44 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



long, respectively, and had hatched during Decem- 

 ber 1949 and January 1950, from eggs of the 

 Winthrop brood of 1949 shipped to the Leaven- 

 worth station in November 1919. They arrived 

 at the Winthrop station during the epizootic, and 

 were held with insignificant losses until the next 

 spring when they were planted. It appears that 

 neither the general water supply nor the food 

 was a source of infection and that careful sani- 

 tary measures were effective in limiting the 

 spread of the disease. 



It is believed that the disease at Winthrop, 

 although complicated by the presence of bacterial 

 pathogens, was similar to the disease at Leaven- 

 worth. This is evidenced by the lack of response 

 to sulfonamide, antibiotic, or pyridylmercuric 

 acetate therapy, and by the similar pathology. 

 Hemorrhagic areas were observed on the fins and 

 body surface, and evidence of inflammation was 

 seen on the air bladder, visceral fat, and intestine. 

 The intestine was often congested and filled with 

 a yellowish fluid, the stomach with a whitish fluid. 



DISCUSSION 



The literature on virus diseases among fish is 

 not extensive and deals mainly with lymphocystis. 

 The lymphocystis virus disease of fish is char- 

 acterized by fibroblasts which have undergone 

 an enormous hypertrophy. References can be 

 found in an article by Alexandrowicz (1951) 

 and articles by Weissenberg (1951), some dating 

 back to 1911. 



Layman (1919) decribed a virus disease called 

 red disease of carp. The disease was produced 

 experimentally in healthy carp by rubbing an 

 abraded area with a bacteria-free filtrate pre- 

 pared from the skin of diseased carp. The dis- 

 ease had an incubation period of ■) days in warm 

 water and of 3 weeks in cold water. Usually 

 the first victims were the ripe fish, but 2V2- to 

 3-month-old and 10- to 11-month-old fish were 

 frequently attacked. The diseased fish were char- 

 acterized by apathy, erection of scales, ascites, 

 popeye, skin ulcers, and protrusion of the anal 

 region. The intestine was inflamed, and the feces 

 were dense, partially transparent, and stringy. 

 The liver and gall bladder were enlarged. The 

 liver was light green and dark in parts and finally 

 became, partially necrotic. The spleen was some- 

 what enlarged and very anemic in appearance. 

 An acute form of this disease developed in early 

 spring and abated by summer, while a chronic 

 form progressed throughout the summer until 

 the end of September. 



A disease described by Pacheco and Guimaraes 

 (1933) was attributed to a filtrable virus. The 

 disease was called cryo-iehtyozoose because the 

 virus acted on fish at low temperatures. The 

 virulence diminished or even disappeared entirely 

 at a temperature higher than 16° C. (60.8° F.). 



The disease was characterized by a high mortality, 

 apathy, congestion at the base of the pectoral 

 fins, pale gills and viscera — especially the liver; 

 a mucous secretion in the stomach and mouth ; and 

 bile that was sticky and amber-colored. 



Magarinos Torres and Pacheco (1934) later de- 

 scribed this disease as stomatitis and demonstrated 

 cytoplasmic inclusions in epithelial cells from 

 the floor of the mouth where cloudy swelling was 

 present. They were dealing with the Acara, a 

 fish in an entirely different order from that con- 

 taining the .salmon. 



Xo inclusion bodies that could be regarded as 

 indicating virus infection were encountered in 

 the blueback-salmon or kokanee fingerlings 

 studied in the present investigation. Occasional 

 red spherical cytoplasmic bodies were seen in the 

 epithelial cells of the mouth and a few other areas. 

 These were usually from -2 to 5 microns in diam- 

 eter. Such bodies were found a little more com- 

 monly in diseased fish than in healthy fish of the 

 same age. They resemble closely the bodies that 

 have been previously described in a variety of 

 human conditions and were thought by some to 

 be associated with specific virus infections. 

 However, they have been shown to be commonly 

 present in the pharyngeal epithelium of normal 

 humans (Macaulay 1951). 



It appears possible that the disease described 

 by the South American investigators is the same 

 as that described in the present paper. It should 

 be noted that their work involved fish of a differ- 

 ent order from those we studied. Whether the two 

 diseases are the same cannot be determined from 

 present evidence. Findings in the present study 

 suggested that only fish of the species 0. nerka 

 were susceptible. Infection did not occur in 0. 



