Early in the season, it's quite common to run into Fleas on Squirrels. We don't hunt Rabbits till after the second frost and don't see them much during this time. Regardless, no need to panic. They mostly go to the groin area where it stays warmer.
That is the groin area of the game.
As stated, a good shower is in order that evening. A bigger concern is Deer Ticks. Most of the ticks we run into, are Wood Ticks and they are okay but the Deer Ticks are another matter. Don't pass up a good meal because of Fleas.
Be Safe !!!