Submitted to: Journal of Insect Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/7/2004
Publication Date: 11/7/2004
Citation: Gregory, P.G., Evans, J.D., Rinderer, T.E., De Guzman, L.I. 2005. Conditional immune gene suppression of honey bees parasitized by varroa mites. Journal of Insect Science. 5(7):1-5. Interpretive Summary: Varroa mites affect many aspects of colony life in honey bees. While feeding on both developing and adult bees, these mites can cause lower body weights and reduced survival. Varroa mites are also known to carry diseases between bees. This study was aimed at determining how the immune defenses of bees respond to parasitism by Varroa mites. Bees showed a decreased immune response when exposed to mites, although this response was improved in bees facing very heavy mite loads. This study fulfills one aspect of a longterm project to understand the mechanisms used by bees to survive better in the face of Varroa mites. The information will be helpful in defining new aspects of mite resistance, and can be used by researchers to explore ways of improving this trait.
Technical Abstract: Ectoparasitic mites in the genus Varroa are the primary parasites of domesticated honey bees worldwide. Since mites are known to transfer pathogens to bees, it may be adaptive for bees to respond to mite presence by upregulating their immune responses. Countering this, mites could benefit through suppressing the honey bee immune response if this facilitates feeding on their main food source, bee hemolymph. To better understand the humoral immune response of bees parasitized by Varroa mites, parasitized and control bees were screened for expression levels of two antibacterial peptides known to be immune-responsive, abaecin and defensin. Transcript levels for these antibacterial peptides changed in a non-linear fashion with respect to mite parasitism. Bees exposed to low or moderate numbers of mites had fewer immune-related transcripts compared to both bees that never faced mites and bees with high mite loads. While many of the bees scored showed signs of bacterial infection, presence of bacteria was uncorrelated with both mite numbers and immune-response levels. All bees tested negative for two viruses known to be vectored by mites.