Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Threats to Teemo with this build
You essentially counter almost all ADC's, the exception: ADC's played with abillities. Once you get fed, you will be hard to kill. You will have a lot of movement speed and you will dodge enemies abillities easly. The only problem is that you will be easy killed in team fights , thats why you will act like adc.