Has we didn't see Merle dead on the floor, but we saw the Gov shoot Merle we can assume he was killed by the gunshot wound, Merle must have turned without being bitten.
Weird how this hasn't really been mentioned since the start of the season by the prison gang since Rick told them the truth about people turning when dead even though they haven't been bitten.
The Governor didnt shoot Merle in the head on purpose so that a walker would bite him and then Rick's group would find him when they got to the location as a zombie.
I didn't care much for Merle, besides this episode honestly. In terms of overall show development and plot progression him and Mishonne are the ones I care for the least.
