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AUTHOR AND EDITOR INFORMATION

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Author: Venkat R Minnaganti, MD, Consulting Staff, Department of Medicine, Winthrop University Hospital; Clinical Instructor, Department of Internal Medicine, Division of Infectious Disease, State University of New York School of Medicine at Stony Brook

Venkat R Minnaganti is a member of the following medical societies: American College of Physicians, American Medical Association, American Society for Microbiology, and Infectious Diseases Society of America

Coauthor(s): 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

Editors: Pranatharthi Haran Chandrasekar, MD, Director of Infectious Disease Fellowship, Professor, Department of Internal Medicine, Harper Hospital, Wayne State University School of Medicine; 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: dog tapeworm, Dipylidium caninum, D caninum, dog flea, cat flea, cysticercoids

INTRODUCTION

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Background

Dipylidiasis is a common tapeworm infection of dogs and cats caused by Dipylidium caninum. Linnaeus first described the condition in 1758.

Dipylidiasis has a worldwide distribution. Humans become infected by accidental ingestion of the intermediate host: the dog or cat flea. The risk of infection to humans is low.

Pathophysiology

Infection occurs through accidental ingestion of the dog or cat flea or the dog louse infected with cysticercoids (the larval form of D caninum).

Cysticercoids develop into adult worms in the small intestine of the host in about 20 days. The adult worm may attain a length of 10-70 cm and is 2-3 mm in diameter. The lifespan of the worm is less than 1 year.

Pathological changes in dipylidiasis have not been described.

Frequency

United States

Dipylidiasis has been reported, but the exact incidence is not known.

International

Dipylidiasis is distributed worldwide, and human infection has been reported in Africa, Argentina, Australia, Chile, China, Europe, Guatemala, India, Japan, and the Philippines.

Sex

Males and females are equally susceptible.

Age

Infection with D caninum is most commonly observed in infants and in children younger than 8 years. Dipylidiasis has been reported in a 5-week-old infant.


CLINICAL

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History

Dipylidiasis is transmitted by accidental ingestion of a dog or cat flea. The adult tapeworm develops in about 20 days; however, since most infections are asymptomatic, the time to development of symptoms in some patients is not known. Symptoms of dipylidiasis are related to the worm burden.

  • Most infections are asymptomatic, although some children may have intestinal disturbances.
  • Abdominal pain with or without diarrhea may be a presenting complaint.
  • Loss of appetite may be another presenting complaint.
  • Allergic manifestations (eg, pruritus, rash) may occur.
  • Increased irritability may be a presenting complaint.
  • Intestinal obstruction is a rare complication.

Physical

  • Physical examination findings may be unremarkable.
  • Proglottids of the parasite adherent to perianal hair may be observed as a whitish yellow object.

Causes

  • D caninum: Increased incidence of infection occurs in children in contact with dogs.


DIFFERENTIALS

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Ascariasis
Diphyllobothriasis
Pinworm
Salmonellosis

Other Problems to be Considered

Hymenolepiasis


WORKUP

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Lab Studies

  • No blood tests diagnose dipylidiasis.
  • Eosinophilia may be present.
  • Examination of the stool specimen may show the characteristic egg packets and proglottids of D caninum.
    • Eggs in packets are typical of dipylidiasis.
    • Individual eggs are rarely observed in feces.
    • Proglottids may be observed in singles or in chains and often resemble rice grains in stool.
    • Proglottids may become adherent to perianal hair and may be observed as a whitish yellow object when dry.
  • Examination of stool specimens from several different days may be necessary.


TREATMENT

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Medical Care

  • Dipylidiasis is more common in children and is usually asymptomatic.
  • Anthelmintics
    • Praziquantel and niclosamide are the preferred drugs for treatment of infection with D caninum.
    • Ivermectin has no effect on D caninum.

Diet

  • No specific dietary recommendations are necessary for patients with dipylidiasis, although a low-protein and lactose-free diet is advised until the symptoms of abdominal pain and diarrhea are resolved.

Activity

  • No restrictions are necessary.


MEDICATION

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The goals of pharmacotherapy are to reduce morbidity, prevent complications, and eradicate infection.

Drug Category: Anthelmintics

Dipylidiasis responds well to treatment with anthelmintics. Praziquantel and niclosamide are the preferred drugs and are usually administered as a single oral dose. A follow-up dose is usually unnecessary.

Drug NamePraziquantel (Biltricide)
DescriptionBroad-spectrum anthelmintic that increases cell membrane permeability in susceptible worms, resulting in loss of intracellular calcium, massive contractions, and paralysis of musculature. This is followed by attachment of phagocytes to parasites and death. Available as 600-mg coated tablet and is well absorbed from the GI tract.
Adult Dose5-10 mg/kg PO once
Pediatric Dose<4 years: Not established
>4 years: Administer as in adults
ContraindicationsDocumented hypersensitivity; ocular cysticercosis
InteractionsHydantoins may reduce serum praziquantel concentrations, possibly leading to treatment failures
PregnancyB - Usually safe but benefits must outweigh the risks.
PrecautionsDestruction of parasite within eyes can cause irreparable lesions (ocular cysticercosis should not be treated with praziquantel); caution while driving or performing other tasks requiring alertness on the day of and following treatment; minimal increases in liver enzymes reported; when schistosomiasis or fluke infection is associated with cerebral cysticercosis, hospitalize patient for duration of treatment; breastfed infants should be deferred from breastfeeding for at least 72 h after treatment

Drug NameNiclosamide (Niclocide)
DescriptionNarrow-spectrum anthelmintic poorly absorbed when administered PO. Available as a 500-mg chewable tablet that must be thoroughly chewed to obtain maximal effect.
Adult Dose2 g PO once
Pediatric Dose11-34 kg: 1 g PO once
>34 kg: 1.5 g PO once
ContraindicationsDocumented hypersensitivity
InteractionsNone reported
PregnancyB - Usually safe but benefits must outweigh the risks.
PrecautionsNausea, retching, and abdominal pain may occur; alcohol should not be taken during treatment


FOLLOW-UP

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Further Outpatient Care

  • Examination of the patient's stool for eggs and proglottids of D caninum may be performed at 1 and 3 months after treatment to ensure cure.
  • A repeat dosing of anthelmintics is usually unnecessary.

Deterrence/Prevention

  • Flea control is the most effective way to prevent infection in humans and pets.
    • Spraying of cats and dogs with flea powder is effective in reducing the risk of infection.
    • Aerosol insecticides are effective for flea control in large areas.
  • Do not allow children to play in areas soiled with cat or dog feces.
  • Practice good hygiene measures, especially handwashing after contact with cats and dogs.
  • Promptly treat cats and dogs if they are known to harbor tapeworms.

Complications

  • Intestinal obstruction can be a rare complication.

Prognosis

  • Prognosis is excellent.

Patient Education

  • Emphasize the importance of handwashing, especially after contact with cats and dogs.


MISCELLANEOUS

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Medical/Legal Pitfalls

  • Gravid proglottid may be mistaken for a pinworm.
  • Stool examination may be falsely negative because of migration of the gravid proglottids from the fecal mass to the walls of the specimen container.

Special Concerns

  • Exclude other parasitic infections.


MULTIMEDIA

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Media file 1:  Adult tapeworm of Dipylidium caninum. Image provided courtesy of the Centers for Disease Control and Prevention (CDC).
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Media type:  Photo

Media file 2:  Proglottid of Dipylidium caninum. Image provided courtesy of the Centers for Disease Control and Prevention (CDC).
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Media type:  Photo

Media file 3:  Proglottid of Dipylidium caninum stained with carmine. Image provided courtesy of the Centers for Disease Control and Prevention (CDC).
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Media type:  Photo

Media file 4:  Egg packets of Dipylidium caninum. Image provided courtesy of the Centers for Disease Control and Prevention (CDC).
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Media type:  Photo

Media file 5:  Egg packets of Dipylidium caninum. Image provided courtesy of the Centers for Disease Control and Prevention (CDC).
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Media type:  Photo

Media file 6:  Egg of Dipylidium caninum. Image provided courtesy of the Centers for Disease Control and Prevention (CDC).
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Media type:  Photo

Media file 7:  Life cycle of Dipylidium caninum. Image provided courtesy of the Centers for Disease Control and Prevention (CDC).
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Media type:  Photo


REFERENCES

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Dipylidiasis excerpt

Article Last Updated: May 12, 2006