Case Report tapeworm and

Nancy Craig MD CM CCFP

variety of parasitic infections might be acquired by ingesting raw or undercooked fin fish (Table 1).1-3 A Fish tapeworm, or spp, is acquired by eating raw or undercooked freshwater or anad- romous fish (ie, sea fish that spawn in freshwater rivers, such as sal- EDITOR’S KEY POINTS mon). Marinated and smoked fish can also transmit the worm.4 While • is infection of the cases in previously endemic areas have decreased, likely because of by the broad tapeworm improved sewage treatment processes, cases have increased in other Diphyllobothrium spp acquired from parts of the developed world,5-9 presumably owing to increased con- eating undercooked or raw fish. With the sumption of raw fish.4 The widespread popularity of Japanese sushi increasing popularity of sushi and , (bite-sized pieces of cold cooked rice topped with fish, eggs, or vege- it can be expected that diphyllobothriasis tables and wrapped in seaweed) and sashimi (slices of raw fish) is a will become more common. contributor, but other popular dishes might also be implicated, such as raw salted or marinated fillets (which originate from Baltic and • Diphyllobothriasis infections are often Scandinavian countries), carpaccio (very thin slices of raw fish com- asymptomatic and can persist for years. mon in Italy), tartare maison (raw ) and poisson du lac façon nordique (in French-speaking ), and (lightly marinated • Symptoms include fatigue, constipation, fish in Latin America).4 diarrhea, vague abdominal discomfort, and less commonly vomiting. Case A 43-year-old woman presented to an Edmonton, Alta, emergency • Check for in department with acute onset of diarrhea and vomiting, and was diag- suspected and proven cases. nosed with gastroenteritis. The acute illness resolved, but the patient came to the clinic 8 weeks later complaining of unresolved diarrhea. • Treatment is a single dose of 10 to She was otherwise in good health. There was no history of travel. A 25 mg/kg of . workup was ordered, including the following: complete blood count; vitamin B12 level; liver function and lipase tests; , B, and POINTS DE REPÈRE DU RÉDACTEUR C screening; tissue transglutaminase test; stool for occult blood; and • La diphyllobothriase est une infection stool culture and examination for ova and parasites. de l’intestin grêle causée par le ténia However, the following day, before any of the workup was done, the large Diphyllobothrium sp et acquise en patient passed a 75-cm flat worm. She took it to a laboratory where it mangeant du poisson mal cuit ou cru. was identified as Diphyllobothrium latum segments. All other Étant donnée la popularité grandissante tests ordered came back with normal or negative results, except for an des et du sashimi, on peut s’attendre indeterminate hepatitis A immunoglobulin G. On review, the patient à ce que les cas de diphyllobothriase described herself as a “regular” sushi consumer. She could not recall deviennent plus fréquents. any other raw fish consumption, and no more detail concerning the type or source of her sushi was obtained. She was treated with 600 mg • Les diphyllobothriases sont des infections of praziquantel. Follow-up stool testing for ova and parasites 2 weeks souvent asymptomatiques et elles peuvent later showed negative results. persister pendant des années.

Discussion • Parmi les symptômes, on peut The eggs of Diphyllobothrium species hatch into embryos (coracidia) mentionner la fatigue, la constipation, la after 2 weeks in cool fresh water. These are ingested by (the diarrhée, un vague malaise abdominal et, first intermediate host), where they develop into the first larval stage, or moins souvent, des vomissements. procercoids, over 2 to 3 weeks. When the is eaten by fish, the procercoids migrate into the muscle fibres of the fish where they meta- • Il faut vérifier s’il y a une carence de morphose into the second larval stage, or plerocercoids. Raw fish con- vitamine B12 chez les cas suspectés et sumption by a definitive host (carnivore such as , dogs, diagnostiqués.

This article has been peer reviewed. • Le traitement est l’administration Cet article a fait l’objet d’une révision par des pairs. d’une seule dose de 10 à 25 mg/kg de Can Fam Physician 2012;58:654-8 praziquantel.

654 Canadian Family Physician • Le Médecin de famille canadien | Vol 58: June • juin 2012 Case Report and humans) allows the plerocercoids to attach to the Treatment small-intestine wall. There they develop into the mature Treatment is usually 10 to 25 mg/kg of praziquantel given tapeworm over 3 to 5 weeks. Mature Diphyllobothrium as a single dose.4 Stool culture for ova should be nega- spp can grow from 2 m to 15 m in length, the largest tive a week after treatment; occasionally a second dose known parasite in humans; can live for many years in might be needed.6 While treatment is generally completed the host intestine; and can discharge very large num- in a single dose, segments might continue to be evacu- bers of eggs per day, completing the cycle.4,8,10 ated over a prolonged period, which can be distressing to patients and their families. If vitamin B12 levels are low, Symptoms and investigations they generally return to normal ranges within a period of Diphyllobothrium infections are often asymptomatic. several months.4 While praziquantel is not officially indi- When symptoms occur, they are often mild and vague, cated for this use in Canada, it is the accepted treatment in including fatigue, constipation, and poorly defined the literature. , 2 g as a single dose, is another abdominal discomfort. Laboratory investigations tend accepted treatment, but it is not available in Canada. to present normal results, but might show low vitamin B12 levels or frank pernicious anemia (if the worm Prevention has attached in the proximal small intestine, it can Prevention can be accomplished on a population level by compete for vitamin B12 absorption).4 Often the first good sewage treatment plants interrupting the cycle at the awareness of infection might be passing segments point where eggs are discharged back into the water, when of the tapeworm in the stool,5-7 as the patient in this humans are the definitive host. This is the likely reason report did, whose diarrhea might have been due to for the decline of diphyllobothriasis in previously endemic an unrelated illness. Diagnosis is made by identifica- areas such as Scandinavia4 and coastal areas of Japan.7 tion of ova or sometimes worm segments in the stool On an individual level, consumers should be aware of (Figures 1 and 2). the risks of diphyllobothriasis with consuming uncooked

Vol 58: June • juin 2012 | Canadian Family Physician • Le Médecin de famille canadien 655 Case Report fish. Sushi and sashimi are now available not just in res- and sashimi chefs should use only fish frozen in this taurants, but also in the deli sections of many grocery way. While these freezing protocols are the standards stores. Marketers should consider affixing labels to the required by public health regulations, they are not easy packaging, assuring consumers that proper preparations for public health inspectors to verify. have been completed to minimize risks of fish tapeworm. Those who prepare fish should be aware that cooking at Relevance a temperature of only 55°C for 5 minutes will kill the With the increasing popularity and availability of sushi in larvae; freezing to - 20°C for 7 days, or flash freezing restaurants and grocery stores, one might expect to see to - 35°C for 15 hours, as long as the flesh is less than an increase in the number of cases of diphyllobothriasis 15 cm thick, effectively kills the larvae also.4,5,7,8 Sushi such as this one. Ching described a substantial increase

Table 1. Parasitic infections acquired by ingesting raw fish Category Genus, Species Sources Symptoms Diagnosis Treatment simplex Raw or undercooked Acute (1-2 h after ingestion, Ultrasound: might Spontaneous fish or squid maybe up to 14 d): show small-bowel recovery; occasional sudden, severe, episodic dilatation; thread-like endoscopic removal epigastric distress, gastric filling defects of worms sometimes nausea and vomiting

Chronic: diarrhea, urticaria, occasional coughing up of larvae, intestinal pseudo-obstruction Trematodes Korea, China, Acute (within 1 wk of Stool for ova Praziquantel (liver Taiwan, Vietnam, ingestion): fever, chills, flukes) and Japan; raw or tender hepatomegaly undercooked fish Chronic: asymptomatic; occasional cholangitis or pancreatitis Echinostoma Southeast and east Gastroenteritis, anemia, Stool for ova Mebendazole, Asia; raw or headaches, dizziness, , or undercooked fish stomach pain, diarrhea, praziquantel anorexia, eosinophilia Trematodes Metorchis Raw white sucker 1-15 d incubation; Stool for ova or Praziquantel or (intestinal conjunctus fish (case report in abdominal pain, fever, serology spontaneous flukes) Quebec)1 diarrhea, headache, nausea resolution Heterophyes spp Middle East, Asia; Abdominal pain, diarrhea Stool for ova Praziquantel raw, marinated, or undercooked fish Metagonimus spp Middle East, Asia; Abdominal pain, diarrhea Stool for ova Praziquantel raw, marinated, or undercooked fish Nanophyetus North America; raw, Diarrhea, abdominal pain, Stool for ova Spontaneous salmincola undercooked, or nausea and vomiting, resolution or smoked fish fatigue, weight loss antiparasitic agents Cestodes Diphyllobothrium Raw, undercooked, Abdominal pain, diarrhea, Stool for ova or Praziquantel or latum or marinated fish eosinophilia, occasional passage of proglottids niclosamide* B12 deficiency Protozoa Giardia lamblia North America; Nausea, chills, fever, Trophozoites or cysts Metronidazole home-canned epigastric pain, foul- in stool salmon; China, koi smelling diarrhea (might be pla (ie, fish soup), mucous-mixed, bloody) using uncooked freshwater fish *Praziquantel is indicated in Canada for the treatment of and some liver flukes, but not specifically for fish tapeworm. It is recognized as a treatment for Diphyllobothrium spp elsewhere, as is niclosamide. Niclosamide is not available in Canada. Data from Butt et al,1 van Voorthuis and Weller,2 and Eastburn et al.3

656 Canadian Family Physician • Le Médecin de famille canadien | Vol 58: June • juin 2012 Case Report

Figure 1. Diphyllobothrium latum ova wet mount ) M ( CLS

MLT Photo credit: D.M. Raymondo Photo credit:

Vol 58: June • juin 2012 | Canadian Family Physician • Le Médecin de famille canadien 657 Case Report

Figure 2. Diphyllobothrium latum proglottids ) M ( CLS

MLT Photo credit: D.M. Raymondo Photo credit:

in the number of cases in British Columbia between the Dr Craig is a family physician in Edmonton, AB.

1970s and the early 1980s, attributed to increasing con- Competing interests sumption of uncooked salmon.11 A MEDLINE search using None declared the terms diphyllobothriasis and sushi revealed a num- Correspondence ber of case reports from a variety of places around the Dr Nancy Craig, 528 Wahstao Rd, Edmonton, AB T5T 2Y1; telephone 780 443-0200; e-mail [email protected] world, only 3 of which had North American connections. In all cases, raw or undercooked fish were consumed, References 1. Butt AA, Aldridge KE, Sanders CV. Infections related to the ingestion of seafood. Part 5 often salmon species, but sometimes , char, or pike. II: parasitic infections and safety. Lancet Infect Dis 2004;4(5):294-300. Sushi and sashimi restaurants were specifically implicated 2. Van Voorthuis WC, Weller PF. Helminthic infections. In: Dale DC, editor. Infectious diseases. The clinician’s guide to diagnosis, treatment, and prevention. New York, NY: 7-9 in some reports. Additional cases are likely occurring WebMD Corp; 2003. but are not being reported in the literature. Primary care 3. Eastburn RL, Fritsche TR, Terhune CA Jr. Human intestinal infection with from salmonid . Am J Trop Med Hyg 1987;36(3):586-91. physicians should keep the possibility in mind. 4. Scholz T, Garcia HH, Kuchta R, Wicht B. Update on the human broad tape- worm (genus Diphyllobothrium), including clinical relevance. Clin Microbiol Rev 2009;(1):146-60. Conclusion 5. Shimizu H, Kawakatsu H, Shimizu T, Yamada M, Tegoshi T, Uchikawa R, et al. Given the current popularity of sushi and sashimi Diphyllobothriasis nihonkaiense: possibly acquired in Switzerland from imported Pacific salmon. Intern Med 2008;47(14):1359-62. Epub 2008 Jul 15. in North America, and the rarity of case reports 6. Lee KW, Suhk HC, Pai KS, Shin HJ, Jung SY, Han ET, et al. Diphyllobothrium latum of diphyllobothriasis in North American literature, infection after eating domestic salmon flesh. Korean J Parasitol 2001;39(4):319-21. one might speculate that there is generally good 7. Arizono N, Yamada M, Nakamura-Uchiyama F, Ohnishi K. Diphyllobothriasis associ- ated with eating raw Pacific salmon. Emerg Infect Dis 2009;15(6):866-70. compliance with proper freezing of fish for these prod- 8. Santos FL, de Faro LB. The first confirmed case of Diphyllobothrium latum in Brazil. ucts. However, in cases of vague abdominal complaints Mem Inst Oswaldo Cruz 2005;100(6):585-6. Epub 2005 Nov 8. 9. Llaguno MM, Cortez-Escalante J, Waikagul J, Faleiros AC, Chagas F, Castro C. or unexplained low vitamin B12 levels, it might be Diphyllobothrium latum in a non-endemic country: case report. Rev Soc Bras Med worth asking patients about types of fish consumed, Trop 2008;41(3):301-3. 10. Larsh JE Jr. Helminths and helminthic infections. In: Joklik W, Willett HP, Amos DB, particularly bearing in mind the popularity of sushi and editors. Zinsser microbiology. 17th ed. New York, NY: Appleton-Century-Crofts; 1980. sashimi, and it might be worth checking the stool for p. 1471-2. 11. Ching HL. Fish tapeworm infections (diphyllobothriasis) in Canada, particularly Diphyllobothrium ova. British Columbia. Can Med Assoc J 1984;130(9):1125-7.

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