A recent publication from Lizzette Cambron-Kopco, Robyn M. Underwood, J Krispn Given, and Brock A. Harpur dives into the viral loads of several honey bee stock types to determine how each colony handles viral loads.
The study used formic acid as a treatment for Varroa mites before establishing the new queens to diminish and equalize the Varroa mite populations across colonies. Fifteen experimental colonies were used in the study, with three colonies per stock variation.
The five honey bee stocks used in the study were California, Georgia, Russian, Pennsylvania survivors, and Indiana survivors. These stocks are commonly used in the United States.
Approximately 90 days after the new queen was established, 200 adult worker bees were collected from brood frames of each colony and cold stored until lab analysis could occur. Variations in mite loads were measured traditionally with mite washes sampling 300 honey bees from each colony. The results showed that the number of mites per colony was equal among stocks.
The 200 adult workers were sampled with PCR testing. The study quantified viral loads from individual workers via qRT-PCR of the prevalent viruses, including Deformed Wing Virus A (DWV-A), Deformed Wing Virus B (DWV-B), Israeli Acute Paralysis Virus (IAPV), Black Queen Cell Virus (BQCV), and Lake Sinai Virus 2 (LSV2). The cDNA was synthesized from RNA extracted from the workers, and qPCR was performed to quantify the viral loads.
Mite resistance in the study was not directly measured. However, the study found that Russian, Pennsylvania survivors, and Indiana survivors showed lower levels of DWV titers, likely due to breeding for Varroa mite resistance in these stocks. This suggests that the lower viral loads observed in these stocks may be indicative of their mite resistance.
This study can be applied in the field for beekeepers by emphasizing the importance of understanding the performance of different bee stocks, especially in terms of traits like mite and pathogen resistance. The study’s findings suggest that some bee stocks may exhibit lower viral loads under mite pressure, potentially indicating higher mite resistance.
This information can help hobbyist beekeepers make informed decisions about purchasing queens from different sources, ultimately contributing to the health and productivity of their colonies and stressing the importance of positively selecting for traits like mite-resistance in their own apiaries!
If you would like to read this paper for yourself, you can see it HERE.
Lizzette Cambron-Kopco, Robyn M. Underwood, J Krispn Given, Brock A. Harpur & Margarita M. López-Uribe (2023) Honey bee stocks exhibit high levels of intra-colony variation in viral loads, Journal of Apicultural Research, DOI: 10.1080/00218839.2023.2285153