Varroa destructorand Viruses association in honey bee colonies under different climatic conditions (original) (raw)
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Varroa destructorand Viruses association in honey bee colonies under different climatic conditions
Environmental Microbiology Reports, 2016
Honey bee colonies are threatened by multiple factors including complex interactions between environmental and diseases such as parasitic mites and viruses. We compared the presence of honeybeepathogenic viruses and Varroa infestation rate in four apiaries: commercial colonies that received treatment against Varroa and non-treated colonies that did not received any treatment for the last 4 years located in temperate and subtropical climate. In addition, we evaluated the effect of climate and Varroa treatment on deformed wing virus (DWV) amounts. In both climates, DWV was the most prevalent virus, being the only present virus in subtropical colonies. Moreover, colonies from subtropical climate also showed reduced DWV amounts and lower Varroa infestation rates than colonies from temperate climate. Nevertheless, non-treated colonies in both climate conditions are able to survive several years. Environment appears as a key factor interacting with local bee populations and influencing colony survival beyond Varroa and virus presence.
The role of deformed wing virus in the mortality of varroa infested honey bee colonies
2003
The parasitic mite Varroa destructor has become the most economically important pest of the western honey bee, Apis mellifera. Long term studies undertaken in the UK have revealed that deformed wing virus (DWV), a naturally occurring bee virus, in association with the mite is now the cause of the majority of honey bee colony deaths ascribed to V. destructor. Many of the symptoms previously associated with the mite such as deformed wings, patchy brood patterns and reduced honey bee longevity, can now be explained by the natural history of DWV. The role of V. destructor is primarily as a virus vector. Once DWV is introduced into the haemolymph of parasitised individuals via the feeding activities of the mites, it multiplies rapidly, producing an overtly infected bee. This causes reduced brood survival and wing deformity in some, but not alI infected newly emerging individuals. Those that do survive have a significantly reduced longevity. Adult bees which become infected after they have emerged appear do not show such a marked reduction in longevity and act as reservoirs of DWV infection allowing mites an opportunity to reacquire and transmit the virus to other adult bees and brood The prevalence and persistence of DWV in colonies which were either treated with acarcide or allowed to die was also determined. This revealed that the number of overtly infected adult bees was greater than the number of mite infested bees, whilst the converse was found in the sealed brood. To ensure colony survival in temperate regions, mites must be removed prior to the production of the over-wintering bee population to minimise overt DWV infection in the newly emerging bees.
Since 1999, European beekeepers have reported increased mortality in overwintering honey bee, Apis mellifera L. colonies. Viral infections are often cited as the potential cause for increased mortality. Many honey bee viruses commonly occur within bee populations and in many cases infected colonies appear asymptomatic. There is increasing evidence that the global spread of Varroa destructor has resulted in a significant change in the prevalence, distribution and / or virulence of viruses causing mortality in honey bee colonies. We report here the first survey of the prevalence of five RNA bee viruses and their effect on overwintering survival of Belgian honey bee colonies. In the autumn of 2006, samples of adult bees were removed from 36 apiaries. Adult bee samples were analyzed by using RT-PCR for virus identification. Varroa mite prevalence in these samples was also quantified. A follow up visit of colonies in the spring permitted us to assess colony survivorship which permitted the effect, if any, of autumn varroa loads, virus presence and queen condition on colony survivorship to be ascertained. Although acute bee paralysis virus was the least prevalent of the detected honey bee viruses, it was strongly linked with increased colony mortality.
PLoS ONE, 2014
The honey bee ectoparasitic mite, Varroa destructor, has a worldwide distribution and inflicts more damage than all other known apicultural diseases. However, Varroa-induced colony mortality is more accurately a result of secondary virus infections vectored by the mite. This means that honey bee resistance to Varroa may include resistance or tolerance to virus infections. The aim of this study was to see if this is the case for a unique population of mite-resistant (MR) European honey bees on the island of Gotland, Sweden. This population has survived uncontrolled mite infestation for over a decade, developing specific mite-related resistance traits to do so. Using RT-qPCR techniques, we monitored late season virus infections, Varroa mite infestation and honey bee colony population dynamics in the Gotland MR population and compared this to mite-susceptible (MS) colonies in a close by apiary. From summer to autumn the deformed wing virus (DWV) titres increased similarly between the MR and MS populations, while the black queen cell virus (BQCV) and sacbrood virus (SBV) titres decreased substantially in the MR population compared to the MS population by several orders of magnitude. The MR colonies all survived the following winter with high mite infestation, high DWV infection, small colony size and low proportions of autumn brood, while the MS colonies all perished. Possible explanations for these changes in virus titres and their relevance to Varroa resistance and colony winter survival are discussed.
Journal of Apicultural Research, 2010
The ectoparasitic mite Varroa destructor is a serious pest of the honey bee Apis mellifera. The naturally occurring virus known as deformed wing virus (DWV) has long been linked with the collapse of mite infested honey bee colonies. We therefore surveyed the prevalence and persistence of DWV in four heavily infested untreated colonies (Survey 1), and five heavily infested colonies that were treated with an acaricide (Survey 2). The presence of DWV in samples of adult bees, sealed brood and mites was detected using an Enzyme Linked Immunosorbent Assay (ELISA). Twenty individuals of each type were sampled monthly from each colony over the course of the study. During the summer, the proportion of adults, sealed brood and mites in which DWV was detected increased until either the colony died or was treated. When colonies were treated, thus removing mites from the colony, DWV became undetectable in the sealed bee brood at a similar rate to the loss of mites. The speed at which DWV became undetectable in adult workers depended, however, on the season, reflecting differences in life span between adult workers emerging in summer or winter. If treatment was delayed until October, DWV was still detected in adult bees during the winter even in the absence of mites. To reduce the viral load of the colony, therefore, mite treatment should be started no later than the end of August in order to remove the mites before production of the overwintering bees begins. Prevalencia y persistencia del virus de alas deformadas (DWV) en colonias tratadas con acaricidas y no tratadas de abejas (Apis mellifera) infestadas con Varroa destructor Resumen El ácaro ectoparásito Varroa destructor es una seria plaga de la abeja Apis mellifera. El virus conocido como virus de las alas deformadas (DWV son su siglas en inglés) se ha relacionado con el colapso de las colonias de abejas infestadas con el ácaro. Por lo tanto examinamos el predominio y la persistencia del DWV en cuatro colonias no tratadas fuertemente infestadas (encuesta 1), y cinco colonias fuertemente infestadas que fueron tratadas con un acaricida (encuesta 2). La presencia de DWV en muestras de abejas adultas, de cría sellada y de ácaros fue detectada usando un análisis inmunosorbente de enzima ligado (ELISA). Se muestrearon mensualmente veinte individuos de cada tipo de cada colonia durante el estudio. Durante el verano, la proporción de adultos, de cría sellada y de ácaros en los que se detectó DWV fue aumentando hasta que la colonia murió o fue tratada. Cuando las colonias fueron tratadas, eliminando así los ácaros de la colonia, el DWV llegó a ser indetectable en la cría de la abeja sellada a una tasa similar a la pérdida de ácaros. La velocidad a la cual DWV llegó a ser indetectable en obreras adultas dependió, sin embargo, de la estación, reflejando diferencias en el rango de vida entre las obreras adultas que emergían en verano o en invierno. Si el tratamiento se retrasaba hasta octubre, el DWV todavía fue detectado en abejas adultas durante el
PLOS ONE
Deformed wing virus (DWV) is a lethal virus of honeybees (Apis mellifera) implicated in elevated colony mortality rates worldwide and facilitated through vector transmission by the ectoparasitic mite Varroa destructor. Clinical, symptomatic DWV infections are almost exclusively associated with high virus titres during pupal development, usually acquired through feeding by Varroa mites when reproducing on bee pupae. Control of the mite population, generally through acaricide treatment, is essential for breaking the DWV epidemic and minimizing colony losses. In this study, we evaluated the effectiveness of remedial mite control on clearing DWV from a colony. DWV titres in adult bees and pupae were monitored at 2 week intervals through summer and autumn in acaricide-treated and untreated colonies. The DWV titres in Apistan treated colonies was reduced 1000-fold relative to untreated colonies, which coincided with both the removal of mites and also a turnover of the bee population in the colony. This adult bee population turnover is probably more critical than previously realized for effective clearing of DWV infections. After this initial reduction, subclinical DWV titres persisted and even increased again gradually during autumn, demonstrating that alternative non-Varroa transmission routes can maintain the DWV titres at significant subclinical levels even after mite removal. The implications of these results for practical recommendations to mitigate deleterious subclinical DWV infections and improving honeybee health management are discussed.
Virus infections in Varroa destructor-resistant honeybees
bioRxiv, 2020
Populations of European honeybee subspecies, Apis mellifera, have the ability to adapt naturally to the ectoparasitic mite, Varroa destructor. It is possible that a tolerance to mite-vectored viruses may contribute to colony survival. If this is the case, surviving populations should show lower virus titers and prevalence compared to susceptible populations. Here, we investigated the prevalence and titers of 10 viruses, some known to be associated with V. destructor, in adult workers and pupae as well as mites. Samples were collected from both a mite-surviving and mite-susceptible honeybee population in Norway. Surviving colonies had a lower prevalence of a key virus (DWV-A) associated with V. destructor in individual adult bees sampled, and generally lower titers of this virus in mite infested pupae and mites within the colonies when compared to sympatric, susceptible controls. However, these surviving colonies also displayed higher prevalence and titers of two viruses not associat...
Parasites & Vectors
Background Varroa destructor is the major ectoparasite of the western honey bee (Apis mellifera). Through both its parasitic life-cycle and its role as a vector of viral pathogens, it can cause major damage to honey bee colonies. The deformed wing virus (DWV) is the most common virus transmitted by this ectoparasite, and the mite is correlated to increased viral prevalence and viral loads in infested colonies. DWV variants A and B (DWV-A and DWV-B, respectively) are the two major DWV variants, and they differ both in their virulence and transmission dynamics. Methods We studied the transmission of DWV between bees, parasitic mites and their offspring by quantifying DWV loads in bees and mites collected in in vitro and in situ environments. In vitro, we artificially transmitted DWV-A to mites and quantified both DWV-A and DWV-B in mites and bees. In situ, we measured the natural presence of DWV-B in bees, mites and mites’ offspring. Results Bee and mite viral loads were correlated, a...
Tolerance of Honey Bees to Varroa Mite in the Absence of Deformed Wing Virus
Viruses, 2020
The global spread of the parasitic mite Varroa destructor has emphasized the significance of viruses as pathogens of honey bee (Apis mellifera) populations. In particular, the association of deformed wing virus (DWV) with V. destructor and its devastating effect on honey bee colonies has led to that virus now becoming one of the most well-studied insect viruses. However, there has been no opportunity to examine the effects of Varroa mites without the influence of DWV. In Papua New Guinea (PNG), the sister species, V. jacobsoni, has emerged through a host-shift to reproduce on the local A. mellifera population. After initial colony losses, beekeepers have maintained colonies without chemicals for more than a decade, suggesting that this bee population has an unknown mite tolerance mechanism. Using high throughput sequencing (HTS) and target PCR detection, we investigated whether the viral landscape of the PNG honey bee population is the underlying factor responsible for mite toleranc...