Piscine Intestinal Coccidial Infections in Pearl Gentian Groupers (<i>Epinephelus lanceolatus</i> ♂ × <i>E. fuscoguttatus</i> ♀): Pathogenesis, and Host Intestinal Response

Piscine intestinal coccidia, including Cryptosporidium spp., are significant pathogens in marine aquaculture, particularly affecting juvenile fish and leading to high morbidity and mortality. However, the pathological effects of coccidiosis in pearl gentian grouper (Epinephelus lanceolatus ♂ × E. fuscoguttatus ♀) have not been thoroughly studied. This research aimed to explore the histopathological changes and inflammatory responses linked to oxidative stress-induced tissue damage in juvenile pearl gentian groupers reared in marine cage farming systems. A total of 44 intestinal samples from juvenile groupers were classified as infected and non-infected based on the presence of Cryptosporidium. Nucleotide sequencing and phylogenetic analysis of the partial 18S rRNA gene identified the Cryptosporidium species detected in this study as C. bollandi. Histopathological analysis and immunofluorescence techniques were used to assess reactive oxygen species (ROS) production, DNA damage, and cellular apoptosis. The findings showed a significant increase in inflammatory cell infiltration, ROS production, DNA damage, and cellular apoptosis in infected fish compared to uninfected ones. These results indicate notable pathological alterations associated with C. bollandi infection in juvenile pearl gentian groupers. This research emphasizes the importance of understanding the effects of intestinal cryptosporidiosis on juvenile fish, as these pathological changes contribute to the health challenges that marine aquaculture currently faces.