Whirling Disease Status 



Whirling disease, caused by the myxosporean parasite Myxoholus cerebralis, was 

 first detected in the Blackfoot River in 1995 near Ovando, MT. Since then, the disease 

 has increased in distribution and intensity. It now infects the lower 122 miles of the 

 mainstem Blackfoot River and continues to expand in the lower reaches of some 

 tributaries of Blackfoot River (Figure 55. Tables 13 and 14). 



<2.79 grade 

 >273 grade 



■ Sentlnet cage sKes 



Figure 55. Generalized distribution and grade infections of whirling disease for 2000-01 (left) and 

 2002 and 2003 (right) in the Blackfoot watershed. 



Table 13. Sentinel cage sampling results for six sections of the Blackfoot River in 2002 

 and 2003. 



91 



