SPECIFICITY OF PCR TECHNIQUE USING PRIMERS AMPLIFYING SEGMENTS OF 18S RDNA OF FASCIOLA SPECIES AND 121BP TANDEM REPEAT OF SCHISTOSOMA MANSONI MUTUALLY TESTED AGAINST THE PURE STRAINS AND CLINICAL FECAL SAMPLES OF EACH OTHER
Rabab Fawzi Mohmmad Selem1, Naglaa Ibrahim Azab2
1Medical Parasitology and 2Medical Biochemistry Departments, Faculty of Medicine, Benha University
Human fascioliasis is now an established public health problem in Egypt, its diagnosis is a problematic issue for many reasons, one of which is the well-known parasitic cross reactivity with Schistosoma mansoni parasite which coexists with it in the same geographical areas. PCR technique has been proved to be highly sensitive and specific in diagnosis of many parasitic diseases including schistosomiasis infection. In this study, BfrI and DraI primers amplifying 356 and 263 bp(base pair) segments of Fasciola 18S rDNA were tested with DNA extracted from both of pure Fasciola gigantica & Schistosoma mansoni strains and clinical fecal samples infected with both parasites,the same was done using 121 bp tandem repeats primers of Schistosoma mansoni. PCR using 121 bp tandem repeats primers of Schistosoma mansoni gave positive results with Schistosoma mansoni pure strain and schistosomiasis clinical fecal samples only indicating its specificity in schistosomiasis diagnosis. PCR using BfrI was proved to be positive with both of Schistosoma mansoni & Fasciola gigantica strains and also with 70% of schistosomiasis and 66.6% of fascioliasis clinical fecal samples, while PCR using DraI primers was much more less sensitive in both pure parasitic strains (significantly lower DNA yield) and in clinical fecal samples (corresponding ratios were 30% and 33.3% for schistosomiasis and fascioliasis respectively). In conclusion, PCR using BfrI and DraI primers showed a high level of cross reactivity between Schistosoma mansoni & Fasciola gigantica at both levels of pure strains and clinical fecal samples indicating its low validity in diagnosis of human fascioliasis in areas like Egypt where both parasites coexist.