It takes 4 months for the spores to develop, 

 therefore, these ponds could not be contamin- 

 ated by fish as long as the hatchery house, ponds, 

 and water supply are spore-free. Pick off mor- 

 talities twice daily; incinerate or bury deeply. 



The second series of ponds may be con- 

 crete or earthen . For best results the fish 

 should be 8-12 months or more of age when 

 stocked here. The older the fish when infected, 

 the less serious the disease and it is doubtful 

 that 13-month -old fish can be infected- -certain- 

 ly not heavily . 



Following this routine it is expected that 

 some disease will show up in the last series of 

 ponds. If whirlers and mortalities are inciner- 

 ated, however, one can expect the disease to 

 disappear in 2-3 years. It may be necessary to 

 treat earthen ponds annually for 2-3 years. 



7. No fish from an affected hatchery 

 should be transferred to an unaffected hatchery. 

 However, the disease probably cannot be trans- 

 mitted by eggs (Schiiperclaus, 1931). It must 

 be kept in mind that infected brown trout and 

 lightly infected rainbow and brook trout may 

 serve as carriers although they show no symp- 

 toms. 



8 . Fish from an affected hatchery should 

 not be stocked in fishing waters unless there is 

 no other hatchery on that watershed and no 

 natural trout reproduction or stocked fingerlings. 

 It is better to destroy the infected fish than to 

 take a chance on spreading the disease which has 

 apparently spread from Central Europe to Russia 

 Italy, and now North America in the last decade. 

 Disposal or transport by fishermen of spore - 

 bearing fish is an ever-present threat to spread 

 of the disease. 



Suppression of the disease, but not elimin- 

 ation, with Acetarsone (Stovarsol) at 10 mg per 

 kilogram of fish daily on 3 consecutive days with 

 weekly intervals between each course was re- 

 ported by Scolari (1954). He recommends that 

 it be used for 6 months for (partial) prophylaxi s. 

 Apparently the drug has no serious side effects 

 on the fish . We fed it to several thousand 

 rainbow trout for eleven months at Benner Spring 

 at concentrations as high as 100 times that rec- 



ommended by Scolari (1954) . Althou^ these 

 Acetarsone experiments have not been completed 

 as of this writing, the preliminary results are 

 not promising. We thus believe it should be 

 tested further before recommending it for pro- 

 phylaxis of whirling disease. 



SUMMARY 



Whirling disease (black -tail), caused by 

 the myxosporidean, Myxosoma cerebralis , is 

 reported from the United States. It has made 

 its appearence at 2 trout hatcheries located on 

 the same watershed in Pensylvania and at an- 

 other one in Connecticut. Young rainbow and 

 Eastern brook trout were severly affected. 

 European brown trout were not severely dis- 

 eased, but probably served as "carriers". 



Many attempts to transmit the disease 

 in the laboratory failed. 



The developmental stages of the parasite, 

 histopathology, diagnosis, and control are dis- 

 cussed. The severity of the disease in the 

 hatcheries has been reduced, but not eliminated, 

 by removing fish from the water source and 

 treating the ponds with calcium cyanamide. 



Preliminary experimaits with Acetarsone 

 (Stovarsol), although inconclusive, indicate that 

 the drug is not vary toxic to trout . 



LITERATURE CITED 



Bogdanova, E . A . 



1960. Natural habitat of the myxospor- 

 idean ( Myxosoma cerebralis -whirl- 

 ing disease) at Sakhalin (S. E. Russia). 

 Rep. USSR Academy of Science, Vol. 

 134, no. 6, pp. 1501-1503. 



Davis, H. S. 



1923. Studies on the sporulation and de- 

 velopment of the cysts in a new 

 species of Myxosporidia, Lentospora 

 ovalis . Journal of Morphology, Vol. 

 37, no. 3, pp. 425-542. 



1953. Culture and diseases of game 

 fishes . University of California 

 Press, 332 pp. 



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