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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 Diagnostic Manual 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: [email protected]
___________________________________________________________________________________________________ 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: [email protected] - http://www.oie.int

Source: http://www.fishhealth.ie/NR/rdonlyres/707C46C6-0137-40F7-8205-15D5857196D4/0/OieInfoBacterialKidneyDisease.pdf