Level 48 for this mob isn't correct, as he can be druid Dire Charmed (tried it on a whim and it worked). For what it's worth, he doesn't make that good of a pet, the Dangerous Mine Rats are better for DC.
This mob does indeed spawn where piple's post indicates. Its PH is 'a dangerous mine rat,' which stands out because that's the Tier 4 (out of the 5 in this zone) version of the rat, but the rest of its room is Tier 3 mobs. Also, the Blood Thirsty Rat Hide does not drop every time. Killed it twice today, got two pairs of boots but only one Hide.
I just looted the same item a few minutes ago. Very nice int caster range item indeed. I bet we had killed that rat 30 or so times before it droped. Boots every other time.
I have killed the blood thirsty rat at least three times now in the mines and it drops the boots every single time, along with some blood thirsty rat meat. The rat also seems to spawn in the same place but it has a PH. It spawns in the room that used to have Overseer Dulbish. Just keep the room cleared.
Here is a map showing you where he spawns (look for #3): http://www.eqatlas.com/kunark/nurga1map.html