Identifying Nosema

Three things I found interesting were that nosema only infects adult bees, also the infection begins when bees ingest nosema spores and lastly, when the spore reaches the bee's gut, it explosively uncoils a long straw-like polar filament. The filament penetrates outer gut cells and, in the process infects them. Two things I will look for next time i'm in the apiary is if there is any physical sign that a bee is infected with nosema and what signs they may show. One question I have is what can be done to control the spread of nosema?