Some combination of what you suggest.
They die in 4 days without a blood meal. They also don’t reproduce well on just human blood. Needs to be other animals, preferably cats.
So hiding in blankets enroute is not going to work. They’ll die. But livestock, ya that will work to keep them alive, but breeding will slow.
It has always been a tricky problem since those guys showed the speed of plague spread exceeded rat travel speed.