Avast has not a update yet
How do you know ?
Trend list's aliases for its "AD"-Variant with suffix/letters ranging from
.AA to .BA
so probably, avast just counts differently and Trend's "Bagle.AD" is included as "Beagle-AC" or "Beagle-AB", especially if you look at the date of the VPS (07-07)..
For extensive discussions about differences in virus/variants naming conventions:
-> Please use the board-search