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,11 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]. which identified the causative cestode was Diphyllobothrium nihonkaiense.
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.)
In Japan, D. nihonkaiense is the most common diphyllobothriasis-causing tapeworm.22 Ikuno H., Akao S., Yamasaki H. Epidemiology of Diphyllobothrium nihonkaiense diphyllobothriasis, Japan, 2001-2016. Emerg Infect Dis. 2018;24:1428-34. 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.33 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.,44 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. 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.
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Ethical approvalWritten informed consent was obtained from the patient's parents.
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FundingNone.
References
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1Yamasaki 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].
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2Ikuno H., Akao S., Yamasaki H. Epidemiology of Diphyllobothrium nihonkaiense diphyllobothriasis, Japan, 2001-2016. Emerg Infect Dis. 2018;24:1428-34.
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3Hiroshima 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.
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4Kitamoto 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
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Publication in this collection
10 July 2023 -
Date of issue
2023
History
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Received
09 Feb 2023 -
Accepted
21 Apr 2023 -
Published
05 May 2023