Effects of Synthetic Acaricides and Nosema ceranae (Microsporidia: Nosematidae) on Molecules Associated with Chemical Communication and Recognition in Honey Bees

Abstract

Acaricides and the gut parasite Nosema ceranae are commonly present in most productive hives. Those stressors could be affecting key semiochemicals, which act as homeostasis regulators in Apis mellifera colonies, such as cuticular hydrocarbons (CHC) involved in social recognition and ethyl oleate (EO) which plays a role as primer pheromone in honey bees. Here we test the effect of amitraz, coumaphos, tau-fluvalinate and flumethrin, commonly applied to treat varroosis, on honey bee survival time, rate of food consumption, CHC profiles and EO production on N. ceranae-infected and non-infected honey bees. Different sublethal concentrations of amitraz, coumaphos, tau-fluvalinate and flumethrin were administered chronically in a syrup-based diet. After treatment, purified hole-body extracts were analyzed by gas chromatography coupled to mass spectrometry. While N. ceranae infection was also shown to decrease EO production affecting survival rates, acaricides showed no significant effect on this pheromone. As for the CHC, we found no changes in relation to the health status or consumption of acaricides. This absence of alteration in EO or CHC as response to acaricides ingestion or in combination with N. ceranae, suggests that worker honey bees exposed to those highly ubiquitous drugs are hardly differentiated by nest-mates. Having determined a synergic effect on mortality in worker bees exposed to coumaphos and Nosema infection but also, alterations in EO production as a response to N. ceranae infection it is an interesting clue to deeper understand the effects of parasite-host-pesticide interaction on colony functioning.

Beneficial Bacteria and Plant Extracts Promote Honey Bee Health and Reduce Nosema ceranae Infection

“…Fifty individuals per treatment (three replicates) were confined to experimental cages. Confinement devices consisted in transparent and ventilated plastic jars (900 cm 3 ) with inputs for gravity feeding devices and a removable side door [ 42 ]. Newly emerged honey bees were fed with freshly prepared spores of N. ceranae resuspended in sugar syrup according to Porrini et al [ 43 ].…”

“…Stored pollen (beebread) was used as a protein and lipids source in most of the experiments as pollen was found to deeply influence honeybees response to N. ceranae infection, affecting the disease severity [ 44 ]. It was manually collected from combs and slightly dried in an oven (50 °C for 24 h), homogenised and treated with UV radiation to diminish the viability of any possible N. ceranae spores present in the pollen [ 42 ]. In each assay, honey bees received potable tap water ad libitum.…”

Seed Meals from Brassica nigra and Eruca sativa Control Artificial Nosema ceranae Infections in Apis mellifera

“…Although fumagillin may reduce the N. ceranae infection, its use is not legal in several countries as it may build residues in the bee products and result in antibiotic resistance; thus, promoting parasite proliferation [ 17 ]. Recently, natural and synthetic compounds were tested as a treatment against nosemosis Type C [ 18 , 19 , 20 , 21 , 22 , 23 ]. A commercial dietary supplement based on herbs (garlic and cinnamon) and vitamins, the ApiHerb ® (Chemicals Laif S.p.A., Padua, Italy) showed a significant effect against N. ceranae infections [ 17 , 24 , 25 ] on the microbial profile of the honey bee midgut [ 26 , 27 ].…”

Proteasome Inhibition Is an Effective Treatment Strategy for Microsporidia Infection in Honey Bees

“…Thus, efforts to find new treatment strategies are critical to protect honey bees from this parasite [ 16 , 19 ]. Many promising alternatives strategies for control of N. ceranae infection have now been pursued, including important studies exploring other small molecules, RNAi, probiotics, and various natural compounds ([ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ] and work prior to 2020 reviewed in [ 30 ]). Eukaryotic pathogens can be challenging to combat using chemical antimicrobials because of the phylogenetic closeness with their hosts, and microsporidia are no exception.…”