Varroa destructor is an effective vector of Israeli acute paralysis virus in the honeybee, Apis mellifera

Abstract

The Israeli acute paralysis virus (IAPV) is a significant marker of honeybee colony collapse disorder (CCD). In the present work, we provide the first evidence that Varroa destructor is IAPV replication-competent and capable of vectoring IAPV in honeybees. The honeybees became infected with IAPV after exposure to Varroa mites that carried the virus. The copy number of IAPV in bees was positively correlated with the density of Varroa mites and time period of exposure to Varroa mites. Further, we showed that the mite-virus association could possibly reduce host immunity and therefore promote elevated levels of virus replication. This study defines an active role of Varroa mites in IAPV transmission and sheds light on the epidemiology of IAPV infection in honeybees.Varroatosis is one of the most serious honeybee diseases caused by a parasitic mite, Varroa destructor. Varroa mites use their piercing mouthparts to suck out haemolymph from honeybees. The repeated feeding results in a decline of colony vigour, shortened life span of the honeybees and eventual perishing of colonies (Rosenkranz et al., 2010). Further, the feeding of Varroa mites gives mites the potential to act as vectors of bee diseases, presenting additional threats to bee health. The role of Varroa mite as a vector in the transmission of bee viruses has been well documented (Bowen-Walker et al., 1999;Chen et al., 2004;Shen et al., 2005). However, it has not yet been demonstrated if this mite could act as a vector of Israeli acute paralysis virus (IAPV), a virus that was tightly correlated with honeybee colony collapse disorder (CCD), a malady that has decimated honeybee colonies across the USA (Cox-Foster et al., 2007;vanEngelsdorp et al., 2007) and around the world (Neumann & Carreck, 2010). The present study was undertaken to determine the possible role of Varroa mites in the transmission of IAPV and in the promotion of its replication in honeybees. Moreover, the expression of immune-related gene transcripts, apidaecin and eater that are involved in honeybee humoral and cellular immunity (Ertürk-Hasdemir & Silverman, 2005;Evans et al., 2006;Kocks et al., 2005;Simone et al., 2009) was measured in Varroa-challenged bees. Apidaecin is a proline-rich peptide and one of the most prominent components of the honeybee humoral defence against microbial invasion (Evans et al. 2006). Eater is a member of epidermal growth factor-family protein involved cellular immunity, as it plays an important role in phagocytosis (Ertürk-Hasdemir & Silverman, 2005;Kocks et al., 2005). Two strong bee colonies (i.e. with at least seven frames filled with capped brood and food, and covered with adult bees) and two weak colonies (i.e. with a low-adult bee population and fewer than four frames with a small patch of capped brood) that were determined to be free of IAPV infection by RT-PCR assay were selected for transmission studies. Further, the expression levels of vitellogenin, an indicator of the general health of the colonies (Amdam et al., 2005;Simone et al., 2009), were det...

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

“…This virus was first diagnosed in Israel, where it reportedly caused large scale honeybee mortality and symptoms included trembling wings and paralysis (Maori et al, 2007;Palacios et al, 2008). The detection of IAPV in Varroa mites sampled during this study is therefore of concern, especially since it was recently confirmed that Varroa mites are capable of transmitting IAPV to honeybees (Di Prisco et al, 2011). However, IAPV was only recorded during spring 2010 in two apiaries, showing a low prevalence (Table 2).…”

Controlling honeybee pathogen by using neem and Barbaka plant extracts

“…[1] This disappearing of the bees may lead to serious consequences. Gut microflora and parasitic mites are likely to cause this phenomenon, [2] but little is known about the honeybee gut bacteria, where there might be potential pathogens. However, a well-known honeybee pathogenic bacteria (Paenibacillus larvae) that affects honeybee larvae causes a significant decrease in the honeybee population.…”

Short communication. Presence, quantification and phylogeny of Israeli acute paralysis virus of honeybees in Andalusia (Spain)

“…Thus the present study focused on the potential association of IAPV with colony weakening represented by colonies with worse health status. Worse health status indicators included presence of clear IAPV disease symptoms, such as paralysis, loss of hair or inability to fly, depopulation, kleptoparasitism of stronger neighbouring colonies, diagnosed disease potentially associated with immune depletion such as chalkbrood (Glinski & Buczek, 2003;Aronstein & Murray, 2010); and problems to control Varroa destructor -mite infestation might lead to immunosuppression (Yang & CoxFoster, 2005), which may facilitate IAPV replication, as Varroa destructor has been described as an IAPV vector (Di Prisco et al, 2011). Sanitary status data were collected from the epidemiological surveys conducted by technicians upon sampling.…”

“…More recently, Martin et al (2012) reported similar results on the Hawaiian islands with IAPV loads in the order of 10 7 GEC/bee in covert infections not associated with colony collapse, but with lower prevalences (only 3 colonies of 293 were infected with IAPV). Based on the recent description of the V. destructor mite as a transmitter of IAPV (Di Prisco et al, 2011), future studies should also determine IAPV loads in pupae and V. destructor to better understand the biology of the virus. In this study, only the effect of IAPV presence and load was considered on weakening colonies in Andalusia.…”