Detection of Schistosoma mansoni cercariae in plankton samples by PCR

A PCR assay on the basis of a tandemly repeated DNA sequence was employed for the detection of Schistosoma mansoni in artificial plankton samples. It was highly specific, since as few as 1 fg DNA from this species were sufficient to obtain a clear signal, while 10 pg DNA of Schistosoma rodhaini were required and no PCR products were obtained with even 10 ng DNA of planktonic organisms and any other trematode species tested. In areas with transmission of different Schistosoma species 10 pg DNA should be used for amplification, which would allow detection of 20 S. mansoni cercariae in 0.05 g plankton without interference caused by DNA of other Schistosoma species. In other areas 10 ng DNA from plankton samples can be amplified, detecting less than one S. mansoni cercaria specifically in 0.05 g plankton. This assay might help to identify S. mansoni in samples from field studies, where a multitude of different organisms hinder a correct species identification.