How to counter Bristleback

In lane

Drow Ranger
• Drow Ranger easily stays out of the range of Quill Spray while poking him to death with Frost Arrows. • Later in the game she can build Silver Edge to break his passive ability. • Later in the game she can build Aghanim's Scepter to reduce his health restoration.
Slark
• The damage mitigation of Bristleback is not enough to outsustain the stat steal of Essence Shift.

Viper
• Bristleback is overly reliant on running around the fight and mitigating damage with Bristleback. Viper Strike both slows him and breaks his passive ability.
Necrophos
• Death Pulse and Sadist are enough to outsustain him. • Ghost Shroud is great against Bristleback's full physical damage output. • Heartstopper Aura is always good against high HP heroes especially with the level 20 talent that reduces health restoration. • Bristleback likes to tank spells and attacks which means he might be low enough for a Reaper's Scythe kill.
Anti-Mage
• Bristleback relies on mana to spam Viscous Nasal Goo and Quill Spray to build Warpath stacks, making mana burn great against him.
Fight me!, 2 in this group
• Both of these heroes have a taunt ability, which is great against Bristleback as they make him fight face to face.
Silencer
• Arcane Curse heavily punishes Bristleback's Quill Spray spam. • In lane, Bristleback is very susceptible to Glaives of Wisdom harass.

Silver Edge
• This item breaks Bristleback.
Magic Stick
• Bristleback likes to spam spells in lane and this is a good item against him.
Mana burn, 2 in this group
• Bristleback relies on mana to spam Viscous Nasal Goo and Quill Spray to build Warpath stacks, making mana burn great against him.