Serial passages of larval Echinococcus granulosus from equine origin in mice. II. Infections with sterile cysts.

Sterile secondary E. granulosus cysts less than or equal to 1 mm in diameter, collected from mice 6-13 months after experimental infection were transferred to helminth-free mice. They developed into larger cysts showing fertility and daughter cyst formation at autopsy 9--14 months p.i. Average growth of the largest cyst per mouse, expressed in log volume (microliter), amounted to 0.30 +/- 0.03 per month; average growth of all cysts per mouse, expressed in log weight (mg) amounted to 0.27 +/- 0.02 per month. An inversed ratio was found between total parasite weight and number of cysts injected. The practical importance of these observations is discussed.