Outbreak of francisellosis (Francisella noatunensis subsp. orientalis) in cultured neon jewel cichlids Hemichromis bimaculatus from Morelos, Mexico.

Abstract

Francisellosis is a disease caused by different species of the bacterial genus Francisella and has been diagnosed in a wide variety of animals, including fish. Francisellosis in fish is characterized by the development of non-specific clinical signs as well as the presence of numerous granulomas in several organs (mainly spleen and kidney). Ten neon jewel cichlids Hemichromis bimaculatus were submitted for diagnosis from a farm located in Morelos, Mexico. Gross examination, wet preparations, cytology, histopathology and PCR were performed. Affected fish showed lethargy, erratic swimming, imbalance and gasping. At the post mortem examination, multiple granulomas were observed in the kidney and spleen. Microscopically, granulomatous inflammation was observed in several organs. Species-specific PCR assay using DNA from the affected tissues of H. bimaculatus as a template demonstrated the presence of F. noatunensis subsp. orientalis (Fno) by amplifying a hypothetical protein gene of the Fno species. The end diagnosis of francisellosis is important for Mexican ornamental aquaculture, since it is necessary to implement measures for treatment, prevention, control and diagnosis. This is the first report of francisellosis in the neon jewel cichlid.