my pennies worth it will not be prevented as long as your breeding from birds whose young get the virus or the parents had the virus in their early days and have become carriers. what causes their digestive system to shut down? and how to prevent that? hope some answers come from this thread. from 2012 i saw this and thought i would let it run its course, bad mistake i lost half my YB team before i got meds from vet. since then any yb that does not come when called..goes to basket for a 24hr starve and monitored, I have watched young do the stupidest of things like not knowing where the trap is and try fly to me to get into loft....these i also put in basket for a starve .....its as if the feckers dont know or forget...this could be the first signs and also why a large proportion get lost racing and training ... any how i have used amoxicillan this year when i noticed these things, it was a panic stricken reaction and it done them no harm ...young raced well for the 3 races i got them into. I also thinks it affects the old birds too on a milder form ...but still affects them cheers Mick