That may be the case. Or not.
Again, there is a fundamental error with the premise leading to a totally incorrect perspective. It is for those who wish to ban things to prove things. In common law countries, like the UK, the citizen is free to act as they wish except if prohibited; and it is constitutionally necessary not to ban things without having established good evidence.
In any case, if the BDS has determined a policy of rejecting data from hunts because of a requirement which effectively disqualifies the supporters of stag-hunting from presenting a case, it is a moot point. If one wants to establish the truth of this, then it is incumbent on bodies like the BDS to fund the research. Why not?
It couldn't, because that would be the treatment population. This seems like you misunderstand what a control group is, and perhaps very elementary aspects of how scientific studies are conducted?
Examination, as usually performed prior to sending it into the food chain, or freezer, is not adequate to establish the presence of all disease. What lab do you send yours to?