Anisakiasis

KEY FEATURES

• Nausea, vomiting, and progressive epigastric pain

• Occasionally, acute infection is followed by a chronic course

• Infection is by larval invasion of the stomach or intestinal wall by anisakid nematodes

• Multiple species of the family Anisakidae may occasionally infect humans

• Definitive hosts for these parasites are marine mammals

• Eggs are passed in the feces and ingested by crustaceans, which are then eaten by fish and squid

• When ingested by humans in undercooked seafood, larvae penetrate the stomach or intestinal wall but cannot complete their life cycle

• Most common in Japan

CLINICAL FINDINGS

• Clinical manifestations follow burrowing of worms into the stomach or intestinal wall, leading to

  • Localized ulceration

  • Edema

  • Eosinophilic granuloma formation

• Acute infection

  • Causes severe epigastric or abdominal pain, nausea, and vomiting (usually within 2 days of parasite ingestion)

  • May cause allergic symptoms (eg, urticaria, angioedema, and anaphylaxis)

  • Generally resolves within 2 weeks

• Intestinal involvement can mimic appendicitis

• Chronic symptoms suggest

  • Inflammatory bowel disease

  • Diverticulitis

  • Carcinoma

• Rarely, worms may migrate to other sites or be coughed up

DIAGNOSIS

• Eosinophilia is not usually seen

• Radiographs may identify stomach or intestinal lesions

• Diagnosis is suggested in persons with acute abdominal symptoms after eating raw fish

• Endoscopy may allow visualization and removal of the worm

TREATMENT

• Specific therapy is not indicated

• Endoscopic worm removal hastens recovery

• Parasites are killed by cooking or deep freezing fish