Matt Schaub and the slumping Houston Texans made for easy prey in the 49ers' 34-3 triumph amid Sunday's prime-time spotlight at Candlestick Park.

Tramaine Brock accounted for two of the 49ers' three interceptions and he returned the first for a touchdown only 90 seconds into the eventual rout.

Brock's pick-six on an 18-yard return extended Schaub's historic streak to four consecutive games of having a pass intercepted and returned for a touchdown.

That play also sparked arguably the 49ers' best first-half performance since coach Jim Harbaugh took over in 2011. Their 21-0 halftime lead matched their most-lopsided cushion under Harbaugh: a 24-3 lead Oct. 9 2011 against the Tampa Bay Buccaneers in a 48-3 win.

The win moved the 49ers (3-2) closer to the first-place Seattle Seahawks who fell from the unbeaten ranks with a 34-28 road loss to the Indianapolis Colts. Two weeks ago the 49ers fell to the Colts 27-7.

Sharing second place with the 49ers are the Arizona Cardinals who'll visit Candlestick next Sunday before the 49ers take an extended road trip to Nashville (vs. the Tennessee Titans) and London (vs. the Jacksonville Jaguars).

The 49ers defense matched its season total with three interceptions through Sunday night's first three quarters. Brock made the first two interceptions and defensive end Tony Jerod-Eddie the third as an injury replacement for Ray McDonald who left with a right-biceps injury.

Offensively the 49ers got rushing touchdowns from Frank Gore and Anthony Dixon but it was Vernon Davis' 64-yard touchdown reception early in the fourth quarter that really finished off the Texans who then benched Schaub in favor of T.J. Yates.

On Schaub's first pass attempt of the night Brock broke off covering Keshawn Martin picked off the pass intended for Andre Johnson and returned that theft 18 yards for a 7-0 lead.

It was the first interception this season by a 49ers cornerback. Brock was in the No. 3 role for a second straight game in place of Nnamdi Asomugha who was sidelined again with a hyperextended knee.

Last Sunday Schaub had a pass intercepted and returned for a game-tying touchdown by Richard Sherman in the Seattle Seahawks' 23-20 overtime win in Houston.

The 49ers offense produced a 12-play 65-yard touchdown drive on its first possession capped by a 1-yard scoring run from Gore. It was Gore's team-record 54th rushing touchdown and his 36th in a goal-to-go situation. Colin Kaepernick was 3 of 3 on third-down conversion passes on that drive completing two strikes to Vernon Davis and the other to Anquan Boldin.