Leech larvae!
I think only boiling or filtering would've prevented this infection. What do you think?
Excerpt:
A Chinese boy stopped at a pond for a quick sip on his way home from school. A few weeks later, he was blacking out.
Doctors recently discovered the cause of 11-year-old Xiaobo Chien’s affliction. According to Central European News (via WFLD-TV), a more than 2-inch-long leech was attached to the inside of his throat. It is believe he ingested the blood-sucking worm when it was in its larval form.
The boy lost consciousness when the leech would curl into a ball and block his air passage.
