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Post mortem: Systemic Bacterial infection

On 18 November 2008 a client called with the news that one of his fish died during the night. The fish did not show abnormal behaviour that indicated a potential problem (Maybe he did not notice?). Upon arrival at the pond we followed the normal routine to determine the cause of the fatality. The filter system was clean and we found no sign of accumulated debris. The water parameters tested fine and a skin scrape revealed no parasites.

The purpose of this article is to give the hobbyist some insight into the devastating effects of bacterial infection once it has penetrated the defence systems of a fish. It is also intended to show why systemic infection (septicaemia) is almost incurable because of the massive damage to the internal organs. Some bacterial infections may develop over time and the fish will display bloating (Dropsy, pine cone disease) because the osmoregularory system is compromised. In other cases, the fish is substantially normal and dies suddenly.


As can be seen from the photo, very little external signs of disease were noticeable, like ulcers, bloating (except for normal bulging egg-sacs), scales standing away from the body, or bulging eyes. Reddish streaks in the fins and on the belly indicated bacterial problems and stress. Because of the time and cost involved, the owner indicated that a bacterial culture should not be done. The strain of bacteria that caused this systemic infection was obviously very aggressive and to wait a week for results would be too long. It was decided to do a post mortem to confirm that it was not injury related, and to determine steps to protect the rest of the collection.


The gills are pale (possible a combination of blood loss and infection), with excessive slime causing the lamellae to stick together. There are also signs of necrotic areas indicating bacterial damage.




Inflammation of body cavity, swim bladder and internal bleeding


The kidney, liver and spleen are totally destroyed. It resembles a paste.

All other fish seemed fine. They were active and none displayed symptoms like lethargy, pale gills, or bloating. "Antibac" and salt were added to the pond as a precaution. On 7 December 2008 no other problems were reported.


Last Updated on Thursday, 22 January 2009 22:58