Trichostrongylus colubriformis Nematode Infections in Humans, France

To the Editor: In April 2009, a 47-year-old woman in Saint-Jeannet in southern France reported stomach aches, abdominal bloating, and occasional diarrhea. Blood analyses found an increased eosinophil level (8,800 cells/mm 3), which represented 52% of 16,900 leukocytes/mm 3. Parasitologic examinations for helminths were conducted with 6 fecal specimens obtained during June 9– July 2, 2009. Analyses included direct wet mount microscopic examination, Merthiolate–iodine–formaldehyde concentration, formalin–ethyl acetate concentration, and Baermann larval extraction. Results of direct examination and the Baermann technique were negative for all samples. The formalin–ethyl acetate concentration technique detected a parasite egg (Figure, panel A) and fi rst-stage larvae. Fecal cultures grew mature third-stage larvae (length 700–800 μm, 16 intestinal cells, length of the sheath <40 μm), belonging to the genus Trichostrongylus (Figure, panel B). Because of the ambiguous morphologic features of this genus, a molecular approach was necessary for specifi c identifi cation (1,2). Identical symptoms developed in 2 children of the patient and in 2 friends. The mother of the patient had additional symptoms (weight loss 5 kg in 1 month and 35,000 eosinophils/ mm 3 , which represented 85% of 43,200 leukocytes/mm 3). However, results of fecal examinations were negative for these 5 persons. DNA was extracted separately from 2 third-stage larvae (Figure, panel B) by using the DNA Tissue Mini Kit (QIAGEN, Hilden, Germany). To amplify internal transcribed spacer 2 (ITS2) sequences, we used primers NC1: 5′-ACGTCTGGTTCAGGGTT GTT-3′ (forward) and NC2: 5′-TTAG TTTCTTTTCCTCCGCT-3′ (reverse) (3,4), which were used by Hoste et al. for Trichostrongylus spp. typing (3). ITS2 rDNA was sequenced, and third-stage larvae sequences were registered in GenBank (accession nos. HQ174256 and HQ174257). Complete (100%) homology was obtained with known sequences (3,4) for adult Trichostrongylus colubriformis nematodes from sheep (GenBank accession nos. S69220, X78063, and EF427624). Parasite sequences also showed 100% homology with the main haplotype observed in humans in Laos (2). If one considers the absence of intraspecifi c variability within T. colubriformis nematodes (3,4), the specimens isolated from the patient and most likely from the other 5 persons presumed to be affected in this outbreak belong to this species. The 6 symptomatic patients were treated according to published recommendations (5) with albendazole, 400 mg/day for 10 days. Clinical remission was obtained in <3 days, and eosinophil counts returned to reference levels 3 months later. Specifi c questioning of the 6 persons indicated that the source of infection most likely was a …