Tool singer Maynard James Keenan was initially reluctant to perform this song live. The reason, according to what was said by band members in the May 2001 issue of Oor Magazine is that Keenan threw his voice out as a result of this song (the vocals for which were, luckily, recorded after all the others on Lateralus).
"He couldn't talk for a day after we recorded his vocals. There's never been a song in which he screamed like this. But maybe we should think of another solution for that live, that's another possibility." -Danny Carey (Tool's drummer)
"And they can hassle me all they want about 'Ticks & Leeches,' I won't do it live. Three weeks it cost me. I couldn't sing a high note." -Maynard James Keenan
Eventually the band did agree on another way to perform the song live. The first concert they performed it at was on 9 October, 2001 in Fort Lauderdale, Florida. During the song, Keenan sings into some type of device that drastically distorts his voice, adding a lot of what sounds like white noise to it. This likely amplifies his voice in some way as well so Keenan can create something similar to the screeching on the studio recording of the song without throwing his voice out again.