You are in: eMedicine Specialties > Pediatrics: General Medicine > Parasitology HymenolepiasisArticle Last Updated: Feb 6, 2008AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  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 Editors: Glenn J Fennelly, MD, MPH, Director, Division of Pediatric Infectious Diseases, Jacobi Medical Center; Associate Professor, Department of Pediatrics, Albert Einstein College of Medicine; 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: diarrhea, dwarf tapeworm, gastrointestinal infection, GI infection, hymenolepiasis, Hymenolepididae, Hymenolepis diminuta, H diminuta, Hymenolepis nana, H nana, parasite, parasitic infection, rodent tapeworm, hand-to-mouth infection, abdominal pain, anal pruritus, nasal pruritus, urticaria INTRODUCTIONSection 2 of 10
  BackgroundHymenolepis nana is the cestode that most commonly infects humans, especially school-aged children. In contrast, only a few hundred human infections with the rodent tapeworm, Hymenolepis diminuta, a tapeworm for which the human is an incidental host, have been reported. Hymenolepiasis most frequently occurs in warm, dry regions of the developing world, where exposure to human feces results in hand-to-mouth infection. Direct person-to-person spread of H nana may occur. PathophysiologyHumans become infected with H nana when they ingest infective eggs, most commonly by direct fecal-oral exposure. The eggs pass into the ileum and hatch into oncospheres (the larval form), which penetrate the lamina propria of the villus. Within 3-4 days, the larvae mature into the preadult cysticercoid, which then enters the gut lumen to attach to the mucosae of the villus. Mature adults, measuring 35-45 mm in length and comprising 150-200 proglottids, result within about 3 weeks. Self-mating between adjacent proglottids generates hundreds of eggs, some of which penetrate intestinal villa and some of which pass into the feces. Occasionally, rodents may ingest the eggs in feces and serve as incidental hosts and reservoirs for spread of infection. Although infection usually does not produce infection, autoinfection (which is common) or intense exposure may result in a symptomatic infection caused by a heavy parasite burden. Human infection with H diminuta results from accidental ingestion of insects (immature fleas, flour beetles, meal worms, cockroaches) that carry the parasite in their body cavities. Infective eggs are ingested by insects and hatch in their guts. After hatching, they invade into the body cavity and become cysticercoid larvae, which are infectious for humans. After the insects are consumed and digested, the larvae are released in the small intestine and mature within 25 days into 50-cm adults. When the adult tapeworm begins to pass eggs, insect hosts can become infected again. Most infections produce no symptoms.1 FrequencyUnited StatesInfection is most common in the Southeast (1% of school children in one study) and among institutionalized children. Among more than 200,000 stool specimens submitted to the state laboratories in 1987 for ova and parasite analysis, 0.4% were positive for H nana. Because most infections do not produce symptoms, the true incidence is likely considerably higher. InternationalInfection is most common in children aged 4-10 years, in dry, warm regions of the developing world. H nana infection affects millions of people, primarily children, worldwide. Estimated rates of infection in various regions range from 0.1-58%. Regions with high reported infection rates include Sicily (46%), Argentina (34% of school children), and southern areas of the former Soviet Union (26%). In contrast, only 0.1% of stools examined at a children's hospital in Calgary were positive for H nana. Most cases with associated neurologic symptoms have been reported from the former Soviet Union. Mortality/MorbidityMorbidity is uncommon, only occurring when parasite burden is very high. Death has not been reported in association with this infection. RaceNo racial predisposition is known for hymenolepiasis. SexNo sex predilection is known for hymenolepiasis. AgeInfection can occur in persons of any age; however, because of the increased likelihood of exposure to human feces, school-aged children have the highest risk of hymenolepiasis. Infection in adolescents tends to clear spontaneously, and hymenolepiasis is uncommon among adults. CLINICALSection 3 of 10
HistoryThe vast majority of infections produce no symptoms. Symptom frequency seems to correlate with increasing worm burden. Among children with clinical infection, symptoms (in order of decreasing frequency) include restlessness, irritability, diarrhea, abdominal pain, restless sleep, anal pruritus, and nasal pruritus. Rare symptoms include anorexia, increased appetite, vomiting, nausea, bloody diarrhea, hives, extremity pain, headache, dizziness, behavioral disturbances, and seizures. PhysicalAside from rare abdominal tenderness or urticaria, physical examination is typically unrevealing. CausesRarely, infection can result from ingestion of foodstuffs contaminated with insects. However, infection generally follows hand-to-mouth exposure to feces (fecal-oral) in situations in which personal hygiene and/or sanitary disposal of human sewage is inadequate. DIFFERENTIALSSection 4 of 10
Amebiasis Ancylostoma Infection Appendicitis Ascariasis Campylobacter Infections Cholera Colic Colitis Constipation Crohn Disease Cryptosporidiosis Cytomegalovirus Infection Diarrhea Dientamoeba Fragilis Infection Diphyllobothrium Latum Infection Echovirus Enterobiasis Enteroviral Infections Fascioliasis Food Poisoning Gastroenteritis Giardiasis Hemolytic-Uremic Syndrome Hepatitis A Hookworm Infection Intestinal Enterokinase Deficiency Intestinal Malrotation Intestinal Protozoal Diseases Intestinal Volvulus Intussusception Isosporiasis Lactose Intolerance Malabsorption Syndromes Meckel Diverticulum Peptic Ulcer Disease Protein-Losing Enteropathy Salmonella Infection Shigella Infection Short Bowel Syndrome Sinus of Valsalva Aneurysm Small-Bowel Obstruction Soy Protein Intolerance Sprue Taenia Infection Ulcerative Colitis Volvulus Whipworm Yersinia Enterocolitica Infection
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| Drug Name | Praziquantel (Biltricide) |
|---|---|
| Description | The DOC, praziquantel is 80-100% effective in cases in which the burden of tapeworms is not great. Although it is FDA approved and available in the United States, its use is considered investigational for this indication. |
| Adult Dose | 25 mg/kg PO as a single dose; tab should be taken with food and swallowed whole with liquids (do not chew) |
| Pediatric Dose | Administer as in adults |
| Contraindications | Documented hypersensitivity; spinal or ocular cysticercosis |
| Interactions | Hydantoins may reduce serum praziquantel concentrations, possibly leading to treatment failures |
| Pregnancy | B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals |
| Precautions | Caution with severe hepatic disease; possible dizziness and drowsiness |
| Drug Name | Niclosamide (Niclocide) |
|---|---|
| Description | Effective, but unavailable in the United States. Inhibits mitochondrial oxidative phosphorylation and glucose uptake in parasite. Treatment course is 7 d because it does not reach the cysticercoids in the lamina propria. |
| Adult Dose | 2 g PO as a single dose, followed by 1 g PO qd for 6d Tab to be chewed completely at least 2 h before a meal |
| Pediatric Dose | <11 kg: Not established 11-34 kg: 1 g PO as a single dose, followed by 500 mg PO qd for 6d >34 kg: 1.5 g PO as a single dose, followed by 1 g PO qd for 6d Tab to be chewed completely at least 2 h before a meal |
| 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 |
| Drug Name | Paromomycin (Humatin) |
|---|---|
| Description | An alternative to praziquantel, but requires a 7-d course of therapy. Amebicidal and antibacterial aminoglycoside obtained from a strain of Streptomyces rimosus, active in intestinal amebiasis. Recommended for Diphyllobothrium latum, Taenia saginata, Taenia solium, Dipylidium caninum, and Hymenolepis nana. |
| Adult Dose | 45 mg/kg PO qd for 7 d |
| Pediatric Dose | Administer as in adults |
| Contraindications | Documented hypersensitivity; intestinal obstruction |
| Interactions | Nephrotoxic potential may increase with concurrent administration of other aminoglycosides, penicillins, cephalosporins, amphotericin B, and loop diuretics |
| Pregnancy | C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus |
| Precautions | Possible GI disturbances, hematuria, rash, ototoxicity, and hypercholesterolemia |
| Drug Name | Nitazoxanide (Alinia) |
|---|---|
| Description | Inhibits growth of Cryptosporidium parvum sporozoites and oocysts and Giardia lamblia trophozoites. Elicits antiprotozoal activity by interfering with pyruvate-ferredoxin oxidoreductase (PFOR) enzyme-dependent electron transfer reaction, which is essential to anaerobic energy metabolism. Available as a 20-mg/mL oral susp. Off-label use for H nana. |
| Adult Dose | Not established |
| Pediatric Dose | <1 year: Not established 1-4 years: 100 mg (5 mL) PO q12h for 3 d with food 4-11 years: 200 mg (10 mL) PO q12h for 3 d with food >11 years: Not established |
| Contraindications | Documented hypersensitivity |
| Interactions | Tizoxanide (nitazoxanide metabolite) is >99.9% bound to plasma protein and may potentially increase toxicity of other highly plasma protein-bound drugs |
| Pregnancy | C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus |
| Precautions | May cause abdominal pain, diarrhea, vomiting, or headache; administer with food; caution when coadministered with other highly plasma protein-bound drugs with narrow therapeutic indices |
Article Last Updated: Feb 6, 2008
