Believe it or not, I’ve heard a lot about blood flukes recently. It started about a week ago during a pretty awesome episode of Radiolab. And if you’re not familiar with NPR’s Radiolab, you should be.
A pretty well-known science writer by the name of Carl Zimmer, who has written entire books on the subject of parasites. Seeing as the name of this episode was Parasites, the hosts pretty smartly got him on the show. One of his examples of awesome, amazing parasites was the blood fluke.
Blood flukes are a type of flatworms that live in Africa and often find their way into humans. There, a male and female hook up – monogamously I might add – and stay connected together, the male feeding the female, for years. Sometimes they can just sit around dormant, not doing much but hanging out in the free food zone. But eventually, the female starts sending eggs out into the blood stream.
This is where things get messy.
The eggs will often just flow out of the body through feces, going out into the world to infect new hosts. Some of them, however, will end up in the liver. The immune system is not happy about this. It gets all hot and bothered, attacks the hell out of the eggs, and damages the liver in the process, causing all sorts of problems. The problems don’t have to start right away, though. In fact, there have been cases of people suddenly getting symptoms of their parasites 40 years after having picked them up in Africa.
This, naturally, provides a great storyline for the television show House. One episode features a girl having picked up the parasite from her father, who had traveled to Africa decades ago. The parasite has since died off – thus not showing up on MRIs and the like – but its eggs are still causing inflammation and damage.
Both of these examples have shown up in my world in the past couple of months. So imagine my surprise when the University of Illinois puts out a paper on how these little buggers manage to stay alive in our bodies for so long.
Being a type of flatworm, blood flukes are related to the planarian. These little guys are famous in the scientific world for their ability to regenerate. Actually, you can take a tiny square of flesh out of the back of a planarian and it will regrow an entire new body – brain and all. They accomplish this feat though a steady supply of a type of stem cell called neoblasts.
One day a University of Illinois postdoc by the name of James J. Collins III thought to himself, “Hey, if these guys are related, maybe blood flukes have these neoblasts too and that’s why they can live so long inside a human.”
Lo and behold, he was right.
A new study recently published shows that blood flukes do indeed have these types of stem cells. Collins and his coworkers marked a group of proliferating cells that looked and behaved like planarian newblasts with fluorescent markers. The glow was passed on to daughter cells as they procreated, which the scientists used to track the new cells as some of them migrated to the gut or muscle and became parts of those tissues.
“We label the cells when they’re born and then we see what they grow up to become,” Collins said. “This is not conclusive evidence that these cells are equivalent to the planarian neoblasts, but it is consistent with the hypothesis that they are.”
Going a bit further, the researchers then used genetics to turn off a gene coding for a growth factor receptor similar to the one found in planarians. Once the switch was flipped, the proliferating cells gradually died out. The discovery of this gene – and potentially other genes – that control the production of these stem cells is pretty major. I mean after all, if researchers could discover a way to turn off these genes through pharmaceuticals, they might find a way to stop the 230 million annual cases of blood fluke infections worldwide.
The paper, “Adult Somatic Stem Cells in the Human Parasite, Schistosoma mansoni,” was published in Nature by Collins and University of Illinois cell and developmental biology professor Phillip Newmark.