It was alleged that colonies of bees taken to a tropical area were able to survive without treatments for Varroa due to the climate.  I do not accept this hypothesis at all as we here in Cyprus and in other countries in the Middle East have to treat the hives to control Varroa.  If we don't treat at least once a year we will loose the colonies.  Temperatures are frequently over 40c. here during the summer and the colonies rarely cluster except for the occasional frosty night in February.  Further more, before the arrival of Varroa, there existed many thousands of colonies that were hived in mud pipes, with natural small cell combs, not one of these "pipe" hives was able to survive the onslaught of Varroa - despite being on a "natural" system, with natural sized combs and diet.  This is not only true for Cyprus, but for many places, some of which are very remote and the bees had never had contact with "enlarged" drones.  
Re secondary infections - Lusby- it is said that secondary infections such as AFB etc. will disappear after we change our combs to small cell.  I say the secondary infections in the Lusby's operation have ceased because they changed the combs i.e. all brood combs are fairly new.  This is just the normal sanitary measure that any good beekeeper, commercial or otherwise, would do to keep his bees free of these types of disease.
 Roger White
Superbee Cyprus