A Race Between Humans, Dogs, and Worms: Guinea Worm Eradication Setbacks

One of the principles of eradicating a human infectious disease from the planet is that the disease cannot have another host. For example, smallpox only infected humans. It could greatly complicate -- and likely derail -- an eradication effort if, in addition to finding and isolating infected humans, a wily animal species was added to the mix. 

The 2nd human infectious disease on the chopping block is Guinea Worm, or dracunculiasis. This infection, which is caused by an invasive worm which must be meticulously winded out of the body, has been beaten back to just a few African nations and, under the direction of President Carter's center, has been on its last legs (of course, worms don't have legs). The key to preventing infection is to keep those infected with the worm from placing themselves in water sources to prevent the worm from discharging its infectious form into the water in which others drink (filters are also used to prevent ingestion). 

In 2016, there have been just 19 cases in Chad, Ethiopia, and South Sudan. However those 19 cases are not the full picture as they represent a 25% increase over the same period in 2015 (there were a total of 22 cases in 2015). More ominous to me is the discovery that dogs and baboons are getting infected. It's almost as if the worm, sensing its impending annihilation, has pulled out all stops to stave off extinction and jumped into other species in a manner reminiscent of the demon spirit in the movie Fallen. This phenomenon could make it very hard to fully eradicate this pathogen as wild dogs, for example, can easily contaminate drinking water sources and undo the progress that has occurred with human cases.

Of course, it is no accident that the disease persists in only specific countries as the underlying problem is access to safe drinking water untainted by guinea worm. Civilization, then, is the ultimate way to eradicate this disease. If civilizing forces accelerate sufficiently to bring safe drinking water to the Chad, Ethiopia, and South Sudan, the issue of infections in dogs and other animals may not be so pivotal as feared. However, the provision of safe drinking water is a Herculean task and, if it proves unachievable in the near term, the race between humans, a worm, and dogs will carry more import for the human race than the Olympics.

2013 Eradication Final Score: Polio 8 countries, Guinea Worm 4

Since I work on a daily basis with DA Henderson, the man who led the only successful effort to eradicate smallpox from the planet (see his excellent book), the eradication of other infectious diseases are always something I track. 

Since smallpox, only the cattle disease rinderpest has been eradicated. 

Two major eradication efforts are currently underway with varying degrees of success. One is focused on polio, the other on guinea worm disease. Polio remains in 8 countries; guinea worm disease (dracunculiasis) in 4.

To eradicate polio is actually a tripartite task,  as the disease is caused by three types of poliovirus. Poliovirus type 2 was eliminated in 1999 and type 3 is likely on the verge of eradication. Type I is a different story, however, and has proven difficult to extinguish and has been abetted by social and political developments conducive to its spread. 

In 2013, polio cases increased by approximately 62% (from 2012) largely as a result of importation of cases to countries from which it had been previously driven out (Cameroon, Kenya, Somalia, Ethiopia, and Syria).

Polio remains endemic in 3 countries: Afghanistan, Pakistan, and Nigeria. In Afghanistan and Pakistan there have been several reports of violence directed against vaccinators by the Taliban. There is also an excellent book on the topic of polio in Pakistan detailing the structural problems involved there.

Guinea worm disease, on the other hand, experienced a 73% decline in cases from 2012 and remains in South Sudan, Ethiopia, Mali, and Chad.

As the new year unfolds, it will be fascinating to track the progress--and setbacks--of these two programs. For a good overview of eradication in general, see this book.