Clinical Features:
Diphyllobothriasis can be a long-lasting infection (decades).  Most infections are asymptomatic.  Manifestations may include abdominal discomfort, diarrhea, vomiting, and weight loss.  Vitamin B₁₂ deficiency with pernicious anemia may occur.  Massive infections may result in intestinal obstruction.  Migration of proglottids can cause cholecystitis or cholangitis.

Laboratory Diagnosis:
Microscopic identification of eggs in the stool is the basis of specific diagnosis.  Eggs are usually numerous and can be demonstrated without concentration techniques.  Examination of proglottids passed in the stool is also of diagnostic value.

Diagnostic findings

• Microscopy
• Morphologic comparison with other intestinal parasites

Treatment:
Praziquantel* is the drug of choice.  Alternatively, Niclosamide can also be used to treat diphyllobothriasis.  See recommendations in The Medical Letter for complete information.

* This drug is approved by the FDA, but considered investigational for this purpose.