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

Spring viraemia of carp (SVC) is an infectious disease responsible for severe economic losses for various cyprinid species, particularly common carp (Cyprinus carpio carpio). The causative agent is the SVC virus (SVCV), a member of the Sprivivirus genus, Rhabdoviridae family, and a List 1 pathogen notifiable by the World Organization for Animal Health. This study describes the diagnosis of an SVCV pathogen isolated in October 2015 from wild common carp inhabiting a natural lagoon in central Mexico. While neither an epidemic nor fish mortalities were reported, the collected killed specimens exhibited clinical signs of disease (e.g., exopthalmia, moderate abdominal distension and haemorrhaging, as well as internal haemorrhages and adhesions). Histological results of injuries were consistent with the pathology caused by SVCV. This finding was supported by the isolation of a virus in EPC and BF‐2 cells and subsequent RT‐PCR confirmation of SVCV. The phylogenetic analyses of partial SVCV glycoprotein gene sequences classified the isolates into the Ia genogroup. These findings make this the first report of SVCV detection in Mexico, extending the southern geographical range of SVCV within North America. However, since this pathogen was detected in fish inhabiting a natural body of water without tributaries or effluents, it is difficult to estimate the risk of SVCV for other wild/feral cohabitating cyprinid species in the lagoon. The status of this virus is also unknown for other bodies of water within this region.

Section: Methodsmentioning

confidence: 99%

First detection of spring viraemia of carp virus in common carp (Cyprinus carpio L.) affected by a septicaemic disease in Mexico

Ortega

Cañas-López

Irgang

et al. 2019

“…Tilapia francisellosis is a systemic visceral granulomatous disease that causes high mortality and huge economic losses in tilapia farming worldwide, including in Taiwan (Hsieh, Tung, Tu, Chang, & Tsai, ), USA (Birkbeck, Feist, & Verner‐Jeffreys, ; Colquhoun & Duodu, ; Mauel et al, ; Soto, Baumgartner, Wiles, & Hawke, ), Brazil (Leal, Tavares, & Figueiredo, ), Columbia (Iregui, Vasquez, Rey, & Verjan, ), Costa Rica (Soto, Hawke, Fernandez, & Morales, ), UK (Jeffery, Stone, Feist, & Verner‐Jeffreys, ; Ramírez‐Paredes et al, ; Shahin et al, ), Mexico (Ortega et al, ), China (Lin et al, ) and Thailand (Jantrakajorn & Wongtavatchai, ; Nguyen, Dong, Senapin, Pirarat, & Rodkhum, ). The aetiologic agent of tilapia francisellosis is a Gram‐negative facultative intracellular bacterium belonging to F. noatunensis subsp.…”

Section: Introductionmentioning

confidence: 99%

Molecular characterization and pathogenicity of Francisella noatunensis subsp. orientalis isolated from cultured tilapia (Oreochromis sp.) in Taiwan

Pulpipat

Lin²,

Chen³

et al. 2019

Francisella noatunensis subsp. orientalis is a causative agent of systemic granulomatous disease in tilapia. The present study was designed to understand the genetic and phenotypic diversities among Taiwanese Fno isolates obtained from tilapia (n = 17) and green Texas cichlid (Herichthys cyanoguttatus) (n = 1). The enzymatic profiles of the isolates were studied using the API ZYM system. Phylogenetic tree analysis of the 16S rRNA and housekeeping gene and pulsed‐field gel electrophoresis (PFGE) were carried out to determine the genotypic characters of all isolates. The phylogenetic tree showed similarity of 99%–100% nucleotide sequences of 16S rRNA and housekeeping genes compared to the Fno references genes from GenBank database. Comparatively, the results revealed an identical profile of enzymatic and PFGE pattern which was distincted from that of F. philomiragia. To understand the pathogenicity, the isolates were intraperitoneal injected to tilapia the gross lesions were observed concomitant with natural outbreak. Median lethal dose upon Nile tilapia and red tilapia were 9.06 × 103 CFU/fish and 2.08 × 102 CFU/fish, respectively. Thus, our data provide understanding the epidemiology of Taiwanese Fno isolates, and help in development of future control and prevention.

“…However, with the rapid development of the tilapia culture industry, various bacterial diseases frequently outbreak due to intensified culture and high stocking density conditions of intensive farming. Pathogens, such as streptococcosis (Anshary, Kurniawan, Sriwulan, Ramli, & Baxa, ; Verner‐Jeffreys et al., ), edwardsiellosis (Kwon, Nam, Kim, & Kim, ; Park & Jeong, ; Soto, Illanes, Revan, Griffin, & Riofrio, ; Soto et al., ), columnaris disease (Dong, Lafrentz, Pirarat, & Rodkhum, ; Sebastiao, Nomura, Sakabe, & Pilarski, ), francisellosis (Assis, Tavares, Pereira, Figueiredo, & Leal, ; Ortega et al., ; Sebastiao, Pilarski, Kearney, & Soto, ) and motile aeromonas septicaemia (Dong et al., ; Li & Cai, ; Soto‐Rodriguez, Cabanillas‐Ramos, Alcaraz, Gomez‐Gil, & Romalde, ), have resulted in substantial economic losses to the local aquaculture industries.…”

Section: Introductionmentioning

confidence: 99%

Aeromonas shuberti as a cause of multi‐organ necrosis in internal organs of Nile tilapia, Oreochromis niloticus

Liu

Chang

Zhang

et al. 2018

A disease with white spots in internal organs of Nile tilapia occurred in Zhanjiang, southern China. Multiple, white nodules, 0.8-2.2 mm in diameter, were scattered throughout the liver, spleen and kidney of diseased fish. Signs of nodules reproduced after artificial infection with the isolated strain. Isolated bacteria were Gram-negative, facultative anaerobic, motile, short rod-shaped, with a length of 1.2-2.2 μm. Morphological and biochemical tests, as well as phylogenetic analysis, all strongly indicated that the isolate from tilapia is identical to Aeromonas schubertii (A. schubertii) which temporary named LF1708 strain. Antibiotic sensitivity assays showed the LF1708 is sensitive to 24 of 27 tested antibiotics. Pathogenicity test revealed that the isolate at the dose of 3.75 × 10 CFU/g killed 100% of experimental tilapia within 2 days and the dose of 1 × 10 CFU/g killed 100% of experimental zebrafish within 1 day. Histopathology of diseased tilapia infected with A. schubertii showed numerous necrotic lesions widely distributed in spleen, liver and kidney, and infiltration with a large number of bacteria. To our knowledge, this was the first report that associated A. schubertii with mortality in tilapia.