para>H. nana, H. diminuta, and D. caninum most common in children. ‚
EPIDEMIOLOGY
Incidence
- Cestode infections relatively rare in United States, common in certain countries
- Associated with immigrant populations and specific cultural culinary habits
- Endemic where fecal contamination impacts water or food supplies or close contact with domestic animals.
- Predominant age: All ages can be affected.
- Predominant sex: male = female
- Cysticercosis affects 50 million worldwide, and in endemic areas is the leading cause of adult epilepsy; ~2,000 cases/year diagnosed in United States.
ETIOLOGY AND PATHOPHYSIOLOGY
Ingestion of the infective form of the parasite, either by eating contaminated food (meat, fish) or infected insects in cereals or grains, or through fecal " “oral contamination ‚
- Adult worms consist of a head (scolex), which attaches to the host 's GI tract and a segmented body (strobila), with individual segments (proglottid) containing sets of male and female reproductive organs that produce eggs.
- The life cycle of all but H. nana requires an intermediate host, where species grow as larval forms in tissue that is then ingested by the final host, where they develop into adult forms.
- H. nana can complete all stages of development in humans and autoinfect.
RISK FACTORS
- Taenia: consumption of raw beef or pork, particularly in Africa, Central America, and Asia
- Cysticercosis: a tapeworm carrier who is a close contact; water contaminated with sewage
- Diphyllobothrium: eating raw or undercooked fish, particularly in Northern Europe and Japan
- H. nana: more frequent in children, institutionalized, malnourished, or immunodeficient patients
- E. granulosis: sheep dogs highest risk for hydatid cyst disease
- E. multilocularis: contact with foxes, coyotes; mostly found in northern latitudes
GENERAL PREVENTION
- Treat infected animals, populations, and screen household contacts, immigrants.
- Proper sewage and waste management; hand hygiene, sanitary food preparation in endemic areas
- Proper cooking, freezing, or irradiation of beef, pork, and fish.
DIAGNOSIS
HISTORY
- Often asymptomatic; if present, symptoms vary with infecting organism and typically include a variety of GI symptoms: nausea, abdominal pain, anorexia, weight loss
- T. saginata (beef tapeworm): may note passage of eggs or proglottids, which can be felt crawling out of anus; nausea, abdominal pain, change in appetite, weakness, weight loss, allergic symptoms, urticaria, and pruritus
- T. solium (pork tapeworm)
- Intestinal worm: noted passing eggs or proglottids; occasional minor abdominal complaints similar to T. saginata
- Larval migration: cysticercosis most common in brain and skeletal muscle; neurologic manifestations such as new-onset seizures, focal neurologic deficits, hydrocephalus, headache, vomiting, visual changes, and dizziness
- D. latum (fish tapeworm): noted passing eggs or proglottid segments or vomiting segment of worm; occasionally mild abdominal discomfort, weight loss; worm has marked affinity for vitamin B12; 40% decreased B12 levels, 2% megaloblastic anemia with glossitis; 20 million humans infected worldwide
- Echinococcosis: often asymptomatic for years
- Liver cysts: abdominal pain, right upper quadrant mass, obstructive jaundice
- Cyst rupture: fever, urticaria, pruritus, anaphylaxis
- Pulmonary cyst: cough, chest pain, hemoptysis
- Other organs possible: bone, CNS, cardiac conduction defects, pericarditis
- H. nana (dwarf tapeworm): anorexia, abdominal pain, and diarrhea. H. diminuta (rodent tapeworm): pass eggs in stool, headache, mild GI symptoms
- D. caninum (dog tapeworm): occasionally abdominal pain, diarrhea, anal pruritus, urticaria; may observe proglottid in diaper or stool
PHYSICAL EXAM
Often nonspecific. Most common physical examination finding may be passage of flatworm segment. ‚
DIFFERENTIAL DIAGNOSIS
- Nontapeworm gastroenteritis
- Irritable bowel syndrome
- Intestinal obstruction
- Cholecystitis or biliary obstruction
- B12 deficiency from nontapeworm etiologies
- Tumors (abscesses, malignant, benign)
- Idiopathic epilepsy
- Pneumonia, pulmonary abscess (pulmonary hydatid cysts)
DIAGNOSTIC TESTS & INTERPRETATION
- Stool evaluation for ova and parasites (repeat 2 to 3 times if negative)
- Antibody testing by ELISA to differentiate T. saginata eggs from T. solium
- Enzyme-linked immunoelectrotransfer blot: test of choice for cysticercosis (less sensitive if calcified or single cyst), Echinococcus
- DNA probes for T. saginata or T. solium
- Macrocytic anemia (diphyllobothriasis)
- Intestinal tapeworms occasionally seen by small-bowel enteroclysis, capsule endoscopy
- Cysticercosis: MRI or CT scan
- Echinococcus cysts: start with US for liver, chest x-ray or chest CT for pulmonary; tissue biopsy
- Peripheral eosinophilia an inconsistent finding (<15%)
Diagnostic Procedures/Other
- Excisional biopsy of cysticercosis cyst
- Perianal inspection for eggs or proglottids
Test Interpretation
- Intestinal tapeworms: no pathologic findings
- Cysticercosis: cysts, 5 to 10 mm in soft tissue; calcified cysts in CNS, muscle
- Echinococcus: cysts in liver, lung, other tissues on radiologic studies
TREATMENT
GENERAL MEASURES
- Supportive care
- Asymptomatic cysticercosis may resolve spontaneously without treatment. Calcified (nonviable) cysticerci not benefitted by antihelminthics (1,2)[C]
- Albendazole plus steroid for symptomatic neurocysticercosis decreases number of active lesions and long-term seizure frequency (3)[B],(4)[C]. Prior to initiating corticosteroids and antiparasitics to treat cysticercosis, evaluate for ocular cysticercosis, latent tuberculosis, and strongyloidiasis.
- Antiepileptics for neurocysticercosis
MEDICATION
First Line
The preferred treatment is praziquantel for most intestinal cestodes and albendazole for tissue/larval cestodes (5)[C]. ‚
- Praziquantel (Biltricide)
- Single dose of 10 mg/kg for taeniasis, diphyllobothriasis, Dipylidium infection, and most other intestinal cestodes (cure rate >95%)
- Single dose of 25 mg/kg for H. nana in adults or children, repeat in 10 days (cure rate >95%)
- 50 to 100 mg/kg/day divided TID for 14 to 30 days for children and adults for cysticercosis (albendazole preferred drug)
- Albendazole (Albenza)
- Dose: weight >60 kg: 400 mg BID with meals; weight <60 kg: 10 to 15 mg/kg/day given BID (max 800 mg/day)
- For Echinococcus hydatid cysts, give for 28 days, 14 days off, repeat for three cycles; can be 3 to 6 months; long term for alveolar Echinococcus
- For neurocysticercosis, albendazole is drug of choice; give for 8 to 30 days, may repeat
- Absorption improved when taken with fatty foods; avoid use in pregnant women; consider monitoring CBC with long-term treatments
- Niclosamide (2 g single dose) alternative to praziquantel for diphyllobothriasis, Dipylidium, H. nana, intestinal Taenia
- Precautions: If present, intraocular cysts should be surgically removed before antiparasitic treatment to avoid eye damage from inflammatory response (5)[C].
- Praziquantel: mild but frequent dizziness, myalgias, nausea, diarrhea, abdominal pain
- Albendazole: diarrhea and abdominal pain, leukopenia, increased transaminase levels
- Significant possible interactions
- Phenytoin and carbamazepine can induce the metabolism of praziquantel by cytochrome P450, causing treatment failure.
- Cimetidine, dexamethasone, and praziquantel can increase the concentration of albendazole.
- Corticosteroids may decrease the concentration of praziquantel.
SURGERY/OTHER PROCEDURES
- Cysticercosis can be removed surgically; shunt for hydrocephalus. Endoscopic surgery is favored for ventricular cysts (6)[C].
- Echinococcus hydatid cysts
- Surgery based on location of cyst.
- Surgical risks may make medical therapy preferred; risk anaphylaxis or spread with leaked fluid
- Albendazole pre- and postsurgical treatment for 1 month is recommended.
- PAIR therapy (puncture, aspiration, injection of a scolicidal agent, reaspiration) an alternative to surgery for cystic echinococcosis (7)[A].
INPATIENT CONSIDERATIONS
Admission Criteria/Initial Stabilization
Complications of cysts ‚
ONGOING CARE
FOLLOW-UP RECOMMENDATIONS
Patient Monitoring
- Examine several stool specimens for ova and parasites at 3 months for Taenia species and 1 month for other intestinal tapeworms.
- Follow neurocysticercosis with CT scans.
DIET
As tolerated ‚
PATIENT EDUCATION
- Cook beef, pork, fish thoroughly
- Proper freezing of meat or fish prior to eating raw.
- Good hand hygiene
- Treat infected domestic animals; flea, rodent control
PROGNOSIS
- Medications cure >95% of intestinal tapeworms.
- H. nana often self-cured by adolescence
- Echinococcosis can be severe or fatal.
- Neurocysticercosis: intraparenchymal cysts often benign; extraparenchymal (subarachnoid, ventricular, cisternal) more serious
COMPLICATIONS
- Larval form of T. solium can cause systemic cysticercosis, including neurocysticercosis with seizures, neurologic defects
- Echinococcus hydatid cysts may cause abnormalities in the organ involved. Cyst rupture can cause spread and anaphylaxis.
- B12 deficiency with D. latum
- Proglottid of T. saginata rarely can obstruct appendix, pancreatic and bile ducts.
- D. latum occasionally can cause intestinal obstruction, cholangitis, and cholecystitis.
REFERENCES
11 Brunetti ‚ E, White ‚ ACJr. Cestode infestations: hydatid disease and cysticercosis. Infect Dis Clin North Am. 2012;26(2):421 " “435.22 Brunetti ‚ E, Kern ‚ P, Vuitton ‚ DA, et al. Expert consensus for the diagnosis and treatment of cystic and alveolar echinococcosis in humans. Acta Trop. 2010;114(1):1 " “16.33 Baird ‚ RA, Wiebe ‚ S, Zunt ‚ JR, et al. Evidence-based guideline: treatment of parenchymal neurocysticercosis: report of the Guideline Development Subcommittee of the American Academy of Neurology. Neurology. 2013;80(15):1424 " “1429.44 Garcia ‚ HH, Nash ‚ TE, Del Brutto ‚ OH. Clinical symptoms, diagnosis, and treatment of neurocysticercosis. Lancet Neurol. 2014;13(12):1202 " “1215.55 Kappagoda ‚ S, Singh ‚ U, Blackburn ‚ BG. Antiparasitic therapy. Mayo Clin Proc. 2011;86(6):561 " “583.66 McManus ‚ DP, Gray ‚ DJ, Zhang ‚ W, et al. Diagnosis, treatment, and management of echinococcosis. BMJ. 2012;344:e3866.77 Nasseri-Moghaddam ‚ S, Abrishami ‚ A, Taefi ‚ A, et al. Percutaneous needle aspiration, injection, and re-aspiration with or without benzimidazole coverage for uncomplicated hepatic hydatid cysts. Cochrane Database Syst Rev. 2011;(1):CD003623.
CODES
ICD10
- B71.9 Cestode infection, unspecified
- B71.0 Hymenolepiasis
- B70.0 Diphyllobothriasis
- B69.0 Cysticercosis of central nervous system
- B67.90 Echinococcosis, unspecified
- B68.0 Taenia solium taeniasis
- B69.9 Cysticercosis, unspecified
- B68.9 Taeniasis, unspecified
ICD9
- 123.9 Cestode infection, unspecified
- 123.6 Hymenolepiasis
- 123.4 Diphyllobothriasis, intestinal
- 123.8 Other specified cestode infection
- 122.9 Echinococcosis, other and unspecified
- 123.0 Taenia solium infection, intestinal form
- 123.1 Cysticercosis
- 123.2 Taenia saginata infection
- 123.3 Taeniasis, unspecified
- 123.5 Sparganosis [larval diphyllobothriasis]
SNOMED
- Cestode infection (disorder)
- Hymenolepis nana infection (disorder)
- Diphyllobothriasis (disorder)
- Cysticercosis (disorder)
- Taenia solium infection (disorder)
- Larval echinococcosis
- Taenia saginata infection (disorder)
- Infection by Taenia (disorder)
- Cysticercosis of central nervous system
CLINICAL PEARLS
- Tapeworm infections in humans are often asymptomatic.
- For asymptomatic neurocysticercosis, treatment may not be necessary. Calcified cysts generally do not need antiparasitic therapy.
- Symptomatic neurocysticercosis should be treated with albendazole and a corticosteroid.
- After completing treatment for tapeworm infections, recheck stool for eggs after 1 month for Hymenolepis and Diphyllobothrium and after 3 months for Taenia to ensure eradication.