First identification of Francisella noatunensis subsp. orientalis causing mortality in mexican tilapia oreochromis spp

Francisellosis, an emerging disease in tilapia Oreochromis spp., is caused by the fac ultative, intracellular bacterium Francisella noatunensis subsp. orientalis, which is present in var ious countries where tilapia farming is commercially important. We confirmed the presence of francisellosis in Mexican tilapia cultures in association with an outbreak during the second semes ter of 2012. Broodstock fish presented a mortality rate of approximately 40%, and disease was characterized by histologically classified granulomas, or whitish nodules, in different organs, mainly the spleen and kidney. Through DNA obtained from infected tissue and pure cultures in a cysteine heart medium supplemented with hemoglobin, F. noatunensis subsp. orientalis was ini tially confirmed through the amplification and analysis of the 16S rRNA gene and the internal transcribed spacer region. Phylogenetic analysis of these genes demonstrated close similarity with previously reported F. noatunensis subsp. orientalis sequences obtained from infected tilapia from various countries. The identification of this subspecies as the causative agent of the outbreak was confirmed using the iglC gene as a target sequence, which showed 99.5% identity to 2 F. noatunen sis subsp. orientalis strains (Ethime-1 and Toba04). These findings represent the first documented occurrence of francisellosis in Mexican tilapia cultures, which highlights the importance of estab lishing preventative measures to minimize the spread of this disease within the Mexican aqua - culture industry.

Notas

Indexación: Scopus.

Palabras clave

Francisellosis, Freshwater Aquaculture, Mexico, Tilapia

Citación

Diseases of Aquatic Organisms. Open Access. Volume 120, Issue 3, Pages 205 - 215. 9 August 2016

DOI

10.3354/dao02999

URI

https://repositorio.unab.cl/xmlui/handle/ria/53391

Colecciones

Fac.CV - Artículos de Revista

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