The disease is largely confined to dairy cattle and to their cross-bred
offspring. The UK has spent thirty years systematically breeding its herds
for high yields, using bulls which can sire tens of thousands of offspring,
often incestuously. As virtually all race horses can trace their ancestry
to three stallions in the eighteenth century, so virtually all dairy cattle
are the offspring of a few bulls, themselves drawn from a common background.
Might we, therefore, be seeing a disorder which has a genetic aetiology
rather than something caused by a mysterious infectious agent (or
environmental factor, such as organophosphorus dips and warble fly sprays,
as has been suggested)? The implications are considerable: a genetic BST
could have no effect on those who eat meat from sick animals. One could
eliminate it within a generation. One can easily test for this: the
individual gentic records of all UK dairy cows are stored centrally and
it would be simple to test this view.
ohgs at chatham.demon.co.uk