Histopathology of Gill, Liver, and Pancreas, and Serum Enzyme Levels of Channel Catfish Infected withAeromonas hydrophilaComplex

Abstract

Channel catfish Ictalurus punctatus infected with Aeromonas hydrophila complex were examined 2-21 d after they were moved from earthen ponds to tanks. These infections by A. hydrophila complex were categorized into three groups: (1) motile aeromonad septicemia (MAS; systemic infection and signs of disease), (2) cutaneous (infection limited to skin and the underlying muscle), and (3) latent (systemic infection but no external signs of disease). Hepatic necrosis was associated with all types of infections but was most consistently present and sometimes more severe in fish with MAS. Hepatic steatosis was also associated with MAS. Systemically infected fish, including fish with latent infections, tended to have pancreatic atrophy and necrosis. There was a lack of infiltrating leukocytes in necrotic areas of the liver and intrahepatic exocrine pancreas of infected fish, and there was no consistent relationship between infection by A. hydrophila complex and hepatic hemorrhage or hemosiderosis. Spongiosis of gill epithelium was present in fish with any of the three infection types, but fish with MAS had a more severe branchitis, as indicated by leukocytic infiltration and dilation of the central venous sinus. Fish with MAS or latent infections had enlarged nuclei in the branchial epithelium. There was a significant relationship between these gill lesions and the occurrence or severity of hepatic and pancreatic lesions. The mean activities of aspartate aminotransferase and lactate dehydrogenase were significantly increased in fish with MAS but not in fish with one of the other types of infections.

Pathological findings of experimental Aeromonas hydrophila infection in Nile tilapia (Oreochromis niloticus)

“…In present study, pigments such as haemosiderin, lipofuscin, and hematoidine were not observed in the liver and spleen of any case. In the liver; detection of subcapsular, perivascular and peripacreatic lymphocyte infiltration was consistent with those in literature (1,7,9,13,24).…”

“…Also Ventura & Grizzle (13) reported that fish with only cutaneous infections may have several types of concealed lesions including increased amounts of lipofuscin and haemosiderin in the liver and spleen; however most visceral organs were not necrotic. In present study, pigments such as haemosiderin, lipofuscin, and hematoidine were not observed in the liver and spleen of any case.…”

“…There also be a severe branchitis, as indicated by leukocytic infiltration and dilation of the central venous sinus (13). Chronic motile aeromonad infections manifest themselves primarily as ulcerous forms of disease, in which dermal lesions with focal hemorrhage and inflammation are apparent.…”

Histopathological Studies of Experimentally Infected Shing, <i>Heteropneustes fossilis</i>with <i>Aeromonas hydrophila</i> Bacteria

“…in the kidney of ulcer diseased farmed fishes. Diseased catfish, with external signs or having latent infection could be diagnosed through histopathological study of various organs like skin, muscle, gill, kidney and liver as practiced by many workers (Ventura and Grizzle, 1988;Grizzle and Kiryu, 1993;Ruksana, 1998). Histopathological technique is one of the most important procedures for disease diagnosis in fishes.…”

Untitled

“…Histopathologically, fish may exhibit epithelial hyperplasia in the foregut, leptomeningeal congestion in the brain, as well as a thrombosis and inflammation in the perisclerotic region and corneal epithelium of the eye (Fuentes and Perez, 1998). There may also be a severe branchitis, as indicated by leucocytic infiltration and dilation of the central venous sinus (Grizzle and Kiryu, 1993). Systemic infections are characterized by diffuse necrosis in several internal organs and the presence of melanin-containing macrophages in the blood (Ventura and Grizzle, 1988).…”