RT-PCR analysis of Deformed wing virus in honeybees (Apis mellifera) and mites (Varroa destructor)

Abstract

Deformed wing virus (DWV) is a honeybee viral pathogen either persisting as an inapparent infection or resulting in wing deformity. The occurrence of deformity is associated with the transmission of DWV through Varroa destructor during pupal stages. Such infections with DWV add to the pathology of V. destructor and play a major role in colony collapse in the course of varroosis. Using a recently developed RT-PCR protocol for the detection of DWV, individual bees and mites originating from hives differing in Varroa infestation levels and the occurrence of crippled bees were analysed. It was found that 100 % of both crippled and asymptomatic bees were positive for DWV. However, a significant difference in the spatial distribution of DWV between asymptomatic and crippled bees could be demonstrated: when analysing head, thorax and abdomen of crippled bees, all body parts were always strongly positive for viral sequences. In contrast, for asymptomatic bees viral sequences could be detected in RNA extracted from the thorax and/or abdomen but never in RNA extracted from the head. DWV replication was demonstrated in almost all DWV-positive body parts of infected bees. Analysing individual mites for the presence of DWV revealed that the percentage of DWV-positive mites differed between mite populations. In addition, it was demonstrated that DWV was able to replicate in some but not all mites. Interestingly, virus replication in mites was correlated with wing deformity. DWV was also detected in the larval food, implicating that in addition to transmission by V. destructor DWV is also transmitted by feeding.

Seasonal prevalence of pathogens and parasites in the savannah honeybee (Apis mellifera scutellata)

“…The absence of DWV from the honeybee and Varroa mite samples collected during this study was unexpected given its high prevalence in apiaries around the world (Allen and Ball, 1996;Baker and Schroeder, 2008;Berényi et al, 2006;Chen and Siede, 2007;Ellis and Munn, 2005;Martin et al, 1998;Tentcheva et al, 2004a) and the close association of DWV with Varroa mites (Bailey and Ball, 1991;Bowen-Walker et al, 1999;Dainat et al, 2012a;Gisder et al, 2009;Martin et al, 2012;Yang and CoxFoster, 2005;Yue and Genersch, 2005). Recently, DWV was also found to be absent from wild A. m. scutellata drones collected in a South African Nature Reserve and honeybee samples from Uganda (Kajobe et al, 2010).…”

Evidence for antiseptic behaviour towards sick adult bees in honey bee colonies

“…consumption of food resources) and increased risk of epidemics. Deformed wing virus infected bees pose a threat for the colony as: (1) quite all the A. mellifera colonies are naturally infested by the Varroa destructor mite and the phoretic mites are able to horizontally transmit DWV to adult healthy bees when feeding on the bees' haemolymph (Santillán-Galicia et al, 2010); (2) DWV can be transmitted horizontally to larvae via larval food containing DWV (Gisder et al, 2009;Yue and Genersch, 2005); (3) the detection of DWV in the midgut content (Fievet et al, 2006) and bee faeces implies the possibility of a faecal-oral-route of transmission between adult bees. Even if handling sick individuals could increase horizontal transmission risk, there are evidence that this behaviour could be also trigger immunization of the hygenic individuals as demonstrate in termites (Traniello et al, 2002), in ants (Ugelvig and Cremer, 2007) and in bumblebee (Sadd and Schmid-Hempel, 2006).…”

Occurrence of parasites and pathogens in honey bee colonies used in a European genotype-environment interactions experiment

“…Deformed wing virus (DWV) is one of the most prevalent and commonly reported viruses in honey bees (Tentcheva et al, 2004;Ellis and Munn, 2005;Gauthier et al, 2007) and is strongly associated with V. destructor (Yue and Genersch, 2005;de Miranda et al, 2013). The presence of the mite has been shown to increase prevalence of the virus while at the same time reducing its diversity by selecting for a single strain (Martin et al, 2012).…”