"So, naturalists observe, a flea has smaller fleas that on him prey; and these have smaller still to bite ’em; and so proceed ad infinitum."
- Jonathan Swift
December 3, 2010
December 3 - Schistosoma mansoni
Schistosoma mansoni is an unusual parasitic trematode of humans. Unusual, because unlike most other trematodes, schistosomes are dioecious, i.e. have separate sexes and also unusual in that they are longer and more worm-like than most other flukes. Eggs are released in the host's feces and hatch into miracidia, which go on to infect freshwater snails and reproduce to form cercaria. The cercaria then seek out human hosts and penetrate their skin and make their way to the blood stream. The worms seek out a member of the opposite sex and if one is found, the pair will settle down in mesenteric blood vessels and begin to start a family. The couple is monogamous - the female actually lives within a groove in the male's body called the gynaecophoric canal (as shown in photo) and there she will churn out more than 300 eggs a day. S. mansoni is a major public health threat in parts of Africa, Asia, and South America where is causes a chronic disease known as either schistosomiasis or bilharzia.