Edwardsiellosis in freshwater angelfish (pterophyllum scalare)

Abstract

The freshwater angelfish (Pterophyllum scalare) with its many varieties is one of the most popular species in the ornamental market. The moribund freshwater angelfish individuals (20-25 g in weight) were sampled from an ornamental fish production facility to determine the cause of mortalities started immediately in fish without any other visible finding except the loss of appetite. The mortality rate in the population was as high as 50% within a week. Bacteriological samples were taken from internal organs for the identification of the causative agent. Hemorrhage in the eyes, loss of scales and skin depigmentation were the most obvious external finding in the moribund fish. Internally the liver was pale, the spleen was enlarged and the intestinal walls were thinned. According to conventional biochemical and physiological tests and 16S rRNA gene sequencing, all isolated bacteria were identified as Edwardsiella tarda. The antimicrobial susceptibility test performed using the disk diffusion test showed that the E. tarda strains we obtained were sensitive to enrofloxacin, sulfamethoxazole with trimethoprim, furazolidone and flumequine but resistant to ampicillin and tetracycline antibiotics.