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Diseases of Aquatic Organisms

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DAO is a hybrid research journal on all aspects of disease phenomena in aquatic organisms.

Online: ISSN 1616-1580

Print: ISSN 0177-5103

DOI: https://doi.org/10.3354/dao

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Volume contents
Dis Aquat Org 120:205-215 (2016)

DOI: https://doi.org/10.3354/dao02999

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First identification of Francisella noatunensis subsp. orientalis causing mortality in Mexican tilapia Oreochromis spp.

ABSTRACT: Francisellosis, an emerging disease in tilapia Oreochromis spp., is caused by the facultative, intracellular bacterium Francisella noatunensis subsp. orientalis, which is present in various 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 semester 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 initially 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. noatunensis 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 establishing preventative measures to minimize the spread of this disease within the Mexican aquaculture industry.

KEYWORDS

Francisellosis Freshwater aquaculture Mexico Tilapia

Cesar Ortega (Corresponding Author)

  • Centro de Investigación y Estudios Avanzados en Salud Animal (CIESA), Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma del Estado de México, Carretera Toluca-Atlacomulco Km. 15.5, Toluca 50200, Mexico
cos_mx@hotmail.com

Gerardo Mancera (Co-author)

  • Centro de Investigación y Estudios Avanzados en Salud Animal (CIESA), Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma del Estado de México, Carretera Toluca-Atlacomulco Km. 15.5, Toluca 50200, Mexico

Ricardo Enríquez (Co-author)

  • Laboratorio de Biotecnología y Patología Acuática, Instituto de Patología Animal, Facultad de Ciencias Veterinarias, Campus Isla Teja, Universidad Austral de Chile, Independencia 641, Valdivia 5090000, Chile

Augusto Vargas (Co-author)

  • Laboratorio de Biotecnología y Patología Acuática, Instituto de Patología Animal, Facultad de Ciencias Veterinarias, Campus Isla Teja, Universidad Austral de Chile, Independencia 641, Valdivia 5090000, Chile
  • Centro FONDAP, Interdisciplinary Center for Aquaculture Research (INCAR), PO Box 160-C, Concepción 4030000, Chile

Simón Martínez (Co-author)

  • Centro de Investigación y Estudios Avanzados en Salud Animal (CIESA), Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma del Estado de México, Carretera Toluca-Atlacomulco Km. 15.5, Toluca 50200, Mexico

Raúl Fajardo (Co-author)

  • Centro de Investigación y Estudios Avanzados en Salud Animal (CIESA), Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma del Estado de México, Carretera Toluca-Atlacomulco Km. 15.5, Toluca 50200, Mexico

Ruben Avendaño-Herrera (Co-author)

  • Centro FONDAP, Interdisciplinary Center for Aquaculture Research (INCAR), PO Box 160-C, Concepción 4030000, Chile
  • Laboratorio de Patología de Organismos Acuáticos y Biotecnología Acuícola, Facultad de Ciencias Biológicas, Universidad Andrés Bello, 2520000 Viña del Mar, Chile
  • Centro de Investigación Marina Quintay (CIMARQ), Universidad Andres Bello, Quintay, Chile

María José Navarrete (Co-author)

  • Laboratorio de Biotecnología y Patología Acuática, Instituto de Patología Animal, Facultad de Ciencias Veterinarias, Campus Isla Teja, Universidad Austral de Chile, Independencia 641, Valdivia 5090000, Chile

Alex Romero (Co-author)

  • Laboratorio de Biotecnología y Patología Acuática, Instituto de Patología Animal, Facultad de Ciencias Veterinarias, Campus Isla Teja, Universidad Austral de Chile, Independencia 641, Valdivia 5090000, Chile

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