Kiddo tends to grab random books from the library, so here is the story of how schistosomiasis was wiped out in Japan.
For a long time, in a specific small region, there was a deadly disease called "Chihoubyo," a word that translates as "That Local Disease." Sufferers would waste awayn their stomach would swell, and eventually they would weaken and die.
In the early 1900's in the Meiji Era, a dying woman willed her body to a doctor who wanted to study the disease. There was a lot of religious and cultural resistance to autopsies at the time, so this was a big deal. The autopsy found loads of tiny eggs clogging a blood vessel next to her liver. So they knew the disease was caused by some sort of 'bug,' a parasite.
Next, one of the doctors had a cat that seemed to have the same illness. They autopsied the cat and found eggs in the same place.
People figured out that the parasite was in the rice fields, but the book glosses over how they decided that. Next step was to figure out how it gets inside people.
They took two cows and tied them up in a contaminated field. One had its legs covered in funny booties, and the other had its mouth covered so it wouldn't drink the water. The one with exposed legs became sick, so they concluded the parasite enters through exposed skin.
It would have been possible to start taking protective measures at this point, but the book doesn't mention if people did. The next step was to study the life cycle of the parasite. It doesn't go into how they figured it out, but the parasite matures in a specific freshwater snail after hatching from an egg.
So people decided, "Fuck them snails! Ichor for the ichor god! Shells for the shell throne!"
First, they tried picking the snails by hand. But there were too many and they couldn't make a dent.
Next, they naturally tried using flamethrowers to burn the snails. But this, too, was not enough.
After that, they dumped one hundred tons of lime into the prefectures waterways. This poisoned a lot of snails and probably all the other wildlife, but it still wasn't enough.
Finally, they started to pave all the countless waterways that feed the rice fields with concrete. Japan loves to pave riverbeds. Furthermore, they made sure the waterways ran straight so the flow would be fast and inhospitable to snails.
Over the course of twenty years, they paved two thousand one hundred kilometers of riverbeds. They annihilated the natural environment of those fuckin' snails, and cases of The Local Disease gradually dropped to zero. The flatworm which caused the disease, schistosoma japonicum, has been wiped out in Japan.
The same disease still persists in China, the Philippines, Indonesia, and other places. It can now be treated cheaply with medicine. It is considered a neglected tropical disease.
In Japan, though, it isn't a problem. They wiped it out with a decades-long massive construction project alike to a civilizational wonder. They took an axe to the delicate ecology that supports the rice fields and kept hacking until they won and the snails lost.
I have complicated feelings about these sorts of large-scale interventions into the natural environment. At the same time, I can't argue with the results.
Fuck them snails.
