Diagnostic Performance of Schistosoma Real-Time PCR in Urine Samples from Kenyan Children Infected with Schistosoma haematobium: Day-to-day Variation and Follow-up after Praziquantel Treatment
The diagnosis of active schistosomiasis and the subsequent therapeutic regimen based on Kato-Katz test (KK) are highly compromised in the low-endemic area (LEA). Recognition of individuals with decreased or no egg-excretion and assessment of drug response became impaired. Therefore, the appropriate assessment of surveillance strategies like chemotherapy use is inaccurate. To overcome these limitations, we describe results of the diagnosis of active schistosomiasis by using, in addition to microscopy and serology, DNA-detection assay pre and post-chemotherapy. In 108 individuals, KK, serology, and realtime PCR were performed for diagnosis of schistosomiasis. In 32 out of 108 individuals, had schistosomiasis based on laboratorial diagnosis, and 14 individuals who accepted treatment with praziquantel were followed up to 2 years post-chemotherapy. Positive egg excretion and DNA fragments were demonstrated in 8/108 (7.4%) individuals. IgE levels were detectable in 8/8 egg-excretors, although IgG1 was reactive in 7/8 egg-excretors. DNA amplification was able to demonstrate active infection in 24 individuals even without egg-excretion and/or IgG1 reactivity. Post-chemotherapy, lack of amplified DNA correlated with a therapeutic response in 7 out of 14 individuals after 6 months. Follow up showed that 2 years later all but one presented DNA amplification. Furthermore, a significant decrease in IgG1 and IgE reactivity also correlated with drug responses at 2 years post-therapy. This proof-of-concept study suggests that DNA detection might become an essential tool to diagnosis schistosomiasis in LEA where light infection with low parasite burden predominates. Real-time PCR is a robust approach for revealing schistosomiasis active infection despite no detection of egg excretion and /or immunoreactivity. Also, results highly suggested that real-time PCR can be reliably used to assess therapeutic responses and permit monitoring strategies for schistosomiasis surveillance in LEAs.