Systemic Citrobacter freundii Infection among Sunfish Mola mola in Matsushima Aquarium

Abstract

An epizootic attributable to enterobacteriaceae Citrobacter freundii was observed among sunfish Mola mola in Matsushima Aquarium, Japan. During May to September, 1981, twenty-five out of twenty-nine sunfish died in the aquarium. Almost all the infected sunfish showed the same characteristic pathological changes, that is, hemorrhagic exanthema upheaved from skin surface and multiple lipoid granuloma in the kidney. Citrobacter freundii was isolated from the various organs examined. Pure cultures were obtained from kidney granuloma and the spleen, the results indicating that Citrobacter freundii was the most likely pathogen. Bacteriological examination of the sea water circulating in the aquarium showed high levels of various enterobacteriaceae, such as Klebsiella, Enterobacter and Proteus, in addition to Citrobacter freundii. These findings suggested the urine-water-oral transmission route within the aquarium. Several antibiotics were administered but none were effective in treating the infected sunfish. However, after disinfecting the sea water with chlorine sunfish infection with Citrobacter freundii terminated. The unique pathogenecity of Citrobacter freundii to sunfish will be discussed regarding host range in sea water. © 1982, The Japanese Society of Fisheries Science. All rights reserved.