Microbial Profile of the Ventriculum of Honey Bee (Apis mellifera ligustica Spinola, 1806) Fed with Veterinary Drugs, Dietary Supplements and Non-Protein Amino Acids

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.

Alterations in the Microbiota of Caged Honeybees in the Presence of Nosema ceranae Infection and Related Changes in Functionality

Several studies have outlined that changes in the honeybee gut microbial composition may impair important metabolic functions supporting the honeybees' life. Gut dysbiosis may be caused by diseases like Nosema ceranae or by other anthropic, environmental or experimental stressors. The present work contributes to increasing knowledge on the dynamics of the gut microbiome acquisition in caged honeybees, an experimental condition frequently adopted by researchers, with or without infection with N. ceranae, and fed with a bacterial mixture to control N. ceranae development. Changes of the gut microbiota were elucidated comparing microbial profile of caged and open-field reared honeybees. The absolute abundance of the major gut microbial taxa was studied with both NGS and qPCR approaches, whereas changes in the functionality were based on RAST annotations and manually curated. In general, all caged honeybees showed important changes in the gut microbiota, with [Formula: see text]-proteobacteria (Frischella, Gilliamella and Snodgrassella) lacking in all caged experimental groups. Caged honeybees infected with N. ceranae showed also a strong colonization of environmental taxa like Citrobacter, Cosenzaea and Morganella, as well as possibly pathogenic bacteria such as Serratia. The colonization of Serratia did not occur in presence of the bacterial mixture. The functionality prediction revealed that environmental bacteria or the supplemented bacterial mixture increased the metabolic potential of the honeybee gut microbiome compared to field and caged controls.

Antimicrobial Activity from Putative Probiotic Lactic Acid Bacteria for the Biological Control of American and European Foulbrood Diseases

The balance of the gut microbiome is important for the honey bee’s growth and development, immune function and defense against pathogens. The use of a beneficial bacteria-based strategy for the prevention and biocontrol of American foulbrood (AFB) and European foulbrood (EFB) diseases in honey bees offers interesting prospects. Lactic acid bacteria (LAB) are common inhabitants of the gastrointestinal tract of the honey bee. Among LABs associated with bee gut microbiota, Lactiplantibacillus plantarum (previously Lactobacillus plantarum) and Apilactobacillus kunkeei (formerly classified as Lactobacillus kunkeei) are two of the most abundant species. In this study, four Lactiplantibacillus plantarum strains and four Apilactobacillus kunkeei strains, isolated from the gastrointestinal tract of honey bee (Apis mellifera L.) were selected for their in vitro inhibition ability of Paenibacillus larvae ATCC 9545 and Melissococccus plutonius ATCC 35311. In addition, these LABs have been characterized through some biochemical and functional characteristics: cell surface properties (hydrophobicity and auto-aggregation), carbohydrates assimilation and enzymatic activities. The antimicrobial, biochemical and cell surface properties of these LABs have been functional to their candidature as potential probiotics in beekeeping and for the biocontrol of AFB and EFB diseases.

Bee Stressors from an Immunological Perspective and Strategies to Improve Bee Health

Honeybees are the most prevalent insect pollinator species; they pollinate a wide range of crops. Colony collapse disorder (CCD), which is caused by a variety of biotic and abiotic factors, incurs high economic/ecological loss. Despite extensive research to identify and study the various ecological stressors such as microbial infections, exposure to pesticides, loss of habitat, and improper beekeeping practices that are claimed to cause these declines, the deep understanding of the observed losses of these important insects is still missing. Honeybees have an innate immune system, which includes physical barriers and cellular and humeral responses to defend against pathogens and parasites. Exposure to various stressors may affect this system and the health of individual bees and colonies. This review summarizes and discusses the composition of the honeybee immune system and the consequences of exposure to stressors, individually or in combinations, on honeybee immune competence. In addition, we discuss the relationship between bee nutrition and immunity. Nutrition and phytochemicals were highlighted as the factors with a high impact on honeybee immunity.

Gut Bacterial Flora of Open Nested Honeybee, Apis florea

Honeybees are eusocial insects with close interaction with their surrounding environment. Gut microbiota in honeybees play a significant role in host health, biology, and interaction behavior with the surrounding environment. Apis florea, a wild bee, is the most primitive among all honeybees and is indigenous to the Indian subcontinent. Previous reports on reared honeybee species provide information on the gut microbiome. No such studies are reported on the gut microbiota of the wild honeybee species. This study aimed at studying the gut microbiome of the wild honeybee species, A. florea. The study reports the analysis and the identification of gut bacteria in the wild honeybee species, A. florea, employing culture-based and culture-independent methods. Cultured bacteria were identified and characterized by MALDI-TOF MS and 16S rRNA sequencing. A comprehensive analysis and identification of non-culturable bacteria were performed by 16S rRNA amplicon next-generation sequencing. This approach splits gut bacteria into four bacterial phyla, four families, and 10 genera in major. The dominant taxa identified in A. florea belonged to the family Enterobacteriaceae (79.47%), Lactobacillaceae (12.75%), Oxalobacteraceae (7.45%), and Nocardiaceae (0.13%). The prevailing bacteria belonged to Enterobacter, Lactobacillus, Escherichia-Shigella, Massilia, Klebsiella, Citrobacter, Pantoea, Serratia, Rhodococcus, and Morganella genera, belonging to phyla Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes. This study observed the occurrence of a few bacteria that are not previously reported for their occurrence in other species of the Apis genus, making this investigation highly relevant with regard to the bee microbiome.

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.

Glucosinolate Bioactivation by Apis mellifera Workers and Its Impact on Nosema ceranae Infection at the Colony Level

The microsporidian fungus Nosema ceranae represents one of the primary bee infection threats worldwide and the antibiotic fumagillin is the only registered product for nosemosis disease control, while few alternatives are, at present, available. Natural bioactive compounds deriving from the glucosinolate-myrosinase system (GSL-MYR) in Brassicaceae plants, mainly isothiocyanates (ITCs), are known for their antimicrobial activity against numerous pathogens and for their health-protective effects in humans. This work explored the use of Brassica nigra and Eruca sativa defatted seed meal (DSM) GSL-containing diets against natural Nosema infection in Apis mellifera colonies. DSM patties from each plant species were obtained by adding DSMs to sugar candy at the concentration of 4% (w/w). The feeding was administered in May to mildly N. ceranae-infected honey bee colonies for four weeks at the dose of 250 g/week. In the treated groups, no significant effects on colony development and bee mortality were observed compared to the negative controls. The N. ceranae abundance showed a slight but significant decrease. Furthermore, the GSL metabolism in bees was investigated, and MYR hydrolytic activity was qualitatively searched in isolated bee midgut and hindgut. Interestingly, MYR activity was detected both in the bees fed DSMs and in the control group where the bees did not receive DSMs. In parallel, ITCs were found in gut tissues from the bees treated with DSMs, corroborating the presence of a MYR-like enzyme capable of hydrolyzing ingested GSLs. On the other hand, GSLs and other GSL hydrolysis products other than ITCs, such as nitriles, were found in honey produced by the treated bees, potentially increasing the health value of the final product for human consumption. The results are indicative of a specific effect on the N. ceranae infection in managed honey bee colonies depending on the GSL activation within the target organ.

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.

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).

Vairimorpha (Nosema) ceranae Infection Alters Honey Bee Microbiota Composition and Sustains the Survival of Adult Honey Bees

Simple Summary

The gut microbiota, in addition to the hosts and the pathogens, has become the third factor involved in gut disease developments, including honey bees. Interestingly, various studies reported positive associations between the gut bacteria and the most commonly found microsporidian pathogen instead of negative associations. To investigate the positive associations, a prebiotic that also exists in honey was added in the trials. Bees fed the prebiotics have slightly higher pathogen counts but lower mortalities. Microbiota analyses suggested that bees with the infection have a microbiota composition similar to that of bees with a longer lifespan, and the prebiotic seemed to enhance the similarities. Since microsporidia typically cause chronic infections, the positive associations may serve to sustain the host lifespans which is the optimal outcome for the pathogen that the survived bees can withstand pathogen proliferation and transmit the pathogens. Although the mechanisms underlying the associations were not revealed, this study indicated that nosema disease management in bees through changes in microbiota may shorten the lifespans or enhance both the infection and the bee population. Such results have appeared in recent field studies. More studies will be needed for the disease management using bee gut microbiota.

Abstract

Vairimorpha (Nosema) ceranae is the most common eukaryotic gut pathogen in honey bees. Infection is typically chronic but may result in mortality. Gut microbiota is a factor that was recently noted for gut infectious disease development. Interestingly, studies identified positive, instead of negative, associations between core bacteria of honey bee microbiota and V. ceranae infection. To investigate the effects of the positive associations, we added isomaltooligosaccharide (IMO), a prebiotic sugar also found in honey, to enhance the positive associations, and we then investigated the infection and the gut microbiota alterations using qPCR and 16S rRNA gene sequencing. We found that infected bees fed IMO had significantly higher V. ceranae spore counts but lower mortalities. In microbiota comparisons, V. ceranae infections alone significantly enhanced the overall microbiota population in the honey bee hindgut and feces; all monitored core bacteria significantly increased in the quantities but not all in the population ratios. The microbiota alterations caused by the infection were enhanced with IMO, and these alterations were similar to the differences found in bees that naturally have longer lifespans. Although our results did not clarify the causations of the positive associations between the infections and microbiota, the associations seemed to sustain the host survival and benefit the pathogen. Enhancing indigenous gut microbe to control nosema disease may result in an increment of bee populations but not the control of the pathogen. This interaction between the pathogen and microbiota potentially enhances disease transmission and avoids the social immune responses that diseased bees die prematurely to curb the disease from spreading within colonies.

Screening of Dietary Ingredients against the Honey Bee Parasite Nosema ceranae

Nosema ceranae is a major pathogen in the beekeeping sector, responsible for nosemosis. This disease is hard to manage since its symptomatology is masked until a strong collapse of the colony population occurs. Conversely, no medicaments are available in the market to counteract nosemosis, and only a few feed additives, with claimed antifungal action, are available. New solutions are strongly required, especially based on natural methods alternative to veterinary drugs that might develop resistance or strongly pollute honey bees and the environment. This study aims at investigating the nosemosis antiparasitic potential of some plant extracts, microbial fermentation products, organic acids, food chain waste products, bacteriocins, and fungi. Honey bees were singularly infected with 5 × 104 freshly prepared N. ceranae spores, reared in cages and fed ad libitum with sugar syrup solution containing the active ingredient. N. ceranae in the gut of honey bees was estimated using qPCR. The results showed that some of the ingredients administered, such as acetic acid at high concentration, p-coumaric acid, and Saccharomyces sp. strain KIA1, were effective in the control of nosemosis. On the other hand, wine acetic acid strongly increased the N. ceranae amount. This study investigates the possibility of using compounds such as organic acids or biological agents including those at the base of the circular economy, i.e., wine waste production, in order to improve honeybee 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.

The Gut Microbiota Can Provide Viral Tolerance in the Honey Bee

Adult honey bees host a remarkably consistent gut microbial community that is thought to benefit host health and provide protection against parasites and pathogens. Currently, however, we lack experimental evidence for the causal role of the gut microbiota in protecting the Western honey bees (Apis mellifera) against their viral pathogens. Here we set out to fill this knowledge gap by investigating how the gut microbiota modulates the virulence of a major honey bee viral pathogen, deformed wing virus (DWV). We found that, upon oral virus exposure, honey bee survival was significantly increased in bees with an experimentally established normal gut microbiota compared to control bees with a perturbed (dysbiotic) gut microbiota. Interestingly, viral titers were similar in bees with normal gut microbiota and dysbiotic bees, pointing to higher viral tolerance in bees with normal gut microbiota. Taken together, our results provide evidence for a positive role of the gut microbiota for honey bee fitness upon viral infection. We hypothesize that environmental stressors altering honey bee gut microbiota composition, e.g., antibiotics in beekeeping or pesticides in modern agriculture, could interact synergistically with pathogens, leading to negative effects on honey bee health and the epidemiology and impact of their viruses.

Antibiotic Treatment Decrease the Fitness of Honeybee (Apis mellifera) Larvae

Simple Summary

To determine the biologic function of gut bacteria with no host specificity in honeybee larvae, honeybee larvae were treated with antibiotics for disrupting the gut bacteria. Then, the body weight, development time, and expression of nutrient metabolism genes and immune genes of honeybee larvae were investigated. The results demonstrated that the disruption of gut microbiota by antibiotics weakened the nutrient metabolism, decreased the body weight, extended the development process, and decrease the immune competence of honeybee larvae, indicating the vital roles of gut bacteria in bee larvae fitness.

Abstract

Symbiotic bacteria could increase the nutrient provision, regulate the physiological state, and promote immunity in their insect host. Honeybee larvae harbor plenty of bacteria in their gut, but their functions are not well studied. To determine their effect on honeybee larvae, the 1-day-old larvae were grafted on to 24-well plates from the comb and artificially reared in the lab. They were treated with penicillin–streptomycin to remove the gut symbiotic bacteria. Then, the 5-day-old larvae and the newly emerged adults were weighted. The developmental periods to pupae and eclosion were investigated, respectively. The bacterial amount, expression of developmental regulation genes (ecr and usp), nutrient metabolism genes (ilp1, ilp2, hex 70a, hex 70b, hex 70c, and hex 110), and immunity genes (apidaecin, abaecin, defensin-1, and hymenoptaecin) were determined by qRT-PCR. The result showed that the antibiotics-treated larvae have significantly lower body weights in the 5-day-old larvae and the emerged bees. The expression of ilp2 and hex 70c in 5-day-old larvae was down-regulated. The usp was down-regulated in 5-day-old larvae, but increased in 7-day-old larvae, which disturbed the normal developmental process and caused the extension of eclosion. Moreover, antibiotics treatment significantly decreased the expression of apidaecin and abaecin in 5-day-old larvae, and defensin-1 and hymenoptaecin in 7-day-old larvae, respectively. These results showed that antibiotics could weaken the nutrient metabolism, disturb the development process, and decrease the immune competence of honeybee larvae, indicating the vital roles of gut bacteria in bee larvae fitness, so the antibiotics should be avoided to control microbial disease in honeybee larvae.

The Honeybee Gut Mycobiota Cluster by Season Versus the Microbiota Which Cluster by Gut Segment

Honeybees represent one of the most important insect species we have, particularly due to their pollinating services. Several emerging fungal and bacterial diseases, however, are currently threatening honeybees without known mechanisms of pathogenicity. Therefore, the aim of the current work was to investigate the seasonal (winter, spring, summer, and autumn) fungal and bacterial distribution through different gut segments (crop, midgut, ileum, and rectum). This was done from two hives in Norway. Our main finding was that bacteria clustered by gut segments, while fungi were clustered by season. This knowledge can therefore be important in studying the epidemiology and potential mechanisms of emerging diseases in honeybees, and also serve as a baseline for understanding honeybee health.

Inter- and Intra-Species Diversity of Lactic Acid Bacteria in Apis mellifera ligustica Colonies

Lactic acid bacteria could positively affect the health of honey bees, including nutritional supplementation, immune system development and pathogen colonization resistance. Based on these considerations the present study evaluated predominant Lactic Acid Bacteria (LAB) species from beebread as well as from the social stomach and midgut of Apis mellifera ligustica honey bee foragers. In detail, for each compartment, the diversity in species and biotypes was ascertained through multiple culture-dependent approaches, consisting of Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE), 16S rRNA gene sequencing and Randomly Amplified Polymorphic DNA-Polymerase Chain Reaction (RAPD-PCR). The study of a lactic acid bacteria community, performed with PCR-DGGE and sequence analysis targeting the V1-V3 region of the 16S rRNA gene (rDNA), highlighted the presence of a few species, including Apilactobacillus kunkeei, Lactiplantibacillus plantarum, Fructobacillus fructosus, Levilactobacillus brevis and Lactobacillus delbrueckii subsp. lactis. Depending on the different compartments, diverse levels of biodiversity in species were found. Particularly, a very low inter-species biodiversity was detected in the midgut that was prevalently dominated by the presence of Apilactobacillus kunkeei. On the other hand, the beebread was characterized by a reasonable biodiversity showing the presence of five species and the predominance of Apilactobacillus kunkeei, Lactiplantibacillus plantarum and Fructobacillus fructosus. The RAPD-PCR analysis performed on the three predominant species allowed the differentiation into several biotypes for each species. Moreover, a relationship between biotypes and compartments has been detected and each biotype was able to express a specific biochemical profile. The biotypes that populated the social stomach and midgut were able to metabolize sugars considered toxic for bees while those isolated from beebread could contribute to release useful compounds with functional properties. Based on this knowledge, new biotechnological approaches could be developed to improve the health of honey bees and the quality of bee products.

Effect of Api-Bioxal® and ApiHerb® Treatments against Nosema ceranae Infection in Apis mellifera Investigated by Two qPCR Methods

Nosema ceranae is a worldwide distributed midgut parasite of western honey bees, leading to dwindling colonies and their collapse. As a treatment, only fumagillin is available, causing issues like resistance and hampered bee physiology. This study aimed to evaluate ApiHerb^® and Api-Bioxal^® as treatments against N. ceranae. The efficacy was tested using two qPCR methods based on the 16S rRNA and Hsp70 genes. In addition, these methods were compared for their aptitude for the quantification of the infection. For this, 19 colonies were selected based on the presence of N. ceranae infections. The colonies were divided into three groups: treated with ApiHerb, Api-Bioxal with previous queen caging and an untreated control. All colonies were sampled pre- and post-treatment. The bees were analyzed individually and in duplicate with both qPCR methods. All bees in the pre-treatment tested positive for N. ceranae. Both treatments reduced the abundance of N. ceranae, but ApiHerb also decreased the prevalence of infected bees. Analysis with the 16S rRNA method resulted in several orders of magnitude more copies than analysis with the Hsp70 method. We conclude that both products are suitable candidates for N. ceranae treatment. From our analysis, the qPCR method based on the Hsp70 gene results as more apt for the exact quantification of N. ceranae as is needed for the development of veterinary medicinal products.