environmental/diagnostic assay data sheet

Anisakid worm PCR test

Anisakiasis or herring worm disease is a parasitic disease caused by infection with larvae of worms of the genera Anisakis or Pseudoterranova. These worms, normally found in many species of marine fish, squid and other marine organisms, can also invade the stomach and intestine of humans. Anisakids share common features of all nematodes, such as vermiform body plan, round cross section and lack of segmentation. Currently, nine species are genetically recognized in the genus Anisakis, and among them A. simplex and A. pegreffii are the major causes of human anisakiasis.

Transmission of this disease occurs when humans eat raw or undercooked fish or squid infected with these larvae. The disease is particularly common in locations such as Japan in which raw fish is often consumed. However, due to internationalization of Japanese culture, more and more people enjoy eating raw fish and squid; thus, the incidence of people infected with these worms is increasing.

People infected with these worms typically develop abdominal pain, nausea, and vomiting within hours of ingesting the larvae. If larvae continue growing in the small intestine, it may result in an inflammatory mass, and produce symptoms resembling Crohn’s disease in one to two weeks. However, symptoms of anisakiasis typically resolves spontaneously after several weeks; rarely, it persists for months. Only in some cases, removal of the larvae via endoscopy or surgery is required. However, people who produce immunoglobulin E in response to this parasite may subsequently have an allergic reaction, including anaphylaxis, after eating fish infected with these worms.

These larvae can resist pickling, salting, and smoking.  If raw fish consumption is desired, the fish can be frozen at -20⁰C or below for 7 days before consumption, as freezing can kill the larvae. However, quality of fish can be compromised by freezing. If unfrozen fish flesh is used to make good sashimi, the source of the fish should be tested to screen for the presence of larvae. Molecular detection by PCR is increasingly being used to detect and confirm the presence of these worms in fresh fish and squid (Lim et al., 2015). PCR can also identify nonviable larvae in frozen fish.

Utilities:

• Confirm and identify Anisakis and Pseudoterranova worms in fish or squid
• Screen fish or squid for these parasites
• Shorten the time required to confirm a clinical diagnosis of the infection

References:
Lim, H., Jung, B.K., Cho, J., Yooyen, T., Shin, E.-H., & Chai, J.Y. (2015). Molecular Diagnosis of Cause of Anisakiasis in Humans, South Korea. Emerging Infectious Diseases, 21(2), 342–344.

Specimen requirements: Fresh, frozen or fixed worm or partial worm, or 0.2 ml fresh, frozen or preserved fish or squid flesh suspected of containing larvae.

Contact Zoologix if advice is needed to determine an appropriate specimen type for a specific diagnostic application. For specimen types not listed here, please contact Zoologix to confirm specimen acceptability and shipping instructions.

For all specimen types, if there will be a delay in shipping, or during very warm weather, refrigerate specimens until shipped and ship with a cold pack unless more stringent shipping requirements are specified. Frozen specimens should be shipped so as to remain frozen in transit. See shipping instructions for more information.

Turnaround time: 2 business days

Methodology: Qualitative real time polymerase chain reaction

Normal range: Nondetected