Everyone has their own ideas. I guess you need to decide what your beekeeping philosophy is:http://www.bushfarms.com/beesphilosophy.htm
Assuming your philosophy is that chemicals are good and antibiotics are good, then you can look up what is being used in that regard. Even what the "experts" recommend changes constantly. Many of the methods of delivering antibiotics has changes over the years as they realize that the previous method did not work so well. Now even the scientific research is coming to the conclusion that treating with antibiotics only makes them ore susceptible to the very things you are trying to prevent:http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0033188
The biofilm of lactic acid bacteria that naturally lives in a bees gut protects them from AFB, EFB and Nosema and all the preventative treatments for those things destroys that protection. Essential oils also do (Honey B Healthy etc.). Sugar syrup disrupts, but doesn't entirely destroy it...
But ignoring that, you might want to consider than Fumidil, the "standard" treatment for Nosema, causes birth defects in mammals and because of this is illegal throughout most of the world. A bee hive is a food container and we are mammals...http://www.bushfarms.com/beespests.htm
So, what I do is I don't treat for any of those and let the ecology of the colony and their bee bread and their guts find a natural balance.