The Detection of Circulating Cell-Free DNA for the Diagnosis of Schistosoma in Immigrants from African Countries in Italy

The rising migration and travel from and towards endemic areas has brought renewed concerns about many parasitic infections, including neglected tropical diseases, such as schistosomiasis. Although serology is the most widely used method for the screening of schistosomiasis in non-endemic countries, this technique lacks sensitivity, especially to distinguish between past and ongoing infections. More recently, a molecular test based on the detection of Schistosoma cell-free DNA in the serum has been proposed as a diagnostic procedure for parasitosis. To test the performance of a blood PCR assay, this work investigated 102 serum samples collected from migrants coming from endemic areas by using primers specific to genomic regions of S. mansoni and S. haematobium patients. The results were then compared with the detection of specific IgG Abs with serological tests. Molecular analysis detected Schistosoma DNA in 32 patients. Among them, we characterized nine S. haematobium, 20 S. mansoni, and three coinfections. Compared with molecular assay, serological analysis detected specific antibodies against Schistosoma antigens in 52 out of 102 patients. Concordance between the two tests was found in 76 out of 102 patients (74.51%): in particular, both diagnostic tests were positive in 29 patients (28.43%) and negative in 47 (46.08%). The specificity of the molecular test was 94%. Overall, our data suggest that serological diagnosis could be combined with the molecular approach, providing the clinician with the serotyping of the parasite and useful information about the infection as well as the required further diagnostic procedures.