Dynamic Pathologic Study Of Ictalurus Punctatus(Channel Catfish)Infected With Aeromonas Veronii

Pathological model was established by using Aeromonas Veronii intraperitoneal and soak Channel Catfish(Ictalurus punctatus).Record the clinical signs of each group after challenge, five fish of each group were killed1h,2h,4h,6h,12h,24h,48h,72h and96h later and any fish that died were examined. The liver, kidney, spleen, intestine, brain, heart, gill, eye and muscle were fixed in paraformaldehyde for48h to72h. Samples of the tissues were processed to paraffin wax blocks and sections, and were stained with haematoxylin and eosin, using immunohistochemistry to determine the pathogen in the tissue.Similar clinical symptoms and pathological changes of the two infection were observed and consistent with natural infection. Mainly showed mental fatigue, walk slowly, outliers in travelling alone and anorexia. Grossly symptome showed that gill filament hyperemia and hemorrhage and slight swelling; haemorrhaging in abdominal cavity; hepatomegaly, renomegaly and with severe congestive and hemorrhage; meningeal congestion, intestinal bloat, intestinal cavity filled with much yellowish mucus. First observed clinical signs in intraperitoneal injection group, then soak infection group appeared clinical signs in24h later.The symptoms of soak infection group were more obvious, and can observe folding or wrinkling of theintestinal wall or intussusceptions occasionally.The histopathological findings of dead and moribund fish in intraperitoneal and soak infection group were similar and the degree of lesions had clear time effect. Systemic inflammation, organs denaturation and necrosis, especially kidney, spleen, liver were observed generally between two patterns. Tissues showed serious hyperemia and hemorrhage, large number of monocyte, neutrophil infiltration, splenic lymphocyte reduction, serious hyperemia and gore were observed in blood vessels, neutrophil and macrophage infiltration around vessels generally.Immunohistochemistry still show a similar distribution between two infection, antigen in various organs within the positive signals mainly scattered in phagocytic cells, blood, dead zone interstitial cells and parenchima such as parenchima. Intraperitoneal infection group detected the positive signal eariler than the soak infection group in the same tissue, distributed in kidney, spleen, liver mainly.Only soak infection group detected positive signal in brain and gill, but no detection in skin, muscle, heart, intestinal and eye. The distribution of the bacteria further confirmed the results of the study of the histopathology, kidney, spleen and liver are the target organs in Channel Catfish injected by Aeromonas Veronii JF490063.