An imported case of Haplorchis taichui infection diagnosed with molecular genomics in France

We report here on an imported case of Haplorchis taichui infection in a Western country. Given their rarity in these countries, such diagnoses of heterophyid flukes can be particularly difficult.

The stool of a 70-year-old Laotian woman with eosinophilia was sent to the laboratory for examination. Microscopic observations based on direct examination and two concentration methods were performed on the fecal sample. After extraction of DNA from the sample, Sanger sequencing of the internal transcribed spacer 2 (ITS2) region and the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene was carried out.

Ellipsoid eggs with a convex operculum and abopercular knob were observed on microscopic examination, suggestive of fluke eggs, but there was no morphological criterion to distinguish between opisthorchiid and heterophyid eggs. Results of ITS2 and cox1 sequencing matched the intestinal fluke Haplorchis taichui.

This case report points out that small trematode eggs can hardly be used to distinguish between opisthorchiid and heterophyid flukes in fecal examinations, and underlines the need for molecular genomic studies to establish an accurate species diagnosis.