Evidence for a long-term effect of a single dose of praziquantel on Schistosoma mansoni-induced hepatosplenic lesions in northern Uganda

Treatment with praziquantel reduces the prevalence and intensity of Schisto soma mansoni infection. However, reversibility of periportal fibrosis of th e liver, which potentially leads to fatal complications, is not unequivocal ly substantiated. In the Nile District of Uganda, 460 patients were parasit ologically (Kato-Katz method) and ultrasonographically examined during Octo ber 1991, October 1992, and May 1994. Treatment with praziquantel at a dosa ge of 40 mg per kilogram of body weight was given in October 1991 and Octob er 1992 to 460 individuals (group A). Another 192 patients were seen during the baseline study in October 1991 and missed the follow-up in October 199 2 but took part in the second follow-up in May 1994. Thus, they received pr aziquantel only once in October 1991 (group B) and had an interval of 2.7 y ears until the next investigation in May 1994. Periportal thickening (PT) o f the liver was assessed by ultrasound at each time point. Praziquantel the rapy reduced the prevalence of S. mansoni in group A from 84% in 1991 to 31 % in 1992 and 30% in 1994. The respective intensities of infection (geometr ic means of egg output) were 81 eggs per gram (epg) of stool in 1991, 31 ep g in 1992, and 30 epg in 1994. Periportal thickening was found in 46% of pa tients in 1991, 32% of patients in 1992, and 35% of patients in 1994. Rever sibility of PT was influenced by age (markedly lower reversibility in indiv iduals older than 30 years) and sex (women and girls responded less favorab ly than did men and boys). Surprisingly, no significant difference was dete cted between group A and group B with respect to reversibility of PT. The o utcome between the 2 groups did not differ significantly. This may indicate that a single dose of praziquantel (as given to group B) may have a longer lasting effect than previously thought, that is, more than 2.5 years.