Nocardiosis in some ornamental fishes in Iran

Nocardiosis is a systemic disease in fish in which lesions are frequently localized in the integument and several internal organs, with the nodular lesions characteristic of granulomata. The zoonotic species of Nocardia (N. asteroides) is a pathogen of humans and many animals. Considering the lack of information about the status of Nocardia species in fish species in Iran, the widespread use of aquariums, and possible transmission of zoonotic diseases from ornamental fishes to human, primary study for detecting this bacterium was performed. In this study, 100 freshwater aquarium fishes (apparently healthy and unhealthy) were purchased from some shops located in Tehran, Tabriz, Zanjan, and Shahindej cities completely randomly and transferred to the laboratory. Fish samples were examined for the Nocardia genus and N. asteroides using nested polymerase chain reaction (PCR) assay. In the macroscopic examination, no granulomatous lesions were detected. PCR examination showed that one healthy fish and three sick fish (with clamped fin, lethargy, and slow-motion sings) were infected by Nocardia. But PCR amplification of N. asteroids by specific primers did not amplify DNA gyrase gene sequences of N. asteroids. This study is the first known identification of Nocardia -infected ornamental fishes in Iran.