Fig. 2.

Morphology of Opisthorchis viverrini eggs. (A) Photographic and diagrammatic representations of O. viverrini egg morphological characteristics used to assess viability and (B) microscopic observation of snail feces to assess egg ingestion and hatching rates. The picture shows a well/clean open shell, suggesting successful hatching of the miracidia (black arrow) resulting from mechanical and biochemical stimuli. Alternatively, degraded eggs frequently still harbor their operculum and present air bubbles, suggesting the loss of osmotic balance and death of the miracidia.