Diphyllobothrium nihonkaiense infections in a family

Abstract

Diphyllobothrium latum and Diphyllobothrium nihonkaiense are morphologically similar to each other, and only genetic method can differentiate clearly between the 2 species. A strobila of diphyllobothriid tapeworm discharged from a 7-year-old boy was analyzed to identify the species by mitochondrial cytochrome c oxidase subunit 1 (cox1) gene sequencing. He and his family (total 4 persons) ate slices of 3 kinds of raw fish 16 days before visiting our outpatient clinic. All family members complained of abdominal pain and watery diarrhea. They all expelled tapeworm strobilae in their stools. They were treated with a single oral dose of praziquantel and then complained of no more symptoms. The cox1 gene sequencing of the strobila from the boy revealed 99.9% (687/688 bp) similarity with D. nihonkaiense and only 93.2% (641/688 bp) similarity with D. latum. Thus, we assigned this tapeworm as D. nihonkaiense. This is the first report of D. nihonkaiense infection in a family in Korea, and this report includes the 8th pediatric case in Korea. The current report is meaningful because D. nihonkaiense infection within a family is rare.

Keywords: Diphyllobothrium latum; Diphyllobothrium nihonkaiense; cox1 gene; praziquantel; raw fish; tapeworm.

Fig. 1.

Neighbor-joining tree of human Diphyllobothrium tapeworms based on nucleotide sequences of the cox1 gene. Numbers above the branches detect the bootstrap values (1,000 replicates). The scale bar represents the estimated number of nucleotide substitutions per nucleotide site. The phylogenetic tree reveals that the cox1 gene from our case was closer to D. nihonkaiense than D. latum.