Natural and experimental infections of Campylobacter cryaerophila in rainbow trout: Gross pathology, bacteriology, clinical pathology and chemotherapy

Campylobacter cryaerophila was isolated from naturally infected rainbow tro ut (Oncorhynchus mykiss), and its pathogenicity was tested by intramuscular injection using 1-year-old rainbow trout and scattered mirror carp (Cyprin us carpio). C. cryaerophila did not induce experimental infection in scatte red mirror carp. Natural and experimental infections caused mortalities in rainbow trout with gross clinical abnormalities such as exophthalmia, damag e of liver, bloody kidney and haemorrhagic heart and swollen intestine. Glu cose, cholesterol, triglyceride and haematocrit levels in blood of both nat urally and experimentally infected fish were significantly decreased as com pared to healthy fish. Significant decreases were observed in the serum glu tamate oxalacetate transaminase level of experimentally infected fish and s erum total protein value of naturally infected fish. Albumin levels of seru m were not significantly different among the three treatments. Sensitivitie s of three isolates of C. cryaerophila against 51 chemotherapeutants were d etermined. Minimum inhibitory concentrations of formalin and enrofloxacin t o the isolates were between 3.5-4.5 mu L/mL and 0.025-1 mu L/mL, respective ly. Oral applications of enrofloxacin after bath disinfections with formali n controlled the natural infections.