Histochemical and ultrastructural analysis of pathology and cell responses in gills of channel catfish affected with proliferative gill disease.

The article discusses a study on Icalurus punctatus, a pond-reared channel catfish with proliferative gill disease (PGD) caused by Henneguya species, a myxozoan parasite, using light and transmission electron microscopy, to characterize the inflammatory response during infection. In the study, the early lesions lacked inflammatory response around the disrupted cartilage, a chondrocyte response was not apparent, and the parasite was not present, indicating that the cartilage breaks occur before inflammation and arrival of the parasite in the gill. The study concluded that other chondrocytes in the lesions had ultrastructural features suggesting cell death.