It is a very very complicated topic, and there are no simple answers. I studied badgers for 30+ years when in East Leics. I was thinking about this today, as I came across several badger setts today as I was mushroom hunting, and so many signs of badgers. Why of why is there no TB in badgers here in Eastern FRance/Switzerland? Could it be because there is no TB in cattle? As badgers flip open cow pats to feed on grubs growing within- if cattle are infected, badgers will become infected, too- and the vicious circle is established.
TB in cattle in the UK has spread like wild-fire due to uncontrolled movement of cattle from herd to herd, and area to area. After the terrible foot and mouth outbreak a few years ago, the North-East was re-populated with cattle from the South West, were TB was rife!!! So many herds are behind with their TB testing, and still move cattle around. I have huge sympathy for farmers losing live-stock - but some of them are their worst enemy. It was shown for instance that feed troughs are often contaminated by badgers as they feed in them at night - but farmers stubbornly refuse to cover troughs in areas where badgers have clearly been feeding near cattle barns.
A cull sounds very simple... and yet. When independent scientists were asked to prove the link between badgers and TB, they thought the research would be conclusive within a year. But the independent scientists were baffled by the complexity of the results. They trialed 3 different areas. 1 where all the badgers were culled, irrespective of TB, 1 where all the badgers tested for TB were culled, and 1 were no badgers were culled. Guess where TB increased rapidly? Area 1, where all the badgers were culled!! The scientists could NOT believe this and tested again, again, each time with the same results.
Fact is, badgers live in very close clans, where foreign badgers, and any badger who is diseased, is not tolerated and forcefully evicted. Those badgers then become fugitives, and often die as they are not able to find a clan, and therefore a territory where they can feed. But if an area becomes free of badgers, then they can move in and try and make a 'living' there - thus areas cleared of badgers become vacuum for any diseased badger out there- hence the increase of badger to cattle transmission.
Therefore, badgers would have to be ALL killed for it to work- and this is just impossible, for so many reasons. There is a huge numbers of farmers and land-owners who will refuse to let the killers on their land. Already in some areas the guys going to shoot the badgers have requested to be masked so no retaliation from the local population will be endured. Can you imagine masked men coming to the woods near your village- with powerful guns- no name, no identification number and wearing a balaclava- and forcing their way onto your land, without permission, to start shooting every night for weeks. I knew every badger sett in Leicestershire, and about 50 % of them were very close to housing, public parks, shops, industry, etc.
TB thrives in stressed individuals and herds, just like it thrived in poor areas of Britain - better husbandry, feeds, a maximum of one calf per year, and an effective testing and immunisation programme is much more likely to deliver a big reduction in TB in cattle, and in badgers = the biggest scapegoat in a long time.