Virulenzmechanismen der Viren von Honigbienen

• Forschungsstelle: BLV
• Projektnummer: 1.08.01
• Projekttitel Englisch: Virulence mechanisms of honeybee viruses

Schlüsselwörter (Englisch)

Apis mellifera, behavioural ecology, DWV (Deformed Wing Virus), honeybee, overwintering, virulence, viruses.

Kurzbeschreibung (Englisch)

Honeybees are essential pollinators in Switzerland. Beekeepers were recently confronted in Switzerland and worldwide by reoccurring severe colony losses in winter. This is a serious challenge and may lead to economic and ecologic effects given adequate measures are not taken by both beekeepers and veterinary authorities. Viruses were suspected to play a role for these winter losses but their diagnosis was problematic. The recent development of diagnostic tools enabled accurate diagnosis and showed that weak and dead colonies have more often higher viral loads. However, the causal link between virus loads and the loss of colonies remains unclear. Similarly, the role of Varroa destructor is not well understood. Here we will investigate the proximate virulence mechanisms at the colony level and the role of V. destructor using Deformed Wing Virus (DWV) and winter bees as model systems. We will address life expectancy of winter bees with persistent infestations but without clinical symptoms, behavioural and physiological changes in such workers and the impact of V. destructor on virulence. This will clarify the relevance of viruses for winter losses, thereby initiating emergency measurements and the development of adequate methods to reduce the detrimental impact on beekeepers and agriculture in Switzerland (estimated costs per year ~52.5 Mio CHF; see Appendix 1) and elsewhere.

Projektziele (Englisch)

We are aiming to identify the proximate virulence mechanisms of honeybee viruses at the individual and colony level, which are indicated by circumstantial evidence but have not actually been proven yet. This may provide the causal link between the observed high viral loads and the decline and loss of colonies during and after overwintering in the field. We will focus on life expectancy of winter bees (goal 1), behavioural and physiological changes in workers induced by persistent viral infestations (goal 2) and the role of the ectoparasitic mite V. destructor for the virulence of these viruses (goal 3). We will also approximate genetic variance of resistance to viral diseases, which is a first step towards breeding of virus resistant strains. These goals will provide the crucial background information, which will help to mitigate the effects of severe winter losses on beekeeping and pollination in Switzerland. Please refer to 7.4 for details on the respective intermediate goals. Given negative results of this study will potentially indicate that viruses are not inducing subclinical effects and thereby colony losses (what we consider very unlikely), it will then nevertheless enable to exclude a major suspect from the world-wide bee losses problem. Thus, this study will provide a win-win situation for both beekeepers and the BVET independent of its actual outcome.

Umsetzung und Anwendungen (Deutsch)

31.05.2007: Umsetzung: Empfehlungen für Imker Grundlagen zur Bekämpfung des Bienensterbens (Selektionssitzung 2007/mvo)

Umsetzung und Anwendungen (Englisch)

The project will provide essential information on the virulence mechanisms of honeybee viruses at the individual and colony level and on the role of V. destructor. This will enable the BVET and other Swiss authorities to adequately adjust honeybee diagnosis and beekeeping. Given our data will support that V. destructor is crucial for virulence and that viruses do contribute to colony losses, then immediate measures need to be taken. These will include e.g. even stricter standards for V. destructor mite control in Switzerland. Furthermore, imports of colonies and/or queens should include virus diagnoses. Moreover, our institute will adjust its research towards methods for reducing the impact of viruses, e.g. application of propolis, which has antiviral activities. This will help mitigating the recent severe winter losses of honeybee colonies in Switzerland and other temperate regions of the world (rest of Europe, USA, China), which cause enormous costs (~52.5 Mio CHF per year only in Switzerland; see Appendix 1). In any case, our project will enable the BVET to find answers for one of the major hypotheses for the massive losses of honeybee colonies, which have recently raised considerable public attention in Switzerland and worldwide.

Publikationen / Ergebnisse (Englisch)

Dainat, B.; Ken, T.; Berthoud, H.; Neumann, P. (2009) The ectoparasitic mite Tropilaelaps mercedesae (Acari: Laelapidae) as a vector of honeybee viruses, Insectes Sociaux 56: 40–43.

Dainat, B.; Chen, YP.; Evans, JD.; Neumann, P. (2011) Sampling and RNA quality for diagnosis of honey bee viruses using quantitative PCR, Journal of Virological Methods, 174: 150–152.

Dainat, B.; Kuhn, R.; Cherix, D.; Neumann, P. (2011) A scientific note on the ant pitfall for quantitative diagnosis of Varroa destructor, Apidologie, 42:740–742.

Dainat, B.; Chen, YP.; Neumann, P.; Evans, JD. (2012) Predictive Markers of Honey Bee Colony Collapse, PLoS ONE, 7: 2, e32151

Dainat, B.; vanEngelsdorp, D.; Neumann, P. (2012) Colony collapse disorder in Europe, Environmental Microbiology Reports 4: 1, 123–125

Dainat, B.; Evans, JD.; Chen, YP.; Neumann, P. (2012) Dead or Alive: Deformed Wing Virus and Varroa destructor Reduce the Life Span of Winter Honeybees. Appl. Environ. Microbiol. 78: 4, 981.

Dainat, B.; Evans, JD.; Chen, YP.; Neumann, P.(2010) Honey bee drifting in Winter under infection pressure: a surviving mechanisms? in preparation.

Dainat, B.; Evans, JD.; Gauthier, L.; Neumann, P. (2012) Ubiquitous occurrence of trypanosomatid parasites in honeybee colonies, Apis mellifera L. In Proceedings des Eurbee 5, European conference of Apidology, 3-7 Sept 2012, p.100. Manuscript in prep.

10 conference proceedings

16 publications in Beekeeping journals (in I, F, D).

Zugehörige Dokumente

• 1.08.01 Datenblatt [PDF] 09 kB
• AEM_2012.pdf [PDF] 530 kB
• Predictivemarker.pdf [PDF] 453 kB
• RNA_VirusesDiagnosis_final_JvirMeth_2011.pdf [PDF] 177 kB