Tag Archives: guinea worm

The end of the Guinea worm?

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.

Working to Eradicate A Painful Parasite

By Kim Smiley

The lifecycle of the Guinea worm is the stuff of nightmares.  This parasite is ingested by a host as larvae, mate and mature inside the host and then the adult female painfully emerges to lay her eggs. The adult female is between two to three feet long and the thickness of a spaghetti noodle.  The only way to get rid of the parasite is to wrap it around a stick and slowly pull it out, a process that takes several weeks or even months.

Individuals who are infected by this parasite can suffer for months, making it difficult to work and feed their families.  There is no immunity to Guinea worms so it’s possible for people to suffer year after year if they continue to ingest the larvae of the Guinea worms.  There is also no drug to treat Guinea worm disease and there is no vaccine that prevents infections.

But there is hope in the fight against this excruciating disease.  The number of cases of Guinea worm disease has decreased dramatically.  In 1986 there were an estimated 3.5 million cases of Guinea worm disease spread across 21 countries in Asia and Africa.  In 2011, there were only 1,058 reported cases of Guinea worm disease in four African countries.

How was this possible?  The first step in answering that question is to understand more about the disease.  The problem of Guinea worm disease can be illustrated by building a Cause Map, an intuitive root cause analysis format.  By asking “Why” questions, causes can be added to the Cause Map and the problem can be analyzed.    Why are people getting the disease?  People are drinking water that is contaminated with copepods, also called water fleas, which are infested with larvae of Guinea worms.  There is also typically no other supply of safe drinking water and the water wasn’t treated or filtered prior to consumption.

Painful blisters form when the female Guinea worm emerges from the body and people put their sores into the same water used for drinking (because it is usually the only water available) to help relieve the burning sensation.   The female Guinea worm then releases hundreds of thousands of guinea worm larvae once she senses water.  Guinea worm larvae is eaten by the water fleas.  The infected water fleas are small and ingested along with the water, which restarts the whole process.

This process had been going on for thousands of years, affecting millions and millions of people.  Its remains have even been found in Egyptian mummies.  But simple changes have nearly eliminated the disease.  In fact, Guinea worm disease is predicted to be the first human disease ever eradicated without a vaccine and only human disease to be eradicated other than small-pox.

Relatively simple changes have made all the difference in the world.  People were educated about how to prevent the disease.  Millions of straws with filters were handed out to villagers to strain out the infected water fleas and prevent the parasite from entering the body.  Efforts were also made to treat water with larvicide and provide access to uncontaminated drinking water.

Without new hosts, the Guinea worm larvae died.  Once the lifecycle was broken, the disease disappeared from many regions.  There are now only four countries that reported any cases of the disease last year, the vast number being in war torn South Sudan where public health efforts have been difficult to sustain.

Click on “Download PDF” above to view a high level Cause Map of this issue