By Kim Smiley
Guinea worm disease is poised to become the second human disease to be eradicated (after smallpox). In the 1980s, there were millions of cases of Guinea worm disease each year and the number has plummeted to only two confirmed cases so far in 2016, both believed to have been contained before the disease had a chance to spread. This accomplishment is particularly impressive considering that there is no cure or vaccine for Guinea worm disease. In fact, the most effective “cure” for the disease used today is the same one that has been used for thousands of years – to wrap the worm around a stick and slowly pull it out. (Read our previous blog “Working to Eradicate a Painful Parasite” to learn more about the problems caused by Guinea worm disease.)
So how has this horrible disease been fought so effectively? We need to understand how the disease spreads to understand how the cycle was broken. (Click on “Download PDF” to see a Process Map of the Guinea worm lifecycle.) The Guinea worm is a human parasite that spreads from host to host through the water supply. The (rather disgusting) lifecycle begins with Guinea worm embryos squirming and wiggling in a freshwater pond, hoping to attract the attention of unsuspecting water fleas. Once consumed by a water flea, the Guinea worm embryos drill out of the water flea’s digestive tract, move around the body cavity and feed on the water flea. When a human then drinks the water containing the infected water flea, the lifecycle continues.
The water flea is dissolved by digestive juices in the human’s stomach and the Guinea worm embryo drills out of the intestines and crawls into the abdominal blood vessels, remaining in the body for several months until it reaches sexual maturity. If the human is unlucky enough to be hosting both a male and female Guinea worm, the parasites will mate. The male then die and millions of embryos grow in the female. The female worm will usually make her way to the host’s leg or foot, pierce the skin and release an irritant that creates a painful blister.
Human hosts will often put the fiery blister into water to soothe the pain. The female worm senses the water and releases thousands of embryos from her mouth. She doesn’t release all her embryos at once, but will continue to release embryos when she senses water over a period of time. If the embryos happen to land in a pond with water fleas, the whole painful process can start anew.
Once the lifecycle of the Guinea worm was understood, communities and aid organizations were able to use the information to disrupt the lifecycle and prevent the Guinea worm from spreading. Some aid organizations helped provide access to clean drinking water or straws with filters that removed water fleas and prevented Guinea worm infections. In other places, the Guinea worm larvae were killed by treating the water with larvicide. But the most effective solution has been simply keeping infected people out of the water supply. Once most people understood the consequence of putting Guinea worm blisters in drinking water they simply (if painfully) avoided the ponds used for drinking water, but some communities also implemented new laws and fines or posted guards at water holds to ensure that no infected individuals went into the water. These methods have proven very effective and the Guinea worm is now one of the most endangered animals on the planet.
The key to fighting the Guinea worm was education. The most effective solutions were simple and low-tech. No modern vaccine or modern medical knowledge was needed to prevent Guinea worm infections, just knowledge about how the disease spread. Guinea worms have been infecting people for millions of years (they have even been seen in Egyptian mummies), and the lifecycle could have been broken long ago if it had been better understood.