Chapter 35 



Studies on a Marine Parasitic Ciliate 

 as a Potential Virus Vector'^ 



LiSELOTTE MOEWUS 



INTRODUCTION 



X here has been much speculation on the role of viruses in 

 the causation of diseases of fish. Indirect evidence and some 

 direct evidence has been evolved. In general it may be said 

 that the present state of knowledge of virology of the aquatic 

 world is very limited. Epidemic outbreaks at seasonal intervals 

 have been observed in ponds of fish hatcheries and in aquaria, 

 that is, in envii'onments with relatively smaU bodies of water 

 and high population densities. Transmission experiments witli 

 crude extracts of the diseased organs or of skin lesions have 

 been successful in some cases. Ultiacentiifugates and bacteria- 

 free filtrates have been found to be infective in other instances 

 (9, 10). Electron microscopic studies have revealed tlie particu- 

 late natru'e of the carp pox virus and of the Bauclifellwassersucht 

 of trout (9). By cytological investigations, the presence of in- 

 clusion bodies in tumor cells of several species of fish has been 

 demonstrated (9). Nothing is known about viruses in a typical 

 natural marine envii'onment. This is not suiprising because it 

 is rather difficult to obsei've sick fish in the ocean. 



The present report details work with a parasitic marine 

 cihate discovered by the author in the course of studies with 

 Dr. M. Michael Sigel while developing a methodology for marine 

 virology and in a search for viruses in marine animals. Among 

 the animals employed we encountered several sealiorses which 

 carried timiorlike nodules on their bodies. When one tiunor was 

 cut up and pieces of tissue were placed on plasma clot in culture 

 tubes and incubated at 20 C, in three out of four cultures 



Supported by the Office of Naval Research grant Nonr 840(15), 



366 



