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Deformed wing virus in western honey bees (Apis mellifera) from Atlantic Canada and the first description of an overtly-infected emerging queen
Abstract
Deformed wing virus (DWV) in western honey bees (Apis mellifera) often remains asymptomatic in workers and drones, and symptoms have never been described from queens. However, intense infections linked to parasitism by the mite Varroa destructor can cause worker wing deformity and death within 67 hours of emergence. Ten workers (eight with deformed wings and two with normal wings) and three drones (two with deformed wings and one with normal wings) from two colonies infected with V.destructor from Nova Scotia, Canada, and two-newly emerged queens (one with deformed wings and one with normal wings) from two colonies infected with V. destructor from Prince Edward Island, Canada, were genetically analyzed for DWV. We detected DWV in all workers and drones, regardless of wing morphology, but only in the deformed-winged queen. This is the first report of DWV from Atlantic Canada and the first detection of a symptomatic queen with DWV from anywhere.
... Also, the accumulation of virions (BQCV, DWV, and IAPV) in the wax of queen cells (and the possibility of subsequent virus transmission) should not be discounted during late larval or early pupal stages when a queen's body is in contact with the wax [65]. Unlike in workers and drones, where horizontal transmission is greatly facilitated by the parasitic mite Varroa destructor that vectors many different viruses [66][67][68], queen larvae cannot acquire viruses from Varroa because they do not infest developing queen cells, except in exceedingly rare cases of colonies with very high Varroa mite infestation [69,70]. Developing queens with any disease symptoms are likely to be destroyed by worker bees, which selects for low virulence but could also be a direct reason why viruses are detected so sporadically in the different stages of queen development or in newly emerged queens [60]. ...
... In particular, pathological effects of viruses in queens are not well defined, because pathological signs are difficult to observe from a single individual that lives in the center of the colony and is presumably replaced quickly by her nestmates with a new queen when health-compromised. Therefore, direct health impacts of queens have only been studied for few viruses-typically in the laboratory or in older queens with advanced infections [44,70,91]. ...
... Pathological DWV symptoms in queens seem to be restricted to colonies with a highly abundant Varroa population that causes high DWV viral titer. In these cases, queens can exhibit crippled wings [70] and degenerate ovaries, albeit without strict correlation between DWV titer and ovary degradation [44]. DWV infection was also found to be negatively correlated with stored sperm count [75], which may cause queen supersedure. ...
The honey bee queen is the central hub of a colony to produce eggs and release pheromones to maintain social cohesion. Among many environmental stresses, viruses are a major concern to compromise the queen’s health and reproductive vigor. Viruses have evolved numerous strategies to infect queens either via vertical transmission from the queens’ parents or horizontally through the worker and drones with which she is in contact during development, while mating, and in the reproductive period in the colony. Over 30 viruses have been discovered from honey bees but only few studies exist on the pathogenicity and direct impact of viruses on the queen’s phenotype. An apparent lack of virus symptoms and practical problems are partly to blame for the lack of studies, and we hope to stimulate new research and methodological approaches. To illustrate the problems, we describe a study on sublethal effects of Israeli Acute Paralysis Virus (IAPV) that led to inconclusive results. We conclude by discussing the most crucial methodological considerations and novel approaches for studying the interactions between honey bee viruses and their interactions with queen health.
... Symptomatic bees with wing deformities or with normal wings that were small and sluggish [44] were observed in each of eight randomly selected beehives before the examination of injury numbers caused by T. mercedesae mites to newly emerged honey bees. We randomly collected 243 newly emerged crippled/mite-infested adult bees from eight monitored beehives using blunt-tipped forceps, taking extra care to avoid damage to bee bodies. ...
... Mite infestations in the capped brood cells of honey bee workers might also influence the emergence development and damage adult foraging ability such as crippled wings [21,27,44]. However, consistent with our prediction, we found a higher number of injuries in the bee larvae than in the bee pupae. ...
Tropilaelaps mercedesae, one of the most devastating parasitic mites of honey bee Apis mellifera hosts, is a major threat to honey products by causing severe damage to honey bee colonies. Here, we recorded injury numbers caused by T. mercedesae to different body parts of the larval, pupal, and crippled adult stages of honey bee A. mellifera. We evaluated the relationship between infestation rate and injury numbers per bee for both larvae and pupae. We also noted the total bee numbers per beehive and examined the relationship between the infestation rate and population size. T. mercedesae infested all developmental stages of honey bees, with the highest injury numbers in the abdomens of bee pupae and the antennas of crippled adult bees. Although larvae received more injury numbers than pupae, both infestation rate and injury numbers decreased as the larval stage progressed to the pupal stage. The infestation rate increased as the population size per beehive decreased. This study provided new perspectives to the understanding of changes in the effects of T. mercedesae infestations on different developmental stages of honey bees. It also showed useful baseline information for screening honey bee stock that might have high defensive behaviors against mite infestation.
... Closely related to DWV – if not variants of DWV – are Kakugo virus (KV) isolated from allegedly aggressive A. mellifera worker bees from Japan [69, 109] and V. destructor virus-1 (VdV-1) isolated from varroa mites [104, 135]. The main host of DWV is unquestionably the European honey bee, Apis mellifera, where it has become globally distributed in the wake of V. destructor [3, 11, 16, 29, 36, 37, 64, 100, 106, 111, 122, 130]. DWV infections could also be demonstrated in the Asian honey bee (Apis cerana) and the dwarf bee (Apis florea) [3, 55] as well as recently in bumble bees (Bombus terrestris, Bombus pascuorum) displaying wing deformities [71]. ...
... E. coli-injected NW bees reached the same DWV RNA titer as observed in DW bees indicating that the high DWV RNA titers seen in deformed bees can also be induced by injecting E. coli into healthy looking bees that had been suffering from V. destructor parasitization during pupal development. Hence, the authors provide correlative evidence of a partially impaired immune response towards exposure to E. coli, although not of a general immunosuppression, in adult bees that suffered as pupae from mite parasitism [130]. The authors concluded that V. destructor causes immunosuppression in parasitized bees thereby inducing DWV replication since they also found a positive correlation between mite infestation level of pupae and probability and, especially , the severity of wing deformity in the emerging bee. ...
Until the late 1980s, specific viral infections of the honey bee were generally considered harmless in all countries. Then, with the worldwide introduction of the ectoparasite mite Varroa destructor, beekeepers encountered increasing difficulties in maintaining their colonies. Epidemiological surveys and laboratory experiments have demonstrated that the newly acquired virulence of several viruses belonging to the family Dicistroviridae (acute bee paralysis virus, Kashmir bee virus and Israeli acute paralysis virus) in Europe and the USA had been observed in relation with V. destructor acting as a disseminator of these viruses between and within bee colonies and as an activator of virus multiplication in the infected individuals: bee larvae and adults. Equal emphasis is given to deformed wing virus (DWV) belonging to the Iflaviridae. Overt outbreaks of DWV infections have been shown to be linked to the ability of V. destructor to act not only as a mechanical vector of DWV but also as a biological vector. Its replication in mites prior to its vectoring into pupae seemed to be necessary and sufficient for the induction of a overt infection in pupae developing in non-viable bees with deformed wings. DWV in V. destructor infested colonies is now considered as one of the key players of the final collapse. Various approaches for combating bee viral diseases are described: they include selection of tolerant bees, RNA interference and prevention of new pathogen introduction. None of these approaches are expected to lead to enhanced bee-health in the short term.
... Then, workers from the ~30 artificially infested and ~30 non-artificially cells were manually emerged from each frame by gently removing the wax cell capping (Dietemann et al., 2013). Each artificially emerged worker was visually inspected for clinical symptoms of disease (i.e., shortened abdomen and/or deformed wings) (Williams et al., 2009), and only individuals free of symptoms were used for the experiment. Each cell was assessed for the presence of a female mite and her offspring to ensure appropriate V. destructor infestation status (Straub et al., 2019). ...
Collaborative brood care by workers is essential for the functionality of eusocial Apis mellifera honey bee colonies. The hypopharyngeal food glands of workers play a crucial role in this context. Even though there is consensus that ubiquitous ectoparasitic mites Varroa destructor and widespread insecticides, such as neonicotinoids, are major stressors for honey bee health, their impact alone and in combination on the feeding glands of workers is poorly understood. Here, we show that combined exposure to V. destructor and neonicotinoids antagonistically interacted on hypopharyngeal gland size, yet they did not interact on emergence body mass or survival. While the observed effects of the antagonistic interaction were less negative than expected based on the sum of the individual effects, hypopharyngeal gland size was still significantly reduced. Alone, V. destructor parasitism negatively affected emergence body mass, survival, and hypopharyngeal gland size, whereas neonicotinoid exposure reduced hypopharyngeal gland size only. Since size is associated with hypopharyngeal gland functionality, a reduction could result in inadequate brood care. As cooperative brood care is a cornerstone of eusociality, smaller glands could have adverse down-stream effects on inclusive fitness of honey bee colonies. Therefore, our findings highlight the need to further study how ubiquitous stressors like V. destructor and neonicotinoids interact to affect honey bees.
... While clinical symptoms such as crippled wings and shortened abdomens have rarely been reported in queens as a consequence of DWV infection (Williams et al. 2009), internally, DWV may cause extreme cases of ovarian degradation (Gauthier et al. 2011). Morphological symptoms are often seen in drones, especially because Varroa mites prefer to parasitize drones, likely because of their longer development time enabling higher mite reproduction. ...
While managed honey bees are not fully domesticated compared to other livestock systems, beekeepers share many of the challenges associated with animal husbandry. Specifically, the intensification of beekeeping practices, high densities of beehives, and introduced exotic parasites have elevated parasites and pathogens to be among the top management concerns. Compared to many of the parasitic mites and bacterial brood diseases (where beekeepers have numerous management choices and chemotherapies), there are relatively few options to mitigate the many viral pathogens in honey bee colonies to optimize bee health. Here, we review many of the economically important viral pathogens of honey bees, our current understanding of the pathogens and their effect on the honey bee host, and our vision for a path forward to mitigate their effects on colony health.
... Its complete genome, with a single reading frame encoding a 328-kDa polyprotein, was published in 2006 (Lanzi et al., 2006). Its prevalence in A. mellifera colonies in some parts of the world can reach 100 % (Williams et al., 2009), where it spreads horizontally through oral transmission (Mazzei et al., 2014) and vertically through infected semen and eggs (de Miranda and Fries, 2008). Such DWV infections are typically asymptomatic or "covert," with the virus found in all bee tissues (de Miranda and Genersch, 2010). ...
Deformed wing virus (DWV) is a single-stranded positive sense RNA virus that mainly infects honey bees (Apis mellifera) and can have devastating impacts on the colony. Recent studies have shown the presence of this virus in several species of Apis spp. and some other Hymenoptera, but our knowledge of their host range is very limited. We screened previously sequenced RNAseq libraries from different tissues of Vietnamese Walking Stick, Medauroidea extradentata (Phasmatodea) for DWV. We only found this virus in six libraries from anterior and posterior midgut tissue. From the midgut libraries we were able to construct a complete DWV genome sequence, which consisted of 10,140 nucleotides and included one open reading frame. Pairwise genome comparison confirmed strong similarity (98.89 %) of these assembled sequences with only 113 SNPs to the original DWV genome. We hypothesize the M. extradentata acquired this virus via a foodborne transmission by consuming DWV-infected material such as pollen or leaves contaminated with virus infected bee faeces.
... More indicative for DWV, associated with a severe Varroa infestation load, are crippled wings in freshly hatched honeybees ( Figure 4B). Williams et al. describe a ranking in six categories, according to the severity of wing abnormities [36]. Hairless black abdomens are seen in case of a CBPV infection [24] or as a result of genetics, alimentation within honeydew flow period or for mechanical reasons. ...
Veterinarians are educated in prevention, diagnosis and treatment of diseases in various vertebrate species. As they are familiar with multifactorial health problems in single animals as well as in herd health management, their knowledge and skills can be beneficial for the beekeepers and honeybee health. However, in education and in practice, honeybees are not a common species for most veterinarians and the typical veterinary diagnostic methods such as blood sampling or auscultation are not applicable to the superorganism honeybee. Honeybee colonies may be affected by various biotic and abiotic factors. Among the infectious agents, RNA-viruses build the largest group, causing covert and overt infections in honeybee colonies which may lead to colony losses. Veterinarians could and should play a more substantial role in managing honeybee health—not limited to cases of notifiable diseases and official hygiene controls. This review discusses the veterinary diagnostic approach to adult bee examination with a special focus on diagnosis and differential diagnosis of the common virus diseases Acute Bee Paralysis Virus (ABPV)-Kashmir Bee Virus (KBV)-Israeli Acute Paralysis Virus (IAPV)-Complex, Chronic Bee Paralysis Virus (CBPV) and Deformed Wing Virus (DWV), as well as coinfections like Varroa spp. and Nosema spp.
... Here we report SHB associated with T. putrescentiae mites and possessing deformed wings resembling clinical symptoms of DWV. We conducted differential diagnostics to evaluate the cause of the observed clinical symptoms (Williams et al., 2009). ...
Insect wing deformities can be caused by viruses, mites and other environmental stressors during development. Here, we conducted differential diagnostics of deformed wings in small hive beetles, Aethina tumida (SHB). Adults with and without deformed wings from individual and mass rearing were evaluated for mites, Tyrophagus putrescentiae, and for deformed wing virus with PCR. Viral load or mite number were similar for SHB with deformed wings and unaffected beetles. Because deformed wings were only observed in individually pupating SHB, a humidity challenge most likely explains the observed clinical symptoms. Our observations support the importance of differential diagnostics.
... To foster drone emergence and feeding, ~50 adult worker from each colony were added to their respective drone frame 64 . Post-emergence, drones and workers without clinical symptoms of disease [65][66][67] were randomly placed in standard hoarding cages [250 cm 3 ] 68 . ...
Interactions between stressors are involved in the decline of wild species and losses of managed ones. Those interactions are often assumed to be synergistic, and per se of the same nature, even though susceptibility can vary within a single species. However, empirical measures of interaction effects across levels of susceptibility remain scarce. Here, we show clear evidence for extreme differences in stressor interactions ranging from antagonism to synergism within honeybees, Apis mellifera. While female honeybee workers exposed to both malnutrition and the pathogen Nosema ceranae showed synergistic interactions and increased stress, male drones showed antagonistic interactions and decreased stress. Most likely sex and division of labour in the social insects underlie these findings. It appears inevitable to empirically test the actual nature of stressor interactions across a range of susceptibility factors within a single species, before drawing general conclusions.
... This prediction has since been supported by several studies; for example, Budge et al. (100) found that only DWV was able to negatively affect colony strength in a predictable manner; colonies testing positive for DWV were likely to have fewer combs of bees or brood. Gauthier et al. (101) conducted a large survey of honeybee queens and found that DWV infections had little impact on the health and functional status of the queen, although DWV-infected queens with the deformed wing phenotype do exist (102). This may be linked to the finding that Varroa mites rarely invade brood cells containing developing queen pupae (103), so they can become infected by DWV only via an oral route or during feeding by a phoretic mite. ...
... One-day later (i.e., one day before adult emergence) several hundred cells per colony were carefully and individually uncapped to obtain the required number of experimental workers. Each worker was visually examined to estimate appropriate cohort age 41 , mite infestations 39 , and clinical symptoms of disease 44 . The proportion of individuals showing clinical symptoms of DWV (crippled wings and/or shortened abdomens 21,45 ) were recorded and used as a proxy of virus levels 45 as well as a predictive marker of colony mortality 21 . ...
The Western honeybee, Apis mellifera, is the most important managed pollinator globally and has recently experienced unsustainably high colony losses. Synergistic interactions among stressors are believed to be primarily responsible. However, despite clear evidence of strong effect on honeybee longevity of widely-employed neonicotinoid insecticides and of the ubiquitous ectoparasitic mite Varroa destructor, no data exist to show synergistic effects between these two stressors. Even though neonicotinoids had no significant impact by themselves, we here show for the first time a synergistic time-lag interaction between mites and neonicotinoids that resulted in significantly reduced survival of long-lived winter honeybees. Even though these mites are potent vectors of viruses, the virus-insecticide interaction had no significant impact. The data suggest a previously overlooked mechanism possibly explaining recent unsustainably high losses of managed A. mellifera honeybee colonies in many regions of the world. Future mitigation efforts should concentrate on developing sustainable agro-ecosystem management schemes that incorporate reduced use of neonicotinoids and sustainable solutions for V. destructor mites.
... Degrees of Wing Deformity in Deformed Wing Virus-Affected Bees as Proposed by Williams et al.17 ...
Deformed wing virus (DWV) is a single-stranded RNA virus of honey bees (Apis mellifera L.) transmitted by the parasitic mite Varroa destructor. Although DWV represents a major threat to honey bee health worldwide, the pathological basis of DWV infection is not well documented. The objective of this study was to investigate clinicopathological and histological aspects of natural DWV infection in honey bee workers. Emergence of worker honey bees was observed in 5 colonies that were clinically affected with DWV and the newly emerged bees were collected for histopathology. DWV-affected bees were 2 times slower to emerge and had 30% higher mortality compared to clinically normal bees. Hypopharyngeal glands in bees with DWV were hypoplastic, with fewer intracytoplasmic secretory vesicles; cells affected by apoptosis were observed more frequently. Mandibular glands were hypoplastic and were lined by cuboidal epithelium in severely affected bees compared to tall columnar epithelium in nonaffected bees. The DWV load was on average 1.7 × 10 ⁶ times higher (P <.001) in the severely affected workers compared to aged-matched sister honey bee workers that were not affected by deformed wing disease based on gross examination. Thus, DWV infection is associated with prolonged emergence, increased mortality during emergence, and hypoplasia of hypopharyngeal and mandibular glands in newly emerged worker honey bees in addition to previously reported deformed wing abnormalities.
... BQCV, as an opportunistic pathogen, is likely to contribute to colony losses only in combination with other factors [44]. BQCV load in our study peaked in spring, although its replication usually peaks in summer [47]. ...
Background:
Honey bee population decline threatens the beekeeping sector, agriculture and global biodiversity. Early detection of colony mortality may facilitate rapid interventions to contain and prevent mortality spread. Among others, deformed wing virus (DWV) is capable of inducing colony losses, especially when combined with Varroa destructor mite. Since the bee immune system plays a crucial role in ensuring that bees are able to face these pathogens, we explored whether expression of immune genes could serve as biomarkers of colony health.
Results:
Herein, we describe a preliminary immunological marker composed of two immune genes (relish and defensin), which provide insight on honey bee antiviral defense mechanism. Of the tested genes, relish expression correlated with the presence of DWV-Varroa complex, while decreased defensin expression correlated with poor resistance to this complex.
Conclusions:
The monitoring of these genes may help us to better understand the complex physiology of honey bees's immune system and to develop new approaches for managing the health impacts of DWV infection and varroa infestation in the field.
... DWV multiplies slowly, and it is closely associated with the mite V. destructor (Ball and Allen 1988;Martin 2001;Highfield et al. 2009). It causes visible deformities in severely infected adult bees and is associated with high winter loss of bees (Highfield et al. 2009;Williams et al. 2009;de Miranda and Genersch 2010). Both BQCV and SBV cause visible symptoms in immature bees but also affect adults. ...
... Although we did not test colony level traits, any reduction in the number of effective matings results in a reduced colony-level genetic diversity. The latter has been shown to affect colony productivity and survival, and therefore may represent a possible cryptic threat to honeybee colony health [41] in addition to the suite of pests and pathogens that may also affect honeybees [75,76]. ...
Neonicotinoid insecticides can cause a variety of adverse sub-lethal effects in bees. In social species such as the honeybee, Apis mellifera, queens are essential for reproduction and colony functioning. Therefore, any negative effect of these agricultural chemicals on the mating success of queens may have serious consequences for the fitness of the entire colony. Queens were exposed to the common neonicotinoid pesticides thiamethoxam and clothianidin during their developmental stage. After mating, their spermathecae were dissected to count the number of stored spermatozoa. Furthermore, their worker offspring were genotyped with DNA microsatellites to determine the number of matings and the genotypic composition of the colony. Colonies providing the male mating partners were also inferred. Both neonicotinoid and control queens mated with drones originating from the same drone source colonies, and stored similar number of spermatozoa. However, queens reared in colonies exposed to both neonicotinoids experienced fewer matings. This resulted in a reduction of the genetic diversity in their colonies (i.e. higher intracolonial relatedness). As decreased genetic diversity among worker bees is known to negatively affect colony vitality, neonicotinoids may have a cryptic effect on colony health by reducing the mating frequency of queens.
... The latter have usually a lower virus prevalence [53,129,133], suggesting that the virus replicates in adult queens. DWV has been found to infect the head, fat body, gut, and ovaries of queens [95,130,182,183], although crippled wings have seldom been reported in queens as a consequence of DWV infections [185]. A high virus titer in reproductive tissues can lead to ovarian degeneration or possibly affect stored sperm viability [130]. ...
Western honey bees, Apis mellifera, live in highly eusocial colonies that are each typically headed by a single queen. The queen is the sole reproductive female in a healthy colony, and because long-term colony survival depends on her ability to produce a large number of offspring, queen health is essential for colony success. Honey bees have recently been experiencing considerable declines in colony health. Among a number of biotic and abiotic factors known to impact colony health, disease and queen failure are repeatedly reported as important factors underlying colony losses. Surprisingly, there are relatively few studies on the relationship and interaction between honey bee diseases and queen quality. It is critical to understand the negative impacts of pests and pathogens on queen health, how queen problems might enable disease, and how both factors influence colony health. Here, we review the current literature on queen reproductive potential and the impacts of honey bee parasites and pathogens on queens. We conclude by highlighting gaps in our knowledge on the combination of disease and queen failure to provide a perspective and prioritize further research to mitigate disease, improve queen quality, and ensure colony health
... Cette phase est particulièrement critique, car la larve et la pupe ne sont pas nourries durant toute la période du couvain operculé et le prélèvement d'hémolymphe par le parasite ne peut pas être compensé par l'hôte (Donzé, 1995). Plusieurs auteurs rapportent également que le virus des ailes déformées (DWV) peut être la cause des malformations des ailes (Gauthier et al., 2008 ;Williams et al., 2009). ...
RESUME Le Varroa destructor constitue réellement l'un des ennemis majeurs des abeilles. Il a été détecté en Algérie en 1981, dans la coopérative apicole d'Oum Theboul El Kala (est de l'Algérie). Actuellement, ce parasite s'est propagé dans tous le pays. Afin d'étudier l'impact de Varroa destructor sur la morphométrie alaire et sur les composants du système immunitaire de l'abeille, des échantillons d'abeilles ouvrières nourrices, saines et parasitées ont été collectés des ruchers de la coopérative apicole de Oued Aissi (Tizi-Ouzou), située au nord de l'Algérie. Ce parasite a affecté d'une façon significative la longueur et la largeur de l'aile antérieure, les angles 31, 33 et 34. Aucun effet significatif (P>0,05) n'a été détecté pour les angles 32, 35 et 36. L'effet immunopathogène de Varroa destructor sur les abeilles nourrices se traduit par une diminution significative (P= 0,001) du nombre total des hémocytes (THC), l'une des mesures du composant du système immunitaire, le plus couramment employée. ABSTRACT Varroa destructor is a major enemy of honeybees. It was found in Algeria in 1981 in the apiary Oum Theboul El Kala (East Algeria). This parasite spread rapidly from there. In order to study the impact of the Varroa destructor on wing morphometry and the immune system components of the honeybee, samples of healthy worker honeybees and parasitized nurses were collected from the apiary of Oued Aissi (Tizi-Ouzou) located in the North of Algeria. This parasite significantly affected the length and the width of the fore wings, the angles 31, 33 and 34. No significant effect (P>0,05) was detected for the angles 32, 35 and 36. The immune pathogen effect of the Varroa destructor on the nurse honeybees was expressed by a significant reduction (P=0,001) in the total number of hemocytes (THC),
... Pupae were transferred to modified 1.5 ml ventilated microcentrifuge tubes and maintained under previously described conditions to allow proper development to maturity. Within 24 h of removal from the cells, each individual was weighed and examined for deformed wings according to Williams et al. (2009). Each bee was subsequently marked with a worker Opalith platelet (Neumann et al., 2003), and transferred to plastic hoarding cages (Retschnig et al., 2014a,b). ...
Historically an ectoparasite of the native Giant honey bee Apis dorsata, the mite Tropilaelaps mercedesae has switched hosts to the introduced western honey bee Apismellifera throughout much of Asia. Few data regarding lethal and sub-lethal effects of T. mercedesae on A. mellifera exist, despite its similarity to the devastating mite Varroa destructor. Here we artificially infested worker brood of A.mellifera with T. mercedesae to investigate lethal (longevity) and sub-lethal (emergence weight, Deformed wing virus (DWV) levels and clinical symptoms of DWV) effects of the mite on its new host. The data show that T. mercedesae infestation significantly reduced host longevity and emergence weight, and promoted both DWV levels and associated clinical symptoms. Our results suggest that T.mercedesae is a potentially important parasite to the economically important A. mellifera honey bee.
... This virus is transmitted both vertically and horizontally [16]. While DWV usually persists as an asymptomatic infection, the virus can be re-activated when triggered by various host stress, causing symptoms of illness in infected bees [17]. The manifestations of the disease caused by DWV infection include shrunken and crumpled wings, decreased body size, discoloration in adult bees and a reduction in life span. ...
Deformed wing virus (DWV), black queen cell virus (BQCV), sacbrood virus (SBV), Kashmir bee virus (KBV), acute bee paralysis virus (ABPV) and chronic bee paralysis virus (CBPV) are the most common RNA viruses in bee population worldwide. To determine the prevalence of these viruses in Apis cerana in Yunnan Province, China, 270 adult Eastern worker bee (A. cerana) samples have been collected from nine major bee breeding regions in Yunnan province for screening. Our data showed that BQCV, DWV, KBV and SBV are widely prevalent in Yunnan Province. The total prevalence rates of KBV, DWV, SBV and BQCV in Yunnan province were 3%, 14.8%, 24.1% and 36.3%, respectively. BQCV was detected in all selected regions except Jinghong City. The prevalence of KBV in Tengchong County is the first evidence, to our knowledge, showing that Eastern bees could be infected by KBV. The highest infection rate of SBV was found in Kunming city (56.7%). Sequence analysis demonstrated high nucleotide homology between the isolated BQCV, DWV, KBV and SBV strains. Phylogenetic analysis showed that except SBV (YNO7), Yunnan isolates can be likely clustered into independent branches, which indicates the possibility of geographic origins.
... Bee defensin-1 has potent activity against the mycelia fungi and yeast [78], protozoa [79], mites, viruses [80], gram-positive bacteria and some species of gram-negative bacteria [3,48,81]. However, defensin-1 may not have a great effectiveness on anti-biotic resistant bacteria. ...
For thousands of years, honey has been used for medicinal applications. The beneficial effects of honey, particularly its anti-microbial activity represent it as a useful option for management of various wounds. Honey contains major amounts of carbohydrates, lipids, amino acids, proteins, vitamin and minerals that have important roles in wound healing with minimum trauma during redressing. Because bees have different nutritional behavior and collect the nourishments from different and various plants, the produced honeys have different compositions. Thus different types of honey have different medicinal value leading to different effects on wound healing. This review clarifies the mechanisms and therapeutic properties of honey on wound healing. The mechanisms of action of honey in wound healing are majorly due to its hydrogen peroxide, high osmolality, acidity, non-peroxide factors, nitric oxide and phenols. Laboratory studies and clinical trials have shown that honey promotes autolytic debridement, stimulates growth of wound tissues and stimulates anti-inflammatory activities thus accelerates the wound healing processes. Compared with topical agents such as hydrofiber silver or silver sulfadiazine, honey is more effective in elimination of microbial contamination, reduction of wound area, promotion of re-epithelialization. In addition, honey improves the outcome of the wound healing by reducing the incidence and excessive scar formation. Therefore, application of honey can be an effective and economical approach in managing large and complicated wounds.
... In fact, Parasitellus may even be benefi cial to bumble bees by feeding on their parasitic nematodes (Schousboe 1987). Other mesostigmatans occur in beehives in Canada, but are parasites (e.g., Varroa destructor Anderson and Trueman, Williams et al. 2009), predators of microarthropods, or have unknown feeding habits (Eickwort 1994). ...
... Other viruses closely linked to varroa but that are endemic to bees, such as acute bee paralysis virus and relatives [4], and deformed wing virus [5], tend to be more evenly co-distributed with varroa. Honeybee queens are almost never infested with varroa mites either as pupae or adults [40,41] but can still be infected with deformed wing virus through oral and sexual transmission [5,42,43] such that virus, even if initially undetectable, is inevitably available for proliferation when mites are first introduced to the system [44,45], stabilizing the co-distribution. The distribution of BeeMLV does not fit this pattern. ...
Around 14 distinct virus species-complexes have been detected in honeybees,
each with one or more strains or sub-species. Here we present the initial characterization
of an entirely new virus species-complex discovered in honeybee (Apis mellifera L.) and
varroa mite (Varroa destructor) samples from Europe and the USA. The virus has a naturally
poly-adenylated RNA genome of about 6500 nucleotides with a genome organization
and sequence similar to the Tymoviridae (Tymovirales; Tymoviridae), a predominantly
plant-infecting virus family. Literature and laboratory analyses indicated that the virus had
not previously been described. The virus is very common in French apiaries, mirroring the
results from an extensive Belgian survey, but could not be detected in equally-extensive Swedish and Norwegian bee disease surveys. The virus appears to be closely linked
to varroa, with the highest prevalence found in varroa samples and a clear seasonal
distribution peaking in autumn, coinciding with the natural varroa population development.
Sub-genomic RNA analyses show that bees are definite hosts, while varroa is a possible
host and likely vector. The tentative name of Bee Macula-like virus (BeeMLV) is therefore
proposed. A second, distantly related Tymoviridae-like virus was also discovered in varroa
transcriptomes, tentatively named Varroa Tymo-like virus (VTLV).
... cheva et al., 2004. Berenyi et al., 2006. Chantawannakul et al., 2006. Forgach et al., 2008. Sanpa and Chantawannakul, 2009. DWV is already widely studied in recent years (Grabensteiner et al., 2000.. Huang, 2000. Benjeddou et al., 2001Bakonyi et al., 2002. Tentcheva et al., 2004. Chen et al., 2005. Genersch and Yue, 2005Chantawannukul et al., 2006. Williams et al., 2009Martin et al., 2010;Zioni et al., 2011;Yanez et al., 2012). It is the virus most frequently found in the samples analyzed. Its frequency increases in the hives, from spring to autumn. It is closely related to V. destructor, which plays both the role of the vector and viral activator. Nearly 98% of the colonies analyzed contain V. destruc ...
Honeybees are threatened by over 18 viruses, nowadays deformed wing virus (DWV) is known to be one of the most prevalent virus worldwide.. This is the first study in Algeria and most North Africa region which is evaluating the prevalence of the DWV in beehives. The objective of this study is to evaluate the impact of this virus on honey bees mortality, and its relationship to infestation with the Varroa destrutor parasitic mite. We conducted this study on an apiary located in the central region of Algeria. PCR results showed the presence of DWV in Apis mellifera intermissa honey bee colonies, where 42% of the samples are infected with the virus. We highlighted the role of V. destructor and its association with the DWV and the mortality recorded in the same apiary.
... Deformed wing virus is one of the most prevalent and is widely distributed, usually being found wherever honey bees are present (Martin et al. 2012). Deformed wing virus is closely associated with the mite V. destructor (Ball and Allen 1988;Martin 2001;Highfield et al. 2009), causes visible deformities in severely infected adult bees and is associated with high levels of winter loss of bee colonies (Highfield et al. 2009;Williams et al. 2009;de Miranda and Genersch 2010). Black queen cell virus is also common in adult bees throughout the world, and has been implicated as a cause of increased colony loss when found in combination with the microsporidian Nosema apis Zander (Dissociodihaplophasida: Nosematidae) (Chen and Siede 2007). ...
The occurrence, quantification, and distribution patterns of deformed wing virus (DWV) and sacbrood virus (SBV), (family Iflaviridae); black queen cell virus (BQCV), Israeli acute paralysis virus (IAPV), Kashmir bee virus (KBV), and acute bee paralysis virus (ABPV) (family Dicistroviridae), and chronic bee paralysis virus (CBPV) (unclassified), were characterised in 80 “healthy” honey bee (
Apis mellifera
Linnaeus; Hymenoptera: Apidae) colonies and 23 “unhealthy” colonies by employing reverse transcription polymerase chain reaction (RT-PCR) for virus identification and quantitative real-time polymerase chain reaction (qPCR) for quantification. All seven viruses were common but the most prevalent viruses were DWV, followed by BQCV and IAPV. For most viruses, prevalence in surviving but unhealthy colonies in spring did not differ from that of healthy baseline colony levels in fall suggesting spring prevalence level would not be a useful metric for diagnosis of factors contributing to colony loss. Sacbrood virus was the only virus that was more prevalent in unhealthy colonies from Manitoba, Canada than in healthy from colonies across Canada but did not differ from healthy colonies within Manitoba. Multiple infections were ubiquitous with a few colonies having simultaneous infection with as many as five viruses. Among the three viruses quantified by qPCR, DWV had the highest relative concentrations in pooled samples of worker bees. Deformed wing virus was the only virus within healthy colonies that differed in fall concentration among provinces and was at high levels in unhealthy colonies. Black queen cell virus was positively correlated with IAPV across all samples. Our study provides the first major baseline study of viruses in Canadian honey bees.
... Symptomatic individual workers live < 67 h after emergence (Ya n g and Cox-Foster 2007) but there are no data on DWV infected queen longevity. Deformed wing virus has been found in workers and drones regardless of wing morphology, but only in newly emerged queens with deformed wings (Williams et al. 2009). In our study, DWV was found in normally developed laying mated queens mating nuclei. ...
Viral infection could have an impact on the success of queen rearing and a potential effect on reduced queen quality. Newly mated honey bee (Apis mellifera carnica) queens were collected from mating nuclei in queen rearing operations in Slovenia. Altogether, 81 queens were sampled from 27 rearing apiaries in 2006 and 72 queens from 24 apiaries in 2008. Queens were analysed for the presence of four viruses: acute bee paralysis virus (ABPV), black queen cell virus (BQCV), sacbrood virus (SBV) and deformed wing virus (DWV) by using reverse transcription polymerase chain reaction (RT-PCR). In 2006, 12%, 9% and 1% prevalence was found for ABPV, DWV and SBV, respectively; BQCV was not detected. Two years later, DWV, BQCV, SBV and ABPV were detected in 58%, 24%, 11% and 10% bee queens, respectively. In 2006, fourteen out of twenty-seven apaiaries were virus free, whereas in 2008 only three out of twenty-four apiaries were virus free. This is the first evidence of virus infection occurring in newly mated queens from mating nuclei in rearing apiaries. The possible impacts of queen rearing technology and epidemiological influences on virus infection are discussed in this study.
... Èçâåñòíî, ÷òî ï÷åëû, çàðàaeåííûå V. destructor, ïîãèáàþò ïðè âîçäåéñòâèè áàêòåðèè Esherichia coli è îòëè÷àþòñÿ îò çäîðîâûõ îñîáåé áîëüøèì ÷èñëîì ðàçðóøåííûõ êëåòîê ãåìîëèìôû è ñîäåðaeàíèåì â íèõ âèðóñíûõ ÷àñòèö [42]. Ïîêàçàíî, ÷òî èììóíîñóïðåññîðíîå äåéñòâèå è òÿaeåëûå êëèíè÷åñêèå ïðèçíàêè âîçðàñòàþò ïðè óâåëè÷åíèè óðîâíÿ çàðàaeåííîñòè êëåùàìè [43]. ...
Specific conditions of life of the honeybee require effective mechanisms of anti-infectious protection, one of the most important components of which are dephenyl Sina - a family of antimicrobial peptides. In honeybee defensins are present as two different peptides -defensina 1 and 2 having a similarity between only 55.8%. Defensin 1, synthesized in the salivary glands, plays an important role in social immunity, whereas defensin 2, synthesized by cells of the fat body and hemolymph, is an important factor in the individual immunity of the honey bee. Defensins inducible, controlled interaction Toll and Imd signaling pathways and have a broad spectrum of antimicrobial action.
Специфические условия жизни медоносной пчелы требуют наличия эффективных механизмов противоинфекционной защиты, одним из важнейших компонентов которой являются дефен-сины — семейство антимикробных пептидов. У медоносной пчелы дефенсины присутствуют в виде двух разных пептидов —дефенсина 1 и 2, обладающих сходством между собой лишь на 55.8 %. Дефенсин 1, синтезируемый в слюнных железах, выполняет важную роль в социальном иммунитете, тогда как дефенсин 2, синтезируемый клетками жирового тела и гемолимфы, является важным фактором в системе индивидуального иммунитета медоносной пчелы. Дефенсины индуцибельны, контролируются взаимодействием Toll и Imd сигнальных путей и обладают широким спектром антимикробного действия.
Ilyasov R.A., Gaifullina L.R., Saltykova E.S., Poskryakov A.V., Nikolaenko A.G. Defensins in the Honeybee Antiinfectious Protection. Journal of Evolutionary Biochemistry and Physiology, 2013, V. 49 (1), P. 1-9.
... The honeybees infected by V. destructor are known to die under the effect of bacteria Esherichia coli and differ from the health individuals by the higher number of destructed hemolymph cells and by their content of virus particles [41]. It has been shown that the immuno- suppressor effect and severe clinical signs rise with increase of the mite infection level [43]. ...
Specific conditions of life of the honeybee require effective mechanisms of anti-infectious protection, one of the most important components of which are dephenyl Sina - a family of antimicrobial peptides. In honeybee defensins are present as two different peptides -defensina 1 and 2 having a similarity between only 55.8%. Defensin 1, synthesized in the salivary glands, plays an important role in social immunity, whereas defensin 2, synthesized by cells of the fat body and hemolymph, is an important factor in the individual immunity of the honey bee. Defensins inducible, controlled interaction Toll and Imd signaling pathways and have a broad spectrum of antimicrobial action.
Специфические условия жизни медоносной пчелы требуют наличия эффективных механизмов противоинфекционной защиты, одним из важнейших компонентов которой являются дефен-сины — семейство антимикробных пептидов. У медоносной пчелы дефенсины присутствуют в виде двух разных пептидов —дефенсина 1 и 2, обладающих сходством между собой лишь на 55.8 %. Дефенсин 1, синтезируемый в слюнных железах, выполняет важную роль в социальном иммунитете, тогда как дефенсин 2, синтезируемый клетками жирового тела и гемолимфы, является важным фактором в системе индивидуального иммунитета медоносной пчелы. Дефенсины индуцибельны, контролируются взаимодействием Toll и Imd сигнальных путей и обладают широким спектром антимикробного действия.
Ilyasov R.A., Gaifullina L.R., Saltykov E.S., Poskryakov A.V., Nikolenko A.G. Antimicrobial protection of defensins in the honeybees. Journal of Evolutionary Biochemistry and Physiology. 2012, v. 48 (5) . P. 425-432.
... During each frame assessment, bees were scanned visually for ,1 min for signs of the following diseases. Deformed wing is a continuum of signs (image in [38]) that can occur (rarely) in the absence of deformed wing virus (DWV) [33,39]. Briefly, one or both wings become stunted or curled in adults. ...
Few areas of the world have western honey bee (Apis mellifera) colonies that are free of invasive parasites Nosema ceranae (fungi) and Varroa destructor (mites). Particularly detrimental is V. destructor; in addition to feeding on host haemolymph, these mites are important vectors of several viruses that are further implicated as contributors to honey bee mortality around the world. Thus, the biogeography and attendant consequences of viral communities in the absence of V. destructor are of significant interest. The island of Newfoundland, Province of Newfoundland and Labrador, Canada, is free of V. destructor; the absence of N. ceranae has not been confirmed. Of 55 Newfoundland colonies inspected visually for their strength and six signs of disease, only K-wing had prevalence above 5% (40/55 colonies = 72.7%). Similar to an earlier study, screenings again confirmed the absence of V. destructor, small hive beetles Aethina tumida (Murray), tracheal mites Acarapis woodi (Rennie), and Tropilaelaps spp. ectoparasitic mites. Of a subset of 23 colonies screened molecularly for viruses, none had Israeli acute paralysis virus, Kashmir bee virus, or sacbrood virus. Sixteen of 23 colonies (70.0%) were positive for black queen cell virus, and 21 (91.3%) had some evidence for deformed wing virus. No N. ceranae was detected in molecular screens of 55 colonies, although it is possible extremely low intensity infections exist; the more familiar N. apis was found in 53 colonies (96.4%). Under these conditions, K-wing was associated (positively) with colony strength; however, viruses and N. apis were not. Furthermore, black queen cell virus was positively and negatively associated with K-wing and deformed wing virus, respectively. Newfoundland honey bee colonies are thus free of several invasive parasites that plague operations in other parts of the world, and they provide a unique research arena to study independent pathology of the parasites that are present.
... DWV is a 30 nm icosahedral particle consisting of a single, positive strand RNA genome [8], typical for ifl aviruses, a genus of the family Ifl aviridae, within the order Picornavirales [9,10]. As widely and globally distributed, DWV is the most studied of all honeybee viruses [4,[11][12][13][14][15][16][17][18]. DWV has been detected in adult bees, their pupae and larvae [19], as well as in Varroa mites [12] and Tropilaelaps mercedesae [20]. ...
A survey of deformed wing virus and acute bee paralysis virus in honey bee colonies from Serbia using real-time RT-PCR
Author(s): Simeunović Predrag, Stevanović Jevrosima, Vidanović Dejan, Nišavić Jakov, Radović Dejan, Stanišić Ljubodrag, Stanimirović Zoran
Keywords:DWV, ABPV, Varroa destructor, Serbian apiaries
In this study 55 honey bee colonies from different Serbian regions were monitored for the presence of Deformed Wing Virus (DWV) and Acute Bee Paralysis Virus (ABPV) using TaqMan-based real-time RT-PCR assay. The results revealed the presence of DWV in each sampling location, and ABPV in 10 out of 11 apiaries. High frequency of DWV (76.4%) and ABPV (61.8%) positive samples in asymptomatic colonies can be the consequence of inefficient and postponed Varroa treatment concerning the role of this mite in the transmission and activation of honey bee viruses. The real-time RT-PCR technique described in this paper is proved to be the most reliable method for this kind of investigation.
... DWV is the best characterised of the approximately 18 viruses known to infect honey bees (Ribière et al. 2008; de Miranda and Genersch 2010). It is present in all developmental stages and castes (Yue and Genersch 2005; Chen et al. 2005; Tentcheva et al. 2006) and, at high titres, causes characteristic wing deformities, shortened abdomens, discolouring, social and behavioural abnormalities and a severely reduced lifespan of adult honey bee workers, drones and queens (Bowen-Walker et al. 1999; Yue and Genersch 2005; Iqbal and Mueller 2007; Williams et al. 2009; de Miranda and Genersch 2010). DWV can be transmitted horizontally among adult bees through trophallaxis and from adult bees to larvae through glandular food secretions (Nordström 2000; Chen et al. 2005; Iqbal and Mueller 2007). ...
Deformed wing virus (DWV) represents an ideal model to study the interaction between mode of transmission and virulence in
honey bees since it exhibits both horizontal and vertical transmissions. However, it is not yet clear if venereal–vertical
transmission represents a regular mode of transmission for this virus in natural honey bee populations. Here, we provide clear
evidence for the occurrence of high DWV titres in the endophallus of sexually mature drones collected from drone congregation
areas (DCAs). Furthermore, the endophallus DWV titres of drones collected at their maternal hives were no different from drones
collected at nearby DCAs, suggesting that high-titre DWV infection of the endophallus does not hinder the ability of drones
to reach the mating area. The results are discussed within the context of the dispersal of DWV between colonies and the definition
of DWV virulence with respect to the transmission route and the types of tissues infected.
... Nine queens showed DWV titres close to the level of deformed-wing workers, but none of these queens exhibited any obvious signs of disease. Incidences of crippling overt infection in queens have seldom been reported (Williams et al., 2009). Queens are unlikely to be exposed to the virus during the developmental stages, as queen cells are not attractive to varroa mites. ...
The well-being of a colony and replenishment of the workers depends on a healthy queen. Diseases in queens are seldom reported, and our knowledge on viral infection in queens is limited. In this study, 86 honey bee queens were collected from beekeepers in Denmark. All queens were separately tested by two real-time PCRs: one for the presence of Deformed Wing Virus (DWV), and one that would signal sequences of Acute Bee Paralysis Virus, Kashmir Bee Virus as well as Israeli Acute Paralysis Virus. Worker bees accompanying the queen were also analysed. The queens could be divided into three groups based on the level of infection in their head, thorax, ovary, intestines and spermatheca. Four queens exhibited egg-laying deficiency, but visually all queens appeared healthy. Viral infection was generally low for AKI copies with 134 tissues out of 430 (31 %) showing the presence of viral infection ranging from 101 to 105 copies. For DWV, 361 tissues out of 430 (84 %) showed presence of viral infection (DWV copies ranging from 102 to 1012), with 50 tissues showing viral titres greater than 107 copies. For both AKI and DWV, the thorax was the most frequently infected tissue and the ovaries were least frequently infected. Relative to total mass the spermatheca showed significantly higher DWV titres than other tissues. The ovaries had the lowest titre of DWV. No significant differences were found between tissues for AKI. A subsample of 14 queens yielded positive results for the presence of negative strands thus showing active viral replication in all tissues.
... As another strategy to alter the infectivity of the baculovirus, we also prepared a pseudotype baculovirus (VP1/GFP) that displayed the VP1 of DWV as a fusion protein with GP64 on the surface of the baculovirus envelope (Figure 1a, bottom panel). DWV is known to infect various tissues of worker honeybees (Yue and Genersch 2005;Lanzi et al. 2006), most prominently in the pupal stage (Chen et al. 2005a), and also infect queen honeybees (Chen et al. 2005b;Williams et al. 2009). Insect picorna-like viruses including DWV resemble the mammalian picornaviruses, i.e., both have a single-stranded RNA as the genome and the form, an icosahedral capsid composed of four types of virion proteins (VP1-VP4; Lanzi et al. 2006). ...
The potential uses of baculovirus as a gene vector to queen honeybees were examined in this study. We used a green fluorescent
protein-expressing baculovirus with wild-type envelope and two pseudotype viruses of which one overexpressed GP64 and the
other expressed a virion protein of a honeybee virus on the envelope. After injection of these baculoviruses into queen pupae,
infection was detected in the fat bodies, but not in the ovaries. Pupae injected with a titer of 1 × 105 infectious units survived to eclose, and the infection was also detected in the fat bodies of adult queen honeybees, suggesting
that baculoviruses can transiently express genes in the fat bodies, and therefore, can be used for further analysis of gene
functions. In addition, although the viruses examined in this study failed to express the reporter gene in the ovaries, the
infection in the fat bodies suggests that baculoviruses could be potentially useful for transgenesis, if appropriately developed.
Keywordshoneybee–virus vector–gene transfer–transgenesis–pseudotype
... As outlined above, true covert infections are characterized by (i) the presence of viral particles or sequences in the absence of diseases symptoms, (ii) vertical transmission, and (iii) occasional overt outbreaks as proof of maintained virulence. The first characteristic 'presence of DWV in the absence of disease symptoms' has been proven at the individual-insect-level for all three adult castes, i.e. workers, drones and queens and all earlier life stages via RT-PCR methods and in situ-hybridization (Chen et al., 2005a,b;Fievet et al., 2006;Gauthier et al., 2007;Williams et al., 2009;Yue and Genersch, 2005). 'Presence of DWV in the absence of obvious disease symptoms' at the colony level is implicated in several epidemiological studies revealing that DWV is the most prevalent virus in mite-infested colonies regardless of whether the colonies are strong, weak or even about to collapse (Berenyi et al., 2006;Forgach et al., 2008;Nielsen et al., 2008;Sanpa and Chantawannakul, 2009;Tentcheva et al., 2004b). ...
Deformed wing virus (DWV; Iflaviridae) is one of many viruses infecting honeybees and one of the most heavily investigated due to its close association with honeybee colony collapse induced by Varroadestructor. In the absence of V.destructor DWV infection does not result in visible symptoms or any apparent negative impact on host fitness. However, for reasons that are still not fully understood, the transmission of DWV by V.destructor to the developing pupae causes clinical symptoms, including pupal death and adult bees emerging with deformed wings, a bloated, shortened abdomen and discolouration. These bees are not viable and die soon after emergence. In this review we will summarize the historical and recent data on DWV and its relatives, covering the genetics, pathobiology, and transmission of this important viral honeybee pathogen, and discuss these within the wider theoretical concepts relating to the genetic variability and population structure of RNA viruses, the evolution of virulence and the development of disease symptoms.
Sap-sucking insects often transmit plant viruses but also carry insect viruses, which infect insects but not plants. The impact of such insect viruses on insect host biology and ecology is largely unknown. Here, we identified a novel insect-specific virus carried by brown citrus aphid (Aphis citricidus), which we tentatively named Aphis citricidus picornavirus (AcPV). Phylogenetic analysis discovered a monophyletic cluster with AcPV and other unassigned viruses, suggesting that these viruses represent a new family in order Picornavirales. Systemic infection with AcPV triggered aphid antiviral immunity mediated by RNA interference, resulting in asymptomatic tolerance. Importantly, we found that AcPV was transmitted horizontally by secretion of the salivary gland into the feeding sites of plants. AcPV influenced aphid stylet behavior during feeding and increased the time required for intercellular penetration, thus promoting its transmission among aphids with plants as an intermediate site. The gene expression results suggested that this mechanism was linked with transcription of salivary protein genes and plant defense hormone signaling. Together, our results show that the horizontal transmission of AcPV in brown citrus aphids evolved in a manner similar to that of the circulative transmission of plant viruses by insect vectors, thus providing a new ecological perspective on the activity of insect-specific viruses found in aphids and improving the understanding of insect virus ecology.
Deformed wing virus (DWV) is a single-stranded positive-sense RNA virus which mainly infects honey bees (Apis mellifera) and can have devastating impacts on the colony. Recent studies have shown the presence of this virus in several species of Apis spp. and some other Hymenoptera, but our knowledge of their host range is very limited. We screened previously sequenced RNAseq libraries from different tissues of Vietnamese Walking Stick, Medauroidea extradentata (Phasmatodea) for DWV. We only found this virus in six libraries from anterior and posterior midgut tissue. From the midgut libraries, we were able to construct the complete genome sequence of DWV, which consisted of 10,140 nucleotides and included one open reading frame. Pairwise genome comparison confirmed strong similarity (98.89%) of these assembled sequences with only 113 SNPs to the original DWV genome. Perhaps M. extradentata acquired this virus via a food borne transmission by consuming DWV-infected material such as pollen or leaves contaminated with virus-infected bee faeces.
Deformed wing virus (DWV) has become the most well-known, widespread, and intensively studied insect pathogen in the world. Although DWV was previously present in honeybee populations, the arrival and global spread of a new vector, the ectoparasitic mite Varroa destructor, has dramatically altered DWV epidemiology. DWV is now the most prevalent virus in honeybees, with a minimum average of 55% of colonies/apiaries infected across 32 countries. Additionally, DWV has been detected in 65 arthropod species spanning eight insect orders and three orders of Arachnida. Here, we describe the significant progress that has been made in elucidating the capsid structure of the virus, understanding its ever-expanding host range, and tracking the constantly evolving DWV genome and formation of recombinants. The construction of molecular clones, working with DWV in cell lines, and the development of immunohistochemistry methods will all help the community to move forward. Identifying the tissues in which DWV variants are replicating and understanding the impact of DWV in non-honeybee hosts are major new goals.
Honey bees are major pollinators of crops throughout the world. The global stock of
honey bees does not meet the demand for their pollination services. As such, maintaining the
global honey bee stocks is important, as a decrease will reduce the available pollination services
that are already threatened. Those pollination services are required for production of many
agricultural products throughout the world. One problem that honey bees are facing that
reduces their efficiency as pollinators and honey producers is infection by parasites like viruses
including Deformed Wing Virus.
This paper proposes a diagnostic test to detect Deformed Wing Virus that can be
performed outside of a laboratory setting with minimal equipment. The time it takes to mail
samples to a lab extends the time between a beekeeper requesting a diagnosis and receiving one.
Paper-based ELISA (a molecular diagnostic technique described later) takes advantage of the
specificity of ELISA, a cheap substrate (paper) that allows results to be quantified by analyzing
an image taken by a smartphone or desktop scanner, producing results in just fifteen minutes.
This proposal outlines the methods for creating phage-display derived antibodies, creating paper
based plates, calibrating the paper-based ELISA assay and executing the assay. It also includes
the rationale for why this project is worthwhile and results to date of efforts taken towards
creating this assay.
Bee viral infections worldwide leading to colonies' depopulation have emerged as a threat to bee keeping. To date, nearly 20 RNA viruses, of Dicistroviridae, Iflaviridae, Nodaviridae families mostly, were detected in honeybee Apis mellifera (O.F. Grobov et al., 2006; C. Runckel et al., 2011). Also DNA viruses have been found, e.g. iridovirus (Iridoviridae), potentially causing losses of bee colonies (J.J. Bromenshenk et al., 2010), Aphid Lethal Paralysis virus (Dicistroviridae), Big Sioux River virus (Dicistroviridae), Lake Sinai Virus strain 1 and 2 (Nodaviridae) (C. Runckel et al., 2011) however, their role in bee mortality has yet to be understood. The most important bee viruses known to date are deformed wing virus (DWV), acute bee paralysis virus, (ABPV), chronic bee paralysis virus (CBPV), Kashmir bee virus, (KBV), sacbrood virus, (SBV), Black queen cell virus (BQCV). These viruses can persist in honey bees (Apis mellifera L.) without apparent symptoms, however, Varroa destructor infestation causes a viral epidemic, diminishing bee colonies. The range of V. destructor, the main viral infections' vector (D. Tentcheva et al., 2004), was confined to that of A. cerana being ecologically balanced. However, not long ago this mite crossed the species barrier from the Asian hive bee A. cerana to our own Western honey bee A. mellifera (R.S. Poltorzhitskaya, 2008). The introduction of V. destructor into the A. mellifera population has become one of the major contributing factors to colony collapse disorder (D. van Engelsdorp et al., 2008; R.M. Johnson et al., 2009; F. Nazzi et al., 2012). Moreover, the mite Varroa affect the immune response and metabolism of honey bees and allow its vectored viruses to propagate to high viral loads. At present there is an objective need for a closer look into bee viruses implicated in bee colony losses reported worldwide. So far as Varroa mite is an obligate parasite of A. mellifera during whole ontogenesis, the Varroa control notably ensures the well-being of bee colonies. In this review, an overview of the world distribution and the impact of the major viruses (DWV, ABPV, CBPV, SBV, BQCV, KBV) on bee health and colony survival is presented. We also discuss approaches to virus control. Overall, the strategy combining new Varroa management practices (A.A. Fedorova et al., 2011), selection of Varroa-resistant bees and novel treatments against viruses will help sustain the honey bee population.
Three hundred eleven honeybee samples from twelve countries in the Middle East and North Africa (MENA) (Jordan, Lebanon, Syria, Iraq, Egypt, Libya, Tunisia, Algeria, Morocco, Yemen, Palestine and Sudan) were analyzed for the presence of deformed wing virus (DWV). The prevalence of DWV throughout the MENA region was pervasive, but variable. The highest prevalence was found in Lebanon and Syria, with prevalence dropping in Palestine, Jordan and Egypt before increasing slightly moving westwards to Algeria and Morocco Phylogenetic analysis of a 194 nucleotide section of the DWV Lp gene did not identify any significant phylogenetic resolution among the samples, although the sequences did show consistent regional clustering, including an interesting geographic gradient from Morocco through North Africa to Jordan and Syria. The sequences revealed several clear variability hotspots in the deduced amino acid sequence, that furthermore showed some patterns of regional identity. Furthermore, the sequence variants from the Middle East and North Africa appear more numerous and diverse than those from Europe. This article is protected by copyright. All rights reserved.
Honey bees defensin have a high level of polymorphism and exist as two peptides - defensin 1 and
2. Defensin 1 is synthesized in the salivary glands and is responsible for social immunity. Defensin
2 is synthesized by cells of the fat body and hemolymph is responsible for individual immunity.
Defensins are inducible and controlled by the interaction of Toll and Imd signaling pathways and
have a broad spectrum of antimicrobial action. The use of chitosan as an immunomodulator has
been shown to lead to an increase in the expression levels of defensin and abaecin in the honey bee
organism. Stimulation of the transcriptional activity of the defensin genes will allow for the control
of a honey bee colony’s immunity level, and reduce the using of antibiotics and other chemicals.
Ilyasov R.A., Gaifullina L.R., Saltykova E.S., Poskryakov A.V., Nikolenko A.G. Review of the Expression of Antimicrobial Peptide Defensin in Honey bees Apis mellifera L. Journal of Apicultural Science. 2012. Vol.56 No.1. P.115-124.
We sequenced small (s) RNAs from field collected honeybees (Apis mellifera) and bumblebees (Bombuspascuorum) using the Illumina technology. The sRNA reads were assembled and resulting contigs were used to search for virus homologues in GenBank. Matches with Varroadestructor virus-1 (VDV1) and Deformed wing virus (DWV) genomic sequences were obtained for A. mellifera but not B. pascuorum. Further analyses suggested that the prevalent virus population was composed of VDV-1 and a chimera of 5'-DWV-VDV1-DWV-3'. The recombination junctions in the chimera genomes were confirmed by using RT-PCR, cDNA cloning and Sanger sequencing. We then focused on conserved short fragments (CSF, size > 25 nt) in the virus genomes by using GenBank sequences and the deep sequencing data obtained in this study. The majority of CSF sites confirmed conservation at both between-species (GenBank sequences) and within-population (dataset of this study) levels. However, conserved nucleotide positions in the GenBank sequences might be variable at the within-population level. High mutation rates (Pi>10%) were observed at a number of sites using the deep sequencing data, suggesting that sequence conservation might not always be maintained at the population level. Virus-host interactions and strategies for developing RNAi treatments against VDV1/DWV infections are discussed.
Honey bee virus research is an enormously broad area, ranging from subcellular molecular biology through physiology and behaviour, to individual and colony-level symptoms, transmission and epidemiology. The research methods used in virology are therefore equally diverse. This article covers those methods that are very particular to virological research in bees, with numerous cross-referrals to other BEEBOOK papers on more general methods, used in virology as well as other research. At the root of these methods is the realization that viruses at their most primary level inhabit a molecular, subcellular world, which they manipulate and interact with, to produce all higher order phenomena associated with virus infection and disease. Secondly, that viruses operate in an exponential world, while the host operates in a linear world and that much of the understanding and management of viruses hinges on reconciling these fundamental mathematical differences between virus and host. The article concentrates heavily on virus propagation and methods for detection, with minor excursions into surveying, sampling management and background information on the many viruses found in bees.
A variety of methods are used in honey bee research and differ depending on the level at which the research is conducted. On an individual level, the handling of individual honey bees, including the queen, larvae and pupae are required. There are different methods for the immobilising, killing and storing as well as determining individual weight of bees. The precise timing of developmental stages is also an important aspect of sampling individuals for experiments. In order to investigate and manipulate functional processes in honey bees, e. g. memory formation and retrieval and gene expression, microinjection is often used. A method that is used by both researchers and beekeepers is the marking of queens that serves not only to help to locate her during her life, but also enables the dating of queens. Creating multiple queen colonies allows the beekeeper to maintain spare queens, increase brood production or ask questions related to reproduction. On colony level, very useful techniques are the measurement of intra hive mortality using dead bee traps, weighing of full hives, collecting pollen and nectar, and digital monitoring of brood development via location recognition. At the population level, estimation of population density is essential to evaluate the health status and using beelines help to locate wild colonies. These methods, described in this paper, are especially valuable when investigating the effects of pesticide applications, environmental pollution and diseases on colony survival.
Methods are described for working with Nosema apis and Nosema ceranae in the field and in the laboratory. For fieldwork, different sampling methods are described to determine colony level infections at a given point in time, but also for following the temporal infection dynamics. Suggestions are made for how to standardise field trials for evaluating treatments and disease impact. The laboratory methods described include different means for determining colony level and individual bee infection levels and methods for species determination, including light microscopy, electron microscopy, and molecular methods (PCR). Suggestions are made for how to standardise cage trials, and different inoculation methods for infecting bees are described, including control methods for spore viability. A cell culture system for in vitro rearing of Nosema spp. is described. Finally, how to conduct different types of experiments are described, including infectious dose, dose effects, course of infection and longevity tests.
--We have developed a least-squares minimization approach to depth determination from magnetic data. By defining the anomaly value T(0) at the origin and the anomaly value T(N) at any other distance (N) on the profile, the problem of depth determination from magnetic data has been transformed into finding a solution to a nonlinear equation of the form f(z)=0. Formulas have been derived for a sphere, horizontal cylinder, dike, and for a geologic contact. Procedures are also formulated to estimate the effective magnetization intensity and the effective magnetization inclination. A scheme for analyzing the magnetic data has been formulated for determining the model parameters of the causative sources. The method is applied to synthetic data with and without random errors. Finally, the method is applied to two field examples from Canada and Arizona. In all cases examined, the estimated depths are found to be in good agreement with actual values.
Using molecular methods we provide evidence of the first detection of deformed wing virus (DWV) infection in the U.S. By reverse transcription polymerase chain reaction (RT-PCR), DWV was detected in different stages of honey bees, including adult bees with deformed wings, normal-appearing adult bees, eggs, larvae, and pupae. While the virus was also detected in the parasitic mite, Varroa destructor, the detection of DWV in eggs and larvae suggests there are alternate ways for the virus to spread within colonies. The detection of virus in normal-appearing adults also suggests that virus titers may have to reach certain levels in pupae before the infection is manifested by deformed wings.
1. The ecto-parasitic mite Varroa destructor is a serious world-wide pest of the honeybee Apis mellifera and has being linked with the death of millions of colonies, although its role in colony death has remained elusive. 2. A simulation model was developed to explain the link between the mite and collapse of the host bee colony, given that colony death does not always occur. We investigated the effects of two pathogens, deformed wing virus (DWV) and acute paralysis virus (APV), vectored by the mite, on the host colony. 3. Two previously published simulation models, a bee and a mite, were combined and adapted for use in temperate climates with a variety of bee diseases. The model was constructed using Modelmaker ® software, which allows the progression of a disease in the host colony to be followed daily. 4. The population dynamics generated by the model were similar to those observed in a natural honeybee colony. When DWV- or APV-transmitting mites were introduced into the colony, its adult worker bee population collapsed either during winter or spring for DWV, or autumn to spring for APV. This corresponds well with field observations
Under field conditions, Varroa jacobsoni were shown to be highly effective vectors of deformed wing virus (DWV) between bees. Adult female mites obtained from honeybee pupae naturally infected with DWV contained virus titers many times in excess of those found in their hosts and, beyond that, which might be expected from a concentration effect. It is therefore possible that DWV may be capable of replicating within V. jacobsoni. Bees which tested positive for DWV exhibited characteristic morphological deformity and/or they died during pupation. Asymptomatic bees had much lower virus titers than those which were deformed or had died during pupation. It is therefore suggested that for DWV to cause pathology it must be present in pupae above a certain concentration. The amount of DWV vectored by V. jacobsoni will depend on the mites' level of infection, which will in turn depend on whether they had fed previously on dead or deformed bees and also on the rate of replication of the virus within the mites. Consequently, developing bees infested with large numbers of mites could suffer a high incidence of deformity if the mites are heavily infected or harbor an especially virulent strain of virus. A positive relationship was found between increasing numbers of mites on individual bees and the incidence of morphological deformity and death. This probably reflected the large number of viral particles transmitted by the mites, which resulted in many multiply infested bees dying before emergence. These results demonstrate the importance of the role of viruses when considering the pathology of V. jacobsoni and that much of the pathology previously associated with the effects of mite feeding could be attributed directly to secondary pathogens vectored by V. jacobsoni. Copyright 1999 Academic Press.
To obtain the active human recombinant uridine diphosphate glucuronosyltransferase 1A3 (UGT1A3) enzyme from Chinese hamster lung (CHL) cells.
The full-length UGT1A3 gene was amplified by reverse transcription-polymerase chain reaction (RT-PCR) using total RNA from human liver as template. The correct fragment confirmed by sequencing was subcloned into the mammalian expression vector pcDNA3.1 (+), and the recombinant vector was transfected into CHL cells using a calcium phosphate method. Expressed UGT1A3 protein was prepared from CHL cells resistant to neomycin (G418). Then the protein was added into a reaction mixture for glucuronidation of quercetin. The glucuronidation activity of UGT1A3 was determined by reverse phase-high performance liquid chromatography (RP-HPLC) coupled with a diode array detector (DAD). The quercetin glucuronide was confirmed by hydrolysis with beta-glucuronidase. Control experiments were performed in parallel. The transcriptions of recombinants were also determined by RT-PCR.
The gene was confirmed to be an allele (UGT1A3-3) of UGT1A3 by DNA sequencing. The fragment was introduced into pcDNA3.1 (+) successfully. Several colonies were obtained under the selection pressure of G418. The result of RT-PCR showed transcription of recombinants in mRNA level. Glucuronidation assay and HPLC analysis indicated UGT1A3 expressed heterologously in CHL cells was in an active form, and one of the gulcuronides corresponding to quercetin was also detected.
Correct sequence of UGT1A3 gene can be obtained, and active UGT1A3 enzyme is expressed heterologously in CHL cells.
Deformed wing virus (DWV) can cause wing deformity and premature death in adult honeybees, although like many other bee viruses,
DWV generally persists as a latent infection with no apparent symptoms. Using reverse transcription (RT)-PCR and Southern
hybridization, we detected DWV in all life stages of honeybees, including adults with and without deformed wings. We also
found DWV in the parasitic mite Varroa destructor, suggesting that this mite may be involved in the transmission of DWV. However, the detection of the virus in life stages
not normally associated with mite parasitism (i.e., eggs and larvae) suggests that there are other modes of transmission.
The levels of DWV in different life stages of bees were investigated by using TaqMan real-time quantitative RT-PCR. The amounts
of virus varied significantly in these different stages, and the highest levels occurred in pupae and in adult worker bees
with deformed wings. The variability in virus titer may reflect the different abilities of bees to resist DWV infection and
replication. The epidemiology of DWV is discussed, and factors such as mite infestation, malnutrition, and climate are also
considered.
Varroa mites (Varroa destructor) are ectoparasites of honey bees (Apis mellifera) and cause serious damage to bee colonies. The mechanism of how varroa mites kill honey bees remains unclear. We have addressed the effects of the mites on bee immunity and the replication of a picorna-like virus, the deformed wing virus (DWV). The expression of genes encoding three antimicrobial peptides (abaecin, defensin, and hymenoptaecin) and four immunity-related enzymes (phenol oxidase, glucose dehydrogenase, glucose oxidase, and lysozyme) were used as markers to measure the difference in the immune response. We have demonstrated an example of an ectoparasite immunosuppressing its invertebrate host with the evidence that parasitization significantly suppressed expression of these immunity-related genes. Given that ticks immunosuppress their vertebrate hosts, our finding indicates that immunosuppression of hosts may be a common phenomenon in the interaction and coevolution between ectoparasites and their vertebrate and invertebrate hosts. DWV viral titers were significantly negatively correlated with the expression levels of the immunity-related enzymes. All bees had detectable DWV. Mite-infested pupae developed into adults with either normal or deformed wings. All of the deformed-wing bees were greatly infected by DWV (≈10⁶ times higher than varroa-infested but normal-winged bees). Injection with heat-killed bacteria dramatically promoted DWV titers (10⁵ times in 10 h) in the mite-infested, normal-winged bees to levels similar to those found in mite-infested, deformed-wing bees. Varroa mites may cause the serious demise of honey bees by suppressing bee immunity and by boosting the amplification of DWV in bees exposed to microbes.
• antimicrobial peptides
• immunosuppression
• innate immunity
• varroa mite
• honey bee
Transmission mechanisms of six honeybee viruses, including acute bee paralysis virus (ABPV), black queen cell virus (BQCV),
chronic bee paralysis virus (CBPV), deformed wing virus (DWV), Kashmir bee virus (KBV), and sacbrood bee virus (SBV), in honey
bee colonies were investigated by reverse transcription-PCR (RT-PCR) methods. The virus status of individual queens was evaluated
by examining the presence of viruses in the queens' feces and tissues, including hemolymph, gut, ovaries, spermatheca, head,
and eviscerated body. Except for head tissue, all five tissues as well as queen feces were found to be positive for virus
infections. When queens in bee colonies were identified as positive for BQCV, DWV, CBPV, KBV, and SBV, the same viruses were
detected in their offspring, including eggs, larvae, and adult workers. On the other hand, when queens were found positive
for only two viruses, BQCV and DWV, only these two viruses were detected in their offspring. The presence of viruses in the
tissue of ovaries and the detection of the same viruses in queens' eggs and young larvae suggest vertical transmission of
viruses from queens to offspring. To our knowledge, this is the first evidence of vertical transmission of viruses in honeybee
colonies.
Honeybees originating from 10 different countries (Austria, Poland, Germany, Hungary, Slovenia, Nepal, Sri Lanka, the United Arab Emirates, Canada, and New Zealand) located on four continents were analyzed for the presence of deformed wing virus (DWV) nucleic acid by reverse transcription-PCR. Two target regions within the DWV genome were selected for PCR amplification and subsequent sequencing, i.e., a region within the putative VP2 and VP4 structural-protein genes and a region within the RNA helicase enzyme gene. DWV nucleic acid was amplified from 34 honeybee samples representing all the above-mentioned countries with the notable exception of New Zealand. The amplification products were sequenced, and phylogenetic analyses of both genomic regions were performed independently. The phylogenetic analyses included all sequences determined in this study as well as previously published DWV sequences and the sequences of two closely related viruses, Kakugo virus (KGV) and Varroa destructor virus 1 (VDV-1). In the sequenced regions, the DWV genome turned out to be highly conserved, independent of the geographic origins of the honeybee samples: the partial sequences exhibited 98 to 99% nucleotide sequence identity. Substitutions were most frequently observed at the same positions in the various DWV sequences. Due to the high level of sequence conservation, no significant clustering of the samples in the phylogenetic trees could be identified. On the other hand, the phylogenetic analyses support a genetic segregation of KGV and VDV-1 from DWV.
Deformed wing virus (DWV) is a viral pathogen of the European honeybee (Apis mellifera), associated with clinical symptoms and colony collapse when transmitted by the ectoparasitic mite Varroa destructor. In the absence of V. destructor, DWV infection does not result in visible symptoms, suggesting that mite-independent transmission results in covert infections. True covert infections are a known infection strategy for insect viruses, resulting in long-term persistence of the virus in the population. They are characterized by the absence of disease symptoms in the presence of the virus and by vertical transmission of the virus. To demonstrate vertical transmission and, hence, true covert infections for DWV, a detailed study was performed on the vertical-transmission routes of DWV. In total, 192 unfertilized eggs originating from eight virgin queens, and the same number of fertilized eggs from the same queens after artificial insemination with DWV-negative (three queens) or DWV-positive (five queens) semen, were analysed individually. The F0 queens and drones and F1 drones and workers were also analysed for viral RNA. By in situ hybridization, viral sequences were detected in the ovary of an F0 queen that had laid DWV-positive unfertilized eggs and was inseminated with DWV-positive semen. In conclusion, vertical transmission of DWV from queens and drones to drone and worker offspring through unfertilized and fertilized eggs, respectively, was demonstrated. Viral sequences in fertilized eggs can originate from the queen, as well as from drones via DWV-positive semen.
To evaluate natural bee mortality a comparison was made between Gary traps (which are normally used for this purpose) and a new type of trap called «underbasket». The results obtained with the latter when used over a longer period of time appear more reliable, as the underbasket does not seem to lead to cleaning behaviour in the worker bees, as happens with Gary traps.
To determine the roles of varroa mites in activating or vectoring viral infections, we performed quantitative comparison of viral infections between bees with and without mites by dot blot analysis and enzyme-linked immunosorbent assay (ELISA). Under natural and artificial mite infestations, bee pupae contained significantly higher levels of Kashmir bee virus (KBV) and deformed wing virus (DWV) RNAs and KBV structural proteins than mite-free pupae. Moreover, in mite-infested bee pupae, DWV had amplified to extremely high titers with viral genomic RNA being clearly visible after separation of total bee RNA in agarose gels. Linear regression analysis has shown a positive correlation between the number of mites introduced and the levels of viral RNAs. The detection of viral RNAs in the nymph and adult mites underline the possible role of varroa in virus transmission. However, most groups of virus-free adult mites (9/12) were associated with bee pupae heavily infected by viruses, suggesting that the elevated viral titers in mite-infested pupae more likely resulted from activated viral replication. Based on these observations and our concurrent research demonstrating suppressed immune responses in bees infested with mites, we propose that parasitization by varroa suppresses the immunity of honey bees, leading to activation of persistent, latent viral infection.
Individual honey bee Apis mellifera L. queens were examined for the presence of six honey bee viruses including acute bee paralysis virus, chronic bee paralysis virus, black queen cell virus, deformed wing virus, Kashmir bee virus, and sacbrood virus. All viruses, except ABPV, were detected in the samples. Among queens examined for virus infections, 93% had multiple virus infections. The detection of viruses in queens raises the possibility of a vertical transmission pathway wherein infected queens can pass virus through their eggs to their offspring.
Deformed wing virus (DWV) is a honeybee viral pathogen either persisting as an inapparent infection or resulting in wing deformity. The occurrence of deformity is associated with the transmission of DWV through Varroa destructor during pupal stages. Such infections with DWV add to the pathology of V. destructor and play a major role in colony collapse in the course of varroosis. Using a recently developed RT-PCR protocol for the detection of DWV, individual bees and mites originating from hives differing in Varroa infestation levels and the occurrence of crippled bees were analysed. It was found that 100 % of both crippled and asymptomatic bees were positive for DWV. However, a significant difference in the spatial distribution of DWV between asymptomatic and crippled bees could be demonstrated: when analysing head, thorax and abdomen of crippled bees, all body parts were always strongly positive for viral sequences. In contrast, for asymptomatic bees viral sequences could be detected in RNA extracted from the thorax and/or abdomen but never in RNA extracted from the head. DWV replication was demonstrated in almost all DWV-positive body parts of infected bees. Analysing individual mites for the presence of DWV revealed that the percentage of DWV-positive mites differed between mite populations. In addition, it was demonstrated that DWV was able to replicate in some but not all mites. Interestingly, virus replication in mites was correlated with wing deformity. DWV was also detected in the larval food, implicating that in addition to transmission by V. destructor DWV is also transmitted by feeding.
Varroa mites (Varroa destructor) are serious ectoparasites of honey bees (Apis mellifera). This research addresses the impact of varroa mites on survivorship, viral incidence, and physiological traits of newly-emerged worker bees. RT-PCR confirmed our previous finding that varroa parasitization was linked to high levels of deformed wing virus (DWV). In non-treatment bees, varroa parasitization combined with increased viral levels altered survivorship curves from long-survival to shorter-survival types. After challenge with live Escherichia coli, the survivorship of mite-parasitized bees was significantly lower than mite-free bees. Deformed-wing, mite-parasitized bees died on average within 1 day, even without E. coli challenge. This was correlated with the absence of an important enzyme activity in insect immunity, phenol oxidase, lacking even in those bees challenged with immuno-elicitors. The lack of inducible phenol oxidase activity indicated that the bee immune system is not fully competent upon adult emergence. Varroa parasitism also significantly reduced body weight of the parasitized bees, but body weight was not significantly correlated with the survivorship of mite-parasitized bees. Our research indicates that the combination of mite parasitization, the interaction of DWV and microbes, and a developmental immune incompetency attribute to decreased worker survivorship and have a negative impact on colony fitness.
Deformed wing virus in honey bees (Apis mellifera). B.Sc. (Hons) Thesis
- B A Taylor
Taylor, B.A., 2008. Deformed wing virus in honey bees (Apis mellifera). B.Sc. (Hons)
Thesis, Acadia University, Nova Scotia, Canada.