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International audience; AbstractVarroa destructor is an external parasite of Apis mellifera and feeds on the haemolymph of pupae and adult bees, vectoring numerous viral pathogens, in particular the deformed wing virus (DWV). However, the changes in haemolymph protein composition after Varroa infestation are unknown. The objective of this study was to investigate alterations in the haemolymph proteome in relation to Varroa parasitism. Using two-dimensional difference gel electrophoresis and MALDI-TOF/TOF mass spectrometry, we identified changes in 44 haemolymph proteins in response to the parasite and one in protein originated from DWV. The following pathways were affected by Varroa infestation, including carbohydrate metabolism, detoxification and oxidative stress response, nutrient reservoir activity, oxidoreductase activity and the olfactory system. Several physiological functions of honey bees, such as energy metabolism, detoxification, metamorphosis and chemosensing, may be disrupted by Varroa.

International audience; 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.

Since 2006, disastrous colony losses have been reported in Europe and North America. The causes of the losses were not readily apparent and have been attributed to overwintering mortalities and to a new phenomenon called Colony Collapse Disorder. Most scientists agree that there is no single explanation for the extensive colony losses but that interactions between different stresses are involved. As the presence of Varroa in each colony places an important pressure on bee health, we here address the question of how Varroa contributes to the recent surge in honey bee colony losses, Seit 2006 werden in Europa und Nordamerika katastrophale Völkerverluste gemeldet. Die Ursachen dieser Verluste waren nicht leicht zu erklären, sie wurden als überwinterungsbedingte Mortalitäten bewertet und unter dem Begriff Colony Collapse Disorder (CCD) zusammengefasst. Die meisten Wisenschaftler stimmen dahingehend überein, dass diesen Völkerverlusten keine Einzelursache zugrunde liegt, sondern, dass vermutlich verschiedene Stressfaktoren zusammenwirken. Da der Varroa-Befall einen wichtigen Druck auf die Gesundheit der Bienen in den Völkern darstellt, gingen wir der Frage nach, inwiefern Varroa an den seit kurzem beobachteten Völkerverlusten beteiligt sein kann. Verschiedene physikalische und physiologische Faktoren mit negativer Wirkung der Varroa-Milbe auf die Gesundheit der einzelnen Biene und den Volkszusammenhang sind bereits bekannt. So führt das wiederholte Saugen von Hämolymphe zu Verletzungen der Bienen, zu erniedrigten Werten im Proteingehalt, sowie dem Lebend- und Trockengewicht und zur Behinderungen in der Organentwicklung. Die parasitische Milbe und die von ihr übertragenen Viren führen zu morphologischen Fehlentwicklungen, reduzierter Widerstandskraft und Lebenserwartung und zu negativen Effekten auf die Flugdauer und Heimfindungsfähigkeit der Sammlerinnen. Die Milbe schwächt das Immunsystem der Bienen, indem die Expression von Genen der Immunantwort reduziert wird. Zusammen mit erhöhten DWV-Viren-Titern reduziert sie damit die Lebensfähigkeit der Arbeiterinnen und die Koloniefitness. Die Rolle der Varroa-Milbe als Vektor in der horizontalen und vertikalen Übertragung von Viren ist hingehend bekannt, und Ko-Infektionen von V. destructor mit verschiedenen Viren wurden bereits als wichtige Faktoren im Varroa-bedingten Zusammenbruch von Völkern beschrieben. V. destructor muss deshalb weiterhin als eine ernsthafte Bedrohung der Honibiene gelten, und weiterhin werden Honigbienenpopulationen weltweit durch diese parasitische Milbe dezimiert. Die Hypothese, dass CCD durch eindringende Varroa-Milben und ihre immunsuppressiven Fähigkeiten hervorgerufen wird, ist damit nicht auszuschliessen und wird durch die Befunde von vanEngelsdorp et al. (2009) gestärkt. Die Varroa-Milbe ist seit Jahren in den meisten Ländern vertreten, aus denen auch Völkerverluste gemeldet werden. Obwohl die Milbenpopulationen kontrolliert werden können, kann trotzdem spekulativ postuliert werden, dass die Verluste zumindest teilweise durch einen Varroa-Befall der Völker bedingt sein können. Welche Veränderungen in der Varroa-Biologie können also die jetzigen Verluste im Vergleich zu denen vor 20 Jahren erklären? Wir diskutieren potentielle Ursachen, einschliesslich Veränderungen in der Biologie und Populationsdynamik von Varroa und ihrem Wirt, der Kontrolle von Varroa durch Akarizide, indirekte Effekten der Varroa-Behandlungen, sowie synergistische Effekte multipler Faktoren

The Western honey bee, Apis mellifera, is the most important animal pollinator in agriculture worldwide providing more than 90% of the commercial pollination services. Due to the development in agriculture the demands for honey bee pollination are steadily increasing stressing the pollination capacity of the global managed honey bee population. Hence, the long-term decline of managed honey bee hives in Europe and North-America is of great concern and stimulated intensive research into the possible factors presumably causing honey bee colony collapse. We here present a four-year study involving more than 1200 bee colonies from about 120 apiaries which were monitored for the entire study period. Bee samples were collected twice a year to analyze various pathogenic factors including the ectoparasitic mite Varroa destructor, fungi (Nosema spec., Ascosphaera apis), the bacterium Paenibacillus larvae, and several viruses. Data on environmental factors, beekeeping management practice, and pesticides were also collected. All data were statistically analyzed in respect to the overwintering mortality of the colonies. We can demonstrate for several factors that they are significantly related to the observed winter losses of the monitored honey bee colonies: (i) high varroa infestation level, (ii) infection with deformed wing virus (DWV) and acute bee paralysis virus (ABPV) in autumn, (iii) queen age, and (iv) weakness of the colonies in autumn. No effects could be observed for Nosema spec. or pesticides. The implications of these findings will be discussed.

The mating sign that each drone leaves when mating with a queen essentially consists of mucus gland proteins. We employed a Representational Difference Analysis (RDA) methodology to identify genes that are differentially expressed in mucus glands during sexual maturation of drones. The RDA library for mucus glands of newly emerged drones was more complex than that of 8 day-old drones, with matches to 20 predicted genes. Another 26 reads matched to the Apis genome but not to any predicted gene. Since these ESTs were located within ORFs they may represent novel honey bee genes, possibly fast evolving mucus gland proteins. In the RDA library for mucus glands of 8 day-old drones, most reads corresponded to a capsid protein of deformed wing virus, indicating high viral loads in these glands. The expression of two genes encoding venom allergens, acid phosphatase-1 and hyaluronidase, in drone mucus glands argues for their homology with the female venom glands, both associated with the reproductive system.

The occurrence and spatial distribution of deformed wing virus (DWV), black queen cell virus (BQCV), and Kashmir bee virus (KBV) were assessed in 294 honeybee colonies in Spain by employing a SYBR-Green based real time RT-PCR. 60% of them were positive for both DWV and BQCV, and those two viruses were detected in 84% and 68% of the samples, respectively. Conversely, KBV was detected in only 1.7% of the samples. Increments in the number of bee colonies per region, adjusted by the number of samples collected, were associated with increased risk of finding DWV, BQCV, and KBV, as estimated by mixed Bayesian regression models. The residual risk for DWV, BQCV, and KBV decreased northerly and westerly, suggesting that factors or forces that favour the presence of these viruses could be more prevalent in southern and eastern regions of Spain. Results will be useful in the design and implementation of effective honeybee viral disease control and surveillance programs in Spain.

We have developed a specific assay for the detection of deformed wing virus (DWV) in Apis mellifera L. and Varroa destructor based on the reverse transcriptase polymerase chain reaction (RT-PCR) technology. Primers were designed from the sequence of a 4700 nucleotides cDNA fragment located in the 3'-end of the DWV genome. This fragment encodes a single open reading frame of 1565 amino acids showing similarity to viral RNA dependent RNA polymerase consensus motif. RT-PCR assays from DWV infected individual mite or bee produced a 395 nucleotide DNA fragment clearly identifiable by agarose gel electrophoresis. The signal in bees having deformed wings was significantly higher than in normal ones. A search for DWV in 40 colonies showed that DWV is broadly distributed in bee colonies and mites. As an average, greater virus prevalence of virus was detected in bees collected in autumn compared to bees collected in spring or during the summer period. deformed wing virus (DWV) / diagnosis / bee virus / Varroa destructor

Actuellement nous ne connaissons pas en Europe de colonies d'abeilles ou l'on puisse laisser la population d'acariens V. jacobsoni se developper librement sans que celle-ci n'occasionne des degâts aux colonies. Il est de plus en plus evident que la cause de l'effondrement des colonies n'est pas due directement a l'infestation par l'acarien, mais due plutot aux infections virales que l'on sait, ou suppose, etre liees a V. jacobsoni [2, 8, 10, 11]. Le virus de la paralysie aigue (APV) a ete trouve dans differents pays dans des colonies fortement infestees [2]. On n'a pourtant jamais montre sur le terrain que l'APV causait la mort des colonies s'il n'y avait pas d'infestation simultanee par V. jacobsoni [2, 6]. La presence de plus en plus frequente dans les colonies infestees d'abeilles ayant des ailes non developpees ou deformees a ete associee a l'infection par le virus des ailes difformes (DWV) [13]. Ce virus a ete trouve dans des colonies fortement infestees en Europe, Afrique et Asie [2] et sa presence a ete mise en relation avec l'effondrement de colonies fortement infestees par l'acarien au Royaume-Uni [17]. Cette etude vise a rechercher la frequence des virus dans les colonies nullement, faiblement ou fortement infestees de huit ruchers repartis dans les pays nordiques. Deux ruchers experimentaux totalisant 13 colonies ont ete etablis en 1994, dans lesquels on a laisse la population d'acariens se developper librement jusqu'a la mort des colonies. Cinq ruchers avec une infestation faible ou controlee et un rucher non infeste ont ete egalement echantillonnes durant un an au moins. Le taux de mort naturelle de l'acarien a ete suivi dans toutes les colonies experimentales. Des echantillons d'abeilles vivantes ont ete preleves tous les mois et neuf virus differents ont ete recherches par immunodiffusion. Des abeilles mortes d'un rucher fortement infeste (Gotland) ont ete prelevees tous les mois durant l'annee de l'effondrement de la colonie. Des analyses serologiques pour detecter les virus ont ete effectuees sur un total de 411 echantillons d'abeilles provenant de 42 colonies. On n'a trouve aucun degât ni aucun symptome de maladie dans aucun des six ruchers qui etaient faiblement ou pas du tout infestes et les seuls virus detectes dans ces ruchers etaient le virus (CWV) et le virus (BQVC) (tableau I). Le virus le plus frequemment detecte chez les abeilles vivantes dans tous les ruchers a ete le CWV. Dix pour cent environ des echantillons d'abeilles vivantes etaient positifs a l'antiserum du CWV et cinq des ruchers avaient au moins une colonie presentant des quantites detectables de ce virus a chaque echantillonnage en 1994. La detection du CWV chez les abeilles vivantes etait neanmoins independante de la taille de la population d'acariens et, dans cette etude, on n'a pas pu montrer d'etroite relation entre la presence du virus et l'effondrement des colonies. Dans l'une des colonies fortement infestees (Gotland) on a trouve le DWV associe a l'effondrement de la colonie (tableaux I et II). Dans ce rucher infeste de facon variable mais forte, sept des huit colonies sont mortes (figure 1a). Toutes les colonies de ce rucher ont eu au moins un echantillon d'abeilles mortes infecte avec le DWV et dans certaines colonies on a pu detecter le virus dans les echantillons d'abeilles vivantes, plusieurs semaines ou meme plusieurs mois avant l'effondrement total (tableau II). Lorsque dans ce rucher certains niveaux de mortalite des acariens etaient atteints, les echantillons des abeilles vivantes et des abeilles mortes avaient toujours une reaction positive au DWV (figure 2). Pourtant les colonies avec une faible mortalite d'acariens pouvaient elles aussi avoir des echantillons positifs

Populations of Apis mellifera and Apis cerana in China and Vietnam were surveyed in order to study possible pathogen spill-over from European to Asian honeybees. This is the first survey of the prevalence of honeybee pathogens in apiaries in Vietnam, including pathogen prevalence in wild A. cerana colonies never in contact with A. mellifera. The bee samples were assayed for eight honeybee viruses: deformed wing virus (DWV); black queen cell virus (BQCV); sac brood virus (SBV); acute bee paralysis virus (ABPV); Kashmir bee virus (KBV); Israeli acute paralysis virus (IAPV); chronic bee paralysis virus (CBPV); and slow bee paralysis virus (SBPV), for two gut parasites (Nosema ssp.) and for the causative agent for European foulbrood (Melissococcus plutonius). The Vietnamese samples were assayed for Acarapis woodi infestation. No clear evidence of unique inter-specific transmission of virus infections between the two honeybee species was found. However, in wild A. cerana colonies, the only virus infection detected was DWV. With findings of IAPV infections in Chinese samples of A. cerana colonies in contact with A. mellifera, inter-specific transmission of IAPV cannot be ruled out. BQCV was the most prevalent virus in managed colonies irrespective of bee species. We did not detect the causative agent of European foulbrood, M. plutonius in wild or isolated colonies of A. cerana in Vietnam or China; however, low incidence of this pathogen was found in the Asian host species when in contact with its European sister species. No evidence for the presence of A. woodi was found in the Vietnamese samples.