Dead or Alive: Deformed Wing Virus and Varroa destructor Reduce the Life Span of Winter Honeybees

Abstract

Elevated winter losses of managed honeybee colonies are a major concern, but the underlying mechanisms remain controversial. Among the suspects are the parasitic mite Varroa destructor, the microsporidian Nosema ceranae, and associated viruses. Here we hypothesize that pathogens reduce the life expectancy of winter bees, thereby constituting a proximate mechanism for colony losses. A monitoring of colonies was performed over 6 months in Switzerland from summer 2007 to winter 2007/2008. Individual dead workers were collected daily and quantitatively analyzed for deformed wing virus (DWV), acute bee paralysis virus (ABPV), N. ceranae, and expression levels of the vitellogenin gene as a biomarker for honeybee longevity. Workers from colonies that failed to survive winter had a reduced life span beginning in late fall, were more likely to be infected with DWV, and had higher DWV loads. Colony levels of infection with the parasitic mite Varroa destructor and individual infections with DWV were also associated with reduced honeybee life expectancy. In sharp contrast, the level of N. ceranae infection was not correlated with longevity. In addition, vitellogenin gene expression was significantly positively correlated with ABPV and N. ceranae loads. The findings strongly suggest that V. destructor and DWV (but neither N. ceranae nor ABPV) reduce the life span of winter bees, thereby constituting a parsimonious possible mechanism for honeybee colony losses.

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

“…These results are in contrast to other studies around the world where Varroa mites played a significant or central role in colony losses (Bailey and Ball, 1991;Brodschneider et al, 2010;Dainat et al, 2012b;Dietemann et al, 2012;Guzman-Novoa et al, 2010;Ritter, 1981;Rosenkranz et al, 2010;Schäfer et al, 2010;Shimanuki et al, 1994). Also, the close association between Varroa mites and viruses (especially DWV, ABPV) and the subsequent colony losses they usually cause (Berthoud et al, 2010;Dainat et al, 2012a;Martin et al, 2012) were not observed in this study. Even though some apiaries in this study were occasionally infested with multiple pathogens and parasites, no obvious signs of disease were observed; thereby suggesting that the savannah honeybee population studied is resistant to these assaults.…”

“…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).…”

A national survey of managed honey bee 2013–2014 annual colony losses in the USA

“…Mortality can be driven by a number of interacting factors, including the parasitic mite Varroa destructor , other parasites and diseases, nutrition, pesticides, and socioeconomic factors (Berthoud et al 2010;Dainat et al 2012a;Dainat et al 2012b;Ellis et al 2010;Le Conte et al 2010;Potts et al 2010a;vanEngelsdorp and Meixner 2010). From 1947 to 2008, the total US honey bee population has declined by 61 % vanEngelsdorp and Meixner 2010).…”

Viral and intestinal diseases detected in Apis mellifera in Central and Southern Chile

“…In fact, BQCV and DWV are the two most common and prevalent virus infections in A. mellifera worldwide (Zhang et al, 2012). In addition, DWV has been associated with honeybee colony losses, especially in overwintering mortalities in some places in the world (Highfield et al, 2009;McMenamin and Genersch, 2015) and DWV is known to be a lethal pathogen for honeybees when it occurs at high loads in association with the ectoparasite Varroa destructor (Dainat et al, 2012). BQCV mainly affects developing queen larvae and pupae in the capped-cell stage causing the death of future queen bees (Chen and Siede, 2007;McMenamin and Genersch, 2015).…”