Evaluation of PCR‐ELISA and Kato‐Katz techniques for schistosomiasis mansoni cure assessment (LB279)

Abstract

Introduction: The importance of following up therapeutic intervention among individuals diagnosed with schistosomiasis is based on the fact that the expected cure rate for Praziquantel varies around 90% and that non‐cured patients continue to maintain transmission in endemic settings. Methodology: The aim of the study was to evaluate parasitological and molecular biological techniques for the assessment of cure after chemotherapy. The study was carried out in a low transmission area, Pedra Preta, Montes Claros, Minas Gerais, Brazil. To establish the infection rate, a combination of parasitological exams was performed. Four stool samples from 201 inhabitants were analyzed according to the Kato‐Katz method (18 slides) and a commercial test, the TF‐Test®. All patients with positive parasitological exams were treated with a single dose of Praziquantel, 50 mg/kg for adults and 60 mg/kg for children. To establish the cure rate out of the 72 positive patients, 69 were followed up after 30 days, 67 after 90 days and 61 after 180 days of treatment. For the direct comparison between the Kato‐Katz method and the PCR‐ELISA technique, 500mg of the same stool sample of each participant was analyzed, resulting in 12 Kato‐Katz slides per sample. The data analysis involved the determination of the cure rate defined by both diagnostic methods. Results: The cure rate 30 days after treatment by the Kato‐Katz technique was 100% and one positive individual was detected by the PCR‐ELISA (cure rate of 98.5%). Three positives individuals were detected by the PCR‐ELISA 90 days after treatment (cure rate of 95.5%), not identified by analyzing 12 Kato‐Katz slides. The cure rate after 180 days after treatment was 98.4% by Kato‐Katz (1 out of 61) and 96.5% by PCR‐ELISA (2 out of 61), with the final cure rate of 95.1% (3 out of 61). It is worth to note here that 30, 90 and 180 days after treatment the cure rate determined by 2 Kato‐Katz slides was 100%. Conclusions: In situations of very low parasite load, such as after therapeutic interventions; the assessment of cure may require increased number of Kato‐Katz slides or a test with higher sensitivity as PCR‐ELISA.