Deformed wing virus is not related to honey bees' aggressiveness

Guards of Cyprian honey bee colonies, Apis mellifera cypria, display a great defensive behaviour against hornets' attacks. The deformed wing virus (DWV) and the kakugo virus (KV) genomes are very similar, but unlike KV, the presence of DWV is not related to honey bees' aggressiveness. This discrepancy is further discussed

Localization of deformed wing virus infection in queen and drone Apis mellifera L

The distribution of deformed wing virus infection within the honey bee reproductive castes (queens, drones) was investigated by in situ hybridization and immunohistology from paraffin embedded sections. Digoxygenin or CY5.5 fluorochrome end-labelled nucleotide probes hybridizing to the 3' portion of the DWV genome were used to identify DWV RNA, while a monospecific antibody to the DWV-VP1 structural protein was used to identify viral proteins and particles. The histological data were confirmed by quantitative RT-PCR of dissected organs. Results showed that DWV infection is not restricted to the digestive tract of the bee but spread in the whole body, including queen ovaries, queen fat body and drone seminal vesicles

Prevalence and Seasonal Variations of Six Bee Viruses in Apis mellifera L. and Varroa destructor Mite Populations in France

A survey of six bee viruses on a large geographic scale was undertaken by using seemingly healthy bee colonies and the PCR technique. Samples of adult bees and pupae were collected from 36 apiaries in the spring, summer, and autumn during 2002. Varroa destructor samples were collected at the end of summer following acaricide treatment. In adult bees, during the year deformed wing virus (DWV) was found at least once in 97% of the apiaries, sacbrood virus (SBV) was found in 86% of the apiaries, chronic bee paralysis virus (CBPV) was found in 28% of the apiaries, acute bee paralysis virus (ABPV) was found in 58% of the apiaries, black queen cell virus (BQCV) was found in 86% of the apiaries, and Kashmir bee virus (KBV) was found in 17% of the apiaries. For pupae, the following frequencies were obtained: DWV, 94% of the apiaries; SBV, 80% of the apiaries; CBPV, none of the apiaries; ABPV, 23% of the apiaries; BQCV, 23% of the apiaries; and KBV, 6% of the apiaries. In Varroa samples, the following four viruses were identified: DWV (100% of the apiaries), SBV (45% of the apiaries), ABPV (36% of the apiaries), and KBV (5% of the apiaries). The latter findings support the putative role of mites in transmitting these viruses. Taken together, these data indicate that bee virus infections occur persistently in bee populations despite the lack of clinical signs, suggesting that colony disease outbreaks might result from environmental factors that lead to activation of viral replication in bees

Viral load estimation in asymptomatic honey bee colonies using the quantitative RT-PCR technique

Honey bee (Apis mellifera L.) colonies are subjected to many persistent viral infections that do not exhibit clinical signs. The identification of criteria that could identify persistent or latent infections in bee colonies is a challenging task for field investigators and beekeepers. With this aim in view, we developed a molecular method to estimate the viral loads for six different RNA viruses in bee and mite individuals collected from seemingly healthy colonies (360 colonies). The data showed very large viral titres in some samples ($>$10$^{9}$ copies per bee or mite). Discrepancies between adults and pupae viral RNA loads and, in several instances, significant seasonal variations among viruses were observed. The high titres of some RNA viruses recorded in mites confirm that Varroa destructor could promote viral infections in colonies

Comparative analysis of deformed wing virus (DWV) RNA in Apis mellifera and Varroa destructor

A two step quantitative RT-PCR assay was validated to monitor the deformed wing virus (DWV) RNA loads in Apis mellifera L. and Varroa destructor. A pair of primers hybridising in a conserved domain of the putative DWV RNA polymerase gene region was designed. These primers amplified a 69-nucleotide fragment which was quantified using the SYBR-green chemistry. The experimental validation of the method showed that the RNA extraction and cDNA synthesis steps were responsible for the greatest variability in the results while assays repeated on different PCR plates were reproducible. Quantitative RTPCR analysis on drone bee prepupae showed that DWV RNA loads were higher in cells parasitized by several mother mites. In workers, DWV prevalence was directly correlated to mite infestation and DWV was detected in all the bee developmental stages except in eggs. Very important DWV RNA loads could be recorded even in absence of clinical sign; however bees emerging with deformed wings were predominantly infected by DWV. In mites collected on emerging bees, the DWV RNA yields varied from 10(4) to 10(6) copies per mite but might exceed 10(8) copies in some case

Polymerase Chain Reaction detection of deformed wing virus (DWV) in Apis mellifera and Varroa destructor

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 perio