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Anisakiasis

By Richard D. Pearson, MD, Professor of Medicine and Pathology, Associate Dean for Student Affairs, University of Virginia School of Medicine

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Anisakiasis is infection with larvae of worms of the genus Anisakis and related genera such as Pseudoterranova. Infection is acquired by eating raw or poorly cooked saltwater fish; larvae burrow into the mucosa of the GI tract, causing discomfort.

Anisakis is a parasite that resides in the GI tract of marine mammals. Excreted eggs hatch into free-swimming larvae, which are ingested by fish and squid; human infection is acquired by ingestion of these intermediate hosts in a raw or undercooked state. Thus, infection is particularly common in locations such as Japan and cultures in which raw fish is traditionally consumed. Larvae burrow into the stomach and small bowel of humans.

Symptoms and Signs

Symptoms of anisakiasis typically include abdominal pain, nausea, and vomiting within hours of ingesting the larvae. In the small intestine, the infection may result in an inflammatory mass, and symptoms resembling Crohn disease may develop 1 to 2 wk later.

Anisakiasis typically resolves spontaneously after several weeks; rarely, it persists for months.

Diagnosis

  • Upper endoscopy

Anisakiasis is usually diagnosed by upper endoscopy; stool examination is unhelpful, but a serologic test is available in some countries.

Treatment

  • Endoscopic removal of the larvae

  • Albendazole

Endoscopic removal of the larvae is curative.

Treatment of anisakiasis with albendazole 400 mg po bid for 3 to 5 days may be effective, but data are limited.

Prevention

Larvae are destroyed by

  • Cooking to > 63° C (> 145° F)

  • Freezing at ─20° C (─4° F) or below for 7 days

  • Freezing at ─35° C (─31° F) or below until solid, then storing at that temperature for ≥ 15 h, or at ─20° C (─4° F ) for 24 h

Larvae may resist pickling, salting, and smoking.

Key Points

  • Humans acquire Anisakis when they consume the intermediate hosts (fish or squid) that are raw or undercooked; thus, anisakiasis is common in Japan and other cultures where raw fish is traditionally consumed.

  • Anisakiasis typically causes abdominal pain, nausea, and vomiting within hours of ingesting the larvae; an inflammatory mass may form in the small intestine and symptoms may resemble Crohn disease.

  • Anisakiasis typically resolves spontaneously after several weeks.

  • Do upper endoscopy to diagnose anisakiasis.

  • Endoscopic removal of the larvae is curative.

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Drugs Mentioned In This Article

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  • ALBENZA

* This is the Professional Version. *