Limited fertility of the subcutaneous cysts of Echinococcus multilocularis.

Echinococcus multilocularis is a tiny devastating worm that causes alveolar echinococcosis in humans. This disease mainly occurs in the liver but rarely in other organs. We report the subcutaneous encystment of E. multilocularis metacestodes in experimentally infected mice. Subcutaneous cysts had remarkably fewer protoscoleces (2.05 ± 1.47, n = 20) and small irregular-shape vesicles (ISVs) in the lumen as compared to liver cysts (69.6 ± 55.65, n = 10). Moreover, abnormal development of a protoscolex was also observed in a subcutaneous cyst. The results suggest that subcutaneous encystment may have potential adverse effects on the reproductivity and development of protoscoleces, providing potential explanations for high tissue preference of metacestode encystment.