Question of the Day

Renibacterium salmoninarum (bacterial kidney disease, BKD) is best prevented by screening broodstock with qPCR and culling any positives to prevent vertical transmission. Another option is to use ELISA to screen the broodstock and cull the eggs from positives. 

R. salmoninarum is one of the relatively few gram-positive organisms that causes disease in fish and it is economically important.

Fish appear lethargic with darkened skin and sometimes exophthalmia. There may be grayish granulomatous nodules on the kidneys. It is transmitted both horizontally and vertically and disease is more common in younger fish.

Bacterial kidney disease is most common in both farmed and wild salmonids, but also occurs in other fish species. Purchase BKD/Renibacterium-free stock to avoid introducing this into the system.

Previously it was recommended to treat females with erythromycin before spawning. However, this is not FDA-approved for treatment in farmed salmonids (there is an INAD available but not best use of antimicrobials and is difficult to get the drug) and survivors remain carriers.

Image courtesy of The Fish Site.