INFECTED SALMONID CONTAINS SPORES 

 i^. MO TO AT LEAST 3 YRS AFTER 

 BEING INFECTED 



SIDE 



FRONT 



^ 



SPORE RELEASED UPON DEATH 

 OF FISH 



SPORES MAY BE FOUND IN LESIONS 

 IN BONE AND GRANULOMAS FROM ABOUT 

 k MO AFTER INFECTION TILL AT LEAST 

 3 YRS 



SMALL FISH PROBABLY BECOMES 

 INFECTED BY INGESTING SPORES 

 — NOT PROVEN EXPERIMENTALLY 



MULTINUCLEATE SPOROPLASM, NOW 

 CALLED TROPHOZOITE, MAY BE FOUND 

 IN CARTILAGE FROM J+O DAYS TO 3 MO 

 AFTER INFECTION 



POLAR FILAMENTS EXTRUDE IN INTESTINE. 

 SPOROPLASM EMERGES, PROBABLY INVADES 

 INTESTI1S,NAL WALL AND MIGRATES TO HEAD 

 CARTILAGE 



Figure h' — Life cycle of Myxosoma cerebralis . (Note that 

 experimental infection of fish has never been achieved). 



