ABSTRACT

Laboratory diagnosis of Schistosoma mansoni (S.mansoni) and Fasciola represents a challenge especially in areas endemic for both, like Egypt. Different laboratory techniques developed for diagnosis of these infections may either lack sensitivity as in cases of low intensity infection or specificity. The high sensitivity of PCR has encouraged scientists to use it in the diagnosis of different parasitological infections. Cross reactivity between S.mansoni and Fasciola parasites is known to occur in the immunological tests diagnosing either parasite. We aimed to test for the cross reactivity between the two parasites at the PCR level using primers commonly used for amplification of parts of Fasciola or S.mansoni, and to test for the diagnostic importance of the PCR using these primers. In this study, primers amplifying the 121 bp tandem repeats of S.mansoni and BfrI and DraI primers amplifying the 356 and 263 bp segments of Fasciola 18S rDNA respectively, were used to amplify DNA extracted from pure S.mansoni or Fasciola gigantica strains. They were also used to amplify DNA extracted from human fecal samples obtained from Tookh villages, endemic for both S.mansoni and Fasciola. It was found that PCR amplifying the 121 bp tandem repeats of S.mansoni gave positive results with S.mansoni pure strain and not Fasciola strain indicating its specificity in schistosomiasis diagnosis. On the other hand, PCR using BfrI primers was proved to be positive with both S.mansoni & Fasciola strains and also with 80% and 66.6% of human fecal samples with positive S.mansoni and Fasciola respectively. In addition, PCR using DraI primers was positive for both S.mansoni and Fasciola strains, but with significantly lower DNA yield than with using BfrI primers. It was also positive with 40% and 33.3% of human fecal samples with positive S.mansoni and Fasciola respectively. In conclusion, PCR amplifying the 121 bp tandem repeats of S.mansoni can be used efficiently for diagnosis of human schistosomiasis in areas like Egypt endemic for Both Schistosoma and Fasciola. On the contrary, PCR using BfrI or DraI primers has low validity in the diagnosis of human fascioliasis in areas where both parasites coexist.