vermin

Concise Oxford English Dictionary © 2008 Oxford University Press:
vermin/ˈvɜːmɪn/

▶noun [treated as pl.]

• 1 wild mammals and birds which are harmful to crops, farm animals, or game, or which carry disease.

  ■ parasitic worms or insects.

• 2 very unpleasant and destructive people.

– derivatives
verminous adjective.

– origin ME: from OFr., based on L. vermis ‘worm’.