I became interested in this disease because of its symptoms, which are truly unmistakable. You may be familiar with the painfully enlarged body parts—the bulbous limbs defying all sense of proportion—which cripple the patient both physically and with a heavy social stigma. Rather than give a blow-by-blow of the disease’s history and symptoms in excruciating detail, in this blog I want to look at some of the particular aspects that interest me. As you will see, there are some striking features of the disease and its treatment, which deserve special attention.

Firstly, some context: people are usually infected during childhood, when a parasite finds its way from a mosquito into a human host. These parasites are roundworms, otherwise known as nematodes. They are very diverse and, quite remarkably, have adapted to pretty much every environment on the planet; you will find them deep beneath the Earth’s surface and on mountains, in the polar extremities as well as the tropics. To demonstrate just how widespread they are, I like this quote from Nathan Cobb, dubbed the father of this field in the US:

“In short, if all the matter in the universe except the nematodes were swept away, our world would still be dimly recognizable, and if, as disembodied spirits, we could then investigate it, we should find its mountains, hills, vales, rivers, lakes, and oceans represented by a film of nematodes. The location of towns would be decipherable, since for every massing of human beings there would be a corresponding massing of certain nematodes. Trees would still stand in ghostly rows representing our streets and highways. The location of the various plants and animals would still be decipherable, and, had we sufficient knowledge, in many cases even their species could be determined by an examination of their erstwhile nematode parasites.”

But I digress. The worms causing elephantiasis belong to a certain family called the Filariodidea (hence the term filariasis). I’ll describe the parasitic life-cycle in a later blog post, but suffice it to say that the adult worms lodge themselves in the lymphatic system, an extensive network of vessels that carry a clear fluid called lymph. This network is important for two reasons: it returns plasma in the interstitial fluid (which bathes the cells of the body) back to the bloodstream, and it has a critical role in the immune system. It carries white blood cells called lymphocytes, which attack and break down bacteria, viruses and cells that are damaged or cancerous.

When the network is blocked by parasites, fluid builds up to produce the characteristic swelling. In cases of elephantiasis, the disease progresses so that the skin thickens and takes on the appearance of elephant limbs. Swelling of the scrotum is also common (a condition called hydrocele), and these features lead to social stigma and depression.

Given that the lymphatic system is an important in fighting disease, it’s no surprise that elephantiasis is often complicated by secondary skin infections. These acute episodes are particularly unpleasant, and are the main reason for loss of wages and quality of life. This all makes for a particularly nasty tropical disease, one which has troubled humans in tropical countries for millenia.