Dipylidiasis
Updated: Apr 17, 2018
Author: Venkat R Minnaganti, MD, FACP; Chief Editor: Michael Stuart Bronze, MD
Overview
Background
Dipylidiasis is a common tapeworm infection of dogs and cats caused by Dipylidium caninum. Linnaeus first described dipylidiasis in humans in 1758.
Dipylidiasis has a worldwide distribution. Humans become infected by accidental ingestion of dog or cat fleas that contain D caninum cysticercoids (larva). The risk of infection to humans is low.
Pathophysiology
Dipylidiasis in humans occurs through accidental ingestion of the dog or cat flea or the dog louse infected with cysticercoids (the larval form of D caninum). These fleas and lice are the intermediate host for 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 worms have a lifespan of less than 1 year.
Pathological changes due to dipylidiasis have not been described.
Epidemiology
Frequency
United States
A few cases of dipylidiasis have been reported in the United States, 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.[1, 2]
Race
Dipylidiasis does not appear to have a racial predilection.
Sex
Males and females are equally susceptible to dipylidiasis.
Age
Dipylidiasis is most common in infants and in children younger than 8 years. Dipylidiasis has been reported in a 5-week-old infant.[3]
Presentation
History
Dipylidiasis is transmitted by accidental ingestion of a dog or cat flea that contains D caninum cysticercoids. The adult tapeworm develops in about 20 days; however, since most infections are asymptomatic, the time to development of symptoms in some patients is unknown. Symptoms of dipylidiasis are related to the worm burden.
Most infections are asymptomatic, although some children with dipylidiasis may have intestinal disturbances.
Abdominal pain with or without diarrhea may be a presenting symptom.
Loss of appetite may be another presenting symptom.
Allergic manifestations (eg, pruritus, rash) may occur.
Increased irritability may be a presenting symptom.
Intestinal obstruction is a rare complication of dipylidiasis.
Physical
Physical examination findings in patients with dipylidiasis may be unremarkable.
Proglottids of D caninum adherent to perianal hair may be observed as a whitish yellow object.
Causes
Dipylidiasis is caused by infection with D caninum. Children who are regularly in contact with dogs are at an increased risk of infection.
DDx
Differential Diagnoses
Workup
Laboratory Studies
No blood tests are used to diagnose dipylidiasis.
Eosinophilia may be present.[4]
Examination of the stool specimen may show the characteristic egg packets and proglottids of D caninum.
Eggs arranged in packets are typical of dipylidiasis.
Egg packets of Dipylidium caninum. Image provided courtesy of the Centers for Disease Control and Prevention (CDC).
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 on several different days may be necessary.
Treatment
Medical Care
Dipylidiasis is more common in children and is usually asymptomatic.
The anthelmintic agents praziquantel and niclosamide are the preferred drugs for treatment of dipylidiasis. 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 have resolved.
Activity
No activity restrictions are necessary.
Medication
Medication Summary
The goals of pharmacotherapy are to reduce morbidity, to prevent complications, and to eradicate infection.
Anthelmintics
Class Summary
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.
Praziquantel (Biltricide)
Broad-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.
Niclosamide (Niclocide)
Narrow-spectrum anthelmintic poorly absorbed when administered PO. Available as a 500-mg chewable tablet that must be thoroughly chewed to obtain maximal effect.
Follow-up
Further Outpatient Care
The patient's stool should be examined for eggs and proglottids of D caninum 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 dipylidiasis 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. Praziquantel is an effective treatment for pets.
Complications
Intestinal obstruction is a rare complication of dipylidiasis.
Prognosis
Dipylidiasis carries an excellent prognosis.
Patient Education
Emphasize the importance of handwashing, especially after contact with cats and dogs.