Chronic systemic bacterial disease of fish of the family Salmonidae, Caused by Renibacterium salmoninarum Called as BKD, White Boil Disease, Dee Disease, Salmonid Kidney Disease, Serious infection of cultured and Wild Salmonids, Occurs in both Freshwater and Marine Water

1. BACTERIAL KIDNEY
DISEASE
Jadhav Amit W.
Division of Aquaculture
AQC-MA-09-03

2. Introduction
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▰ Chronic systemic bacterial disease of fish of the family Salmonidae
▰ Caused by Renibacterium salmoninarum
▰ Called as BKD, White Boil Disease, Dee Disease, Salmonid Kidney
Disease
▰ Serious infection of cultured and Wild Salmonids
▰ Occurs in both Freshwater and Marine Water
▰ First occurs in early 1930s in wild Atlantic salmon (Salmo salar) in
Scotland

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 Renibacterium salmoninarum

Small, Gram
positive,
PAS positive ,
Non-sporing
bacteria
Non-motile,
Rod shaped
Grows best at
15-18c
usually occurs
in pairs
Poor survival
outside host
Phylum:Actinobacteria
Order: Actinomycetales
Family:
Micrococcaceae
Genus: Renibacterium

4. Place your screenshot here
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▰ Host :- Salmon, Trout, Char
▰ Ability to enter and survive in
phagocytic cells and eggs of its
hosts.
▰ Costly problem in seawater
Atlantic salmon farms and farmed
rainbow trouts
▰ Not restricted to cultivated fish.
The condition has been found in
naturally spawning salmonid
populations.
Spawning rash

5. All Areas of World Where Salmonids occur and Farmed
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Japan
Australia.
Europe
North America
South America

6. Gross signs :-
▰ Due to the slow-growing nature of the bacteria it may
take several months before disease signs appear.
▰ No obvious external signs
▰ anemia-having pale gills
▰ Abdominal Distention – Accumulation of ascitic fluid
▰ Skin blisters, shallow ulcers , Hemorrhages
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7. Clinical Signs :-
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 Major target organ is kidney which has white nodular masses.
 But lesions are also found in heart , spleen and liver.
 These lesions are initially whitish & may have a red hyperaemic
rim but eventually they can become large caseous nodule
granulomata.

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Clinical Signs
kidney and liver granulomas diphtheritic membrane on liver
swollen spleen
heart granulomas

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Histology
granulomas in the posterior kidney of juvenile
chinook salmon Oncorhynchus tshawytscha with
BKD. Hematoxylin and eosin stain
Gram-stained histological section of pancreatic
tissue of a juvenile chinook salmon Oncorhynchus
tshawytscha with systemic BKD

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Diagnosis Procedure
Sample Collection (Collection of kidney tissue)
Enzyme Linked Immunosorbent
Assay (ELISA)
inoculated onto agar
plates or stored in RNAlater medium
Positive
PCR test
Indirect
Fluorescent Antibody Technique (IFAT)

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Laboratory test methods
A. Culture on agar plates:-
swab is taken from the kidney
inoculated onto culture plates of Medium
(Muller Hinton Cysteine Agar (MHCA), Selective Kidney
Disease Medium (SKDM).)
incubated at 15°C for up to
Growth on plates is observed, a range of
confirmatory tests are conducted.

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B. Enzyme Linked Immuno Sorbent Assay
 Recommended by the World Animal Health Organisation (OIE) as a
screening method for BKD
 Small piece of fish kidney tissue is collected in a sterile dry tube
 Test is designed to detect the presence of an antigen of Renibacterium
salmoninarum, known as the P57 protein
 A colorless substrate is added and is used to detect the presence of the
antigen-antibody complex
 If this complex is present a colour change will be observed by the
action of the antibody linked with the enzyme.

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Polymerase Chain Reaction
 A rapid, reliable procedure for detection
• primers for PCR:- p57 protein (major soluble antigen) of R.
salmoninarum
• Forward primer
-5-GCGCGGATCCAAAATAAAAAAAATTTTAGCGCTG-3
• reverse primer
-5-GCGCGGATCCTTGGCAGGACCATCTTTGT-3
• expected PCR product is 376 bp long,

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Arrowheads indicate
positions of the
expected 383 base
pair conventional
PCR (top) and 320
bp nested-PCR
(bottom) products

16. Transmission
 Horizontal disease transmission occur via the water, skin abrasions or
ingestion of infected food.
 Vertical transmission from parent to progeny via the egg , it resides in
the yolk, protected from antiseptics.

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Treatment
 There are no proven therapy that can equivocally cure fish of BKD.
 Only Erythromycin thiocyanate were effective prophylactically against
BKD.
 Oral Erythromycin appears to reduce severity of outbreaks but has not
been proven to cure fish of infection.
 Injection of Erytromycin base into female broodstock before spawning
reduces the incidence of infected eggs( b/w 9 & 56 days before
spawning)
 Eggs should also be treated with potentiated iodine antiseptic after
spawning.

18. Now in India !
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THANKS!
Any questions?