating it.
They want greater funding and have found it hard to get publicity.
David Molyneux, Professor of Tropical Health Sciences at Liverpool School of Tropical Medicine, said: "The BBC is to be congratulated in its decision to show the reality of suffering of millions of men from filariasis.
The symptoms can be shocking
"This condition is hidden for obvious reasons but is treatable by simple surgery and preventative drugs are available, at trivial cost, avoiding the horrors of LF afflicting a next generation.
"No developed country would allow up to half its adult male population to suffer such avoidable gross genital deformity."
And there is hope that future generations can lead a life free from LF.
Near Ya's village the annual drug distribution against LF was underway.
Everyone was taking turns to line up against a stick which had four coloured lines on it.
If they were taller than the first line on the stick they got two tablets; taller than the second they got three tablets and so on.
The health teams throughout Ghana try to visit every community once a year.
If they can do this for at least five years then the transmission of the parasite can be stopped and the disease eliminated.
China managed it in the 1950s, using Communist planning and strict discipline. More recently Egypt and Fiji have had considerable success.
There is now an ambitious programme to eliminate LF globally by 2020.
That will take a huge amount of medicines.
Two of the world's largest pharmaceutical companies - GlaxoSmithKline and Merck - say they will supply the drugs required "for as long as needed" free of charge. It's the biggest drug donation in history.
There was a party atmosphere in the village as everyone lined up for their tablets. It was a chance to break off from work in the fields, or from school and get together.
This looks simple I thought. And yet of the 39 countries in Africa affected by the parasite, just nine have eradication programmes.
The drugs are free, but it takes huge organisation and planning to ensure that every citizen is reached once a year.
That is why campaigners are calling for greater recognition of LF - in order to encourage more funding for the drug distribution programmes.
Professor Johnny Gyapong, from the Ghana Health Service, is in charge of the treatment programme.
He said that with concerted international action LF could be eradicated. The drugs were available, it was simply a question of prioritisation.
"Lymphatic filariasis is largely a hidden and neglected disease, but with grave socio-economic effects.
"It is my view that the media has a role to inform, educate and communicate the appropriate messages relating to the disease, because the condition is manageable.
"So if we put our resources together and get our act together, it is possible that at least we get one disease off the list of many diseases that are troubling the underdeveloped world."