A total of 54 adult patients with chronic intestinal or hepato-intestinal schistosomiasis mansoni were included into a double-blind clinical trial to compare praziquantel and oxamniquine. Following a randomized allocation, 27 patients received praziquantel — 65 mg/kg bwt — and 27 oxamniquine — 18 mg/kg bwt — in a single oral dose divided into two intakes. The incidence, severity and duration of side-effects were similar for the two drugs. The assessment of therapeutical efficacy was based on the quantitative oogram technique via biopsy of the rectal mucosa, performed at the end of 1, 2, 4 and 6 months after treatment. At these same occasions, stool examinations according to Hoffman, Pons & Janer (HPJ) and Kato-Katz (K-K) methods were undertaken to confront their results with the oogram findings. In order to evaluate the immediate effect of the therapy upon the egg laying activity of the parasite, a limited number of patients was submitted to rectal biopsies on the 6th. and 18th. days subsequent to the drug administration. Both drugs proved to be active anti-schistosomal agents as their coefficients of variation, determined from the oograms made immediatly following the treatment, were above 60%. Furthermore, out of 27 patients in each group, 24 treated with praziquantel and 22 with oxamniquine have completed the required six months parasitological follow up period. The respective cure rates in accordance with the oogram, HPJ and K-K findings were: 29.2%, 50% and 91.7% for praziquantel; 22.7%, 50% and 86.3% for oxamniquine. Despite a quite low cure rate, a sharp fall (-83%) in the mean number of living eggs per gram of tissue was observed in the post-treatment oograms. These results indicated that both anti-schistosomal agents were similarly efficacious On the other hand, a striking difference in the cure rates amongst the three parasitological control methods became evident. The oogram was the most accurate one, followed by HPJ and lastly by K-K. Since there was a direct correlation between the number of living eggs in the oogram and the positivity of the stool examinations, the percentage of false-negative results has augmented remarkably after treatment reaching 47.3% with HPJ and 92.9% with K-K. Prior to therapy they were 0% and 64,8%, respectively. The authors infer that the different accuracy of the applied methodology to assess therapeutical efficacy may explain the discrepancy between the cure rate achieved in this clinical trial and those reported by other investigations with either praziquantel or oxamniquine.
Human schistosomiasis mansoni; Therapeutical evaluation; Quantitative oogram technique; Praziquantel; Oxamniquine