You are - Manley, beekeeping in Britain 1948 discusses both foulbroods as well as acarine, chalk brood etc
Most of the current bee diseases have been around for much longer ...
1885 - Foulbrood was identified by Cheshire and Cheyne. It later became known as 'European Foul Brood' - named not because of its origin but by virtue of the fact that the research into its nature was carried out in Europe. Cheshire and Cheyne, however, did not initially believe that there was more than one strain of this disease and it was only latterly when AFB was separated that it became generally known as EFB and identified as a separate brood disease.
1906 - American Foul Brood identified as a separate bacillus to EFB. Dr William E. Howard of Texas, in 1900, reached the conclusion that it was a new one, and referred to it by the names " New York bee disease," or " black brood." Work by Moore and White in 1902 showed that the disease was not new, but was the foulbrood studied by Cheshire and Cheyne. The names " New York bee disease," or " black brood," therefore, were superfluous, and as their use would have added to the confusion that already existed they were discarded and it became generally regarded as 'American Foul Brood' again because the research took place largely in the USA.
1906 - 1913 - Acarine (At that time known as Isle of Wight Disease as the first major outbreak occurred in the IOW). The colony losses on the Isle of Wight in 1906 were attributed to “Isle of Wight Disease” and in the subsequent years all losses in the UK were attributed to it. Investigations into the causes of the Isle of Wight colony losses were first undertaken by an entomologist, AD Imms, who was unable to reach any conclusions. By 1912 Fantham and Porter identified Nosema apis as the most likely cause, but by 1919, following the discovery of the tracheal mite Acarpapis woodi, Dr John Rennie (he wrote Acarine Disease Explained in 1923) and co-workers were convinced that this was the cause of Isle of Wight Disease. Subsequent analysis of their data proved that this could not have been the case and it was likely that the losses in UK bee stocks were caused by a combination of factors including, chronic paralysis virus (unknown at the time), poor weather limiting foraging and overstocking (keeping too many bees for the amount of forage available).
So ... these issues affecting bees have been around for a very long time - but it was only around the early 1900's that the scientific ability and impetus led to them being investigated.
What did change, dramatically, around that time was the World .. prior to WWI the world was a much bigger place .. populations were more static, livestock movement tended to be localised (including bees). I suspect that the wholesale replacement of bee stocks, following the dreadful UK losses of 1906 - 1913, with bees from all over the place, contributed to the spread of brood disease which, previously, would have been contained within a localised area. The research that went in to bee disease around the early 1900's and the establishment of the BBKA and SBA around the same time would have meant that diseases would have become more readily identified and publicised by beekeepers in the UK.
However, it is interesting to note that from the 1920's until well after the second world war that beekeeping in the UK appears to have been less prone to diseases and parasites. Certainly, apocryphal evidence from beekeepers who were around in these 'relaxed' beekeeping times is very much that they were largely 'untroubled' by the problems of brood disease/parasites that we see today. Is this people looking back with rose tinted specatacles or is it that they just didn't 'see' the diseases in the same problem light that we see them today ? Has varroa and its ability to vector bee disease heightened the extent of the problems or is that we have so over-treated in relatively recent but less enlightened times that we have bred out the natural ability of bee stocks to survive and overcome the threats that they face.
Fossil study has identified in recent years that the likes of Acarine, in its various forms, has been around for as long as bees have been around so we have to ask - what has changed ? The answer is a very complicated one I suspect and one that continues to evolve with the changes in our landscape and farming methods and the beekeeping world in general.
It's an interesting subject and very much off topic in this particular thread ... perhaps it should be migrated to a thread of its own ... will keep us going long into winter no doubt !