No matter how clean we keep our animals, there is ALWAYS going to be some risk. One of my ringtail possums had toxoplasmosis a while back luckily it was caught in time and he recovered, it isnt a commonly seen in captive animals or it is mis diagnosed. The vet said that it would have been in the mulch I used in the aviary. It really freaked me out. The Zoo's vet told me that some of thier Meer Cats (sp) also contracted it. and zoos hose down and discinfect thier enclosure constantly.
Dont beat your self up its not something that you could have possibly known could happen.
I know when my possums got toxoplasmosis I went completely nuts cleaning, but I eventually realised that no matter how clean I kept my animals there was always a slight risk something could happen.
All you can do is take all the precautionary steps and pray that nothing happens, or you will go nuts constonatly worrying with what if's.