In histological section the early stages 

 (1-1/2 to 3 month post infection) can be recog- 

 nized by their many small nuclei in the lesions 

 in the head cartilage (figs. 5, 7, and 8). Le- 

 sion-like structures in normal bone formation 

 (fig. 9) resemble whirling disease lesions. 

 Sometimes these contain large multinucleate 

 host cells (giant cells) which may be confused 

 with parasites. 



In histological section of the head the 

 spores stain blue with Giemsa's (figs. 10, 11, 

 13, and 14), blue with carbol toluidin blue 

 (SchSperclaus, 1931) and red with aniline water- 

 saffranin (Plehn, 1904) . 



CONTROL AND TREATMENT 



A modified version of SchSperclaus' 

 (1954) and Tack's (1951) recommendations for 

 control follows: 



1. Destroy all fish from ponds contain- 

 ing fish known to be infected. Incineration or 

 deep burial is recommended. 



4. Disinfection of concrete ponds . Drain 

 ponds and immediately apply calcium cyanamide 

 at about 0.04 lb. /sq. ft. (1780 lb. /acre). Allow 

 to stand 3-4 weeks, clean thoroughly, wet down 

 and repeat treatment. Some of the chemicals 

 listed in 3 above would probably be satisfactory 

 for small ponds . It would take about 10 times 

 as much chemical if used in water-filled ponds. 

 Quicklime and hydroxides are strongly caustic 

 chemical agents and personnel using them 

 should wear protective clothing and use goggles 

 and respirators. 



5. Disinfection of earthen ponds. This 

 is the most difficult aspect because organic 

 matter usually interferes with disinfectants. 

 Drain the ponds and immediately apply calcium 

 cyanamide as in 4 above. Allow to stand a 

 month or more and clean out silt as thorou^ly 

 as possible. Haul out to a farm field for plow- 

 ing under or bury deeply. Fill pond with water, 

 drain and immediately apply calcium cyanamide 

 as before. Flush out and refill ponds 2 weeks 

 or more later and stock with fish; Tack (1951) 

 allowed 6 weeks before adding fingerlings. 



2. Water supply. That which supplies 

 the hatching house fry and early fingerlings (up 

 to 8 months at least) should be spore -free spring 

 or well water. There should be no fish in the 

 water system before it reaches the hatching 

 house. Stream water may be used only if the 

 stream contains no fish. No satisfactory fil- 

 tering device for whirling disease has been 

 described for hatcheries in the United States, 

 but we have heard that sand-charcoal filters 

 have been used successfully in France. 



3. Disinfection of hatching house. Clean 

 thoroughly (this is more important than chemical 

 disinfection). We have found that overnight soak- 

 ing with the following will dissolve the spores or 

 cause them to extrude their polar filaments and 

 probably render them uninfective: sodium hypo- 

 chlorite (commercial or home laundry bleaches) 

 as per instructions on container; zephiran chlor- 

 ide (RoccalR) 800 ppm; sodium hydroxide 1/2 

 percent, calcium oxide (quicklime) 1/2 percent. 

 It is imperative to have spore-free facilities for 

 fry because the younger the fish the more seri- 

 ously they are affected by whirling disease. 



Schaperclaus (1954) recommends quick- 

 lime as the chemical of second choice to be 

 used at the same rate as calcium cyanamide. 

 Snow and Jones (1959) have used quicklime 

 successfully in treating bluegill ponds for fish 

 diseases. We believe that the hot reaction of 

 quicklime which produces a high transient pH 

 is effective in killing spores- -a pond so treated 

 is safe to use 10 days after treatment with no 

 flushing necessary. Sodium hydroxide is prob- 

 ably more effective than Lime but may be more 

 expensive. 



6. Restocking hatchery. Eggs or fry 

 should be obtained from a known uncontam- 

 inated source. Fry should be kept in hatching 

 house as long as possible (3-8 months) because 

 it is usually easier to control the disease here. 

 It is advisable to maintain 2 series of ponds 

 until it is certain that the disease is eradicated. 



The first series of ponds should be con- 

 crete raceways supplied with spore-free water. 

 Use great care not to contaminate with spores 

 or infected fish. Keep fish here only 3 months. 



12 



