Genetic diversity and prevalence of Varroa destructor, Nosema apis, and N. ceranae in managed honey bee (Apis mellifera) colonies in the Caribbean island of Dominica, West Indies

Abstract

Honey bees (Apis mellifera) are arguably the most important insect pollinators of major agricultural crops around the world. Therefore, it is important to assess the health of managed honey bees in every region, particularly in areas where this information remains unknown. In 2015 and 2016, several managed apiaries were surveyed on the Caribbean Island of Dominica, West Indies. We measured the levels of the ectoparasitic mite, Varroa destructor, and analyzed the levels of Nosema apis and Nosema ceranae using spore counts and qPCR. Colonies sampled in 2015 were also analyzed for subspecies composition using mitochondrial DNA. Varroa levels were low overall (1–7 mites per 100 bees), with many colonies exhibiting no mites. In apiaries where varroa counts were performed in both years, there were significantly more mites in 2016 than in 2015. Overall, colonies exhibited low Nosema spp. spore counts, with only 1.33% of the bees analyzed scoring positive for spores. qPCR revealed that of the 30 colonies analyzed, all but six (82.3% of the total) were infected with low levels of N. apis. The prevalence of N. ceranae infection was higher, with 97.1% of the bees analyzed being infected. The majority of colonies analyzed (84.4%) exhibited the M4 haplotype (A. m. mellifera), while the remaining (15.6%) exhibited the C1 haplotype (A. m. ligustica). We did not find any colonies that had the African A. m. scutellata haplotype. This study is the first survey conducted to assess the genetic structure and health status of managed honey bees in Dominica.

Diversidad genética y prevalencia de Varroa destructor, Nosema apis y N. ceranae en colmenas domesticadas de la abeja Apis mellifera en la isla Caribeña de Dominica, Antillas Occidentales

La abeja Apis mellifera es el insecto polinizador más importante de cultivos agrícolas al rededor del mundo. Por esta razón, es importante saber su estado de salud en cada región, particularmente en areas donde no han sido estudiadas. En 2015 y 2016 se hizo un censo en varios apiaros en la isla Caribeña de Dominca en las Antillas Occidentales. Medimos los niveles del ácaro ectoparasitoide Varroa destructor, y se analizaron los niveles de Nosema apis y N. ceranae por medio de conteo de esporas y qPCR. En 2015 también se analizaron colmenas para determinar la composición de subspecies usando ADN mitochondrial. Los niveles de varroa fueron por lo general bajos (de 1 a 7 ácaros por cada 100 abejas) y en muchas de las colmenas no se encontraron ácaros. En apiarios en los que el conteo de varroa fue hecho ambos años se hayaron más ácaros en 2016 que en 2015. En general se encontró un bajo número de esporas de Nosema spp., y en solo el 1.33% de las abejas analizadas se visualizaron esporas. El qPCR reveló que de las 30 colmenas analizadas, todas menos seis (el 82.3% del total) estaban infectadas con niveles bajos de N. apis. La prevalencia de infección de N. ceranae fue más alta, pues 97.1% de las abejas analizadas estaban infectadas. La mayoría de las colmenas (84.4%) salió con el haplotipo M4 (A. m. mellifera) y el resto (15.6%) salió con el haplotipo C1 (A. m. ligustica). No se encontraron colmenas con el haplotipo Africano A. m. scutellata. Este es el primer estudio sobre la estructura genética y el estado de salud de abejas domesticadas en Dominica.

Keywords:

• Apis mellifera
• Dominica
• haplotype
• honey bee
• Nosema apis
• Nosema ceranae
• Varroa destructor

Acknowledgements

We would like to thank Dr. Reginald Thomas from the Ministry of Agriculture and Forestry’s Division of Agriculture in Roseau’s Botanical Gardens, for his help in processing all the permits needed to conduct this study. We also thank the members of the Dominica Bee Keepers Association, especially Mr. Lennox Fagan and Mr. Garth Clark, for helping us locate beekeepers willing to participate in this study. Special thanks to Mr. Bryan Bertrand, “Mr. Busy”, Mr. Randolph Laurence, and the rest of the participating beekeepers for letting us sample their apiaries. We also thank Caitlin Camp, Brent Goebel, and Taylor Wenner for helping to collect varroa count data in 2016.

Disclosure Statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This study was funded in part by JR’s Texas AgriLife Research Hatch Project number TEX09557, by a Neuhaus-Shepardson Faculty Development Grant to JR from Texas A&M University’s College of Agricultural and Life Sciences, the Penn State Schuylkill Research and Development Grant, the Office of Undergraduate Education Research Funds, the Penn State University Schuylkill Faculty and Student Research Endowment, and the Advisory Board for funding both laboratory supplies and undergraduate student funding.