How do you counter Alchemist mid?

After watching some pro games of the alchemist radiance/octarine build I decided to try it myself and holy shit, after a few practice games I went on a streak so I kept playing it. I've won 14 games in a row now as alchemist mid. Doesn't really seem to matter what happens, their whole team tries to gank me, my farm is still decent, and the other heroes on my team crush their lanes. Pudge gets 3 kills on me mid, I still have 40+ cs at 10 minutes with a couple of bounty runes and get a sub 14 minute radiance.
Obviously the reason it is so successful for me is because I'm at lower level so I want to know, what is the proper way to stop this? It seems really hard to stop an alchemist from getting cs with acid spray spam.