RESUMO
Mitochondrial genome analysis of Schistosoma japonicum suggests that diversity of intermediate host snails drove intra-species divergence during its expansion in Asia. We applied the knowledge of this genomic variation to study an unusual patient we recently diagnosed with schistosomiasis. The patient had not visited any schistosomiasis-endemic countries for more than 35 years and had no idea where she became infected. Unusual clinical features of this patient included the absence of egg granulomas in tissue and persistent noncalcified eggs despite multiple praziquantel (PZQ) treatments over 7 years. A digital droplet polymerase chair reaction (PCR) assay that specifically targets the schistosome 1,4 dihydronicotinamide adenine dinucleotide-1 (NADH1) dehydrogenase-1 mitochondrial gene successfully amplified parasite DNA extracted from colon biopsies. DNA sequence analysis of parasite DNA revealed that it was a Philippine strain of S. japonicum. Future molecular studies using stored DNA from patients such as this may provide new insight into why some persons do not respond well to PZQ treatment.
