BACKGROUND: Diagnosis of schistosomiasis remains elusive soon after infection. We evaluated several diagnostic methods in a cluster of travelers with simultaneous freshwater exposure in South Africa.
METHODS: Eosinophil count, schistosome antibody tests, stool and urine microscopy, and serum Dra1 PCR assays were performed at weeks 4-5 (early symptomatic phase), 7-8 (praziquantel treatment), and 13-14 (after treatment). Sequencing was done on serum samples from 3 patients to identify the species.
RESULTS: Of the 34 travelers (16 adults and 18 children), 32 developed symptoms 2-6 weeks after exposure. A raised eosinophil count (>750/µL) was seen in 12 of 33 at weeks 4-5, and in 22 of 34 at weeks 7-8. Schistosoma antibodies were detected in 3 of 33 at weeks 4-5 and in 12 of 34 at weeks 7-8 and weeks 13-14. The Dra1 PCR result was positive in 24 of 33 travelers at weeks 4-5, in 31 of 34 at weeks 7-8, in 25 of 34 at weeks 13-14, and at least once in all. Ova were absent in all urine and stool samples obtained. Sequencing identified Schistosoma mattheei nuclear and Schistosoma haematobium mitochondrial DNA, indicative of a hybrid species.
CONCLUSIONS: The Dra1 PCR confirmed the diagnosis in all exposed travelers at a much earlier stage than conventional tests. The causative species is probably an S. mattheei × S. haematobium hybrid.