Histological observations on schistosomula of Schistosoma japonicum in mouse lung and liver after treatment with praziquantel

Mice were treated intragastrically with praziquantel 300 mg/kg, 3 or 7 d after infection with S. japonicum cercarie.Histological changes of schistosomula were studied at various intervals after the treatment. The results showed that.(1) In Lungs, after 2 h, the tegument of schistosomula showed slight swelling and attachment by a few inflammatory cells.Some of the schistosomula were surrounded by polymorphonuclear leucocytes. After 6-24 h, the tegument showed vacuolization. A few disintegrated schistosomula were found in the lumen of pulmonary alveolus or blood capillary, surrounded by embolus or many inflammatory cell. Normal and dead schistosomula were seen in respiratory and terminal bronchioles after 6-72 h. After 72 h, dead worm granulomas were found. Such histological damages were not found in schistosomula from untreated mice 3-5 d after infection. (2) In liver, after 2-24 h, a few schistosomula showed tegumental swelling and vacuolization in parenchymal tissue and the inflammatory cell reaction surrounding the schistosomula was very slight. After 48 h,only a few dead schistosomula were found.