What causes elaphantiasis?
A parasitic nematode called Wucharia bancroftii that is spread in tropical areas by mosquitos. When the insect bites, microscopic larvae calkled microfilaria are injected, and these first move to the lungs.
Before 1980 this was not recognised, but in fact in tropical Africa, it was accompanied by a condition called "expatriots syndrome" a severe kind of pneumonia that was often fatal to Europeans.
Africans and Melanesians apparently are able to suppress this reaction, and the larvae leave the lungs after a week or so and develop over a year into adult worms that are about three inches long.
These have a particular liking for the lymph nodes in the groin and preferentially block them, particularly on the left hand side. A single infection does not cause the gross deformity seen in indigenes, but repeated infections can so devastate these lymph nodes that a severe form of lymphedema occurs.
Over time this edema causes the tisues to permanently swell, and the skin strtetches to accomodate them. It is an excruciatingly painful condition that eventually leads to the huge leg swelling known as elephantiasis.
Even a single infection though does damage to the nodes, so in old age or obesity, a degree of lymphedema does occur, but it is manageable. The worms live about five years and then die forming cysts. It is these cysts that damage the lymph nodes.