Tapeworm (Diphyllobothrium nihonkaiense) detected by abdominal ultrasonography

A 16-year-old girl presented with anal discharge of a white thread-like object. She denied additional symptoms. She had consumed raw salmon three weeks ago. Physical examination revealed no abnormal findings, and blood tests were unremarkable. However, abdominal ultrasound revealed a hyperechoic strand-like structure (Fig. 1). Stool examination revealed the presence of cestode ova. Therefore, she was admitted to our hospital and treated with oral praziquantel. A tapeworm, roughly 2.5 m long, was extracted from her feces (Fig. 2). Restriction fragment length polymorphism analysis with PCR-amplified cox1 gene fragment was performed,¹ which identified the causative cestode was Diphyllobothrium nihonkaiense.

Fig. 1
Longitudinal view of the rectum showing high echoic strand-like lesion (blue arrows). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 2
The tapeworm unfolded after deworming with praziquantel.

In Japan, D. nihonkaiense is the most common diphyllobothriasis-causing tapeworm.² The diagnosis was based on the appearance after deworming, and the species was correctly identified using a molecular technique. The effectiveness of ultrasound has been reported in several publications.³,⁴ In cases such ours, ultrasound is useful for deciding whether to treat patients with praziquantel because the tapeworms are extracted naturally. In conclusion, abdominal ultrasonography can be useful for diagnosing diphyllobothriasis.

• Ethical approval
  Written informed consent was obtained from the patient's parents.
• Funding
  None.

References

• ¹
  Yamasaki H., Tsubokawa D., Mercado R., Kuramochi T. A simple method for identifying the diphyllobothriids based on mitochondrial DNA analysis. In: Takamiya S, Materials and Methods in Parasitology. Nagoya City (Japan): Sankeisha, 2014:47-49 [in Japanese].
• ²
  Ikuno H., Akao S., Yamasaki H. Epidemiology of Diphyllobothrium nihonkaiense diphyllobothriasis, Japan, 2001-2016. Emerg Infect Dis. 2018;24:1428-34.
• ³
  Hiroshima M., Nakagawa M., Ito Y., Shiba A., Ozawa Y., Shibamoto Y. Ultrasonographic findings of Diphyllobothrium nihonkaiense: a case report. Radiol Case Rep. 2018;14:63-5.
• ⁴
  Kitamoto H., Inoue S., Okamoto K., Inokuma T. Scanning early catches the worm: abdominal ultrasound as a possible screening method for intestinal cestodes. Lancet. 2019;394:1264.

Publication Dates

• Publication in this collection
  10 July 2023
• Date of issue
  2023

History

• Received
  09 Feb 2023
• Accepted
  21 Apr 2023
• Published
  05 May 2023