Received: 12-08-2014 / Accepted: 29-11-2014
Histopathology provides a diagnostic method to detect the effects of irritants and pathogens in different fish organs and it can be used as an indicator for abnormal conditions in aquatic environments. The present study used histopathology to examine lesions on Grass carp (Ctenopharyngo donidella) gills associated with three common parasites. Fifty-eightGrass carp fry infectedwithmetacercaria of Centrocestus formosanus, Dactylogyrus sp. and Ichthyophthirius multifiliis r, were obtained fromfish farm nurseries. Symptoms, prevalenceand intensity were recordedandhistopathological examination was performed on sectioned gill tissuesstained with Haematoxylin-Eosin. Based on the results, the lesions in gill tissues caused by these three parasites exhibited similar characteristics as structural deformation and circulatory disturbances. However, each of them hadits own distinctive characteristics. The infection bymetacercaria of C. formosanuspresented severe lesions associated with moderate to severe hyperplasia of cartilage of the primary lamellae, epithelial hyperplasia, gill hemorrhage, congestion, and disorting andinflammation around the metacercarial cyst. Gills infected with Dactylogyrussp. mainly expressed epithelial hyperplasia, inflammation and lamellae damage due to the mechanical effects of hooks and toxic secretions. I.multifiliis causinghyperplasia and hemorrhage was noted withfurther study needed to clarify the histopathology at different stage of cyst formation.