Narjam

The Narjams were a non-sentient species of flat blue parasites that managed to colonize many worlds due to their ability to grow on the oil reserves of starships. Once they found themselves on a new world, they would often contract a local disease and pass a mutated variant of it back to the locals and native ecosystems through their bites.

Text and facts from the “Narjam” article on Wookieepedia, licensed under CC BY-SA 3.0. Modified for this site.