Bacterial kidney disease

Signs of disease

Important: animals with disease may show one or more of the signs below, but disease may still be present in the absence of any signs.

Disease signs at the tank and pond level

• increasing mortality

Clinical signs of disease in an infected animal

• exophthalmus (pop eye)
• distended stomach and skin lesions
• darkening of skin
• haemorrhages may be observed at the base of the fins or at the vent
• small ulcerations due to the rupture of small cutaneous vesicles

Gross signs of disease in an infected animal

• creamy white granulomas in kidney and sometimes in liver and spleen
• fluid in stomach cavity
• haemorrhages on abdominal wall and in the viscera
• diffuse white membranous layer on one or more internal organs
• enlarged spleen
• holes in muscle blocks

Disease agent

Bacterial kidney disease is caused by the bacterium Renibacterium salmoninarum. It is recognised as a slowly progressive and frequently fatal infection of cultured and wild salmonids in both fresh and marine waters.

Host range

Presence in Australia

EXOTIC—not present in Australia.

Epidemiology

• The causative bacterium is likely to live only within salmonids and not in the environment.
• Other nonsalmonid species have shown infection but only when raised with highly infected salmonids.
• The bacterium is transmitted both horizontally (fish to fish via the water) and vertically (fish to egg through the generations).
• Advanced infection becomes apparent only after the first year of the fish's life.

Differential diagnosis

The differential diagnostic table and the list of similar diseases appearing at the bottom of each disease page refer only to the diseases covered by this field guide. Gross signs observed might well be representative of a wider range of diseases not included here. Therefore, these diagnostic aids should not be read as a guide to a definitive diagnosis, but rather as a tool to help identify the listed diseases that most closely account for the gross signs.

Further images

Sample collection

Because of uncertainty in differentiating diseases using only gross signs, and because some aquatic animal disease agents might pose a risk to humans, you should not try to collect samples unless you have been trained. Instead, you should phone your state or territory hotline number and report your observations. If samples have to be collected, the agency taking the call will advise you on what you need to do. Local or district fisheries/veterinary authorities could advise you on sampling.

Emergency disease hotline

For your state or territory emergency disease hotline number, see Whom to contact if you suspect a disease.

Further reading

The currently accepted procedures for a conclusive diagnosis of BKD are summarised at www.oie.int/eng/normes/fmanual/A_00028.htm