Enteric Coccidiosis in Pearl Gentian Hybrid Grouper (Epinephelus fuscoguttatus ♀️ × E. lanceolatus ♂️) Farmed in Floating Net Cages in Indonesia

Various infectious agents can cause mass mortality in farmed grouper, yet enteric protozoan infections remain underreported, particularly in hybrid grouper cultured in floating net cages (FNCs). This study aimed to determine the cause of mortality outbreak in juvenile pearl gentian hybrid grouper (PGH) (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) in Indonesia. Moribund and freshly dead fish were subjected to parasitological examination, bacteriological isolation, PCR detection of Nervous necrosis virus (NNV) and Megalocytivirus, and histopathological examination of internal organs, with emphasis on intestinal tissues. Findings showed that viral pathogens were not detected, and the prevalence of ectoparasites was low, with normal gill lamellae and no skin lesions. However, gross pathology consistently showed intestinal reddening, while histological examination revealed severe enteritis with villous necrosis, hemorrhage, and abundant coccidian developmental stages (schizonts, microgamonts, and macrogamonts) infiltrating the intestinal mucosa. Enteric coccidiosis was confirmed as the primary cause of mortality in PGH juvenile. To our knowledge, this is the first report of enteric coccidiosis in this species cultured in FNCs in Indonesia.