Read the dictionary definition of louse. All definitions for this word.
1. wingless usually flattened bloodsucking insect parasitic on warm-blooded animals
2. wingless insect with mouth parts adapted for biting; mostly parasitic on birds
3. any of several small insects especially aphids that feed by sucking the juices from plants
4. a person who has a nasty or unethical character undeserving of respect