I can understand the temptation to use Oxytetracycline to treat AFB.
In the UK, there is no approved treatment for AFB. Once the disease is confirmed the affected hives have the bees, comb, frames and honey burned. The boxes are flamed. The apiary is put on lock-down. No bees or equipment can be moved from the site until further examinations show no sign of the problem. Other apiaries around the source are also put on lock-down until checked by a Bee Disease Inspector.
OTC is not approved because, although it clears up the signs of AFB, there is a residual risk of the disease flare up and spread.