Hi Jalil Zorriehzahra, In Brazil we have high incidence of Aeromonas hydrophila in trouts farm and, since 2011, we have record of occurrence of the invasive "chinese" bacteria Weissella sp in rainbow trouts. Such bacterias causes septicemia and hemorrhage in eye orbit. The prevalence occurr  above 15 degrees Celsius water.  I hope had helped you.    P.S. See file attached.

Your description of the recent mortality of your rainbow trout is a characteristic manifestation of Pseudomonas and Aeromonas infections. We encountered similar manifestation in Oreochromis:  darker pigmentation, hemorrhagic and eroded scales and body surface, exopthalmia and mass mortality. 

Could you please answer these qouestion abouth your bacterial isolate ?

Gram ??? 

Motility ???

shape ???

catalase and oxidase test result.

As you know that clinical symptoms are similar in many disease.

Hi Jalil, the disease is called "exophthalmos". Very often reared rainbow trouts suffer of this strange disease caused by Streptococcus iniae.

Isn't the real cause of this disease some aspect of the artifical environment that disrupts the natural balance between microorganisms, or causes the fish to damage themselves, leaving them open to secondary invasion by several bacterial species? 

this may be due to Lactococcus garvieae infection. we have come across similar problem in rainbow trout in India. you can refer the "First report on characterization and pathogenicity study of emerging Lactococcus garvieae infection in farmed rainbow trout, Oncorhynchus mykiss (Walbaum), from India. Trans boundary and Emerging Diseases. 2018;65:1039–1048, DOI: 10.1111/tbed.12843.@Jalil Zorriehzahra

Dear Sumanta,

Thanks for your valued response.

Best wishes