48 MAINTAINING FISHES 



monicida survives only a short time outside of the fish. 

 Carrier fishes are important in its spread (see 

 Snieszko 1958a). 



The species A. liquefaciens and related forms ap- 

 pear to cause several pathogenic conditions in fishes. 

 The different forms appear very similar both mor- 

 phologically and culturally but produce diseases that 

 are quite different. All of the forms are motile, gram 

 negative rods that show bipolar staining. They are 

 credited (by some investigators) with causing infec- 

 tious dropsy, which involves the accumulation of 

 serous fluids in the tissues, and a fatal surface infec- 

 tion of fish following handling. The surface infection 

 is readily controlled by 20 p. p.m. of water-soluble ter- 

 ramycin (veterinarian grade) for 24 hours or more. 

 For dropsy one should use Chloromycetin or terramy- 

 cin in the food or by injection. When used in the 

 food, the antibiotics are fed at the rate of 1.0 milli- 

 gram per 15 grams of fish for a period of four days. 

 When injected, the dose is 0.025 milligrams per gram 

 of fish. Control of bacterial infections by either injec- 

 tion or contact treatment with terramycin is fre- 

 quently very successful. 



At least certain forms of A. liquefaciens are free- 

 living and constitute a normal part of the bacterial 

 flora of natural waters. The development of the sur- 

 face infection of fishes appears to be associated with 

 minor damage to the fish during harvest. 



Columnaris, an important disease of both warm 

 water and cold water fishes, is caused by the bac- 

 terium Chondrococcus columnaris. It produces gray- 

 ish-white areas on a fish's head, gill, fins, body and 

 frequently in the mouth. These spots change to shal- 



