Took 20 frozen bees to the Surrey Beekeepers' Association (Wimbledon Division) for disease diagnosis, and they were given a clean bill of health.
We chopped the heads off some bees, and looked at the trachea for signs of acarine (a mite that infects the airways): all clear. The remaining twenty or so bees, we chopped off the abdomens, ground them up and inspected the resulting goo for nosema, a spore that infects the gut. Again, a clean bill of health.
It's a violent way to diagnose diseases, and it felt cruel. On the other hand, with some 35,000 or more bees, it's for the greater good of the hive.