You are in: eMedicine Specialties > Pediatrics: General Medicine > Parasitology Diphyllobothrium Latum InfectionArticle Last Updated: Feb 4, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 11
  Author: Robert W Tolan Jr, MD, Chief of Allergy, Immunology and Infectious Diseases, The Children's Hospital at Saint Peter's University Hospital; Clinical Associate Professor of Pediatrics, Drexel University College of Medicine Robert W Tolan, Jr, is a member of the following medical societies: American Academy of Pediatrics, American Medical Association, American Society for Microbiology, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, Phi Beta Kappa, and Physicians for Social Responsibility Coauthor(s): Alia Rai, MD, Adolescent Medicine Fellow, Department of Pediatrics, West Virginia University; Martin Weisse, MD, Program Director, Associate Professor, Department of Pediatrics, West Virginia University Editors: Ashir Kumar, MBBS, MD, FAAP, Professor, Department of Pediatrics and Human Development, College of Human Medicine, Michigan State University; Consulting Staff, Department of Pediatrics, EW Sparrow Hospital; Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine.com, Inc; Martin Weisse, MD, Program Director, Associate Professor, Department of Pediatrics, West Virginia University; Daniel Rauch, MD, FAAP, Director, Pediatric Hospitalist Program, Associate Professor, Department of Pediatrics, New York University School of Medicine; Russell W Steele, MD, Professor and Vice Chairman, Department of Pediatrics, Head, Division of Infectious Diseases, Louisiana State University Health Sciences Center Author and Editor Disclosure Synonyms and related keywords: broad tapeworm, cestodes, diphyllobothriasis, Diphyllobothrium latum, D latum, Diphyllobothrium latum infection, fish tapeworm, megaloblastic anemia, sparganosis, vitamin B-12 deficiency, GI obstruction, gastrointestinal obstruction, abdominal pain, celiac disease, congenital malabsorption, glossitis, tachycardia, dyspnea INTRODUCTIONSection 2 of 11
  BackgroundHuman intestinal infection with the fish tapeworm, or broad tapeworm, Diphyllobothrium latum is called diphyllobothriasis. It is endemic in areas where humans frequently consume raw or pickled fish. The associated symptomatology is nonspecific, but megaloblastic anemia is a well-described complication. PathophysiologyCestodes, a subclass of the phylum Platyhelminthes, has 2 orders that infect humans: Cyclophyllidea and Pseudophyllidea. One of the main differentiating points between the genera of the 2 orders is that the genera of the first order typically have a scolex with 4 suckers whereas the genera of the second order have a scolex with 2 opposing sucking grooves. Another important point of differentiation is that Cyclophyllidae has 2 hosts in its life cycle whereas Pseudophyllidea requires 3. Diphyllobothrium is an example of the genera under Pseudophyllidea. The species of this genus are all parasites of fish-eating vertebrates. This article focuses on the organism D latum, for which humans are the definitive host. A full-grown worm can vary in size from 1-15 m and is the longest human tapeworm. It consists of up to 3000-4000 proglottids. The scolex, as mentioned, has 2 sucking grooves, also called bothria. Proglottids are typically wider than they are long (see Media file 3), which is why D latum is called the broad tapeworm. In the gravid state, the worms have a distinctive rosette-like uterus in the center. The uterus sheds eggs into the fecal stream via a ventral pore. The eggs are unembryonated when shed and are operculated. The eggs (see Media file 2) must reach fresh water that contains crustaceans and fish to act as the intermediate host to complete their maturation. During a 10- to 14-day period, they transform into ciliated embryos with 6 hooks (called coracidia) that are released from the open opercula. The coracidia must then be eaten within a short period by crustacea (eg, copepods or water fleas) to undergo the next stage of maturation, which is the first-stage larva or procercoid (see Media file 1). Copepods that contain the procercoid are then eaten by freshwater fish that function as the second intermediate host. Here, the procercoid matures into the plerocercoid or sparganum in the fish muscle fibers. Infected fish are then consumed by progressively larger fish, with the sparganum being passed on, until, finally, the fish is consumed by a human, the definitive host. During the next 3-5 weeks, the plerocercoid larva matures into an adult that can live for up to 10 years. Thus, the plerocercoid larva infects humans who have ingested heated or frozen freshwater fish. Because of the requirement for intermediate hosts, direct human-to-human transmission does not occur; therefore, no isolation measures are required. Although actual results of infestation are not well studied, megaloblastic anemia can result. Some scientists believe the mechanism is related to the site of the worm, its marked affinity for vitamin B-12, and, perhaps, an underlying vitamin B-12 deficiency in patients at the outset. One study demonstrated that when a mixture of vitamin B-12 and gastric juice were placed in the ileum, a hematological remission resulted. This did not occur when the mixture was taken orally. This suggests that D latum preferentially absorbs vitamin B-12 in the blood, preventing vitamin B-12-IF complexes from reaching receptors in the small bowel. FrequencyUnited StatesOutbreaks associated with the increased popularity and availability of fresh salmon (as opposed to canned or frozen salmon) have been described. Also, infestation is related to the popularity of delicacies such as sushi. InternationalThis is a worldwide disease that affects people near freshwater and appropriate intermediate hosts. Areas where consumption of raw/precooked fish is popular tend to have endemicity (eg, northern Europe, Scandinavia). Mortality/Morbidity
RaceNo racial predilection has been reported. SexNo sex predilection has been documented. AgeNo age predilection has been reported. CLINICALSection 3 of 11
HistoryDiphyllobothriasis is typically an asymptomatic condition. Patients do not usually observe passage of segments in the stool as noted in other tapeworm infections. A few reports have documented patients who presented after vomiting a ball of worms that were determined to be fish tapeworms. One study looked at a selection of symptoms in a group of patients who were affected but nonanemic. Increased symptoms of fatigue, extremity numbness, and anorexia occurred in the affected group. Abdominal pain was not a significant symptom. GI obstruction is rare but may occur, especially when numerous worms are present. If this occurs, patients present with acute abdominal pain associated with vomiting, distension, or both. Megaloblastic anemia is well described although very unusual. Studies note that about 40% of patients have decreased serum vitamin B-12 levels, but less than 2% of patients are anemic.1 Patients with an underlying problem (eg, celiac disease or congenital malabsorption) are at higher risk of developing a symptomatic infection. Anemic patients can present with pallor, breathlessness, and neurological symptoms such as weakness, numbness, and disturbances in coordination. The symptoms depend on the severity. PhysicalNo typical examination findings are noted except those found in severe cases of anemia. These can include glossitis, signs of degeneration of the posterior columns of the spinal cord (which include loss of vibratory sense, proprioception, and coordination), tachycardia, pallor, and dyspnea. If the patient presents with obstruction, abdominal tenderness, distension, and peritoneal signs may be present. CausesThe main causative organism is D latum, but, less frequently, other Diphyllobothrium species have been reported as infecting agents. Examples include Diphyllobothrium pacificum, Diphyllobothrium cordatum, Diphyllobothrium ursi, Diphyllobothrium dendriticum, Diphyllobothrium lanceolatum, Diphyllobothrium dalliae, and Diphyllobothrium yonagoensis. DIFFERENTIALSSection 4 of 11
Anemia, Acute Anemia, Chronic Taenia Infection
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| Drug Name | Praziquantel (Biltricide) |
|---|---|
| Description | Used in the treatment of several different infestations and the DOC for diphyllobothriasis. The dose depends on the specific infection. Doses below are specifically for diphyllobothriasis. |
| Adult Dose | 5-10 mg/kg PO once as a single dose |
| Pediatric Dose | >4 years: Administer as in adults |
| Contraindications | Documented hypersensitivity; ocular and spinal cysticercosis |
| Interactions | Alcohol may increase CNS depression; phenytoin and carbamazepine may increase metabolism of the drug, hence decreasing its activity; cimetidine can cause increased serum levels |
| Pregnancy | B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals |
| Precautions | Use with caution in patients with severe hepatic disease or seizure disorders |
| Drug Name | Niclosamide (Niclocide) |
|---|---|
| Description | An anthelmintic used to treat various tapeworm infections and an alternative therapy for diphyllobothriasis. Doses below are for diphyllobothriasis. Inhibits mitochondrial oxidative phosphorylation and glucose uptake in parasite. |
| Adult Dose | 2 g PO once as a single dose pc |
| Pediatric Dose | 40 mg/kg PO once as a single dose |
| 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 |
| Media file 1: Life cycle of Diphyllobothrium. | |
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| Media file 2: Microscopy. Egg of Diphyllobothrium latum with arrow pointing to operculum. | |
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| Media file 3: Microscopy. Proglottids of Diphyllobothrium latum. | |
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Diphyllobothrium Latum Infection excerpt
Article Last Updated: Feb 4, 2008
