Some even believe that the Guinea worm was the inspiration for the design of the caduceus -- the serpent-entwined staff that is now the symbol of the medical profession. The theory springs from the fact that in the ancient world, the proper removal of the worm involved grabbing the exposed tail and gradually winding the body of the worm around a stick -- as pulling too hard would cause the worm to break, resulting in infection and inflammation. Thus, some believe, the symbol of the parasite twisted around a stick became synonymous with the healing arts.
Fortunately, public health efforts appear to have largely turned the tide against Guinea worm infections. According to statistics compiled by The Carter Center http://www.cartercenter.org/health/guinea-worm/index.html -- the disease-fighting nonprofit organization founded by former U.S. President Jimmy Carter -- eradication efforts have reduced the number of cases reported in 20 African nations from 3.5 million in 1986 to just a few thousand last year. And some hope that the disease will be completely eradicated within the next few years.
Arguably the deadliest parasite ever known to man, a microscopic organism known as Plasmodium is responsible for the disease known as malaria. The disease is spread by mosquitoes, and each year between 350 million and 500 million people worldwide fall ill from it, according to statistics from the CDC. Of those stricken, more than a million die.
Those infected with malaria generally have fever, headache, and vomiting, starting 10 to 15 days after contracting the disease from a mosquito bite. The deadliest form of the parasite, called Plasmodium falciparum, can rapidly threaten the lives of its victims by disrupting blood supply to vital organs.
The deadly nature malaria has put it in the crosshairs of global health organizations and charitable institutions alike.
"Malaria still kills more than 1 million people every year," said U.N. Secretary-General Ban Ki Moon during a speech on World Malaria Day in April 2008. "The toll it is taking is unacceptable -- all the more so because malaria is preventable and treatable."
And the solutions for this devastating disease are simple ones. Bednets, insecticides and inexpensive antimalarial drugs all go a long way in the areas where it still threatens humans, primarily in sub-Saharan Africa.
For many, infection with Chagas disease takes place in the dead of night.
When the lights go out in many of the adobe and mud homes inhabited by the rural poor in Central and South America, the triatomine beetle -- also known as the "kissing bug" -- creeps out from the crevices in walls and ceilings, seeking out warm, sleeping bodies.
The bug got its seemingly-romantic nickname because it is attracted to its victims' faces. At night one's face is generally uncovered and gives off body heat. The insect sucks one's blood through a long proboscis. As it feeds, it defecates -- and spreads the disease.
Within the fecal matter of the bug lives an organism known as Trypanosoma cruzi. And if this parasite enters the bloodstream -- perhaps when a sleeping victim wakes up and inadvertently rubs it into the new, itchy wound left by the beetle -- it can lead to Chagas disease, an infection that is both lifelong and life-threatening.