Effect of Immune Inducers on Nosema ceranae Multiplication and Their Impact on Honey Bee (Apis mellifera L.) Survivorship and Behaviors

Evaluation of Functional Properties of Some Lactic Acid Bacteria Strains for Probiotic Applications in Apiculture

This study evaluates the suitability of three lactic acid bacteria (LAB) strains-Lactiplantibacillus plantarum, Lactobacillus acidophilus, and Apilactobacillus kunkeei-for use as probiotics in apiculture. Given the decline in bee populations due to pathogens and environmental stressors, sustainable alternatives to conventional treatments are necessary. This study aimed to assess the potential of these LAB strains in a probiotic formulation for bees through various in vitro tests, including co-culture interactions, biofilm formation, auto-aggregation, antioxidant activity, antimicrobial activity, antibiotic susceptibility, and resistance to high osmotic concentrations. This study aimed to assess both the individual effects of the strains and their combined effects, referred to as the LAB mix. Results indicated no mutual antagonistic activity among the LAB strains, demonstrating their compatibility with multi-strain probiotic formulations. The LAB strains showed significant survival rates under high osmotic stress and simulated gastrointestinal conditions. The LAB mix displayed enhanced biofilm formation, antioxidant activity, and antimicrobial efficacy against different bacterial strains. These findings suggest that a probiotic formulation containing these LAB strains could be used for a probiotic formulation, offering a promising approach to mitigating the negative effects of pathogens. Future research should focus on in vivo studies to validate the efficacy of these probiotic bacteria in improving bee health.

Potential of Wormwood and Oak Bark-Based Supplement in Health Improvement of Nosema ceranae-Infected Honey Bees

Nosema ceranae, a microsporidian parasite, as one of the stressors that contribute to honey bee decline, has a significant negative impact on the longevity, productivity, and reproductive capacity of honey bee colonies. There are several different strategies for Nosema infection control, including natural-based and antibiotic-based products. In this study, we tested wormwood and oak bark-based supplement "Medenko forte" on survival, Nosema infection, oxidative stress, and expression of immune-related genes in artificially N. ceranae-infected bees. The results revealed a positive influence on the survival of Nosema-infected bees, irrespectively of the moment of supplement application (day 1, day 3, or day 6 after bee emergence), as well as reduction of Nosema loads and, consequently, Nosema-induced oxidative stress. Supplementation had no negative effects on bee immunity, but better anti-Nosema than immune-stimulating effects were affirmed based on expression levels of abaecin, defensin, hymenoptaecin, apidaecin, and vitellogenin genes. In conclusion, the tested supplement "Medenko forte" has great potential in the health protection of Nosema-infected bees. However, further investigations need to be performed to elucidate its mechanisms of action.

Pathogen- and host-directed pharmacologic strategies for control of Vairimorpha (Nosema) spp. infection in honey bees

Microsporidia are obligate intracellular parasites of the Fungal Kingdom that cause widespread infections in nature, with important effects on invertebrates involved in food production systems. The two microsporidian species Vairimorpha (Nosema) ceranae (and the less common Vairimorpha (Nosema) apis) can cause individual disease in honey bees and contribute to colony collapse. The efficacy, safety, and availability of fumagillin, the only drug currently approved to treat microsporidia infection in bees, is uncertain. In this review, we will discuss some of the most promising alternative strategies for the mitigation of Vairimorpha spp. with an emphasis on infection by V. ceranae, now the dominant species infecting bees. We will focus on pharmacologic interventions where the mechanism of action is known and examine both pathogen-directed and host-directed approaches. As limiting toxicity to host cells has been especially emphasized in treating bees that are already facing numerous stressors, strategies that disrupt pathogen-specific targets may be especially advantageous. Therefore, efforts to increase the knowledge and tools for facilitating the discovery of such targets and pharmacologic agents directed against them should be prioritized.

Bleomycin reduces Vairimorpha (Nosema) ceranae infection in honey bees with some evident host toxicity

Microsporidia cause disease in many beneficial insects, including honey bees, yet few pathogen control tools are available for protecting these important organisms against infection. Some evidence suggests that microsporidia possess a reduced number of genes encoding DNA repair proteins. We hypothesized that microsporidia would thus be susceptible to treatment with DNA-damaging agents and tested this hypothesis using a novel, rapid method for achieving robust and homogenous experimental infection of large numbers of newly emerged honey bees with one of its microsporidia pathogens, Vairimorpha (Nosema) ceranae. In carrying out these experiments, we found this novel V. ceranae inoculation method to have similar efficacy as other traditional methods. We show that the DNA-damaging agent bleomycin reduces V. ceranae levels, with minimal but measurable effects on honey bee survival and increased expression of midgut cellular stress genes, including those encoding SHSP. Increased expression of UpdlC suggests the occurrence of epithelial regeneration, which may contribute to host resistance to bleomycin treatment. While bleomycin does reduce infection levels, host toxicity issues may preclude its use in the field. However, with further work, bleomycin may provide a useful tool in the research setting as a potential selection agent for genetic modification of microsporidia.IMPORTANCEMicrosporidia cause disease in many beneficial insects, yet there are few tools available for control in the field or laboratory. Based on the reported paucity of DNA repair enzymes found in microsporidia genomes, we hypothesized that these obligate intracellular parasites would be sensitive to DNA damage. In support of this, we observed that the well-characterized DNA damage agent bleomycin can reduce levels of the microsporidia Vairimorpha (Nosema) ceranae in experimental infections in honey bees. Observation of slightly reduced honey bee survival and evidence of sublethal toxicity likely preclude the use of bleomycin in the field. However, this work identifies bleomycin as a compound that merits further exploration for use in research laboratories as a potential selection agent for generating genetically modified microsporidia.

Functional Characterization of A Deformed Epidermal Autoregulatory Factor 1 Gene in Litopenaeus vannamei

Innate immunity is crucial for invertebrate defense against pathogenic infections. Numerous studies have indicated that the Toll-NF-κB pathway plays an important role in this process, particularly in anti-bacterial and anti-fungal immunity. Although the function of this pathway has been studied extensively, there are still uncertainties regarding its role in shrimp. In this study, we investigated the functions of Deformed Epidermal Autoregulatory Factor 1 (LvDEAF1) in Litopenaeus vannamei, a member of the Toll-NF-κB pathway. Our findings revealed that LvDEAF1 interacts with L. vannamei Pellino1 (LvPellino1). LvDEAF1 enhances the promoter activity of certain antimicrobial peptide genes, such as Metchnikowin and Drosomycin, in Drosophila Schneider 2 (S2) cells by binding to the NF-κB binding site. LvDEAF1 and LvPellino1 exhibit positive and synergistic effects. Additionally, the expression of LvDEAF1 is induced by Vibrio parahaemolyticus infection and lipopolysaccharides or zymosan treatment. Knockdown LvDEAF1 expression resulted in a decrease in Penaeidins 4 expression and an increase in the cumulative mortality of shrimp infected with V. parahaemolyticus. These findings indicate that LvDEAF1 plays an important role in the Toll-NF-κB pathway of L. vannamei and is essential for its immune response against pathogens.

The Fungus Nosema ceranae and a Sublethal Dose of the Neonicotinoid Insecticide Thiamethoxam Differentially Affected the Health and Immunity of Africanized Honey Bees

Honey bees (Apis mellifera L.) are affected by different biotic and abiotic stressors, such as the fungus Nosema ceranae and neonicotinoid insecticides, that negatively impact their health. However, most studies so far conducted have focused on the effect of these stressors separately and in European honey bees. Therefore, this study was conducted to analyze the impact of both stressors, singly and in combination, on honey bees of African descent that have demonstrated resistance to parasites and pesticides. Africanized honey bees (AHBs, Apis mellifera scutellata Lepeletier) were inoculated with N. ceranae (1 × 10⁵ spores/bee) and/or chronically exposed for 18 days to a sublethal dose of thiamethoxam (0.025 ng/bee) to evaluate their single and combined effects on food consumption, survivorship, N. ceranae infection, and immunity at the cellular and humoral levels. No significant effects by any of the stressors were found for food consumption. However, thiamethoxam was the main stressor associated to a significant decrease in AHB survivorship, whereas N. ceranae was the main stressor affecting their humoral immune response by upregulating the expression of the gene AmHym-1. Additionally, both stressors, separately and combined, significantly decreased the concentration of haemocytes in the haemolymph of the bees. These findings indicate that N. ceranae and thiamethoxam differentially affect the lifespan and immunity of AHBs and do not seem to have synergistic effects when AHBs are simultaneously exposed to both stressors.

In Vivo Inhibitory Assessment of Potential Antifungal Agents on Nosema ceranae Proliferation in Honey Bees

Nosema ceranae Fries, 1996, causes contagious fungal nosemosis disease in managed honey bees, Apis mellifera L. It is associated around the world with winter losses and colony collapse disorder. We used a laboratory in vivo screening assay to test curcumin, fenbendazole, nitrofurazone and ornidazole against N. ceranae in honey bees to identify novel compounds with anti-nosemosis activity compared to the commercially available medication Fumagilin-B®. Over a 20-day period, Nosema-inoculated bees in Plexiglas cages were orally treated with subsequent dilutions of candidate compounds, or Fumagilin-B® at the recommended dose, with three replicates per treatment. Outcomes indicated that fenbendazole suppressed Nosema spore proliferation, resulting in lower spore abundance in live bees (0.36 ± 1.18 million spores per bee) and dead bees (0.03 ± 0.25 million spores per bee), in comparison to Fumagilin-B®-treated live bees (3.21 ± 2.19 million spores per bee) and dead bees (3.5 ± 0.6 million spores per bee). Our findings suggest that Fumagilin-B® at the recommended dose suppressed Nosema. However, it was also likely responsible for killing Nosema-infected bees (24% mortality). Bees treated with fenbendazole experienced a greater survival probability (71%), followed by ornidazole (69%), compared to Nosema-infected non-treated control bees (20%). This research revealed that among screened compounds, fenbendazole, along with ornidazole, has potential effective antifungal activities against N. ceranae in a controlled laboratory environment.

Insights into the Role of Natural Products in the Control of the Honey Bee Gut Parasite (Nosema spp.)

The honey bee is an important economic insect due to its role in pollinating many agricultural plants. Unfortunately, bees are susceptible to many pathogens, including pests, parasites, bacteria, and viruses, most of which exert a destructive impact on thousands of colonies. The occurrence of resistance to the therapeutic substances used against these organisms is rising, and the residue from these chemicals may accumulate in honey bee products, subsequently affecting the human health. There is current advice to avoid the use of antibiotics, antifungals, antivirals, and other drugs in bees, and therefore, it is necessary to develop alternative strategies for the treatment of bee diseases. In this context, the impact of nosema diseases (nosemosis) on bee health and the negative insults of existing drugs are discussed. Moreover, attempts to combat nosema through the use of alternative compounds, including essential oils, plant extracts, and microbes in vitro and in vivo, are documented.

Effect of amide protoporphyrin derivatives on immune response in Apis mellifera

The intracellular microsporidian parasite Nosema ceranae is known to compromise bee health by induction of energetic stress and downregulation of the immune system. Porphyrins are candidate therapeutic agents for controlling Nosema infection without adverse effects on honeybees. In the present work, the impact of two protoporphyrin IX derivatives, i.e. PP[Asp]₂ and PP[Lys]₂, on Apis mellifera humoral immune response has been investigated in laboratory conditions in non-infected and N. ceranae-infected honeybees. Fluorescence spectroscopy analysis of hemolymph showed for the first time that porphyrin molecules penetrate into the hemocoel of honeybees. Phenoloxidase (PO) activity and the expression of genes encoding antimicrobial peptides (AMPs: abaecin, defensin, and hymenoptaecin) were assessed. Porphyrins significantly increased the phenoloxidase activity in healthy honeybees but did not increase the expression of AMP genes. Compared with the control bees, the hemolymph of non-infected bees treated with porphyrins had an 11.3- and 6.1-fold higher level of PO activity after the 24- and 48-h porphyrin administration, respectively. Notably, there was a significant inverse correlation between the PO activity and the AMP gene expression level (r =  - 0.61696, p = 0.0143). The PO activity profile in the infected bees was completely opposite to that in the healthy bees (r =  - 0.5118, p = 0.000), which was related to the changing load of N. ceranae spores in the porphyrin treated-bees. On day 12 post-infection, the spore loads in the infected porphyrin-fed individuals significantly decreased by 74%, compared with the control bees. Our findings show involvement of the honeybee immune system in the porphyrin-based control of Nosema infection. This allows the infected bees to improve their lifespan considerably by choosing an optimal PO activity/AMP expression variant to cope with the varying level of N. ceranae infection.

Antifungal activity of "HO21-F", a formulation based on Olea europaea plant extract, in honey bees infected with Nosema ceranae

Nosema ceranae is a microsporidium parasite that silently affects honey bees, causing a disease called nosemosis. This parasite produces resistant spores and germinates in the midgut of honey bees, extrudes a polar tubule that injects an infective sporoplasm in the host cell epithelium, proliferates, and produces intestinal disorders that shorten honey bee lifespan. The rapid extension of this disease has been reported to be widespread among adult bees, and treatments are less effective and counterproductive weakening colonies. This work aimed to evaluate the antifungal activity of a prototype formulation based on a non-toxic plant extract (HO21-F) against N. ceranae. In laboratory, honey bees were infected artificially, kept in cages for 17 days and samples were taken at 7 and 14 days post infection (dpi). At the same time, in field conditions we evaluated the therapeutic effect of HO21-F for 28 days in naturally infected colonies. The effectiveness of the treatment has been demonstrated by a reduction of 83.6 % of the infection levels observed in laboratory conditions at concentrations of 0.5 and 1 g/L without affecting the survival rate. Besides, in-field conditions we reported a reduction of 88 % of the infection level at a concentration of 2.5 g/L, obtaining better antifungal effectiveness in comparison to other commercially available treatments. As a result, we observed that the use of HO21-F led to an increase in population size and honey production, both parameters associated with colony strength. The reported antifungal activity of HO21-F against N. ceranae, with a significant control of spore proliferation in worker bees, suggests the promising commercial application use of this product against nosemosis, and it will encourage new research studies to understand the mechanism of action, whether related to the spore-inhibition effect and/or a stimulating effect in natural response of colonies to counteract the disease.

Genotype, but Not Climate, Affects the Resistance of Honey Bees (Apis mellifera) to Viral Infections and to the Mite Varroa destructor

This study was conducted to analyze the effect of genotype and climate on the resistance of honey bee (Apis mellifera) colonies to parasitic and viral diseases. The prevalence and intensity of parasitism by Varroa destructor, or infection by Nosema spp., and four honey bee viruses were determined in 365 colonies of predominantly European or African ancestry (descendants of A. m. scutellata) in subtropical and temperate regions of Mexico. Varroa destructor was the most prevalent parasite (95%), whilst N. ceranae was the least prevalent parasite (15%). Deformed wing virus (DWV) and black queen cell virus (BQCV) were the only viruses detected, at frequencies of 38% and 66%, respectively. Varroa destructor was significantly more prevalent in colonies of European ancestry (p < 0.05), and the intensity of parasitism by V. destructor or infection by DWV and BQCV was also significantly higher in colonies of European descent than in African descent colonies (p < 0.01), although no genotype−parasite associations were found for N. ceranae. Additionally, significant and positive correlations were found between V. destructor and DWV levels, and the abundance of these pathogens was negatively correlated with the African ancestry of colonies (p < 0.01). However, there were no significant effects of environment on parasitism or infection intensity for the colonies of both genotypes. Therefore, it is concluded that the genotype of honey bee colonies, but not climate, influences their resistance to DWV, BQCV, and V. destructor.

Use of Thymol in Nosema ceranae Control and Health Improvement of Infected Honey Bees

Simple Summary

In the European Union, there is no registered product for the control of the honey bee endoparasite Nosema ceranae. Thus, researchers are looking for options for Nosema treatment. The aim of this study was to investigate the effect of a natural essential-oil ingredient (thymol) derived from Thymus vulgaris on honey bees infected with N. ceranae. Thymol exerted certain positive effects (increasing bee survival, immunity, and antioxidative protection), as well as positively affecting the spore loads in Nosema-infected bees. However, when applied to Nosema-free bees, thymol caused certain health disorders; therefore, beekeepers should be careful with its use.

Abstract

Nosema ceranae is the most widespread microsporidian species which infects the honey bees of Apis mellifera by causing the weakening of their colonies and a decline in their productive and reproductive capacities. The only registered product for its control is the antibiotic fumagillin; however, in the European Union, there is no formulation registered for use in beekeeping. Thymol (3-hydroxy-p-cymene) is a natural essential-oil ingredient derived from Thymus vulgaris, which has been used in Varroa control for decades. The aim of this study was to investigate the effect of thymol supplementation on the expression of immune-related genes and the parameters of oxidative stress and bee survival, as well as spore loads in bees infected with the microsporidian parasite N. ceranae. The results reveal mostly positive effects of thymol on health (increasing levels of immune-related genes and values of oxidative stress parameters, and decreasing Nosema spore loads) when applied to Nosema-infected bees. Moreover, supplementation with thymol did not induce negative effects in Nosema-infected bees. However, our results indicate that in Nosema-free bees, thymol itself could cause certain disorders (affecting bee survival, decreasing oxidative capacity, and downregulation of some immune-related gene expressions), showing that one should be careful with preventive, uncontrolled, and excessive use of thymol. Thus, further research is needed to reveal the effect of this phytogenic supplement on the immunity of uninfected bees.

Diet Supplementation Helps Honey Bee Colonies in Combat Infections by Enhancing their Hygienic Behaviour

The hygienic behavior in honey bees is a complex polygenic trait that serves as a natural defense mechanism against bacterial and fungal brood diseases and Varroa destructor mites infesting brood cells. The aim of this study was to evaluate the effect of a dietary amino acids and vitamins supplement “BEEWELL AminoPlus” on hygienic behavior of Apis mellifera colonies combating microsporidial and viral infections. The experiment was performed during a one-year period on 40 colonies alloted to five groups: one supplemented and infected with Nosema ceranae and four viruses (Deformed wing virus - DWV, Acute bee paralysis virus - ABPV, Chronic bee paralysis virus - CBPV and Sacbrood virus – SBV), three not supplemented, but infected with N. ceranae and/ or viruses, and one negative control group. Beside the l isted pathogens, honey bee trypanosomatids were also monitored in all groups.

The supplement “BEEWELL AminoPlus” induced a significant and consistent increase of the hygienic behavior in spite of the negative effects of N. ceranae and viral infections. N. ceranae and viruses significantly and consistently decreased hygienic behavior, but also threatened the survival of bee colonies. The tested supplement showed anti-Nosema effect, since the N. ceranae infection level significantly and consistently declined only in the supplemented group. Among infected groups, only the supplemented one remained Lotmaria passim-free throughout the study. In conclusion, diet supplementation enhances hygienic behavior of honey bee colonies and helps them fight the most common infections of honey bees.

Recent Advances in the Biocontrol of Nosemosis in Honey Bees (Apis mellifera L.)

Nosemosis is a disease triggered by the single-celled spore-forming fungi Nosema apis and Nosema ceranae, which can cause extensive colony losses in honey bees (Apis mellifera L.). Fumagillin is an effective antibiotic treatment to control nosemosis, but due to its toxicity, it is currently banned in many countries. Accordingly, in the beekeeping sector, there is a strong demand for alternative ecological methods that can be used for the prevention and therapeutic control of nosemosis in honey bee colonies. Numerous studies have shown that plant extracts, RNA interference (RNAi) and beneficial microbes could provide viable non-antibiotic alternatives. In this article, recent scientific advances in the biocontrol of nosemosis are summarized.

Functional Properties and Antimicrobial Activity from Lactic Acid Bacteria as Resources to Improve the Health and Welfare of Honey Bees

Simple Summary

Honey bees play a pivotal role in the sustainability of ecosystems and biodiversity. Many factors including parasites, pathogens, pesticide residues, forage losses, and poor nutrition have been proposed to explain honey bee colony losses. Lactic acid bacteria (LAB) are normal inhabitants of the gastrointestinal tract of honey bees and their role has been consistently reported in the literature. In recent years, there have been numerous scientific evidence that the intestinal microbiota plays an essential role in honey bee health. Management strategies, based on supplementation of the gut microbiota with probiotics, may be important to increase stress tolerance and disease resistance. In this review, recent scientific advances on the use of LABs as microbial supplements in the diet of honey bees are summarized and discussed.

Abstract

Honey bees (Apis mellifera) are agriculturally important pollinators. Over the past decades, significant losses of wild and domestic bees have been reported in many parts of the world. Several biotic and abiotic factors, such as change in land use over time, intensive land management, use of pesticides, climate change, beekeeper’s management practices, lack of forage (nectar and pollen), and infection by parasites and pathogens, negatively affect the honey bee’s well-being and survival. The gut microbiota is important for honey bee growth and development, immune function, protection against pathogen invasion; moreover, a well-balanced microbiota is fundamental to support honey bee health and vigor. In fact, the structure of the bee’s intestinal bacterial community can become an indicator of the honey bee’s health status. Lactic acid bacteria are normal inhabitants of the gastrointestinal tract of many insects, and their presence in the honey bee intestinal tract has been consistently reported in the literature. In the first section of this review, recent scientific advances in the use of LABs as probiotic supplements in the diet of honey bees are summarized and discussed. The second section discusses some of the mechanisms by which LABs carry out their antimicrobial activity against pathogens. Afterward, individual paragraphs are dedicated to Chalkbrood, American foulbrood, European foulbrood, Nosemosis, and Varroosis as well as to the potentiality of LABs for their biological control.

The Role of Nosema ceranae (Microsporidia: Nosematidae) in Honey Bee Colony Losses and Current Insights on Treatment

Honeybee populations have locally and temporally declined in the last few years because of both biotic and abiotic factors. Among the latter, one of the most important reasons is infection by the microsporidia Nosema ceranae, which is the etiological agent of type C nosemosis. This species was first described in Asian honeybees (Apis cerana). Nowadays, domestic honeybees (Apis mellifera) worldwide are also becoming infected due to globalization. Type C nosemosis can be asymptomatic or can cause important damage to bees, such as changes in temporal polyethism, energy and oxidative stress, immunity loss, and decreased average life expectancy. It causes drastic reductions in workers, numbers of broods, and honey production, finally leading to colony loss. Common treatment is based on fumagillin, an antibiotic with side effects and relatively poor efficiency, which is banned in the European Union. Natural products, probiotics, food supplements, nutraceuticals, and other veterinary drugs are currently under study and might represent alternative treatments. Prophylaxis and management of affected colonies are essential to control the disease. While N. ceranae is one potential cause of bee losses in a colony, other factors must also be considered, especially synergies between microsporidia and the use of insecticides.

Nosema apis and N. ceranae Infection in Honey bees: A Model for Host-Pathogen Interactions in Insects

There has been increased focus on the role of microbial attack as a potential cause of recent declines in the health of the western honey bee, Apis mellifera. The Nosema species, N. apis and N. ceranae, are microsporidian parasites that are pathogenic to honey bees, and infection by these species has been implicated as a key factor in honey bee losses. Honey bees infected with both Nosema spp. display significant changes in their biology at the cellular, tissue, and organismal levels impacting host metabolism, immune function, physiology, and behavior. Infected individuals lead to colony dysfunction and can contribute to colony disease in some circumstances. The means through which parasite growth and tissue pathology in the midgut lead to the dramatic physiological and behavioral changes at the organismal level are only partially understood. In addition, we possess only a limited appreciation of the elements of the host environment that impact pathogen growth and development. Critical for answering these questions is a mechanistic understanding of the host and pathogen machinery responsible for host-pathogen interactions. A number of approaches are already being used to elucidate these mechanisms, and promising new tools may allow for gain- and loss-of-function experiments to accelerate future progress.

Natural extracts as potential control agents for Nosema ceranae infection in honeybees, Apis mellifera

Nosema disease is one factor that can cause colony decline in honeybees (Apis mellifera L.) worldwide. Nosema ceranae has outcompeted Nosema apis in the Western honeybee (A. mellifera) which is its original host. Fumagilin is an effective antibiotic treatment to control Nosema infection but currently it is forbidden in many countries. In this study, 12 plant extracts were evaluated for their toxicity to adult bees and antimicrosporidian activity under laboratory and field conditions. N. ceranae-infected adult bees were fed ad libitum with 50% sucrose solution containing 1% and 5% (w/v) of each plant extract. Bee mortality in N. ceranae-infected groups fed with plant extracts was higher than that in the control group treated with fumagilin. The results demonstrated that 9 of 12 extracts had high antimicrosporidian activity against N. ceranae and their efficacies were comparable to fumagilin. Spore reduction in infected bees was 4-6 fold less after extract treatment. Following laboratory screening, Annona squamosa, Ocimum basilicum, Psidium guajava and Syzygium jambos were tested in honeybee colonies. Plant extracts of 2% concentration (w/v) inhibited the development of Nosema spores after 30 days of treatment. At the end of experiment (90 days), spores in the plant extract treated groups were lower than in group treated with fumagilin but there was no significant difference. Although, extracts tested in this study showed high toxicity to bee in laboratory cages, they did not show negative affects on bees under whole colony conditions. Therefore, the effectiveness of plant extracts tested in this study was notable and warrants further study as potential Nosema control agents in honey bees. Plant extracts would offer a non-antibiotic alternative for Nosema control and help reduce the overuse of antibiotics in livestock.

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

The microsporidia Nosema ceranae is an obligate intracellular parasite that causes honey bee mortality and contributes to colony collapse. Fumagillin is presently the only pharmacological control for N. ceranae infections in honey bees. Resistance is already emerging, and alternative controls are critically needed. Nosema spp. exhibit increased sensitivity to heat shock, a common proteotoxic stress. Thus, we hypothesized that targeting the Nosema proteasome, the major protease removing misfolded proteins, might be effective against N. ceranae infections in honey bees. Nosema genome analysis and molecular modeling revealed an unexpectedly compact proteasome apparently lacking multiple canonical subunits, but with highly conserved proteolytic active sites expected to be receptive to FDA-approved proteasome inhibitors. Indeed, N. ceranae were strikingly sensitive to pharmacological disruption of proteasome function at doses that were well tolerated by honey bees. Thus, proteasome inhibition is a novel candidate treatment strategy for microsporidia infection in honey bees.

Fungi of entomopathogenic potential in Chytridiomycota and Blastocladiomycota, and in fungal allies of the Oomycota and Microsporidia

The relationship between entomopathogenic fungi and their insect hosts is a classic example of the co-evolutionary arms race between pathogen and target host. The present review describes the entomopathogenic potential of Chytridiomycota and Blastocladiomycota fungi, and two groups of fungal allies: Oomycota and Microsporidia. The Oomycota (water moulds) are considered as a model biological control agent of mosquito larvae. Due to their shared ecological and morphological similarities, they had long been considered a part of the fungal kingdom; however, phylogenetic studies have since placed this group within the Straminipila. The Microsporidia are parasites of economically-important insects, including grasshoppers, lady beetles, bumblebees, colorado potato beetles and honeybees. They have been found to display some fungal characteristics, and phylogenetic studies suggest that they are related to fungi, either as a basal branch or sister group. The Blastocladiomycota and Chytridiomycota, named the lower fungi, historically were described together; however, molecular phylogenetic and ultrastructural research has classified them in their own phylum. They are considered parasites of ants, and of the larval stages of black flies, mosquitoes and scale insects.

Effects of Agaricus bisporus Mushroom Extract on Honey Bees Infected with Nosema ceranae

Simple Summary

Nosema ceranae affects honey bee (Apis mellifera L.) causing nosemosis disease that often induces serious problems in apiculture. Antibiotic fumagillin is the only licenced treatment against nosemosis, but its effectiveness is questioned and its usage associated with risk of bee mortality and appearance of residues in bee products. In search for alternative treatment for the control of nosemosis, water crude extract of Agaricus bisporus was tested on bees in laboratory (cage) experiments. Bee survival and food consumption were monitored together with Nosema infection level and expression of five genes (abaecin, hymenoptaecin, defensin, apidaecin, and vitellogenin) were evaluated in bees sampled on days 7 and 15. Apart from the gene for defensin, the expression of all tested genes was up-regulated in bees supplemented with A. bisporus extract. Both anti-Nosema and immune protective effects of A. bisporus extract were observed when supplementation started at the moment of N. ceranae infection or preventively (before or simultaneously with the Nosema infection).

Abstract

Agaricus bisporus water crude extract was tested on honey bees for the first time. The first part of the cage experiment was set for selecting one concentration of the A. bisporus extract. Concentration of 200 µg/g was further tested in the second part of the experiment where bee survival and food consumption were monitored together with Nosema infection level and expression of five genes (abaecin, hymenoptaecin, defensin, apidaecin, and vitellogenin) that were evaluated in bees sampled on days 7 and 15. Survival rate of Nosema-infected bees was significantly greater in groups fed with A. bisporus-enriched syrup compared to those fed with a pure sucrose syrup. Besides, the anti-Nosema effect of A. bisporus extract was greatest when applied from the third day which coincides with the time of infection with N. ceranae. Daily food consumption did not differ between the groups indicating good acceptability and palatability of the extract. A. bisporus extract showed a stimulative effect on four out of five monitored genes. Both anti-Nosema and nutrigenomic effects of A. bisporus extract were observed when supplementation started at the moment of N. ceranae infection or preventively (before or simultaneously with the infection).

Effect of feeding chitosan or peptidoglycan on Nosema ceranae infection and gene expression related to stress and the innate immune response of honey bees (Apis mellifera)

Nosema ceranae is a microsporidian parasite that causes nosema disease, an infection of the honey bee (Apis mellifera) midgut. Two pathogen-associated molecular patterns (PAMPs), chitosan and peptidoglycan, and N. ceranae spores were fed to worker bees in sucrose syrup and compared to non-inoculated and N. ceranae-inoculated bees without PAMPs. Both chitosan and peptidoglycan significantly increased bee survivorship and reduced spore numbers due to N. ceranae infection. To determine if these results were related to changes in health status, expression of the immune-related genes, hymenoptaecin and defensin2, and the stress tolerance-related gene, blue cheese, was compared to that of control bees. Compared to the inoculated control, bees with the dose of chitosan that significantly reduced N. ceranae spore numbers showed lower expression of hymenoptaecin and defensin2 early after infection, higher expression mid-infection of defensin2 and lower expression of all three genes late in infection. In contrast, higher expression of defensin2 early in the infection and all three genes late in the infection was observed with peptidoglycan treatment. Changes late in the parasite multiplication stage when mature spores would be released from ruptured host cells are less likely to have contributed to reduced spore production. Based on these results, it is concluded that feeding bees chitosan or peptidoglycan can reduce N. ceranae infection, which is at least partially related to altering the health of the bee by inducing immune and stress-related gene expression.

Propolis Extract and Chitosan Improve Health of Nosema ceranae Infected Giant Honey Bees, Apis dorsata Fabricius, 1793

Nosema ceranae is a large contributing factor to the most recent decline in honey bee health worldwide. Developing new alternative treatments against N. ceranae is particularly pressing because there are few treatment options available and therefore the risk of increased antibiotic resistance is quite high. Recently, natural products have demonstrated to be a promising avenue for finding new effective treatments against N. ceranae. We evaluated the effects of propolis extract of stingless bee, Tetrigona apicalis and chito-oligosaccharide (COS) on giant honey bees, Apis dorsata, experimentally infected with N. ceranae to determine if these treatments could improve the health of the infected individuals. Newly emerged Nosema-free bees were individually inoculated with 106N. ceranae spores per bee. We fed infected and control bees the following treatments consisting of 0%, 50%, propolis extracts, 0 ppm and 0.5 ppm COS in honey solution (w/v). Propolis extracts and COS caused a significant increase in trehalose levels in hemolymph, protein contents, survival rates and acini diameters of the hypopharyngeal glands in infected bees. Our results suggest that propolis and COS could improve the health of infected bees. Further research is needed to determine the underlying mechanisms responsible for the improved health of the infected bees.

Nosema ceranae Infections in Honey Bees (Apis mellifera) Treated with Pre/Probiotics and Impacts on Colonies in the Field

Alternatives to the antibiotic fumagillin for the control of Nosema ceranae, a gut parasite of the honey bee, are needed. The prebiotics eugenol, chitosan, and naringenin and the probiotic Protexin^® (Enterococcus faecium) provided in sugar syrup or protein patty either in spring or fall were evaluated for their effects on N. ceranae infection, colony population, honey yield and winter survivorship using field colonies. In the first year, spring treatments with eugenol, naringenin, and Protexin^® significantly reduced N. ceranae infection and increased honey production, while Protexin^® also increased adult bee populations and chitosan was ineffective. Fall treatments increased survivorship and decreased N. ceranae infection the following spring. In the second year, selected compounds were further tested with a larger number of colonies per treatment and only protein patty used in the spring and sugar syrup in the fall. Protexin^® and naringenin significantly decreased N. ceranae infections and increased the population of adult bees after spring treatment, but did not affect honey yields. There were no differences between treatments for colony winter mortality, but surviving colonies that had been treated with Protexin^® and naringenin were significantly more populated and had lower N. ceranae spore counts than control, non-treated colonies. Protexin^® and naringenin were the most promising candidates for controlling N. ceranae and promoting honey bee populations, warranting further investigation. Future research should investigate the optimal colony dose and treatment frequency to maximize colony health.

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

Nosema ceranae is a widespread parasite responsible for nosemosis Type C in Apis mellifera honey bees, reducing colony survival. The antibiotic fumagillin is the only commercial treatment available, but concerns are emerging about its persistence, safety, and pathogen resistance. The use of natural substances from Brassicaceae defatted seed meals (DSMs) with known antimicrobial and antioxidant properties was explored. Artificially infected bees were fed for 8 days with candies enriched with two concentrations, 2% and 4%, of two DSMs from Brassica nigra and Eruca sativa, containing a known amount of different glucosinolates (GSLs). The food palatability, GSL intake, bee survival, and treatment effects on N. ceranae spore counts were evaluated. Food consumption was higher for the two 2% DSM patties, for both B. nigra and E. sativa, but the GSL intake did not increase by increasing DSM to 4%, due to the resulting lower palatability. The 2% B. nigra patty decreased the bee mortality, while the higher concentration had a toxic effect. The N. ceranae control was significant for all formulates with respect to the untreated control (312,192.6 +/- 14,443.4 s.e.), and was higher for 4% B. nigra (120,366.3 +/- 13,307.1 s.e.). GSL hydrolysis products, the isothiocyanates, were detected and quantified in bee gut tissues. Brassicaceae DSMs showed promising results for their nutraceutical and protective effects on bees artificially infected with N. ceranae spores at the laboratory level. Trials in the field should confirm these results.

Effects of Prebiotics and Probiotics on Honey Bees (Apis mellifera) Infected with the Microsporidian Parasite Nosema ceranae

Nosema ceranae is a microsporidian fungus that parasitizes the midgut epithelial cells of honey bees, Apis mellifera. Due to the role that midgut microorganisms play in bee health and immunity, food supplementation with prebiotics and probiotics may assist in the control of N. ceranae. The dietary fiber prebiotics acacia gum, inulin, and fructooligosaccharides, as well as the commercial probiotics Vetafarm Probotic, Protexin Concentrate single-strain (Enterococcus faecium), and Protexin Concentrate multi-strain (Lactobacillus acidophilus, L. plantarum, L. rhamnosus, L. delbrueckii, Bifidobacterium bifidum, Streptococcus salivarius, and E. faecium) were tested for their effect on N. ceranae spore loads and honey bee survivorship. Bees kept in cages were inoculated with N. ceranae spores and single-dose treatments were administered in sugar syrup. Acacia gum caused the greatest reduction in N. ceranae spore numbers (67%) but also significantly increased bee mortality (62.2%). However, Protexin Concentrate single-strain gave similarly reduced spore numbers (59%) without affecting the mortality. In a second experiment, multiple doses of the probiotics revealed significantly reduced spore numbers with 2.50 mg/mL Vetafarm Probotic, and 0.25, 1.25, and 2.50 mg/mL Protexin Concentrate single-strain. Mortality was also significantly reduced with 1.25 mg/mL Protexin Concentrate single-strain. N. ceranae-inoculated bees fed 3.75 mg/mL Vetafarm Probotic had higher survival than N. ceranae-inoculated bees, which was similar to that of non-inoculated bees, while N. ceranae-inoculated bees fed 2.50 mg/mL Protexin Concentrate single-strain, had significantly higher survival than both N. ceranae-inoculated and non-inoculated bees. Protexin Concentrate single-strain is promising as it can reduce N. ceranae proliferation and increase bee survivorship of infected bees, even compared to healthy, non-infected bees.

Association between the Microsatellite Ap243, AC117 and SV185 Polymorphisms and Nosema Disease in the Dark Forest Bee Apis mellifera mellifera

The microsporidian Nosema parasites, primarily Nosema ceranae, remain critical threats to the health of the honey bee Apis mellifera. One promising intervention approach is the breeding of Nosema-resistant honey bee colonies using molecular technologies, for example marker-assisted selection (MAS). For this, specific genetic markers used in bee selection should be developed. The objective of the paper is to search for associations between some microsatellite markers and Nosema disease in a dark forest bee Apis mellifera mellifera. For the dark forest bee, the most promising molecular genetic markers for determining resistance to nosemosis are microsatellite loci AC117, Ap243 and SV185, the alleles of which (“177”, “263” and “269”, respectively) were associated with a low level of Nosema infection. This article is the first associative study aimed at finding DNA loci of resistance to nosemosis in the dark forest bee. Nevertheless, microsatellite markers identified can be used to predict the risk of developing the Nosema disease.