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around the mouth as in enteric redmouth disease. Fish may have a distend- 

 ed abdomen filled with a slightly opaque or bloody fluid (dropsy) or pro- 

 truding eyes (exophthalmia) if fluid accumulates behind the eyeball. Other 

 fish, minnows in particular, may have furuncules like those in furunculosis, 

 which may erupt to the surface, producing deep necrotic craters. Fins also 

 may be inflamed (Figure 83). 



In addition to the presence of fluid in the abdominal cavity, the kidney 

 may be swollen and soft and the liver may become pale or greenish. 

 Petechiae may be present in the peritoneum and musculature. The lower 

 intestine and vent often are swollen and inflamed and may contain bloody 

 contents or discharge. The intestine usually is free of food, but may be 

 filled with a yellow mucus. 



Motile aeromonas septicemia occasionally takes an acute form in warm- 

 water fish and severe losses can occur even though fish show few, if any, 

 clinical signs of the disease. In general, most outbreaks in warmwater fish 

 occur in the spring and summer but the disease may occur at any time of 

 year. Largemouth bass and channel catfish are susceptible particularly dur- 

 ing spawning and during the summer if stressed by handling, crowding, or 

 low oxygen concentrations. Aquarium fish can develop the disease at any 

 time of the year. Among salmonids, rainbow trout seem to be the most sus- 

 ceptible and outbreaks are associated with handling stress and crowding of 



Figure 83. Severe bacterial septicemia in a channel catiish infected vvith an 

 unknown enteric bacterium. (Courtesy National Fish Health Laboratory, Lee- 

 town, West Virginia.) 



