Roundworm—Anisakis causes Anisakiasis is caused by Anisakis marina giving acute abdominal pain, peritonitis and bloody diarrhea. People and animals get the parasite by eating raw (like sushi), pickled or lightly salted fish or squid.
Treatment is with surgery or endoscopic removal. There are medications as well that have been used with some success.
Life Cycle of Anisakis:
Reference: https://www.dpd.cdc.gov/dpdx/HTML/Anisakiasis.htm