ah, wikipedia has a pic of those. the bloodworms I'm familiar with are midge larvae. very diffferent.
they would probably be ok, but as with any new natural food, there can be problems. sometimes things that aren't poisonous to one something are poisonous to something else. if you really want to try, feed one to your least liked fish and wait a few days after watching closely for any adverse reactions. if you don't get any actual info from someone with experience with those things.
I've fed night crawlers and red wigglers without problems, but no actual experience with your type. I've never even seen those before.