Prevention of Schistosoma japonicum infection in mice with long-acting praziquantel implants

Abstract

This work reports the prevention outcomes of a praziquantel (PZQ) implant against the infection of Schistosoma japonicum in mice. The PZQ implant produced stable plasma PZQ concentrations in a range of 100–1300ng/mL for a period of 70days, by releasing PZQ in subcutaneous tissues in a sustained manner. To assess the prevention effects, the mice were infected at varying times after implantation. All the mice were sacrificed at 6weeks after infection for worm and egg recovery and counting, worm morphological examination, determination of egg-hatching rates, and analysis of hepatic histology. The infection was successfully prevented for mice with early infection times (within 2–3weeks), as nearly no worms, paired worms, eggs, or miracidia were recovered. However, in mice with late infection times (after 3weeks), the prevention effects were diminished due to the decreased plasma PZQ concentrations at late times. Interestingly, the implants showed robust prevention effects on repeated infection at 1 and 3weeks. In the infection-prevented mouse livers, no granuloma formation or granulomatous inflammation was observed. The results demonstrated that by blocking the development of infecting miracidia and by deactivating the eggs, the PZQ implants encouragingly prevented the S. japonicum infection and avoided liver damage.