Chapter 1: Nature's Criminals Part 3

The question of how parasites got into the body in the first place or how are they made was still floating around when a new question was added to the pile: what do baby flukes look like? I mean, every organism is born and looks like their parent did as they grow up. But what about parasites? Well Danish zoologist Johan Steenstrup answered this question in the 1830's. He saw fluke-like animals with long tails swim towards snails and make cysts on the insides of their shells. He opened those cysts to discover adult flukes! He found that parasites may travel in one form, but grow into another. With this in mind, and knowing that the snail caries many different "types" or parasites in its body, he figured that the different types of parasites may actually be the same parasite, just in different stages. He proved that spontaneous generation is incorrect and that parasites move from host to host in different forms. These discoveries made other biologists start looking back at parasites and looking at their similarities.

In the 1840's, a German doctor named Friedrich Kuchenmeister added to this discovery. He found that some parasites developed in one part of an organism, but ended up moving to somewhere else in the body to live out it's life. He took bladder worms, the worms Aristotle saw on the pig tongue, and fed them to other animals, believing that these worms and tapeworms were related. He was right. When he opened up the animals later, he found that the bladder worms had moved down to the digestive tract and had grown into adult worms. He even tested this theory on human prisoners sentenced to be killed. He fed them food with the bladder worms in it and months later, after they were executed, he opened them up and saw the tapeworms.

Louis Pasture did studies with broth to prove that bacteria did not spontaneously generate. This launched a better study on bacteria, and scientists found that bacteria was not a parasite like people previously thought. German scientist Robert Koch made rules for classifying bacteria: they had to be associated with a disease and they had to be isolated and grown in a pure culture. Parasites can do none of these things. Protozoa, which is a form of parasite, are more like the cells in our bodies. Bacteria are just sacks of DNA, but protozoa have DNA contained in a nucleus and they have compartments dedicated for making energy and other things they need to function. Using this, scientists divided life into prokaryotes (bacteria) and eukaryotes (protozoa, animals, plants, and fungi). Soon after, scientists found that many fevers and illnesses, like malaria, were not caused by bad air or our own bodies, but by parasites.

Malaria Parasites In Red Blood Cells