Swim Bladder Disorders in Koi Carp (Cyprinus carpio)

Abstract

Swim bladder disorders and consequent buoyancy problems are encountered in ornamental fish, including koi carp. Nevertheless, beyond clinical and pharmacological management, they are largely underdiagnosed. In this study, nine koi carp showing abdominal swelling and abnormal swimming behavior were investigated. Clinical approach, varying from case to case, included ultrasonographic and X-ray investigations, bacteriological analysis of the collected fluid, antimicrobial susceptibility pattern, and possibly histological analysis. Diagnostic imaging, corroborating gross examination, documented swim bladder deformation/dislocation and serous fluid within the swim bladder chambers of most animals. Bacteria belonging to the Aeromonas hydrophila/caviae group and Shewanella xiamenensis were identified. S. xiamenensis strains showed a sensibility to all tested molecules except for one strain, which was resistant to tetracycline and cyprofloxacin. Antibiotic treatment succeeded in the full recovery of three cases in which S. xiamemensis infection was detected. Chronic aerocystitis was histologically documented where tissue was available. The swim bladder histopathological findings highlighted a chronic process that had compromised the quality of life of the animals. A multidisciplinary clinical–pathological and microbiological approach is highly suggested to recognize swim bladder conditions as early as possible, aiming to drive medical intervention and raising the chances of fish survival.

Relationship between gut microbiota and Chinook salmon (Oncorhynchus tshawytscha) health and growth performance in freshwater recirculating aquaculture systems

“…Although we included only apparently healthy fish based on their external appearance, almost half of the salmon sampled in March 2019 (36 out of 78) had fluid in their swim bladders. Besides inflammatory reactions, fluid accumulation is one of the main swim bladder disorders in fish and it has been encountered in ornamental fish, such as koi carp ( Cyprinus carpio ) ( Sirri et al, 2020 ). Physostomous fish like Chinook salmon have their swim bladders connected to the foregut, more specifically with the esophagus and stomach via a short pneumatic duct ( Sado et al, 2020 ).…”

“…Physostomous fish need to refill their swim bladder periodically by swallowing air at the surface, which permits the gas to enter into or be released through the alimentary canal ( Stewart and Hughes, 2014 ). Due to the specific anatomic structure of the pneumatic duct, microorganisms in the digestive tract can potentially enter the duct and migrate into the swim bladder ( Sirri et al, 2020 ). By detecting a reduced microbial diversity, a different microbial composition, and the presence of opportunistic pathogens, we suspected that a potential dysbiosis occurred in Chinook salmon with fluid in their swim bladders.…”