You are in: eMedicine Specialties > Infectious Diseases > MEDICAL TOPICS DiphyllobothriasisArticle Last Updated: Nov 7, 2006AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  Author: Derek Linklater, MD, Assistant Residency Director / ACLS Program Director, Assistant Clinical Professor of Emergency Medicine, TAMU HSC College of, Department of Emergency Medicine, Darnall Army Community Hospital Derek Linklater is a member of the following medical societies: Alpha Omega Alpha, American College of Emergency Physicians, and American Medical Association Coauthor(s): Coburn H Allen, MD, Assistant Professor, Department of Pediatrics, Section of Emergency Medicine and Section of Infectious Diseases, Baylor College of Medicine; Consulting Staff, Texas Children's Hospital Editors: Mark Raymond Wallace, MD, Chief, Clinical Professor, Department of Internal Medicine, Division of Infectious Disease, Naval Medical Center at San Diego; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Thomas M Kerkering, MD, Professor of Medicine and Microbiology, Department of Internal Medicine, Division of Infectious Disease, Brody School of Medicine at East Carolina University; Eleftherios Mylonakis, MD, Clinical and Research Fellow, Department of Internal Medicine, Division of Infectious Diseases, Massachusetts General Hospital; Burke A Cunha, MD, Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital Author and Editor Disclosure Synonyms and related keywords: diphyllobothriasis, cestodes, tapeworms, flatworms, intestinal parasites, scolex, Diphyllobothrium worms, Diphyllobothrium latum, D latum INTRODUCTIONSection 2 of 10
  BackgroundCestodes, more commonly called tapeworms, are symmetric flatworms that parasitize the intestinal tract of vertebrates. Tapeworms consist of a head (scolex), a neck, and a germinal region that consists of a string of separate individual segments that have a full set of progressively maturing reproductive organs. The scolex attaches to the host's intestinal mucosa, and tapeworms grow when segments bud from the scolex. The segments enlarge by developing large numbers of eggs that are subsequently shed in the stool. Cestodes are hermaphroditic and capable of self-fertilization, but Diphyllobothrium eggs must be passed into an aquatic environment to complete their development and become infective. Cestodes do not have a digestive tract at any stage of their development; consequently, they exchange nutrients and waste through their body covering (tegument). The tegument is covered by minute projections called microtriches, which lie in proximity to the host's intestinal villi and greatly increase the absorptive area of the flatworm. PathophysiologyAdult Diphyllobothrium worms range from 1-12 meters in length, have proglottids that are wider than their length, and discharge ovoid eggs that measure 60 µm X 40 µm. The life cycle of Diphyllobothrium species begins with an infected host discharging eggs into a freshwater environment that contains susceptible crustaceans and fish. After the eggs hatch, the embryonic flatworms are ingested by water fleas; in these crustaceans, the first larval stage develops. When a fish devours the infected crustacean, a second larval stage develops, and this larva is infective to the definitive hosts. The juvenile worm develops to maturity in the small intestine of the definitive host and, within 3-5 weeks, begins to produce eggs. Adult Diphyllobothrium worms may survive longer than 10 years. FrequencyUnited StatesIn North America, Diphyllobothrium latum infections have been reported in fish from the Great Lakes; however, no recent reports have been received, and the worm may have ceased to reside in this area. Eskimos have also reported infections, and 6 Diphyllobothrium species are known to reside in Alaskan lakes and rivers. Diphyllobothrium infections are not species specific, and widespread reports describe infection in North American fish-eating birds and mammals. The incidence in the United States has been declining, but the growing popularity of Japanese sushi and sashimi may increase the incidence. Pike, perch, and salmon (80% in a recent case series) are among the fish most commonly infected. InternationalD latum commonly infects humans residing in Europe, Africa, and the Far East. Dietary preferences, night soil (human excrement) fertilization practices, and poor sanitation seem to be responsible for the increased incidences in these countries. Mortality/MorbidityThe worm is not invasive and mortality is rare. Infected individuals are commonly asymptomatic. When present, symptoms are usually related to vitamin deficiencies and anemia. RaceNo known racial predilections exist, except as would be expected based on geographic and cultural factors. SexNo sex predilection has been identified. AgeNo age predilection has been identified. CLINICALSection 3 of 10
History
PhysicalD latum has an unusual affinity for vitamin B-12, and symptoms of infection clinically resemble those of megaloblastic anemia. Most patients have no signs of illness because significant anemia affects less than 2% of the population infected with D latum. The following findings are rare and are most likely related to underlying nutritional anemia:
CausesIngestion of raw or undercooked infected fish and subsequent intestinal infection DIFFERENTIALSSection 4 of 10
Anemia Folic Acid Deficiency Hypothyroidism Megaloblastic Anemia Pernicious Anemia
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| Drug Name | Niclosamide (Niclocide) |
|---|---|
| Description | DOC; inhibits mitochondrial oxidative phosphorylation and glucose uptake in parasite. |
| Adult Dose | 2 g PO once |
| Pediatric Dose | <11 kg: Not established 11-34 kg: 1 g PO once >34 kg: Administer as in adults |
| Contraindications | Documented hypersensitivity |
| Interactions | None reported |
| Pregnancy | B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals |
| Precautions | Associated with GI distress, anorexia, drowsiness, dizziness, headache, and rash; not FDA approved for this indication, although generally accepted as antimicrobial of choice for treating D latum infection |
| Drug Name | Praziquantel (Biltricide) |
|---|---|
| Description | Increases cell membrane permeability in susceptible worms, resulting in loss of intracellular calcium, massive contractions, and paralysis of musculature. Swallow tablets with liquid during meals. Keeping tablets in mouth may result in bitter taste that can produce nausea or vomiting. |
| Adult Dose | 5-10 mg/kg PO once |
| Pediatric Dose | <4 years: Not established >4 years: Administer as in adults |
| Contraindications | Documented hypersensitivity; ocular cysticercosis |
| Interactions | Serum level and effectiveness decrease with hydantoins |
| Pregnancy | B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals |
| Precautions | Associated with GI distress, anorexia, drowsiness, dizziness, and headache; caution while driving or performing other tasks requiring alertness on the day of and day following treatment; minimal increases in liver enzymes reported |
Article Last Updated: Nov 7, 2006
