B a c t e r i a l k i d n e y d i s e a s e ( R e n i b a c t e r i u m s a l m o n i n a r u m )
• Many fish species, and even invertebrates, may be
hosts of the pathogen without clinical manifestation.
CLASSIFICATION OF THE CAUSATIVE AGENT
Eubacteria, family Micrococcaceae, genus
OCCURRENCE
Occurs in feral and farmed populations of salmonids in
Renibacterium salmoninarum is a Gram-positive
almost all areas where they are naturally distributed or
nonsporulating, nonmotile coccobacillus that seems to
have been acclimatised. No conclusive evidence has
act as an obligate parasite. It develops chronically in
been reported for the presence of R. salmoninarum in
salmonid fish and results in late clinical disease.
the salmonid population of Australia, New Zealand, Russia, or some Mediterranean, countries.
RESISTANCE TO PHYSICAL AND CHEMICAL ACTION
Temperature: Optimum temperature for culture: 15°C.
For detailed information on occurrence, see recent
issues of World Animal Health and the OIE Web site.
Disinfectants: may be useful for disinfecting materials.
Incubation period is long, and the clinical signs, often
However, transmission in ovo and the
prompted by environmental causes, usually occur in
natural habitats limit the effectiveness of disinfection procedures.
LINICAL DIAGNOSIS
environment is poorly understood. It has
• Dark coloration, exophthalmia and abdominal
distension result from the destruction of interstitial
• Externally, haemorrhages may be observed at the
microflora, even longer. This duration of
base of the fins or at the vent, and the rupture of
survival could be significant in a hatchery
small cutaneous vesicles results in small
• Greyish nodules or diffuse masses are generally
observed in the kidney, spleen and liver. The kidney
appears enlarged and the abdominal cavity is
Morbidity rate is high, due to vertical transmission.
• Mortality is delayed but may become serious in
• Typical chronic infection characterised by
granuloma scattered in the internal organs. A
phagocytic reaction associated with more or less
complete encapsulation may be observed. Caseous necrosis may be observed in advanced
TRANSMISSION
• Horizontal transmission may be direct, through
contact with diseased fish and contaminated water,
DIFFERENTIAL DIAGNOSIS
or indirect, through handling materials or feeding
• External manifestations are nonpathognomonic, but
the course of the disease and the nature of the
Vertical transmission is the most frequent route of
contamination. The bacteria are present in the
indications. The disease must be differentiated
ovarian fluids and are likely to be the source of the
from other kidney diseases of chronic progression
R. salmoninarum that have been detected in eggs
including pseudo-kidney disease (Carnobacterium piscicola), nephrocalcinosis, and proliferative kidney disease. Confirmation must be by the
SOURCES OF THE AGENT
observation and identification of the bacteria.
• Internal organs or skin tissues in cases of external
LABORATORY DIAGNOSIS Procedures __________________________________________________________________________________________OIE Aquatic Animal Disease Cards, September 2000 SANITARY PROPHYLAXIS
• Isolation and culture under appropriate conditions,
• Identification and culling of carrier broodfish.
completed by bacteriological identification or
• Destruction or slaughtering of infected fish.
specific agglutination, require several weeks.
• Disinfection of premises, materials and raceways.
• Antigen detection in infected tissues is more rapid.
• Introduction of controlled pathogen-free stocks.
• Immunofluorescence (direct/indirect fluorescent
• In infected areas, screening of asymptomatic
carriers before spawning, and selection of breeders
• Enzyme-linked immunosorbent assay (ELISA).
with the lowest levels of infection associated with
• Polymerase chain reaction (PCR).
erythromycin treatment have noticeably reduced the prevalence of the disease.
EDICAL PROPHYLAXIS
Not recommended. No positive correlation has
been demonstrated between the antibody response
• There is presently no possibility of active
and the course of the infection in fish populations.
Chapter 2.2.6. in the OIE DiagnosticManual for Aquatic Animal Diseases, OIE, Paris, France.
Internal organs from diseased fish: kidney and
Chapter 2.2.6. in the OIE International Aquatic Animal
• Tissue prints or smears for the detection of the
Health Code, OIE, Paris, France.
• In maturing females, coelomic fluid is a reliable
material and does not need to kill the fish.
TREATMENT
• No therapy has really proved conclusive in cases of
OIE Reference Experts and Laboratories in 2000 Dr R.J. Pascho Western Fisheries Research Center, U.S. Geological Survey, Biological Resources Division, 6505 N.E. 65th Street, Seattle, Washington 98115 UNITED STATES OF AMERICA Tel.: (1.206) 526.62.82, Fax: (1.206) 526.66.54, E-mail: ron_pascho@usgs.gov ___________________________________________________________________________________________________OIE: 12 rue de Prony, 75017 Paris, France - Tel. 33 (0) 1.44.15.18.88 - Fax: 33 (0) 1.42.67.09.87 E-mail: oie@oie.int - http://www.oie.int