The season is coming to an end. For many fans it's been great fun, for others disappointing, even though one used the same tactics as last year and that worked perfectly back then. There can be several factors that throw spanner in the works.
One comment I hear often made sighing, is that it is as if there are only new diseases appearing. That will not be the case, but as simple as 25 years ago, it is indeed no more. Back then we had everything pretty well under control, like coccidiosis, worms and cancer. Occasionally a cure for respiratory and ready we were. But not today. At least for many enthusiasts. What has changed in that time?
First, the number of pigeons increased greatly in the lofts. Lofts of more than 100 or 200 birds are no exception. To see that in these lofts, the infection pressure can greatly increase, one does not have to be clairvoyant. The fact is that if multiple people or animals, whether or not under stress conditions, get together the change on spreading infections increases. Especially towards beings who have a reduced resistance.
Secondly, throughout the years it has become so common that we treated our pigeons with drugs that even the weaker ones survived. Lots of natural selection that was common in the more distant past is discarded. The reverse thing you see happening to fans who made selection their most important 'medicine'. On those lofts we usually see the infection pressure decrease. This population pigeons on these lofts are less susceptible to infection, on a course of time. On these lofts, when there are new or purchased pigeons, they often do not make it do to the more "Spartan" conditions.
Third, indeed over the years we see that it seems like that there are more diseases and existing illnesses seem harder to beat. Partly this I think is a result of the weakening of the pigeons by the permanent gift of antibiotics. I recently read an article that this is confirmed in part. Giving antibiotics at a young age in humans show for many years after working in the intestinal flora of these children and thus their overall resistance.