Histopathological Characteristics of Grass Carp (Ctenopharyngodon idella) Gills Infested with Parasites

Abstract

     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-eight Grass carp fry infected with metacercaria of Centrocestus formosanus, Dactylogyrus sp. And Ichthyophthirius multifiliis r, were obtained from fish farm nurseries. Symptoms, prevalence and intensity were recorded and histopathological examination was performed on sectioned gill tissues stained 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 had its own distinctive characteristics. The infection by metacercaria of C. formosanus presented severe lesions associated with moderate to severe hyperplasia of cartilage of the primary lamellae, epithelial hyperplasia, gill hemorrhage, congestion, and

disorting and inflammation around the metacercarial cyst. Gills infected with Dactylogyrus sp. mainly expressed epithelial hyperplasia, inflammation and lamellae damage due to the mechanical effects of hooks and toxic secretions. I.multifiliis causing hyperplasia and hemorrhage was noted with further study needed to clarify the histopathology at different stage of cyst formation.