Effect of Oral Administration of 1,3-1,6 β-Glucans in DWV Naturally Infected Newly Emerged Bees (Apis mellifera L.)

Abstract

Honeybee pathogens have an important role in honeybee colony mortality and colony losses; most of them are widely spread and necessitate worldwide solutions to contrast honeybee’s decline. Possible accepted solutions to cope with the spread of honeybee’s pathogens are focused on the study of experimental protocols to enhance the insect’s immune defenses. Honeybee’s artificial diet capable to stimulate the immune system is a promising field of investigation as ascertained by the introduction of 1,3-1,6 β-glucans as a dietary supplement. In this work, by collecting faecal samples of honeybees exposed to different dietary conditions of 1,3-1,6 β-glucans (0.5% and 2% w/w), it has been possible to investigate the Deformed wing virus (DWV) viral load kinetic without harming the insects. Virological data obtained by a one-step TaqMan RT-PCR highlighted the ability of 1,3-1,6 β-glucans to reduce the viral load at the 24th day of rearing. The results indicated that the diet supplemented with 1,3-1,6 β-glucans was associated with a dose-dependent activation of phenoloxidase. The control group showed a higher survival rate than the experimental groups. This research confirmed 1,3-1,6 β-glucans as molecules able to modulate honeybees’ defense pathways, and this is the first report in which the kinetic of DWV infection in honeybee faeces has been monitored by a RT-qPCR.

Detection of Lotmaria passim, Crithidia mellificae and Replicative Forms of Deformed Wing Virus and Kashmir Bee Virus in the Small Hive Beetle (Aethina tumida)

“…However, the multifaceted host–parasite interaction [ 77 ] allows multiple pathways, including oral–oral and fecal–oral transmission. Adult SHBs also may acquire honey bee pathogens by feeding on bee products that are contaminated with multiple microorganism species [ 41 , 47 , 48 , 78 ], cannibalizing bee carcasses, or ingesting infected faeces [ 78 , 79 , 80 ].…”

Effect of Honey and Syrup Diets Enriched with 1,3-1,6 β-Glucans on Honeybee Survival Rate and Phenoloxidase Activity (Apis mellifera L. 1758)

“…This result contradicts the prediction that the supplementation of β-glucans would determine a reduction in the survival rate of the bees. However, Felicioli and colleagues [ 7 ] observed a higher survival rate in newly emerged bees fed only on syrup than those fed with syrup enriched with 0.5% β-glucans in a 24-day experimental trial. In detail, Felicioli and colleagues [ 7 ] investigated the effects of β-glucans administration for 24 days on naturally DWV-infected newly emerged bees.…”

“…However, Felicioli and colleagues [ 7 ] observed a higher survival rate in newly emerged bees fed only on syrup than those fed with syrup enriched with 0.5% β-glucans in a 24-day experimental trial. In detail, Felicioli and colleagues [ 7 ] investigated the effects of β-glucans administration for 24 days on naturally DWV-infected newly emerged bees. The negative effects of β-glucans supplementation in the syrup-based diet of bees recorded by Felicioli and colleagues [ 7 ], and not present in the current investigation, could be due to the synergic negative effect of β-glucans with DWV pathology.…”

“…No suitable and legal drugs that work against bee pathogens are yet available. For this reason, the administration of lactic acid bacteria [ 1 ], essential oils [ 2 ], and supplement diets [ 3 , 4 , 5 , 6 , 7 ] were tested in order to elicit information regarding the immune systems of honeybees, minimize the occurrence of toxic residues in hive products, and prevent the development of resistance phenomena to drugs. A honeybee colony is a super-organism characterized by two levels of innate immunity: a social-scale immunity and an individual-scale immunity [ 8 , 9 ].…”

“…Mowlds et al [ 25 ] observed a potentiated immune response in Galleria mellonella larvae after inoculation with high doses of β-glucans. Furthermore, Mazzei et al [ 23 ] and Felicioli et al [ 7 ] suggested that β-glucans might contribute to increased honeybee resistance to viral infection by observing the effects of oral administration of this natural molecule in a challenge test with deformed wing virus (DWV) on newly emerged bees. The aim of this study was to investigate the effect of the inclusion of β-glucans in honey- and syrup-based diets in apparently healthy newly emerged and nurse bees after 96 h of feeding.…”