Virus Status, Varroa Levels, and Survival of 20 Managed Honey Bee Colonies Monitored in Luxembourg Between the Summer of 2011 and the Spring of 2013

Abstract

Twenty managed honey bee colonies, split between 5 apiaries with 4 hives each, were monitored between the summer of 2011 and spring of 2013. Living bees were sampled in July 2011, July 2012, and August 2012. Twenty-five, medium-aged bees, free of varroa mites, were pooled per colony and date, to form one sample. Unlike in France and Belgium, Chronic Bee Paralysis Virus (CBPV) has not been found in Luxembourg. Slow Bee Paralysis Virus (SBPV) and Israeli Acute Paralysis Virus (IAPV) levels were below detection limits. Traces of Kashmir Bee Virus (KBV) were amplified. Black Queen Cell Virus (BQCV), Varroa destructor Virus-1 (VDV-1), and SacBrood Virus (SBV) were detected in all samples and are reported from Luxembourg for the first time. Varroa destructor Macula- Like Virus (VdMLV), Deformed Wing Virus (DWV), and Acute Bee Paralysis Virus (ABPV) were detected at all locations, and in most but not all samples. There was a significant increase in VDV-1 and DWV levels within the observation period. A principal component analysis was unable to separate the bees of colonies that survived the following winter from bees that died, based on their virus contents in summer. The number of dead varroa mites found below colonies was elevated in colonies that died in the following winter. Significant positive relationships were found between the log-transformed virus levels of the bees and the log-transformed number of mites found below the colonies per week, for VDV-1 and DWV. Sacbrood virus levels were independent of varroa levels, suggesting a neutral or competitive relationship between this virus and varroa.

A derived honey bee stock confers resistance to Varroa destructor and associated viral transmission

“…The crucial methodological and diagnostic implication of this, is that, at a minimum, compared to the viruses tested here, Varroa has significant additive power in predicting colony outcome. This additive effect may be explained by damage to the host’s fat body 12 , 21 , or additional latent pathogen transmission unaccounted for by single target measures 17 , and is corroborated by previous experimental evidence 76 , 83 , 101 , 136 . While such a trend does not dismiss the importance of Varroa -vectored viruses, it does suggest that the harm caused by Varroa feeding itself has been chronically underestimated, and implies that the established paradigm of Varroa -mediated colony loss may be incorrect.…”

“…When considering colony losses, the relative weightings of DWV, or indeed any of the viruses vectored by Varroa , have never been effectively isolated from the effect of Varroa feeding per se 12 . It should be noted that, as demonstrated here, other datasets have found variable causative influences of viral titres upon bee health 138 , and colony mortality 81 , 136 . Further, to date, no studies have been able to decouple Varroa -virus mortality correlations from Varroa mortality correlations at the colony-level.…”

“…Based on this, it is somewhat unclear as to why vectored viruses are assumed to be the prime, if not sole, causative agents of Varroa -mediated colony losses 38 , 139 , especially as the parasite’s mode of feeding necessitates organ damage 12 . Indeed, in certain cases, Varroa levels alone predict mortality, while viral titres fail to do so 83 , 136 . It is well established that by removing or controlling for Varroa mites, associated viruses may be managed indirectly 111 , 112 , thus, there is practical merit in focussing on Varroa , it being the upstream epidemiological factor.…”

Epidemiology of a major honey bee pathogen, deformed wing virus: potential worldwide replacement of genotype A by genotype B

“…a high low Thaduri et al (2018) 2010 Turkey Asia Apis mellifera 6 sites 100% 100% Tozkar et al (2015) 2010 USA N. America Apis mellifera 75 colonies 100% 3% Ryabov et al (2017) 2011 Tunisia Africa Apis mellifera 56 colonies 27% 7% Abdi et al (2018) 2011 UK Europe Bombus spp. 490 workers 3% 8% Fürst et al, 2014 2011–2012 Luxemburg Europe Apis mellifera 20 colonies 90% 100% Clermont et al (2015) 2012 Belgium Europe Apis mellifera 1 colony absent present Benaets et al (2017) 2012–2013 USA (Hawaii) Pacific Apis mellifera 4 NGS libs. a ...…”

Factors Associated with Honey Bee Colony Losses: A Mini-Review

“…Ectoparasitic mite [11,12] Acarapis woodi Tracheal mite [13] Varroa jacobsoni Ectoparasitic mite [14] Tropilaelaps clareae Ectoparasitic mite [15] Deformed wing virus A Viral pathogen [16][17][18][19][20] Deformed wing virus B (VDV1)…”