Seasonal dynamics of seven viruses and Varroa destructor in Apis mellifera colonies: a 4-year survey in Tokyo.

Long-term monitoring of viruses and Varroa destructor within the same honey bee colonies is rare in Japan. Thus, we conducted a 4-year fixed-point survey of three Apis mellifera colonies in Tokyo with monthly screening for seven viruses (using polymerase chain reaction) and Varroa infestation. Deformed wing virus was detected year-round, whereas sacbrood virus and black queen cell virus peaked in spring and summer. Israeli acute paralysis virus appeared sporadically, without seasonal trends. Varroa infestation rates (monitored during the latter 2.5 years) did not correlate with the number of detected virus types and showed no seasonality. Although viral load was not quantified, this long-term dataset provides valuable baseline data on local virus dynamics, providing baseline information on seasonal virus dynamics in managed honey bee colonies in Tokyo.