Telusa Veainu scored twice, Peter Betham and Greg Bateman followed while the Tigers also claimed a first-half penalty try.
The victory rubber-stamped Leicester's place at the top of Pool Four with maximum points from their opening two games, while Stade-Francais' game against Munster was postponed.
For Treviso, this marked a 16th consecutive loss in the Champions Cup and they only had a solitary James Ambrosini kick to show for their efforts.
Treviso came close to beating Leicester at Stadio Monigo three years ago and made a bright start again despite the loss of key players.
However, they failed to register early points when Ambrosini missed a drop-goal effort and Tommaso Iannone went close in the corner after strong work by Francesco Minto.
Bell kicked a seventh-minute penalty when Minto was penalised at the breakdown but it was Leicester's strength in the scrum that created the game's first try.
Prop Matteo Zanusso was sin-binned in the 18th minute for collapsing the set-piece and French referee Mathieu Raynal awarded a penalty try following from the next scrum.
Bell converted but Leicester failed to add further punishment on the scoreboard against 14 men. But two tries in the five minutes before half-time helped the Tigers take control of the tie.
Tom Croft, who had recovered from a back spasm, set up Brendon O'Connor. Dom Barrow followed before Bell slid through a kick for Veainu to score on 36 minutes.
O'Connor was penalised from the restart to allow Ambrosini to kick Treviso's only points.
However, the Italians failed to gather the kick-off, Mathew Tait capitalised and Barrow made yards before Veainu floated his pass for wing Betham to beat two men and score on the stroke of half-time. Bell landed his second conversion for a 22-3 lead at the break.
Treviso were reduced to 14 men for a second time in the game when lock Jean-Francois Montauriol was shown a yellow card in the 50th minute for barging Sam Harrison off the ball after Bell chipped ahead.
Leicester kicked the penalty to the corner and thought they had the bonus point but Veainu was ruled to have lost control of the ball over the line.
Treviso steadied the ship and Italy scrum-half Eduardo Gori caused Leicester problems to frustrate the visitors.
Veainu finally clinched the all-important fourth try in the 67th minute when he stepped through three defenders to cross between the posts. Replacement hooker Bateman then followed in the last minute, shrugging off tackles to score Leicester's fifth try.