Ultrastructural details of tetrathyridia of Mesocestoides spp. from a naturally infected dog.

Natural infection of dogs with Mesocestoides tetrathyridia is uncommon. The present study describes the ultrastructure of this larval form collected from an ascitic dog. The presence of suckers testified that it was a cephalic form. The tegument showed the typical structure composed of an external layer with two types of microtriches and an internal layer made up of cells joined to the external layer by cytoplasmic bridges. Numerous calcareous corpuscles were found in the parenchyma