Schistosoma mansoni: structural damage and tegumental repair after in vivo treatment with praziquantel.

The long-term, in vivo effects of a single, subcurative dose (200 mg/kg body weight of mouse) of praziquantel on the structure of adult Schistosoma mansoni and on the process and speed of tegumental repair are described. In both male and female worms praziquantel caused often extensive damage to the tegument, in the form of surface blebbings, swellings and lesions, and vacuolization and disruption of the subtegumental tissues. Repair of the drug-induced tegumental damage occurred slowly with partial and, more rarely, complete repair only being seen after 65 days post-treatment (p.t.), although signs of damage were still observed, particularly in male worms, at 100 days p.t. In contrast, repair of damage to the subtegumental/parenchymal tissues including the tegumental perikarya occurred relatively quickly, with the majority of worms examined appearing normal by 8-12 days p.t. The possible role(s) of the host immune response in relation to the speed of tegumental repair in vivo is discussed.