Physical factors influencing survival of taeniid eggs

The effect of desiccation has been shown likely to dominate all other natural restrictions on the survival of taeniid eggs in nature. The damage it causes is described, and an explanation is proposed. The effect has been both qualitatively and quantitatively examined by in vitro laboratory methods using eggs which have been exposed to conditions of controlled humidity. Echinococcus granulosus and Taenia pisiformis were found to be significantly more susceptible to damage than either Taenia ovis or Taenia hydatigena. The reliability of the in vitro method has been confirmed for T. pisiformis by in vivo assay. The limiting effect of actinic light and mild heat on egg survival was found to be minimal. Desiccated eggs have been demonstrated to carry an electrostatic charge, which may partly account for their adhesive properties. The significance of these findings to the epidemiology of the associated diseases is briefly discussed.