Deformed Wing Virus (DWV) infection. Impact on honey bee queen health

Size: px

Start display at page:

Download "Deformed Wing Virus (DWV) infection. Impact on honey bee queen health"

Shana Clarke
5 years ago
Views:

1 Federal Departement of Economic Affairs DEA Agroscope Liebefeld-Posieux Research Station ALP Deformed Wing Virus (DWV) infection Impact on honey bee queen health Laurent Gauthier Sept. 18 / 2009

2 Introduction Beekeeping requires more technical knowledge and efforts than before Beekeeping requires good quality queens The queen s fitness may affect the strength of the colony and thus the honey production 3 main problems related to the queen are observed: Queen cell abortion Requeening of young mated queens Drone layer queens 2

3 DWV prevalence and viral loads in : Apiaries Colonies Workers Honey bee tissues DWV infections in queen 3

4 The DWV is highly prevalent in apiaries DWV France 97% Denmark 57% Austria 91% IAPV- SBV CBPV ABPV KBV BQCV Reference 86% 28% 58% 17% 86% Tentcheva et al % 4% 11% 1% 1% Nielsen et al % 9% 68% 0% 30% Berenyi et al.2006 Hungary 72% 2% 0% 37% 0% 54% Forgach et al UK 97% 1,4% 0% 29% 0% 1,4% Baker and Schr Switzerland 100% 61% 23% 70% 0% 46% Berthoud et al Spain 84% 1.7% 68% Kukielka et al

5 Prevalence of viral infections and seasonal variations 100 Positive colonies (%) SPRING SUMMER FALL 0 DWV SBV CBPV ABPV BQCV KBV (N = 360 colonies) (Tentcheva et al. AEM 2004) 5

6 High DWV loads can be detected in colonies at the end of the year ADULTS PUPAE #106 colonies SPRING SUMMER FALL SPRING SUMMER FALL 1 MITES High Low Not detected (Gauthier et al. Apidologie 2007) 6

7 High DWV loads can be detected in workers 99% DWV positive workers DWV Relative expression levels of DWV RNA among 90 workers 7

8 The DWV is detected in various tissues Head Thorax Abdomen: Digestive tract Fat body Reproductive tract (queen and drone) 8

9 The DWV uses different strategies to propagate Horizontal transmission Vertical transmission Varroa mediated transmission 9

10 Detection of DWV in a worker midgut by in situ hybridization 10

11 Detection of DWV in seminal vesicles by in situ hybridization mucosa spermatozoa 11

12 Varroa destructor amplifies viral infections in honey bees Mites infested colonies August 2006 Acaricide treatment October 2006 Bees are collected on frames and analyzed for viral loads and vitellogenin titers 12

13 RNA fold expression TREATED UNTREATED Varroa destructor reactivates viral infections in honey bees DWV 350 RNA fold expression TREATED UNTREATED ABPV 13

14 Varroa destructor / viruses reduce the vitellogenin gene expression in honey bees Vitellogenin RNA expression was reduced by 20 times in untreated bees Altered Physiology in Worker Honey Bees (Hymenoptera: Apidae) Infested with the Mite Varroa destructor (Acari: Varroidae): A Factor in Colony Loss During Overwintering? Amdam et al., J. Econ. Entomol. (2004) 14

15 DWV infects honey bee queens Virgin queens: DWV = 37% (N=40) Mated queens: DWV = 100% (N= 54) Higher DWV prevalence in mated queens 15

16 Relative expression levels of DWV RNA in 24 mated queens (ovaries and abdomen) OVARY ABDOMEN High variations in DWV titers in the samples Higher prevalence in the abdomen High DWV titers in ovaries for some queen samples 16

17 Histological analysis of DWV infections in the ovary Normal ovaries empty ovary 17

18 Detection of DWV in the upper part of the ovary by in situ hybridization 18

19 Detection of DWV in the lower part of the ovary by in situ hybridization DWV RNA is located at the periphery of the oocyte 19

20 Dead cells are observed in some follicles Normal follicles Dead follicles 20

21 Electron microscopy examination show viral paracrystals in the follicular cells Peritoneal epithelium 21

22 Virus paracrystals observed in a follicle by electron microscopy Detail 22

23 Conclusions DWV infections are a potential threat for the honey bee colony health Different strategies for transmission Wide tissue distribution Presence in queen organs (fat body, ovaries, digestive tract, head) Potential effect on the bee physiology The impact of these infections on the whole colony health depends probably of the DWV prevalence among workers and on the virus titers in each infected workers However these infections can be counteracted efficiently by the use of efficient mite treatments 23

24 Collaborators Université de Montpellier and INRA (UMR1231) Marc Ravallec François Cousserans Max Bergoin Diana Tentcheva Julie Fievet Montpellier SupAgro Magali Tournaire Marc Colin Sandrine Jouve Upsalla and Belfast Universities Joachim de Miranda ALP institute Benjamin Dainat 24

- Determining the Causes - Dr. Diana Cox-Foster Pennsylvania State University

Colony Collapse Disorder - Determining the Causes - Dr. Diana Cox-Foster Pennsylvania State University Honey Bees in US Agriculture and the Colony Collapse Disorder Essential for pollination of over 100