scholarly journals Emergence of Rickettsial Infection in Rainbow Trout (Oncorhynchus mykiss) Fry Displaying the Appearance of Red Mark Syndrome in Korea

2019 ◽  
Vol 7 (9) ◽  
pp. 302 ◽  
Author(s):  
Oh ◽  
Giri ◽  
Yun ◽  
Kim ◽  
Kim ◽  
...  
Keyword(s):  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Clinical Signs ◽  
Lateral Side ◽  
Fish Disease ◽  
Rickettsial Infection ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Transmission Electron ◽  
Polymerase Chain ◽  
Distinct Features

Red mark syndrome (RMS) is a fish disease caused by the infection of Rickettsial agents, especially affecting rainbow trout (Oncorhynchus mykiss). The disease is prevalent in many countries in Europe (France, Switzerland, Italy, and Slovenia), South America (Chile), North America (USA), and even Asia (Japan). However, it has not been reported in Korean aquaculture. In February 2019, rainbow trout presenting red spot lesions with swollen features on the lateral side of their body were observed at a hatchery in Korea. Fishes showing those clinical signs were fry weighing 25 ± 5 g. Moreover, the fish showing the red spot lesions were found dead, which suggests an outbreak of a mortality-causing disease. The symptoms were similar to those of RMS, and we identified the presence of Rickettsia-like organisms associated with this disease using polymerase chain reaction (PCR), sequencing, histopathologic examination, and transmission electron microscopy. The distinct features of this infection, compared to that in previous reports, were that RMS occurred in small-sized fish and accompanied mortality. Additionally, the presence of the Rickettsia agent was accompanied with outbreak of the disease. Therefore, this is the first report of RMS outbreak in rainbow trout fisheries in Korea.

Differential expression of corticosteroid receptor genes in rainbow trout (Oncorhynchus mykiss) immune system in response to acute stress

2007 ◽  
Vol 64 (10) ◽  
pp. 1382-1389 ◽  
Author(s):  
Takashi Yada ◽  
Teruo Azuma ◽  
Susumu Hyodo ◽  
Tetsuya Hirano ◽  
E Gordon Grau ◽  
...  
Keyword(s):  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Plasma Cortisol ◽  
Glucocorticoid Receptors ◽  
Acute Stress ◽  
Mrna Levels ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Corticosteroid Receptor ◽  
Polymerase Chain ◽  
Peripheral Blood Leucocytes

Expression of distinct corticosteroid receptor genes, glucocorticoid receptors 1 and 2 (GR-1 and GR-2, respectively) and mineralcorticoid receptor (MR), was quantified by real-time polymerase chain reaction (PCR) in peripheral blood leucocytes (PBL), spleen, and gill of rainbow trout (Oncorhynchus mykiss) after an acute netting stress. Plasma cortisol levels were significantly increased 2 h after stress and returned to prestress levels within 24 h. Consistent with changes in plasma cortisol, GR-2 mRNA levels in PBL increased significantly at 2 h after stress, returning to initial levels by 8 h. In contrast, GR-1 and MR levels in PBL decreased significantly at 24 h after stress, and these reduced levels were maintained for 7 days. Splenic mRNA levels of GR-1 and GR-2 also decreased at 8 h and 24 h after stress, returning to control levels by 7 days, whereas no significant change was observed in MR. In gill, there was no obvious change in corticosteroid receptor mRNA levels after stress, except for a transient decrease at 8 h in MR. These results suggest a variety of roles for the three corticosteroid receptors during immunosuppression in response to acute stress in trout.

scholarly journals A Summer Mortality Outbreak of Lactococcosis by Lactococcus garvieae in a Raceway System Affecting Farmed Rainbow Trout (Oncorhynchus mykiss) and Brook Trout (Salvelinus fontinalis)

Animals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1043
Author(s):  
Paolo Pastorino ◽  
Ana Isabel Vela Alonso ◽  
Silvia Colussi ◽  
Giulia Cavazza ◽  
Vasco Menconi ◽  
...  
Keyword(s):  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Brook Trout ◽  
Salvelinus Fontinalis ◽  
Physiological Stress ◽  
Clinical Signs ◽  
Lactococcus Garvieae ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Mediterranean Countries ◽  
Summer Mortality

Lactococcosis is a fish disease of major concern in Mediterranean countries caused by Lactococcus garvieae. The most susceptible species is the rainbow trout (Oncorhynchus mykiss), suffering acute disease associated with elevated mortalities compared to other fish species. References reported that other salmonids are also susceptible to the disease, but no mortality outbreak has been described to date. The aim of this study was to present a mortality outbreak that occurred in brook trout (Salvelinus fontinalis) farmed in northwestern Italy during the summer of 2018. Fish exhibited clinical signs, such as exophthalmos, diffused hemorrhages localized in the ocular zone, hemorrhagic enteritis, and enlarged spleen. L. garvieae was isolated in all fish. Molecular and epidemiological characterization of the isolates, through Pulsed Field Gel Electrophoresis (PFGE), confirmed the initial hypothesis of water as vehicle of infection favoring transmission between rainbow trout farmed in upstream compartments and brook trout located in downstream tanks. Moreover, several environmental conditions affected and promoted the outbreak, among them the high-water temperature, which probably induced a physiological stress in brook trout, being way above the optimal temperature for this species, increasing the susceptibility to infection.

Susceptibility of pike Esox lucius to VHSV and IHNV and potential transmission to rainbow trout Oncorhynchus mykiss

2020 ◽  
Vol 139 ◽  
pp. 175-187
Author(s):  
J Cabon ◽  
F Almeras ◽  
M Baud ◽  
L Pallandre ◽  
T Morin ◽  
...  
Keyword(s):  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Horizontal Transmission ◽  
Clinical Signs ◽  
Esox Lucius ◽  
Infected Fish ◽  
Control Measures ◽  
Viral Hemorrhagic Septicemia Virus ◽  
Fish Farms ◽  
Rainbow Trout Oncorhynchus Mykiss

Determining the origin of recurrent outbreaks of fish diseases occurring on fish farms is essential for disease prevention and control measures. In this study, we investigated the potential reservoir role of wild fish species living near salmonid farms which were regularly found to be positive for viral hemorrhagic septicemia virus (VHSV). In addition to VHSV, infectious hematopoietic necrosis virus (IHNV) was also isolated from several pike Esox lucius samples collected from a pond near the salmonid farms of interest. All isolates of VHSV and IHNV analyzed had 100% identical partial glycoprotein gene sequences. VHSV pike strain OO128-25 belonged to the Ia genotype and shared 99.1 to 99.5% nucleotide identity with strains recently isolated from the farms. IHNV pike strain OO121-8, European genotype, appeared to be different from strains from France characterized since the first isolation in 1987. Isolates representative of both viral species were highly virulent in rainbow trout Oncorhynchus mykiss. OO128-25 induced 65% mortality in pike fingerlings, whereas only weak mortality was observed with OO121-8, despite characteristic symptoms in infected fish. High levels of specific antibodies to VHSV and IHNV were detected in adult pike in the absence of clinical signs. Infection of rainbow trout in contact with experimentally VHSV- or IHNV-infected pike fingerlings indicates possible horizontal transmission. These results suggest that pike could act as a reservoir for VHSV and IHNV in the wild, providing additional evidence to explain viral persistence and resurgence in certain areas.

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