eMedicine Specialties > Pediatrics: General Medicine > Parasitology

Hymenolepiasis

Robert W Tolan Jr, MD, Chief, Division 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

Updated: Jan 22, 2009

Introduction

Background

Hymenolepis 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.

Pathophysiology

Humans 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

Frequency

United States

Infection 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.

International

Infection 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/Morbidity

Morbidity is uncommon, only occurring when parasite burden is very high. Death has not been reported in association with this infection.

Race

No racial predisposition is known for hymenolepiasis.

Sex

No sex predilection is known for hymenolepiasis.

Age

Infection 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.

Clinical

History

The 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.

Physical

Aside from rare abdominal tenderness or urticaria, physical examination is typically unrevealing.

Causes

Rarely, 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.

Differential Diagnoses

Other Problems to Be Considered

Blastocystis hominis
Coenurosis
Dipylidiasis
Echinococcosis
Endolimax nana
Entamoeba coli
Iodamoeba buetschlii
Sparganosis
Celiac disease

Workup

Laboratory Studies

• One third of infected children have eosinophilia exceeding 5%.
• Diagnosis is made by discovery of eggs in stool specimens.
• Sections of the adult worm most often disintegrate before passage into the stool but rarely may be discovered.

Treatment

Medical Care

Supportive care is typically sufficient as an adjunct to drug therapy.

Consultations

In severe cases, consultation with an infectious diseases specialist or gastroenterologist may be appropriate.

Diet

The symptomatic child with severe infection may better tolerate a bland diet.

Medication

The 3 drugs that have been described for the treatment of hymenolepiasis are praziquantel, niclosamide, and paromomycin. Praziquantel, which is bacteriocidal in a single dose for all the stages of the parasite, is the drug of choice. It is available in the United States, well tolerated, and safe. Nitazoxanide has recently been studied as a new treatment option.^2,3,4,5,6

Anthelmintics

Parasite biochemical pathways are different from the human host; thus, toxicity is directed to the parasite, egg, or larvae. The mechanism of action varies within the drug class. Antiparasitic actions may include the following:

• Inhibition of microtubules, which causes irreversible block of glucose uptake
• Tubulin polymerization inhibition
• Depolarizing neuromuscular blockade
• Cholinesterase inhibition
• Increased cell membrane permeability, resulting in intracellular calcium loss
• Vacuolization of the schistosome tegument
• Increased cell membrane permeability to chloride ions via chloride channels alteration

Praziquantel (Biltricide)

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.

Dosing

Adult

25 mg/kg PO as a single dose; tab should be taken with food and swallowed whole with liquids (do not chew)

Pediatric

Administer as in adults

Interactions

Hydantoins may reduce serum praziquantel concentrations, possibly leading to treatment failures

Contraindications

Documented hypersensitivity; spinal or ocular cysticercosis

Precautions

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

Niclosamide (Niclocide)

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.

Dosing

Adult

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

<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

Interactions

None reported

Contraindications

Documented hypersensitivity

Precautions

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

Paromomycin (Humatin)

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.

Dosing

Adult

45 mg/kg PO qd for 7 d

Pediatric

Administer as in adults

Interactions

Nephrotoxic potential may increase with concurrent administration of other aminoglycosides, penicillins, cephalosporins, amphotericin B, and loop diuretics

Contraindications

Documented hypersensitivity; intestinal obstruction

Precautions

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

Nitazoxanide (Alinia)

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.

Dosing

Adult

Not established

Pediatric

<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

Interactions

Tizoxanide (nitazoxanide metabolite) is >99.9% bound to plasma protein and may potentially increase toxicity of other highly plasma protein-bound drugs

Contraindications

Documented hypersensitivity

Precautions

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

Follow-up

Further Inpatient Care

• Inpatient care is rarely, if ever, necessary.

Further Outpatient Care

• Perform follow-up stool examination for ova and parasites 2 weeks and 3 months after treatment to determine whether reinfection or treatment failure has occurred.

Deterrence/Prevention

• Emphasize good personal hygiene and proper disposal of sewage. Because some rodents can carry the parasite (44% of hamsters in one study), good handwashing after handling pets should be reinforced.
• Use contact precautions because H nana eggs in stool are infectious.

Prognosis

• Prognosis is excellent, with or without treatment.

Patient Education

• Emphasize the importance of good hand washing, personal hygiene, and sanitary living conditions.

Miscellaneous

Medicolegal Pitfalls

• Failure to consider the diagnosis in the appropriate clinical context.

Special Concerns

• Consider other parasitic and fecal-oral–transmitted infections when this disease is encountered.

References

1. Craig P, Ito A. Intestinal cestodes. Curr Opin Infect Dis. Oct 2007;20(5):524-32. [Medline].

2. Chero JC, Saito M, Bustos JA, Blanco EM, Gonzalvez G, Garcia HH. Hymenolepis nana infection: symptoms and response to nitazoxanide in field conditions. Trans R Soc Trop Med Hyg. Feb 2007;101(2):203-5. [Medline].

3. Diaz E, Mondragon J, Ramirez E, Bernal R. Epidemiology and control of intestinal parasites with nitazoxanide in children in Mexico. Am J Trop Med Hyg. Apr 2003;68(4):384-5. [Medline]. [Full Text].

4. Fox LM, Saravolatz LD. Nitazoxanide: a new thiazolide antiparasitic agent. Clin Infect Dis. Apr 15 2005;40(8):1173-80. [Medline].

5. Gilles HM, Hoffman PS. Treatment of intestinal parasitic infections: a review of nitazoxanide. Trends Parasitol. Mar 2002;18(3):95-7. [Medline].

6. Pearson RD. Nitazoxanide As Treatment of Intestinal Parasites in Children. Curr Infect Dis Rep. Feb 2004;6(1):25-26. [Medline].

7. AAP. Other tapeworm infections (including hydatid disease). In: Red Book: Report of the Committee on Infectious Diseases. 2006:646-7, 813.

8. Heukelbach J, Winter B, Wilcke T, et al. Selective mass treatment with ivermectin to control intestinal helminthiases and parasitic skin diseases in a severely affected population. Bull World Health Organ. Aug 2004;82(8):563-71. [Medline].

9. Juckett G. Common intestinal helminths. Am Fam Physician. Nov 15 1995;52(7):2039-48, 2051-2. [Medline].

10. Kabani A, Cadrain G, Trevenen C, et al. Practice guidelines for ordering stool ova and parasite testing in a pediatric population. The Alberta Children's Hospital. Am J Clin Pathol. Sep 1995;104(3):272-8. [Medline].

11. Katz M, Despommier DD, Gwadz RW. Tapeworms of minor medical importance. Parasit Dis. 1989;88-92.

12. Maggi P, Brandonisio O, Carito V, et al. Hymenolepis nana parasites in adopted children. Clin Infect Dis. Aug 15 2005;41(4):571-2. [Medline].

13. Marangi M, Zechini B, Fileti A, et al. Hymenolepis diminuta infection in a child living in the urban area of Rome, Italy. J Clin Microbiol. Aug 2003;41(8):3994-5. [Medline].

14. Marseglia GL, Marseglia A, Licari A, Castellazzi AM, Ciprandi G. Chronic urticaria caused by Hymenolepis nana in an adopted girl. Allergy. Jul 2007;62(7):821-2. [Medline].

15. Mehraj V, Hatcher J, Akhtar S, Rafique G, Beg MA. Prevalence and factors associated with intestinal parasitic infection among children in an urban slum of Karachi. PLoS ONE. 2008;3(11):e3680. [Medline].

16. Olson PD, Yoder K, Fajardo L-G LF, et al. Lethal invasive cestodiasis in immunosuppressed patients. J Infect Dis. Jun 15 2003;187(12):1962-6. [Medline].

17. Quihui L, Valencia ME, Crompton DW, et al. Role of the employment status and education of mothers in the prevalence of intestinal parasitic infections in Mexican rural schoolchildren. BMC Public Health. 2006;6:225. [Medline].

18. Quihui-Cota L, Valencia ME, Crompton DW, et al. Prevalence and intensity of intestinal parasitic infections in relation to nutritional status in Mexican schoolchildren. Trans R Soc Trop Med Hyg. Nov 2004;98(11):653-9. [Medline].

19. Richards FO Jr. Diphyllobothrium, Dipylidium, and Hymenolepis species. In: Principles and Practice of Pediatric Infectious Diseases. 2003:1351-4.

20. Robertson J, Shilkofski N. Drug doses. In: The Harriet Lane Handbook: A Manual for Pediatric House Officers. Philadelphia, Pa: Mosby; 2005:679-1009.

21. Rokni MB. The present status of human helminthic diseases in Iran. Ann Trop Med Parasitol. Jun 2008;102(4):283-95. [Medline].

22. Schantz PM. Tapeworms (cestodiasis). Gastroenterol Clin North Am. Sep 1996;25(3):637-53. [Medline].

23. Tanowitz HB, Wittner M. Hymenolepiasis. In: Hunter's Tropical Medicine. 1991:839-41.

24. Turner JA. Cestodes. In: Textbook of Pediatric Infectious Diseases. 2004:2797-816.

25. Weisse ME, Raszka WV Jr. Cestode infection in children. Adv Pediatr Infect Dis. 1996;12:109-53. [Medline].

26. Wittner M, Tanowitz HB. Other cestode infections. In: Tropical Infectious Diseases: Principles, Pathogens, and Practice. 1999:1026-30.

Keywords

hymenolepiasis, abdominal pain, anal pruritus, diarrhea, dwarf tapeworm, gastrointestinal infection, GI infection, hand-to-mouth infection, Hymenolepididae, Hymenolepis diminuta, H diminuta, Hymenolepis nana, H nana, nasal pruritus, parasite, parasitic infection, rodent tapeworm, urticaria

Contributor Information and Disclosures

Author

Robert W Tolan Jr, MD, Chief, Division 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, MD 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
Disclosure: GlaxoSmithKline Honoraria Speaking and teaching; MedImmune Honoraria Consulting; MedImmune Honoraria Speaking and teaching; Merck Honoraria Speaking and teaching; Novartis Honoraria Speaking and teaching; sanofi pasteur Grant/research funds Unrestricted research grant; sanofi pasteur  Consulting; sanofi pasteur Honoraria Speaking and teaching; Tap Honoraria Speaking and teaching; Baxter Healthcare Honoraria Speaking and teaching

Medical Editor

Glenn J Fennelly, MD, MPH, Director, Division of Pediatric Infectious Diseases, Jacobi Medical Center; Associate Professor, Department of Pediatrics, Albert Einstein College of Medicine
Glenn J Fennelly, MD, MPH is a member of the following medical societies: Pediatric Infectious Diseases Society
Disclosure: Nothing to disclose.

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner

Managing Editor

Martin Weisse, MD, Program Director, Associate Professor, Department of Pediatrics, West Virginia University
Martin Weisse, MD is a member of the following medical societies: Ambulatory Pediatric Association, American Academy of Pediatrics, and Pediatric Infectious Diseases Society
Disclosure: Nothing to disclose.

CME Editor

Daniel Rauch, MD, FAAP, Director, Pediatric Hospitalist Program, Associate Professor, Department of Pediatrics, New York University School of Medicine
Daniel Rauch, MD, FAAP is a member of the following medical societies: Ambulatory Pediatric Association, American Academy of Pediatrics, and Society of Hospital Medicine
Disclosure: Baxter Honoraria Consulting; Pfizer Honoraria Consulting

Chief Editor

Russell W Steele, MD, Head, Division of Pediatric Infectious Diseases, Ochsner Children's Health Center; Clinical Professor, Department of Pediatrics, Tulane University School of Medicine
Russell W Steele, MD is a member of the following medical societies: American Academy of Pediatrics, American Association of Immunologists, American Pediatric Society, American Society for Microbiology, Infectious Diseases Society of America, Louisiana State Medical Society, Pediatric Infectious Diseases Society, Society for Pediatric Research, and Southern Medical Association
Disclosure: None None None

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