its a fluke called Nanophyetus salmincola, and has a life cycle similar to Henneguya Salminicola, which are the puss balls in meat, aka "tapioca disease"...

never let your dogs eat uncooked fish, or lick blood, or slime, or anything...

best is to just not let them eat fish at all, although some cook it and feed it to their dogs...

i wouldnt...