Varroa mites (Varroa jacobsoni) are external parasitic mites of honey bees. The mites are one of the major contributing factors to the recent serious honey bee loss in USA. Varroa mites endanger honey production and pollination. Our research addresses how the mites kill honey bees by investigating the impacts of Varroa mites on honey bee immunity and pathology. We hypothesize that Varroa mites depress the honey bee immune response to various pathogens. A critical enzyme and marker of some cellular immune functions is phenoloxidase (PO). To test our hypothesis, we measured the PO activity and also used E. coli as an immune challenger by injecting it into the bees to investigate their survivorship. We compared three types of bees: normal bees without mites, bees with mites and normal wings, and bees with mites and deformed wings. We found that the feeding of Varroa mites on a bee did not always cause the wing deformity; but wing deformity was always accompanied with Varroa mites. No wing deformity was observed in bees without mites. The degree of wing deformity was significantly related to the Varroa mite density. After challenge with E. coli, bees infested with mites but with normal wings lived a significantly shorter time than normal bees. The bees with deformed wings lived the shortest. This indicates that Varroa mites suppress of immune response of honey bees. The normal bees survived the longest. Bees with mites and normal wings survived significantly shorter than the normal bees. Bees with both mites and deformed wings die rapidly even without bacterial challenge. No phenoloxidase activity is found in newly emerged bees at 0 to 48 hrs, suggesting they are immuno-incompetent at this developmental time point. Also, no PO activity could be detected in bees treated with a variety of immuno-elicitors in this period.
Species 1: Hymenoptera Apidae Apis mellifera (honey bee)
Species 2: Acari Varroidae Varroa jacobsoni
Keywords: immun response
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA