Prevalence and population genetics of the emerging honey bee pathogen DWV in Chinese apiculture

Abstract

Honey bees are agriculturally important, both as pollinators and by providing products such as honey. The sustainability of beekeeping is at risk through factors of global change such as habitat loss, as well as through the spread of infectious diseases. In China and other parts of Asia, beekeepers rely both on native Apis cerana and non-native Apis mellifera, putting bee populations at particular risk of disease emergence from multi-host pathogens. Indeed, two important honey bee parasites have emerged from East Asian honey bees, the mite Varroa destructor and the microsporidian Nosema ceranae. As V. destructor vectors viral bee diseases, we investigated whether another key bee pathogen, Deformed Wing Virus (DWV), may also have originated in East Asian honey bee populations. We use a large-scale survey of apiaries across china to investigate the prevalence and seasonality of DWV in managed A. mellifera and A. cerana colonies, showing that DWV-A prevalence was higher in A. mellifera, with a seasonal spike in prevalence in autumn and winter. Using phylogenetic and population genetic approaches, we show that while China and East Asian DWV isolates show comparatively high levels of genetic diversity, these bee populations are not a source for the current global DWV epidemic.

Seasonal variation of viral infections between the eastern honey bee (Apis cerana) and the western honey bee (Apis mellifera)

“…The discrepancies between these studies might be due to climate differences among the different countries or the genetic differences in the honey bees or viruses. The infection rate of DWV in A. mellifera increased during summer, which agreed with previous surveys conducted in France and China (Diao et al, 2019;Tentcheva et al, 2004) and could be related to the increase in V. destructor density from spring to summer (Gloria et al, 2017).…”

“…Informed by our pilot study and previous epidemiological surveys in China (Ai et al, 2012; Diao et al, 2019; Li et al, 2012; Yañez et al, 2015; Yang et al, 2013), we focused on the five most common bee viruses (BQCV, CBPV, DWV‐A, IAPV, and SBV). qRT–PCR was performed using 1 μl cDNA as the template in 10 μl reactions, using THUNDERBIRD SYBR qPCR Mix (Toyobo) with a StepOne Plus Real‐Time PCR System (Applied Biosystems).…”

“…A. mellifera and A. cerana are bee species used in the beekeeping industry in China at a national level and are often kept close to each other. While large‐scale epidemiological investigations of honey bee viruses in China have been conducted in previous studies (Ai et al, 2012; Diao et al, 2019; Li et al, 2012; Yang et al, 2013), a broader comparative analysis of viral infections in both host species simultaneously would yield critical insights into the relationship between viruses and their hosts. Furthermore, most viruses infecting honey bees are RNA viruses that have extremely high mutation rates, which could have important epidemiological consequences.…”

Diversity and Global Distribution of Viruses of the Western Honey Bee, Apis mellifera

“…Some of these viruses rapidly evolved towards a vector-borne lifestyle [78] with increased rates of prevalence and virulence [104,139]. As a result, the annual prevalence and titer patterns of these viruses were altered, with a peak later in the season, following the Varroa population dynamics within colonies [103,127,131,[140][141][142]. Models show that transmission by the mite greatly modifies the in-hive dynamics of DWV, resulting in an imbalanced age structure of overwintering bees leading to the death of infected workers and eventually the colony during the following winter or spring [143].…”

Ten Years of Deformed Wing Virus (DWV) in Hawaiian Honey Bees (Apis mellifera), the Dominant DWV-A Variant Is Potentially Being Replaced by Variants with a DWV-B Coding Sequence

“…Blue dots on a red background indicate that DWV-A is dominant, but DWV-B is present conversely red dots on a blue background indicate that DWV-B is dominant, but DWV-A is present. The map was constructed by combining global level DWV data [ 33 , 34 ] with more detailed country level info as follows: Argentina (Buenos Aires and Sante Fe) [ 35 ], Australia [ 36 ], Brazil [ 37 ], Chile [ 38 ], China [ 39 ], Cuba [ 40 ], Ethiopia (Tigray) [ 41 ], Fernando de Noronha [ 25 ], France [ 20 ], Germany [ 32 ], Hawaii [This study, 26], Kenya [ 42 ], Papua new guinea [ 13 ], South Africa [ 30 ], Tunisia [ 43 ], Turkey [ 44 ], UK [ 16 ], Uruguay [ 45 ], USA [ 16 ]. The studies used to create this diagram were not required to have used the same primer set as our study.…”