Light and electron microscopic studies on Schistosoma mansoni Granulomas of mouse livers following treatment with praziquantel.

The disintegration of Schistosoma mansoni and their eggs was studied in the liver of mice after termination of the infection by praziquantel. Egg granulomas, which were already present at the time of treatment, attained their maximal diameter of 380 microns after 2-3 weeks. Within the following 5 weeks, granulomas very rapidly regressed in size to only 165 microns. Directly after treatment, worms were trapped in the liver where they were quickly invaded by granulocytes and subsequently phagocytosed within 3 weeks. Worm granulomas measured 700 and 900 microns after 3 and 8 weeks, respectively, but then regressed rapidly to only 550 microns after 12 weeks. Liver lesions appeared to regress more rapidly after praziquantel than after treatment with other schistosomicidal drugs.