Now if and when it shows in your loft,eradicate the carriers,much better in the long run to naturally repress the host,than treat all willy nilly with anti biotics,which in turn will create a more virulent and lethal bacteria,capable of even more damage,and on and on it goes,actually to think for one moment you can best Nature is more Luddite thinking than other lines of thought,you may tweak or fool it for a period of time,but man can never best it,to think so is foolish,and back to original question Losses,there are many reasons,sickness being just one,a whole barrell load of them,my own favourite is there is too much crap being bred,twice as many rings issued this season as there was 30 years ago,yet only half the fanciers now in the game as there was 30 years ago,what is this telling us.