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The four species of Varroa: a. V. jacobsoni dorsal view; b. V. jacobsoni ventral view; c. V. destructor dorsal view; d. V. destructor ventral view; e. V. rindereri; f. V. underwoodi.  

The four species of Varroa: a. V. jacobsoni dorsal view; b. V. jacobsoni ventral view; c. V. destructor dorsal view; d. V. destructor ventral view; e. V. rindereri; f. V. underwoodi.  

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Very rapidly after Varroa destructor invaded apiaries of Apis mellifera, the devastating effect of this mite prompted an active research effort to understand and control this parasite. Over a few decades, varroa has spread to most countries exploiting A. mellifera. As a consequence, a large number of teams have worked with this organism, developing...

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... [1]But new research suggests that the mite actually feeds on the fat bodies of bees. [2]The parasitization of mite makes western honeybees lose nutrition and causes serious direct harm, including loss of flight ability, decreased immunity, shortened life span and so on. In severe cases, it can lead to the collapse of the whole bee colony. ...
... Using radioisotope labeling, researchers claimed that the mites feed on the hemolymph of bees [2]. However, recent studies have shown that the mites feed on fat bodies rather than hemolymph [9]. ...
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Varroa destructor is the most serious threat for western honeybees worldwide. It parasitizes mostly on honeybee's pupae and larvae, resulting in impaired development, decreased immunity, residual wings, loss of flight ability, and even direct death. At the same time, it can cause a series of diseases, greatly infesting bee colonies. This paper introduces the classification, distribution and biological characteristics of Varroa destructor, and discusses its transmission mode, harm form and common control measures.
... were assessed on the 6th of June 2017 following the Liebefeld method 67,69 . Portable electronic scales were used to weigh entire hives. ...
... Total adult bee, brood and pollen loads were calculated by multiplying the area by 125 (adult bees) or 400 (brood and pollen) as required for standard LR (Langstroth) frames 68 . Varroa load was measured simultaneously by the Powdered Sugar method 69 . ...
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Honeybee health and the species’ gut microbiota are interconnected. Also noteworthy are the multiple niches present within hives, each with distinct microbiotas and all coexisting, which we termed “apibiome”. External stressors (e.g. anthropization) can compromise microbial balance and bee resilience. We hypothesised that (1) the bacterial communities of hives located in areas with different degrees of anthropization differ in composition, and (2) due to interactions between the multiple microbiomes within the apibiome, changes in the community of a niche would impact the bacteria present in other hive sections. We characterised the bacterial consortia of different niches (bee gut, bee bread, hive entrance and internal hive air) of 43 hives from 3 different environments (agricultural, semi-natural and natural) through 16S rRNA amplicon sequencing. Agricultural samples presented lower community evenness, depletion of beneficial bacteria, and increased recruitment of stress related pathways (predicted via PICRUSt2). The taxonomic and functional composition of gut and hive entrance followed an environmental gradient. Arsenophonus emerged as a possible indicator of anthropization, gradually decreasing in abundance from agriculture to the natural environment in multiple niches. Importantly, after 16 days of exposure to a semi-natural landscape hives showed intermediate profiles, suggesting alleviation of microbial dysbiosis through reduction of anthropization.
... Inspections occur mainly for three reasons: regulatory inspections, confirmation of Varroa status of commercialized queens or nucleus colonies, or to address beekeeper concern of poor colony health. Varroa inspection data are based on the standard alcohol wash method (Dietemann et al., 2013) and reported as a total count per 300 bees. These counts were converted to a value of mites per 100 bees, referred to subsequently as the "Varroa rate. ...
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Elevated colony losses have continued to be an issue for Canadian beekeepers for more than a decade. Numerous studies have identified unmanaged Apis mellifera colony infestation by the Varroa destructor mite as a main cause of the problem. V. destructor spread externally of the hive through a phoretic stage in their life cycle. Consequently, their movement outside the hive is influenced by honey bee flight behaviours, which can range to multiple kilometers from the originating hive in any direction. V. destructor are therefore of regional concern as neighboring colonies and yards share nearby forage which can serve as fomites. Additionally, mites can be transmitted through bee behaviours such as robbing and drifting, thus impacting surrounding colonies. Understanding the distribution of mites across a population is key for surveillance and equitable allocation of resources. Spatial patterns of V. destructor infestations in Southern Ontario, Canada, were investigated using a combination of cluster analysis, scan statistics, and geostatistical modelling, using 5 years of provincial apiary inspection data, from 2015 to 2019. A collection of disease clusters of V. destructor infestations was identified and found to be stable over multiple years with several other individual clusters occurring sporadically throughout Southern Ontario during the same study period. Universal kriging was applied to the V. destructor data in combination with regional colony density, and land use data as covariates, producing an isopleth map of the prevalence risk for V. destructor infestation. No substantial link between V. destructor infestation and environmental factors was found. This study highlights the need for more data and investigation to determine the cause of the identified clusters and areas of elevated risk. These results are hypothesis-generating but simultaneously provide information for government agencies, industry organizations, and beekeepers into the spatial distribution of V. destructor at a macro scale.
... This feat of accelerated reproduction would ostensibly require the foundress mite have access to a nutritionally dense food source in addition to a means of rapid conveyance of these nutrients to the developing oocyte. Reproduction occurs on brood that will cease to be a viable reproductive host upon emerging as an imago in 12 days and the first 3 days of interaction with this brood involves no egg production leaving only 9 days (2,13). Any mites that have not reached maturity by the end of this period die (2). ...
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The rapid reproductive capacity of Varroa destructor is among the most significant adaptations underpinning its success as a parasite. To exploit their honey bee host, the parasite must rapidly produce offspring that fully develop into adults and mate in an inflexible 9-day window. Inability to meet this deadline brings the fitness of the foundress mite to zero establishing heavy evolutionary pressure to accelerate reproduction & subsequent development of offspring. Our work fills in gaps in our understanding of a key pathway in this process. Varroa have a poorly-understood ability to pass heretofore unidentified host proteins through their body with minimal digestion/degradation. Via Native-PAGE, we were able to confirm that nine proteins shared with honey bee fat body tissue accumulate intact in the eggs of the foundress mite. As such, we hypothesized that the proteins were several egg yolk precursors synthesized and stored in the fat body. Using antibodies raised against honey bee vitellogenin (Vg) we positively identified this egg yolk precursor via SDS-PAGE and subsequent Western Blot. We then analyzed samples of honey bee fat body tissue, gravid Varroa, so-called phoretic Varroa, and Varroa eggs via HPLC MS/MS to identify the remaining host proteins and determine their relative abundance. We detected egg yolk precursors in the large lipid transfer protein superfamily, in addition to hexamerin storage proteins, and miscellaneous motor/transfer proteins integral to embryonic development (transferrin, myosin heavy chain, and heat shock protein 60). Varroa lack the capacity to produce some of these proteins and instead employ kleptoparasitism on a molecular level to provision their developing ova, a pathway not described in any other host/parasite relationship, hereafter referred to as kleptocytosis. These different families of proteins are normally produced by the female and conveyed to the vitellogenic egg cell through protein specific receptor-mediated pathways. Such pathways would exclude foreign proteins. We hypothesize that the need to rely on a receptor-mediated pathway is circumvented via the specialized nutritive reproductive tissue, the lyrate organ. Through microCT imaging we detail the connection between the developing ovum and this dual-lobed organ. Better understanding of this pathway presents a novel target for Varroa management as the treatment need only accomplish slowing acquisition or deposition of host proteins thereby disrupting the ability of the mite to meet the temporal demand of its host.
... In the laboratory using binocular microscopes and ring lights, we investigated if each cell had been recapped, by carefully inverting the cell cap and estimating the size of the recapping on a scale from 1 to 5, which in worker brood equates roughly to a 1-5 mm scale. The age of the pupae was recorded using changes in eye or body colour 28 and if infested each of the mite stages were recorded 28 . Mite exuviate indicated the presence of an adult male or female and was important in determining multiple invaded cells and the number of mated female offspring. ...
... In the laboratory using binocular microscopes and ring lights, we investigated if each cell had been recapped, by carefully inverting the cell cap and estimating the size of the recapping on a scale from 1 to 5, which in worker brood equates roughly to a 1-5 mm scale. The age of the pupae was recorded using changes in eye or body colour 28 and if infested each of the mite stages were recorded 28 . Mite exuviate indicated the presence of an adult male or female and was important in determining multiple invaded cells and the number of mated female offspring. ...
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... Colonies can also be screened for visible signs of infection/infestation by pathogens/pests and for the presence of undesirable traits using standard protocols (e.g., Shimanuki and Knox, 2000;Dietemann et al., 2013;Spivak and Reuter, 2016). Some behavioral traits could be screened for using molecular technologies or in the field (Giray et al., 2000;Avalos et al., 2014). ...
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Beekeeping is a cornerstone activity that has led to the human-mediated, global spread of western honey bees ( Apis mellifera L.) outside their native range of Europe, western Asia, and Africa. The exportation/importation of honey bees (i.e., transfer of honey bees or germplasm between countries) is regulated at the national level in many countries. Honey bees were first imported into the United States in the early 1600’s. Today, honey bee movement (i.e., transport of honey bees among states and territories) is regulated within the United States at the state, territory, and federal levels. At the federal level, honey bees present in the country (in any state or territory) can be moved among states and territories without federal restriction, with the exception of movement to Hawaii. In contrast, regulations at the state and territory levels vary substantially, ranging from no additional regulations beyond those stipulated at the federal level, to strict regulations for the introduction of live colonies, packaged bees, or queens. This variability can lead to inconsistencies in the application of regulations regarding the movement of honey bees among states and territories. In November 2020, we convened a technical working group (TWG), composed of academic and USDA personnel, to review and summarize the (1) history of honey bee importation into/movement within the United States, (2) current regulations regarding honey bee movement and case studies on the application of those regulations, (3) benefits associated with moving honey bees within the United States, (4) risks associated with moving honey bees within the United States, and (5) risk mitigation strategies. This review will be helpful for developing standardized best practices for the safe movement of honey bees between the 48 contiguous states and other states/territories within the United States.
... Throughout the course of study observation, colonies were not treated with miticide in order to obtain an accurate representation of naturally occurring Varroa mite levels. To estimate Varroa mite levels per 100 bees, ∼300 nurse bees were sampled from brood frames per colony (stored at −20 • C), washed using detergent, then bees and mites were counted (74,75). A pool of 50 adult bees per colony was simultaneously sampled from two brood frames then stored at −80 • C for colony viral analyses. ...
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Nutrition is an important component of social insect colony health especially in the face of stressors such as parasitism and viral infections. Honey bees are known to preferentially select nectar and pollen based on macronutrient and phytochemical contents and in response to pathogen loads. However, given that honey bees live in colonies, collective foraging decisions may be impacted directly by forager infection status but also by colony health. This field experiment was conducted to determine if honey bee viral infections are correlated with pollen and nectar foraging and if these associations are impacted more by colony or forager infection. By comparing regressions with and without forager and colony variables and through structural equation models, we were able to determine the relative contributions of colony and forager virus loads on forager decisions. We found that foragers had higher numbers and levels of BQCV and CBPV but lower levels of DWV viruses than their respective colonies. Overall, individuals appeared to forage based a combination of their own and colony health but with greater weight given to colony metrics. Colony parasitism by Varroa mites, positively correlated with both forager and colony DWV-B levels, was negatively associated with nectar weight. Further, colony DWV-B levels were negatively associated with individually foraged pollen protein: lipid ratios but positively correlated with nectar weight and sugar content. This study shows that both colony and forager health can simultaneously mediate individual foraging decisions and that the importance of viral infections and parasite levels varies with foraging metrics. Overall, this work highlights the continued need to explore the interactions of disease, nutrition, and genetics in social interactions and structures.
... The adult bees were collected during the beginning of spring, and the outer frames of the hive that did not present brood were selected (Medrzycki et al., 2013). For toxicity test on V. destructor, the mites were collected according to the Standard methods of Varroa research (Dietemann et al., 2013); the mites with a similar physiological stage, were collected from recently capped brood cells. The Petri dishes (four per each concentration) were incubated at 30 • C and 70% RH. ...
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Varroosis is a disease caused by the mite Varroa destructor, and it is considered one of the biggest threats to honey bee populations globally. Mite control is centered on the use of synthetic acaricides, such as amitraz and flumethrine. However, high usage of these chemicals is associated with a wide variety of undesirable effects on bee colonies, including the development of resistance and persistence of harmful residues of acaricides in hive products used by humans. Botanical extracts have been identified as a potentially suitable organic alternative to synthetic acaricides. Essential oils, such as clove, eucalyptus, lemongrass, and oregano, have been found to exhibit acaricidal activity against V. destructor. The main goal of this work was to assess the bioactivity of the Cymbopogon nardus essential oil from two different locations (Argentina and India), and the activity of its major component the monoterpene citronellal. According to our results, complete essential oil from India is more effective in controlling parasitosis than the isolated citronellal component. The essential oil of C. nardus from Argentina demonstrated promise for the control of varroosis, as well as exhibiting low toxicity against bees (LC50 = 11.84 μL/mL). In addition, this essential oil may avoid the problems caused by synthetic acaricides, such as the emergence of resistance foci in Varroa and residues in hive products. Future research needs to investigate the delivery of volatile essentials oils to target mite populations.
... Sampling for genome sequencing At 17 locations, V. destructor mite families (N = 1 to 10 according to mite availability, each family composed of a foundress, her son and one to three daughters) were collected from singly infested capped worker or drone brood cells of A. mellifera and capped drone brood cells of A. cerana in one to three colonies per apiary [16]. Details on the sampling locations, origins of honey bee species and haplotypes are shown in Fig. 1 and Table S1 at DOI https://doi. ...
... Adult female V. destructor mites were collected from worker or drone brood cells of A. mellifera and drone brood cells of A. cerana colonies in the experimental apiary in Hangzhou, China, where both honey bee species were kept [15]. After being kept on A. mellifera workers to mimic the mite's mobile phase for two days, the two lineages of mites were manually transferred to freshly sealed (<6h post sealing) A. mellifera drone brood cells to record the fertility of each mite one day prior to the expected adult emergence (i.e., 13 days after infestation) [16]. ...
Article
Introduction Host shifts of parasites can have devastating effects on novel hosts. One remarkable example is that of the ectoparasitic mite Varroa destructor, which has shifted hosts from Eastern honey bees (Apis cerana) to Western honey bees (Apis mellifera) and posed a major global threat to apiculture and wild honey bees. Objectives and methods: To uncover the mechanisms underlying this rare successful host shift, we conducted a whole-genome analysis of host-shifted and nonshifted V. destructor mites and a cross-fostering infestation experiment. Results We found that oogenesis was upregulated in host-shifted mites on the new host A. mellifera relative to nonshifted mites. The transcriptomes of the host-shifted and nonshifted mites significantly differed as early as 1 h post-infestation of the new hosts. The differentially expressed genes were associated with nine genes carrying nonsynonymous high-FST SNPs, including mGluR2-like, Lamb2-like and Vitellogenin 6-like, which were also differentially expressed, and eIF4G, CG5800, Dap160 and Sas10, which were located in the center of the networks regulating the differentially expressed genes based on protein-protein interaction analysis. Conclusions The annotated functions of these genes were all associated with oogenesis. These genes appear to be the key genetic determinants of the oogenesis of host-shifted mites on the new host. Further study of these candidate genes will help elucidate the key mechanism underlying the success of host shifts of V. destructor.
... Varroa analyses were conducted for all colonies, at all five time points. To quantify the level of Varroa infestation in colonies, a detergent-wash method was employed 114 . The sample of bees was first placed in a mesh-partitioned cup with a solid base, to allow mite retrieval. ...
... survival rates empirically equivalent to Commercial colonies receiving two. Indeed, the benefit of additional mite treatments was generally greater for Commercial colonies, as the majority of Pol-line colonies naturally maintained Varroa levels below the recommended treatment threshold 114 . This has considerable implications both for improving colony survival, and reducing the escalating need for acaricide use 27 . ...
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The ectoparasite Varroa destructor is the greatest threat to managed honey bee (Apis mellifera) colonies globally. Despite significant efforts, novel treatments to control the mite and its vectored pathogens have shown limited efficacy, as the host remains naïve. A prospective solution lies in the development of Varroa-resistant honey bee stocks, but a paucity of rigorous selection data restricts widespread adoption. Here, we characterise the parasite and viral dynamics of a Varroa-resistant honey bee stock, designated ‘Pol-line’, using a large-scale longitudinal study. Results demonstrate markedly reduced Varroa levels in this stock, diminished titres of three major viruses (DWV-A, DWV-B, and CBPV), and a two-fold increase in survival. Levels of a fourth virus that is not associated with Varroa—BQCV—do not differ between stocks, supporting a disruption of the transmission pathway. Further, we show that when decoupled from the influence of Varroa levels, viral titres do not constitute strong independent predictors of colony mortality risk. These findings highlight the need for a reassessment of Varroa etiology, and suggest that derived stocks represent a tractable solution to the Varroa pandemic.