A formal redefinition of the genera Nosema and Vairimorpha (Microsporidia: Nosematidae) and reassignment of species based on molecular phylogenetics

Systematic identity and phylogenetic analysis of Knowlespora clinchi (Knowles et al. 2022) gen. et comb. nov. From pheasantshell mussels (Actinonaiais pectorosa)

A microsporidian parasite infecting the pheasantshell mussel, Actinonaiais pectorosa, was discovered in a freshwater system in the USA. The original description of this species placed it into the holding genus "Microsporidium"; however, the availability of ecological, environmental, histological, electron microscopy, and genetic data, suffice to provide a complete formal taxonomic account of this species. In this note, the genus Knowlespora n. gen. is erected and described to hold the type species: Knowlespora clinchi gen. et comb. nov., originally described as 'Microsporidium clinchi'. A discussion is presented to suggest that this novel species is unlikely to be closely related to other molluscan microsporidians (all of which lack genetic data, to date) and highlights the diversity of oocyte-infecting species across the Microsporidia.

"Migratory beekeeping and its influence on the prevalence and dispersal of pathogens to managed and wild bees"

Demand for food is growing along with the human population, leading to an increase in plant production. Many crops are pollinated by insects, so the global demand for managed pollinators is also increasing. The honey bee has traditionally been considered the main provider of crop pollination services. For providing it beekeepers seasonally transport hives to different locations after the flowering of different crops. These movements could be detrimental to pollinators by: i) stressing honey bees, making them more susceptible to pathogens and parasites; ii) spreading bee parasites and pathogens across locations; iii) increasing the transmission of parasites and pathogens between managed and wild pollinators and vice versa (spillover and spillback, respectively). To understand the impact of migratory beekeeping on bee health, we conducted a systematic review to identify the main trends and provide a complete picture of existing knowledge on the subject. We found 52 studies analysing pathogen-related impacts of migratory beekeeping on honey bees. However, only 16 investigations tested the effect of migratory practices on the prevalence and spread of pathogens and parasites. We found no studies that assessed the impact of migratory beekeeping on the occurrence and spread of pests and diseases in wild bees. In general, migratory beekeeping tends to increase the prevalence of pathogens and parasites in honey bee colonies. However, the results were very heterogeneous, probably due to several uncontrolled underlying factors such as management, biological and geographical factors, and the interactions between them. In conclusion, there is an urgent need for studies to assess the impact of migratory beekeeping on bee health, given the current global bee decline and the expected increase in migratory beekeeping due to climate change and crop pollination demand.

Microsporidia: a promising vector control tool for residual malaria transmission

Long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) have resulted in a major decrease in malaria transmission. However, it has become apparent that malaria can be effectively transmitted despite high coverage of LLINs/IRS. Residual transmission can occur due to Plasmodium-carrying Anopheles mosquitoes that are insecticide resistant and have feeding and resting behavior that reduces their chance of encountering the currently deployed indoor malaria control tools. Residual malaria transmission is likely to be the most significant hurdle to achieving the goal of malaria eradication and research and development towards new tools and strategies that can control residual malaria transmission is therefore critical. One of the most promising strategies involves biological agents that are part of the mosquito microbiome and influence the ability of Anopheles to transmit Plasmodium. These differ from biological agents previously used for vector control in that their primary effect is on vectoral capacity rather than the longevity and fitness of Anopheles (which may or may not be affected). An example of this type of biological agent is Microsporidia MB, which was identified in field collected Anopheles arabiensis and caused complete inhibition of Plasmodium falciparum transmission without effecting the longevity and fitness of the host. Microsporidia MB belongs to a unique group of rapidly adapting and evolving intracellular parasites and symbionts called microsporidia. In this review we discuss the general biology of microsporidians and the inherent characteristics that make some of them particularly suitable for malaria control. We then discuss the research priorities for developing a transmission blocking strategy for the currently leading microsporidian candidate Microsporidia MB for malaria control.

Colonisation Patterns of Nosema ceranae in the Azores Archipelago

Nosema ceranae is a highly prevalent pathogen of Apis mellifera, which is distributed worldwide. However, there may still exist isolated areas that remain free of N. ceranae. Herein, we used molecular tools to survey the Azores to detect N. ceranae and unravel its colonisation patterns. To that end, we sampled 474 colonies from eight islands in 2014/2015 and 91 from four islands in 2020. The findings revealed that N. ceranae was not only present but also the dominant species in the Azores. In 2014/2015, N. apis was rare and N. ceranae prevalence varied between 2.7% in São Jorge and 50.7% in Pico. In 2020, N. ceranae prevalence increased significantly (p < 0.001) in Terceira and São Jorge also showing higher infection levels. The spatiotemporal patterns suggest that N. ceranae colonised the archipelago recently, and it rapidly spread across other islands, where at least two independent introductions might have occurred. Flores and Santa Maria have escaped the N. ceranae invasion, and it is remarkable that Santa Maria is also free of Varroa destructor, which makes it one of the last places in Europe where the honey bee remains naive to these two major biotic stressors.

Microsporidia: a new taxonomic, evolutionary, and ecological synthesis

Microsporidian diversity is vast. There is a renewed drive to understand how microsporidian pathological, genomic, and ecological traits relate to their phylogeny. We comprehensively sample and phylogenetically analyse 125 microsporidian genera for which sequence data are available. Comparing these results with existing phylogenomic analyses, we suggest an updated taxonomic framework to replace the inconsistent clade numbering system, using informal taxonomic names: Glugeida (previously clades 5/3), Nosematida (4a), Enterocytozoonida (4b), Amblyosporida (3/5), Neopereziida (1), and Ovavesiculida (2). Cellular, parasitological, and ecological traits for 281 well-defined species are compared with identify clade-specific patterns across long-branch Microsporidia. We suggest that future taxonomic circumscriptions of Microsporidia should involve additional markers (SSU/ITS/LSU), and that a comprehensive suite of phenotypic and ecological traits help to predict broad microsporidian functional and lineage diversity.

Paromomycin Reduces Vairimorpha (Nosema) ceranae Infection in Honey Bees but Perturbs Microbiome Levels and Midgut Cell Function

Paromomycin is a naturally occurring aminoglycoside antibiotic that has effects on both prokaryotic and eukaryotic microbes. However, previous reports have indicated that it has little effect on microsporidia, including Vairimorpha (Nosema) ceranae, in cell culture models. V. ceranae is one of a number of microsporidia species that cause disease in honey bees and substantial efforts to find new treatment strategies for bees that are infected with these pathogens are ongoing. When testing compounds for potential activity against V. ceranae in whole organisms, we found that paromomycin reduces the infection intensity of this parasite. Critically, the necessary doses of paromomycin have high activity against the bacteria of the honey bee microbiome and cause evident stress in bees. Microsporidia have been shown to lack an essential binding site on the ribosome that is known to allow for maximal inhibition by paromomycin. Thus, it is possible that paromomycin impacts parasite levels through non-cell autonomous effects on microsporidia infection levels via effects on the microbiome or midgut cellular function. As paromomycin treatment could cause widespread honey bee health issues in agricultural settings, it does not represent an appropriate anti-microsporidia agent for use in the field.

Protists in the Insect Rearing Industry: Benign Passengers or Potential Risk?

As the insects for food and feed industry grows, a new understanding of the industrially reared insect microbiome is needed to better comprehend the role that it plays in both maintaining insect health and generating disease. While many microbiome projects focus on bacteria, fungi or viruses, protists (including microsporidia) can also make up an important part of these assemblages. Past experiences with intensive invertebrate rearing indicate that these parasites, whilst often benign, can rapidly sweep through populations, causing extensive damage. Here, we review the diversity of microsporidia and protist species that are found in reared insect hosts and describe the current understanding of their host spectra, life cycles and the nature of their interactions with hosts. Major entomopathogenic parasite groups with the potential to infect insects currently being reared for food and feed include the Amoebozoa, Apicomplexa, Ciliates, Chlorophyta, Euglenozoa, Ichtyosporea and Microsporidia. However, key gaps exist in the understanding of how many of these entomopathogens affect host biology. In addition, for many of them, there are very limited or even no molecular data, preventing the implementation of molecular detection methods. There is now a pressing need to develop and use novel molecular tools, coupled with standard molecular diagnostic methods, to help unlock their biology and predict the effects of these poorly studied protist parasites in intensive insect rearing systems.

Molecular Detection and Differentiation of Arthropod, Fungal, Protozoan, Bacterial and Viral Pathogens of Honeybees

The honeybee Apis mellifera is highly appreciated worldwide because of its products, but also as it is a pollinator of crops and wild plants. The beehive is vulnerable to infections due to arthropods, fungi, protozoa, bacteria and/or viruses that manage to by-pass the individual and social immune mechanisms of bees. Due to the close proximity of bees in the beehive and their foraging habits, infections easily spread within and between beehives. Moreover, international trade of bees has caused the global spread of infections, several of which result in significant losses for apiculture. Only in a few cases can infections be diagnosed with the naked eye, by direct observation of the pathogen in the case of some arthropods, or by pathogen-associated distinctive traits. Development of molecular methods based on the amplification and analysis of one or more genes or genomic segments has brought significant progress to the study of bee pathogens, allowing for: (i) the precise and sensitive identification of the infectious agent; (ii) the analysis of co-infections; (iii) the description of novel species; (iv) associations between geno- and pheno-types and (v) population structure studies. Sequencing of bee pathogen genomes has allowed for the identification of new molecular targets and the development of specific genotypification strategies.

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.

Frontiers in effective control of problem parasites in beekeeping

Demand for better control of certain parasites in managed western honey bees (Apis mellifera L.) remains apparent amongst beekeepers in both Europe and North America, and is of widespread public, scientific, and agricultural concern. Academically, interest from numerous fields including veterinary sciences has led to many exemplary reviews of the parasites of honey bees and the treatment options available. However, summaries of current research frontiers in treating both novel and long-known parasites of managed honey bees are lacking. This review complements the currently comprehensive body of literature summarizing the effectiveness of parasite control in managed honey bees by outlining where significant gaps in development, implementation, and uptake lie, including integration into IPM frameworks and separation of cultural, biological, and chemical controls. In particular, I distinguish where challenges in identifying appropriate controls exist in the lab compared to where we encounter hurdles in technology transfer due to regulatory, economic, or cultural contexts. I overview how exciting frontiers in honey bee parasite control research are clearly demonstrated by the abundance of recent publications on novel control approaches, but also caution that temperance must be levied on the applied end of the research engine in believing that what can be achieved in a laboratory research environment can be quickly and effectively marketed for deployment in the field.

Revising the Freshwater Thelohania to Astathelohania gen. et comb. nov., and Description of Two New Species

Crayfish are common hosts of microsporidian parasites, prominently from the genus Thelohania. Thelohania is a polyphyletic genus, with multiple genetically distinct lineages found from freshwater and marine environments. Researchers have been calling for a revision of this group for over a decade. We provide evidence that crayfish-infecting freshwater Thelohania are genetically and phylogenetically distinct from the marine Thelohania (Clade V/Glugeida), whilst also describing two new species that give further support to the taxonomic revision. We propose that the freshwater Thelohania should be transferred to their own genus, Astathelohania gen. et comb. nov., in a new family (Astathelohaniidae n. fam.). This results in the revision of Thelohania contejeani (Astathelohania contejeani), Thelohania montirivulorum (Astathelohania montirivulorum), and Thelohania parastaci (Astathelohania parastaci). We also describe two novel muscle-infecting Astathelohania species, A. virili n. sp. and A. rusti n. sp., from North American crayfishes (Faxonius sp.). We used histological, molecular, and ultrastructural data to formally describe the novel isolates. Our data suggest that the Astathelohania are genetically distinct from other known microsporidian genera, outside any described family, and that their SSU rRNA gene sequence diversity follows their host species and native geographic location. The range of this genus currently includes North America, Europe, and Australia.

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.

Current Therapy and Therapeutic Targets for Microsporidiosis

Microsporidia are obligate intracellular, spore-forming parasitic fungi which are grouped with the Cryptomycota. They are both opportunistic pathogens in humans and emerging veterinary pathogens. In humans, they cause chronic diarrhea in immune-compromised patients and infection is associated with increased mortality. Besides their role in pébrine in sericulture, which was described in 1865, the prevalence and severity of microsporidiosis in beekeeping and aquaculture has increased markedly in recent decades. Therapy for these pathogens in medicine, veterinary, and agriculture has become a recent focus of attention. Currently, there are only a few commercially available antimicrosporidial drugs. New therapeutic agents are needed for these infections and this is an active area of investigation. In this article we provide a comprehensive summary of the current as well as several promising new agents for the treatment of microsporidiosis including: albendazole, fumagillin, nikkomycin, orlistat, synthetic polyamines, and quinolones. Therapeutic targets which could be utilized for the design of new drugs are also discussed including: tubulin, type 2 methionine aminopeptidase, polyamines, chitin synthases, topoisomerase IV, triosephosphate isomerase, and lipase. We also summarize reports on the utility of complementary and alternative medicine strategies including herbal extracts, propolis, and probiotics. This review should help facilitate drug development for combating microsporidiosis.

Gross Morphology of Diseased Tissues in Nezara viridula (Hemiptera: Pentatomidae) and Molecular Characterization of an Associated Microsporidian

Nezara viridula (L.) (Hemiptera: Pentatomidae), commonly known in the U.S. as the southern green stink bug (SGSB), is a cosmopolitan, highly polyphagous feeder that causes severe damage to a wide range of agronomically important crops such as fruit, vegetable, grain, tobacco, and cotton, throughout much of the United States, and is a global pest of considerable ecological, agricultural, and economical interest. During dissection of female Nz. viridula, conspicuous black and brown spots or lesions were observed on various internal organs. To determine the cause of these spots or lesions, tissues of fat body, spermatheca, ovaries, and ovulated eggs were collected from healthy and infected individuals. The gross morphology of the spots was characterized, and the microorganisms associated with the infection were identified by amplicon sequencing of the V4 region of the small subunit rRNA gene. The presence of a microsporidian pathogen Nosema maddoxi, Becnel, Solter, Hajek, Huang, Sanscrainte, & Estep (Microsporidia: Nosematidae) which has been observed on other species of stink bug, was evidenced for the first time. The characterization of the gross morphology of this associated microsporidian may enable more rapid determination of microsporidia infection in stink bug colonies and field populations.

Age and Season Effect the Timing of Adult Worker Honeybee Infection by Nosema ceranae

The microsporidia Nosema ceranae is an intracellular parasite of honeybees’ midgut, highly prevalent in Apis mellifera colonies for which important epidemiological information is still unknown. Our research aimed at understanding how age and season influence the onset of infection in honeybees and its development in the colony environment. Adult worker honeybees of less than 24h were marked and introduced into 6 different colonies in assays carried out in spring and autumn. Bees of known age were individually analyzed by PCR for Nosema spp. infection and those resulting positive were studied to determine the load by Real Time-qPCR. The age of onset and development of infection in each season was studied on a total of 2401 bees and the probability and the load of infection for both periods was established with two statistical models. First N. ceranae infected honeybees were detected at day 5 post emergence (p.e.; spring) and at day 4 p.e. (autumn) and in-hive prevalence increased from that point onwards, reaching the highest mean infection on day 18 p.e. (spring). The probability of infection increased significantly with age in both periods although the age variable better correlated in spring. The N. ceranae load tended to increase with age in both periods, although the age-load relationship was clearer in spring than in autumn. Therefore, age and season play an important role on the probability and the development of N. ceranae infection in honeybees, bringing important information to understand how it spreads within a colony.

Factors That Determine Microsporidia Infection and Host Specificity

Microsporidia are a large phylum of obligate intracellular parasites that infect an extremely diverse range of animals and protists. In this chapter, we review what is currently known about microsporidia host specificity and what factors influence microsporidia infection. Extensive sampling in nature from related hosts has provided insight into the host range of many microsporidia species. These field studies have been supported by experiments conducted in controlled laboratory environments which have helped to demonstrate host specificity. Together, these approaches have revealed that, while examples of generalist species exist, microsporidia specificity is often narrow, and species typically infect one or several closely related hosts. For microsporidia to successfully infect and complete their life cycle within a compatible host, several steps must occur, including spore germination, host cell invasion, and proliferation of the parasite within the host tissue. Many factors influence infection, including temperature, seasonality, nutrient availability, and the presence or absence of microbes, as well as the developmental stage, sex, and genetics of the host. Several studies have identified host genomic regions that influence resistance to microsporidia, and future work is likely to uncover molecular mechanisms of microsporidia host specificity in more detail.

Impact of Honey Bee Migratory Management on Pathogen Loads and Immune Gene Expression is Affected by Complex Interactions With Environment, Worker Life History, and Season

The effects of honey bee management, such as intensive migratory beekeeping, are part of the ongoing debate concerning causes of colony health problems. Even though comparisons of disease and pathogen loads among differently managed colonies indicate some effects, the direct impact of migratory practices on honey bee pathogens is poorly understood. To test long- and short-term impacts of managed migration on pathogen loads and immunity, experimental honey bee colonies were maintained with or without migratory movement. Individuals that experienced migration as juveniles (e.g., larval and pupal development), as adults, or both were compared to control colonies that remained stationary and therefore did not experience migratory relocation. Samples at different ages and life-history stages (hive bees or foragers), taken at the beginning and end of the active season, were analyzed for pathogen loads and physiological markers of health. Bees exposed to migratory management during adulthood had increased levels of the AKI virus complex (Acute bee paralysis, Kashmir bee, and Israeli acute bee paralysis viruses) and decreased levels of antiviral gene expression (dicer-like). However, those in stationary management as adults had elevated gut parasites (i.e. trypanosomes). Effects of environment during juvenile development were more complex and interacted with life-history stage and season. Age at collection, life-history stage, and season all influenced numerous factors from viral load to immune gene expression. Although the factors that we examined are not independent, the results illuminate potential factors in both migratory and nonmigratory beekeeping that are likely to contribute to colony stress, and also indicate potential mitigation measures.

Microsporidian Pathogens of Aquatic Animals

Around 57.1% of microsporidia occupy aquatic environments, excluding a further 25.7% that utilise both terrestrial and aquatic systems. The aquatic microsporidia therefore compose the most diverse elements of the Microsporidia phylum, boasting unique structural features, variable transmission pathways, and significant ecological influence. From deep oceans to tropical rivers, these parasites are present in most aquatic environments and have been shown to infect hosts from across the Protozoa and Animalia. The consequences of infection range from mortality to intricate behavioural change, and their presence in aquatic communities often alters the overall functioning of the ecosystem.In this chapter, we explore aquatic microsporidian diversity from the perspective of aquatic animal health. Examples of microsporidian parasitism of importance to an aquacultural ('One Health') context and ecosystem context are focussed upon. These include infection of commercially important penaeid shrimp by Enterocytozoon hepatopenaei and interesting hyperparasitic microsporidians of wild host groups.Out of ~1500 suggested microsporidian species, 202 have been adequately taxonomically described using a combination of ultrastructural and genetic techniques from aquatic and semi-aquatic hosts. These species are our primary focus, and we suggest that the remaining diversity have additional genetic or morphological data collected to formalise their underlying systematics.

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.

Comparative Genomics of Microsporidia

The microsporidia are a phylum of intracellular parasites that represent the eukaryotic cell in a state of extreme reduction, with genomes and metabolic capabilities embodying eukaryotic cells in arguably their most streamlined state. Over the past 20 years, microsporidian genomics has become a rapidly expanding field starting with sequencing of the genome of Encephalitozoon cuniculi, one of the first ever sequenced eukaryotes, to the current situation where we have access to the data from over 30 genomes across 20+ genera. Reaching back further in evolutionary history, to the point where microsporidia diverged from other eukaryotic lineages, we now also have genomic data for some of the closest known relatives of the microsporidia such as Rozella allomycis, Metchnikovella spp. and Amphiamblys sp. Data for these organisms allow us to better understand the genomic processes that shaped the emergence of the microsporidia as a group. These intensive genomic efforts have revealed some of the processes that have shaped microsporidian cells and genomes including patterns of genome expansions and contractions through gene gain and loss, whole genome duplication, differential patterns of invasion and purging of transposable elements. All these processes have been shown to occur across short and longer time scales to give rise to a phylum of parasites with dynamic genomes with a diversity of sizes and organisations.

Reviewing the Efficacy of Pollen Substitutes as a Management Tool for Improving the Health and Productivity of Western Honey Bee (Apis mellifera) Colonies

Western honey bees (Apis mellifera L.) collect pollen from flowers as their source of protein, fat, vitamins, and minerals. Beekeepers feed pollen substitutes to their honey bee colonies to mitigate a lack of natural pollen resources in the environment. Despite their widespread use, it is unclear if pollen substitutes are beneficial to colony health and productivity. Herein, we review the literature regarding pollen substitute efficacy in four major categories: (1) consumption/palatability of pollen substitutes, (2) colony productivity, (3) pest and disease response, and (4) physiological response. Collectively, the literature shows a mix of positive, neutral, and negative impacts of pollen substitutes on honey bee colony health. Additionally, we recommend areas for improvement in pollen substitute research. We hope this review will lead to more research on pollen substitutes given nutrition is a key factor impacting the health of managed honey bees globally.

Honey bees with a drinking problem: potential routes of Nosema ceranae spore transmission

Nosema apis and N. ceranae are the two causative agents of Nosema disease in adult honey bees (Apis mellifera L.). Nosema apis has been a recognized parasite for over a century and its epizootiology is well known. In contrast, N. ceranae is an emerging parasite of honey bees, which is now globally prevalent and the dominant Nosema spp. in many parts of the world. Despite this, many gaps in our knowledge exist regarding this species. For example, we do not fully understand all of the routes of transmission of N. ceranae among bees, or how long this parasite is capable of surviving in honey bee colonies. Here we investigated the viability and infectivity of N. ceranae spores in water and 2 M sucrose over time after storage at 33, 20, −12 and −20°C. Spores in both 2 M sucrose and water maintained high viability, except in water at −20°C over the course of the 6-week experiment. Infectivity was variable for spores after storage at all four temperatures, but all were infective at the last time point. The results provide evidence for cold tolerance and suggest that both water and 2 M sucrose (fall bee feed) could act as routes of transmission for N. ceranae. This work also contains information that may help influence management recommendations for the parasite.

Diseases and Pests of Honey Bees (Apis Mellifera)

Infectious and parasitic diseases plague honey bees similarly to that of other food animal species. A complete understanding of each is necessary for a honey bee veterinarian to establish a strong veterinarian-client-patient relationship and make sound treatment recommendations. Control and management of these diseases is paramount to success of the colony and apiary operation. The following is not meant to be an end-all of information on each of the common honey bee diseases but more so a review and photo-documentation of each. A deeper understanding can be established through various other sources previously published and referenced in this document.

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.

The microsporidium Nosema pyrausta as a potent microbial control agent of the beet webworm Loxostege sticticalis

The microsporidium Nosema pyrausta is an important mortality factor of the European corn borer, Ostrinia nubilalis. The present study was aimed at N. pyrausta virulence testing to the beet webworm (BW), Loxostege sticticalis. This agricultural pest, L. sticticalis, was highly vulnerable to N. pyrausta. The parasite's spores were located in salivary glands, adipose tissue, and Malpighian tubules of the infected specimens. Infection was transmitted transovarially through at least 3 laboratory generations, in which BW fitness indices were lower than in the control, and moth emergence and fertility decreased prominently. Transovarial infection was most detrimental to female egg-laying ability, resulting in zero fertility in F3. When propagated in BW, the microsporidium tended to increase its virulence to L. sticticalis, as compared to the Ostrinia isolates. The parasite's ability to infect this host at low dosages and transmit vertically should guarantee its effective establishment and spread within BW populations. In conclusion, N. pyrausta is a promising agent against BW, which is a notorious polyphagous pest in Eurasia.

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.

Generation of a Microsporidia Species Attribute Database and Analysis of the Extensive Ecological and Phenotypic Diversity of Microsporidia

Microsporidia are a large group of fungus-related obligate intracellular parasites. Though many microsporidia species have been identified over the past 160 years, depiction of the full diversity of this phylum is lacking. To systematically describe the characteristics of these parasites, we created a database of 1,440 species and their attributes, including the hosts they infect and spore characteristics. We find that microsporidia have been reported to infect 16 metazoan and 4 protozoan phyla, with smaller phyla being underrepresented. Most species are reported to infect only a single host, but those that are generalists are also more likely to infect a broader set of host tissues. Strikingly, polar tubes are threefold longer in species that infect tissues besides the intestine, suggesting that polar tube length is a determinant of tissue specificity. Phylogenetic analysis revealed four clades which each contain microsporidia that infect hosts from all major habitats. Although related species are more likely to infect similar hosts, we observe examples of changes in host specificity and convergent evolution. Taken together, our results show that microsporidia display vast diversity in their morphology and the hosts they infect, illustrating the flexibility of these parasites to evolve new traits.

A phylogenetic framework to investigate the microsporidian communities through metabarcoding and its application to lake ecosystems

Microsporidia are obligate intracellular eukaryotic parasites known to parasitize many species of the animal kingdom as well as some protists. However, their diversity is underestimated, in part as a consequence of the failure of 'universal' primers to detect them in metabarcoding studies. Besides, due to the inconsistency between taxonomy and phylogenetic data, available databases may assign incorrectly sequences obtained with high-throughput sequencing. In this work, we developed a comprehensive reference database which positions microsporidian SSU rRNA gene sequences within a coherent ranked phylogenetic framework. We used this phylogenetic framework to study the microsporidian diversity in lacustrine ecosystems, focusing on < 150 μm planktonic size fractions. Our analysis shows a high diversity of Microsporidia, with the identification of 1531 OTUs distributed within seven clades, of which 76% were affiliated to clade IV2 and 20% to clade I (nomenclature presented hereby). About a quarter of the obtained sequences shared less than 85% identity to the closest known species, which might represent undescribed genera or families infecting small hosts. Variations in the abundance of Microsporidia were recorded between the two lakes sampled and across the sampling period, which might be explained by spatio-temporal variations of their potential hosts such as microeukaryotes and metazooplankton.

First record of a new microsporidium pathogenic to Gonipterus platensis in Brazil

Microsporidia are naturally occurring fungal-related parasites that can infect nearly all animal hosts, but their biocontrol potential of insect pests is routinely overlooked in agriculture and forestry. This research brings the first report describing the natural occurrence of a microsporidium causing disease in field-collected populations of the invasive eucalyptus snout beetle, Gonipterus platensis (Coleoptera: Curculionidae), a major destructive pest of eucalyptus plantations in Brazil. Adult beetles were collected during field surveys in commercial eucalyptus plantations in southern Brazil to be examined and dissected with typical symptoms to verify presence of microsporidian spores in haemolymph. From 14 plantations in different sites, the natural infection occurrence in these populations ranged from 0 to 65%, while a lab colony exhibited an infection incidence of 70%. Spore density in haemolymph of symptomatic insects averaged 2.1 (± 0.4) × 107 spores/beetle. Symptoms in infected adults were identified by an abnormal abdomen with malformation of the second pair of wings, impairing their flight activity. Electron transmission microscopy of the pathogen showed morphological features similar to species belonging to the genus Nosema or Vairimorpha. Phylogenetic analysis of the full-length small subunit ribosomal RNA gene suggests this pathogen's placement in the genus Vairimorpha, but with a sequence identity of ~ 94% with the nearest neighbours. The low level of sequence identity suggests this pathogen may represent a novel taxon in the genus and further requires whole genome sequencing for definitive taxonomic resolution. These findings provide insights on the natural occurrence of this novel pathogen of this invasive pest in Eucalyptus plantations in Brazil. Further studies are needed to determine potential of this microsporidium in the design of conservative or augmentative biological control programs for this invasive pest.

Susceptibility of the Gypsy Moth Lymantria dispar (Lepidoptera: Erebidae) to Nosema pyrausta (Microsporidia: Nosematidae)

Simple Summary

Microsporidia are widespread insect pathogens and a single species may infect different hosts. Nosema pyrausta from the corn borer was tested against the gypsy moth. Thirty days after larvae were fed with spores, infection was established in the salivary glands and fat body of pupae and prepupae. Up to 10% of insects became infected. The gypsy moth can be referred to as a resistant host of N. pyrausta.

Abstract

The gypsy moth, Lymantria dispar, is a notorious forest defoliator, and various pathogens are known to act as natural regulators of its population density. As a widespread herbivore with a broad range of inhabited areas and host plants, it is potentially exposed to parasitic microorganisms from other insect hosts. In the present paper, we determined the susceptibility of gypsy moth larvae to the microsporidium Nosema pyrausta from the European corn borer, Ostrinia nubilalis. Gypsy moth samples from two localities of Western Siberia were used. N. pyrausta developed infections in the salivary gland and adipose tissue of gypsy moth prepupae and pupae, forming spore masses after 30 days of alimentary exposure to the second instar larvae. Among the experimental groups, the infection levels ranged from 0 to 9.5%. Effects of a covert baculovirus infection, phenylthiourea pretreatment and feeding insects on an artificial diet versus natural foliage were not significant in terms of microsporidia prevalence levels. Thus, L. dispar showed a low level of susceptibility to a non-specific microsporidium. It can be referred to as a resistant model host and not an appropriate substitute host for laboratory propagation of the microsporidium.

Parasites and RNA viruses in wild and laboratory reared bumble bees Bombus pauloensis (Hymenoptera: Apidae) from Uruguay

Bumble bees (Bombus spp.) are important pollinators insects involved in the maintenance of natural ecosystems and food production. Bombus pauloensis is a widely distributed species in South America, that recently began to be managed and commercialized in this region. The movement of colonies within or between countries may favor the dissemination of parasites and pathogens, putting into risk while populations of B. pauloensis and other native species. In this study, wild B. pauloensis queens and workers, and laboratory reared workers were screened for the presence of phoretic mites, internal parasites (microsporidia, protists, nematodes and parasitoids) and RNA viruses (Black queen cell virus (BQCV), Deformed wing virus (DWV), Acute paralysis virus (ABCV) and Sacbrood virus (SBV)). Bumble bee queens showed the highest number of mite species, and it was the only group where Conopidae and S. bombi were detected. In the case of microsporidia, a higher prevalence of N. ceranae was detected in field workers. Finally, the bumble bees presented the four RNA viruses studied for A. mellifera, in proportions similar to those previously reported in this species. Those results highlight the risks of spillover among the different species of pollinators.

Revisiting the phylogeny of microsporidia

Canonical microsporidians are a group of obligate intracellular parasites of a wide range of hosts comprising ~1,300 species of >220 genera. Microsporidians are related to fungi, and many characterised and uncharacterized groups closely related to them have been discovered recently, filling the knowledge gaps between them. These groups assigned to the superphylum Opisthosporidia have provided several important insights into the evolution of diverse intracellular parasitic lineages within the tree of eukaryotes. The most studied among opisthosporidians, canonical microsporidians, were known to science more than 160 years ago, however, the classification of canonical Microsporidia has been challenging due to common morphological homoplasy, and accelerated evolutionary rates. Instead of morphological characters, ssrRNA sequences have been used as the primary data for the classification of canonical microsporidians. Previous studies have produced a useful backbone of the microsporidian phylogeny, but provided only some nodal support, causing some confusion. Here, we reconstructed phylogenetic trees of canonical microsporidians using Bayesian and Maximum Likelihood inferences. We included rRNA sequences of 126 described/named genera, by far the broadest taxon coverage to date. Overall, our trees show similar topology and recovered four of the five main clades demonstrated in previous studies (Clades 1, 3, 4 and 5). Family level clades were well resolved within each major clade, but many were discordant with the recently revised classification. Therefore, revision and some reshuffling, especially within and between Clades 1 and 3 are required. We also reconstructed phylogenetic trees of Opisthosporidia to better integrate the evolutionary history of canonical microsporidians in a broader context. We discuss several traits shared only by canonical microsporidians that may have contributed to their striking ecological success in diverse metazoans. More targeted studies on the neglected host groups will be of value for a better understanding of the evolutionary history of these interesting intracellular parasites.

The first record of Vairimorpha hostounsky sp. nov. Infection in the blue shieldbug, Zicrona caerulea Linnaeus, 1758 (Hemiptera: Pentatomidae)

A microsporidian pathogen was originally identified using molecular techniques from Oulema melanopus L. (Coleoptera, Chrysomelidae) under a "working name" Nosema oulemae, but its description was never published. In the present study, a microsporidian infection was detected in the Blue Shieldbug, Zicrona caerulea for the first time, showing 99.9% SSU rRNA sequence similarity to N. oulemae (Genbank accession U27359). Life cycle, tissue tropism, ultrastructure and phylogenetical relationships with other microsporidia species were disclosed. Nymph and adult stages of the host were infected with mature spores produced in the gut, hemocoel and fat body. Spores of the parasite measured approximately 4.50 ± 0.36 μm in length and 2.46 ± 0.18 μm in width on fresh smears. The number of coils of the polar filament was 9-11. Coils were 109.23 ± 22.92 nm (range: 93.75-268.66; n = 50) in diameter and consisted of seven concentric layers of different electron density and thickness. The spores possessed a relatively thick (174.04 ± 57.65 nm) trilaminar spore wall. Developmental sequence and ultrastructure The SSU rRNA and RPB1 gene sequences were deposited GenBank under accession MT102274 and MW538912. Basing upon the sequence similarity, the isolate from Z. caerulea can be attributed to the species from O. melanopus provisionally designated as N. oulemae. The novel species Vairimorpha hostounsky sp. nov. is described, named after Prof. Zdenek Hostounsky who was the first to discover this parasite.

Patterns of infection in a native and an invasive crayfish across the UK

Invasive crayfish and the introduction of non-native diseases pose a significant risk for the conservation of endangered, white-clawed crayfish (Austropotamobius pallipes). Continued pollution of waterways is also of concern for native species and may be linked with crayfish disease dynamics. We explore whether crayfish species or environmental quality are predictors of infection presence and prevalence in native A. pallipes and invasive signal crayfish (Pacifastacus leniusculus). We use a seven-year dataset of histology records, and a field survey comparing the presence and prevalence of infectious agents in three isolated A. pallipes populations; three isolated P. leniusculus populations, and three populations where the two species had overlapped in the past. We note a lower diversity of parasites (Simpson's Index) in P. leniusculus ('Pacifastacus leniusculus Bacilliform Virus' - PlBV) (n = 1 parasite) relative to native A. pallipes (n = 4 parasites), which host Thelohania contejeani, 'Austropotamobius pallipes bacilliform virus' (ApBV), Psorospermium haeckeli and Branchiobdella astaci, at the sites studied. The infectious group present in both species was an intranuclear bacilliform virus of the hepatopancreas. The prevalence of A. astaci in A. pallipes populations was higher in more polluted water bodies, which may reflect an effect of water quality, or may be due to increased chance of transmission from nearby P. leniusculus, a species commonly found in poor quality habitats.

Silver nanoparticles are effective in controlling microsporidia

Many approaches and technologies have been developed as treatments for microsporidian, infections but effective, broad-spectrum, and sustainable therapeutic approaches have not been found. Silver nanoparticles (AgNPs) have antimicrobial activity and are widely used against many different pathogens. AgNPs provide an opportunity to develop formulations that will control microsporidia. In this study, we synthesized AgNPs via a chemical reduction method and evaluated their formation, morphology, and stability using transmission electron microscopy (TEM) and ultraviolet spectroscopy analysis. We verified that AgNPs could disrupt the spore cell membrane and spore germination of microsporidia Nosema bombycis. This resulted in the release of microsporidia nucleic acids, proteins, and respiratory chain enzymes. The anti-microsporidia activity of AgNPs was studied by measuring the silkworm larvae survival rate and spore genome replication after microsporidia infection. AgNPs have anti-microsporidian activity and could be effective components of formulations for treating or preventing microsporidia infection.

Genetic diversity of Loma acerinae (Microsporidia: Glugeida) from different fish hosts and localities - Short communication

Loma acerinae is a xenoma-forming fish microsporidium described from common ruffe Gymnocephalus cernua (Perciformes: Percidae) and also found in Ponto-Caspian gobies (Gobiiformes: Gobiidae). This casts doubt on the strict host specificity of this parasite. The largest subunit RNA polymerase II (rpb1) was used as a genetic marker of the parasite isolated from six host species of Perciformes (G. cernua from the Baltic Sea), Atheriniformes (Atherina boyeri from the Azov Sea) and Gobiiformes (Neogobius spp. and Zosterisessor ophiocephalus from the Black Sea and Ponticola kessleri from the Caspian Sea basin). Two major rpb1 haplogroups were found with 98.5% identity between the groups. Notably, Haplogroup I was associated with Neogobius spp. samples (n = 6) only, whereas Haplogroup II included the samples from other host species (n = 7). These findings confirm the broad distribution and host range of L. acerinae, but also indicate that certain patterns of host-driven intraspecific polymorphism may exist. Furthermore, the study revealed low similarity between the ribosomal RNA gene sequences of L. acerinae and the type species, Loma morhua (as well as other species of the genus). This suggests loose genetic association within the genus, and may raise the need for the taxonomic revision of L. acerinae.

Identification and localization of Nup170 in the microsporidian Nosema bombycis

As one of the core framework proteins of nuclear pore complex (NPC), nucleoporin Nupl70 acts as a structural adapter between the nucleolus and nuclear pore membrane and maintains the stability of NPC structure through interaction with other proteins. In this study, we identified a Nup170 protein in the microsporidian Nosema bombycis for the first time and named it as NbNup170. Secondary structure prediction showed that the NbNup170 contains α-helices and random coils. The three-dimensional structure of NbNup170 is elliptical in shape. Phylogenetic analysis based on the Nup170 and homologous sequences showed that N. bombycis clustered together with Vairimorpha ceranae and Vairimorpha apis. The immunofluorescence localization results showed that the NbNup170 was located on the plasma membrane of the dormant spore and transferred to the surface of sporoplasm in a punctate pattern when the dormant spore has finished germination, and that NbNup170 was distributed on the nuclear membrane and both sides of the nuclei of early proliferative phase, and only on the nuclear membrane during sporogonic phase in the N. bombycis. qPCR analysis showed that the relative expression level of NbNup170 maintained at a low level from 30 to 78 h post-infection with N. bombycis, then reached the highest at 102 h, while that of NbNup170 was repressed at a very low level throughout its life cycle by RNA interference. These results suggested that NbNup170 protein is involved in the proliferative phase and active during the sporogonic phase of N. bombycis.

Morphological and molecular characterization of a new microsporidium, Janacekia tainanus n. sp. from the adipose tissue of Kiefferulus tainanus (Diptera: Chironomidae) in China

We reported a new microsporidium Janacekia tainanus n. sp. from the adipose tissue of the midge Kiefferulus tainanus Kieffer, 1912 collected from a eutrophic pond in Daye city, Hubei Province, China. Infected chironomid larvae with hypertrophied adipose tissue exhibited porcelain-white. All developmental stages possessed large nuclei. The earliest stages observed were diplokaryotic meronts which were in direct contact with the host adipocyte cytoplasm. Diplokaryotic meronts developed into sporonts with the deposition of electron-dense coagulum on their surface. Multinucleate sporogonial plasmodia developed into uninucleate sporoblasts by the rosette-like division. Mature spores were oval and monokaryotic, measuring 6.14 ± 0.27 (5.65-6.67) µm long and 3.71 ± 0.12 (3.43-3.98) µm wide. Bipartite polaroplast consisted of a narrow anterior lamella and a wide posterior lamella. Isofilar polar filaments coiled 13-17 turns and arranged in one row. The exospore was thin and of no stratification, but remarkably covered with tubular secretions. The electron-lucent endospore was thick and measured 145-352 nm wide. Phylogenetic analysis based on the obtained SSU rDNA sequence indicated that the present species clustered closely with Jirovecia sinensis, a species with rod-shaped mature spores isolated from the coelomocytes of Branchiura sowerbyi. Consistent with the previous result, the monophyletic clade of Jirovecia-Bacillidium-Janacekia was sister to Pseudonosema clade and then collectively nested within Clade V of Class Aquasporidia sensu Vossbrinck and Debrunner-Vossbrinck (2005). The novel species did not form an independent monophyletic lineage with the congener, Janacekia debaisieuxi. Based on the morphological characters and ultrastructural features, as well as SSU rDNA-inferred phylogenetic relationships, a new species in the genus Janacekia, Janacekia tainanus n. sp. was designated. This is the first report of aquatic arthropod-infecting microsporidia in China.

An international inter-laboratory study on Nosema spp. spore detection and quantification through microscopic examination of crushed honey bee abdomens

Nosemosis is a microsporidian disease causing mortality and weakening of honey bee colonies, especially in the event of co-exposure to other sources of stress. As a result, the disease is regulated in some countries. Reliable and harmonised diagnosis is crucial to ensure the quality of surveillance and research results. For this reason, the first European Interlaboratory Comparison (ILC) was organised in 2017 in order to assess both the methods and the results obtained by National Reference Laboratories (NRLs) in counting Nosema spp. spores by microscopy. Implementing their own routine conditions of analysis, the 23 participants were asked to perform an assay on a panel of ten positive and negative samples of crushed honey bee abdomens. They were asked to report results from a qualitative and quantitative standpoint. The assessment covered specificity, sensitivity, trueness and precision. Quantitative results were analysed in compliance with international standards NF ISO 13528 (2015) and NF ISO 5725-2 (1994). Three results showed a lack of precision and five a lack of trueness. However, overall results indicated a global specificity of 98% and a global sensitivity of 100%, thus demonstrating the advanced performance of the microscopic methods applied to Nosema spores by the NRLs. Therefore, the study concluded that using microscopy to detect and quantify spores of Nosema spp. was reliable and valid.

Bumble bees in landscapes with abundant floral resources have lower pathogen loads

The pollination services provided by bees are essential for supporting natural and agricultural ecosystems. However, bee population declines have been documented across the world. Many of the factors known to undermine bee health (e.g., poor nutrition) can decrease immunocompetence and, thereby, increase bees’ susceptibility to diseases. Given the myriad of stressors that can exacerbate disease in wild bee populations, assessments of the relative impact of landscape habitat conditions on bee pathogen prevalence are needed to effectively conserve pollinator populations. Herein, we assess how landscape-level conditions, including various metrics of floral/nesting resources, insecticides, weather, and honey bee (Apis mellifera) abundance, drive variation in wild bumble bee (Bombus impatiens) pathogen loads. Specifically, we screened 890 bumble bee workers from varied habitats in Pennsylvania, USA for three pathogens (deformed wing virus, black queen cell virus, and Vairimorpha (= Nosema) bombi), Defensin expression, and body size. Bumble bees collected within low-quality landscapes exhibited the highest pathogen loads, with spring floral resources and nesting habitat availability serving as the main drivers. We also found higher loads of pathogens where honey bee apiaries are more abundant, a positive relationship between Vairimorpha loads and rainfall, and differences in pathogens by geographic region. Collectively, our results highlight the need to support high-quality landscapes (i.e., those with abundant floral/nesting resources) to maintain healthy wild bee populations.

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

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.

Nosema ceranae (Microspora: Nosematidae): A Sweet Surprise? Investigating the Viability and Infectivity of N. ceranae Spores Maintained in Honey and on Beeswax

Nosema disease is a prominent malady among adult honey bees [Apis mellifera L. (Hymenoptera: Apidae)], caused by the microsporidian parasites, Nosema apis Zander (Microspora: Nosematidae) and N. ceranae Fries et al. 1996. The biology of N. apis is well understood, as this parasite was first described over a century ago. As N. ceranae is an emerging parasite of the honey bee, we do not yet understand how long spores of this parasite survive in honey bee colonies, or all the potential modes of transmission among bees. We investigated the viability and infectivity of N. ceranae spores in honey and on beeswax over time after exposure to 33, 20, -12, and -20°C. Spores in honey maintained viability at freezing temperatures for up to 1 yr and remained viable considerably longer than those on beeswax. Based on this evidence, honey may act as an important reservoir for infective spores to initiate or perpetuate N. ceranae infections in honey bee colonies. This work provides information that may help enhance current management recommendations for apiculturalists.

DEVELOPMENT OF MICROSPORIDIOLOGY IN RUSSIA

The study of microsporidia and microsporidioses of wild animals in Russia has been initiated in the 60-s of the past century. In the European part of country, microsporidia, infecting agricultural insect pests (All-Russian Institute of Plant Protection), freshwater arthropods and fishes (State Research Institute of Lake and River Fisheries) and the blood-sucking insects such as horseflies (Biology Institute, Karelian Scientific Center) were studied. In the Western Siberia, microsporidia of blood-sucking mosquitoes were studied (Tomsk University). As a result, by 2000, as many as 118 species and 47 genera of microsporidia were found, including 20 taxa new to science, from 100 animal species. Currently, descriptions of new taxa and taxonomic revision of the previously described taxa are performed using the molecular phylogenetic analysis. The novel data on speciation of microsporidia have been obtained, and the coevolution of parasites and their host insects have been confirmed for microsporidia of blood-sucking mosquitoes. During the study of the structure and physiology of microsporidia, it has been demonstrated, that the secretory proteins of microsporidia migrate into the nucleus of the host cell; the factors of parasites suppressing host cell apoptosis and the presence of specific organelles related to the energy metabolism have been revealed; the mitosomes have been found in the spores and not the prespore stages of microsporidia. The role of the Golgi complex in the formation of the extrusion apparatus, as well as the absence of the vesicular secretory transport in microsporidia, has been shown for the first time. For the first time in Russia, cases of microsporidia infection in HIV-infected patients have been identified. Currently, attention is paid to the development of a new universal taxonomic system of microsporidia combining molecular characteristics with a description of the structural and developmental features of each taxon of the parasites. Microsporidia possess many remarkable structural and functional differences from any other organisms thus substantiating an independent field of biological research: “microsporidiology”.

A new isolate of Nosema fumiferanae (Microsporidia: Nosematidae) from the date moth Apomyelois (Ectomyelois) ceratoniae, Zeller, 1839 (Lepidoptera: Pyralidae)

In this study, a microsporidian pathogen of the date moth (Apomyelois (Ectomyelois) ceratoniae, Zeller, 1839) also known as the carob moth, is described based on light microscopy, ultrastructural characteristics and comparative molecular analysis. The pathogen infects the gut and hemolymph of A. ceratoniae. All development stages are in direct contact with the host cell cytoplasm. Fresh spores with nuclei arranged in a diplokaryon are oval and measured 3.29 ± 0.23 μm (4.18-3.03 μm, n = 200) in length and 1.91 ± 0.23 μm (2.98-1.66 μm, n = 200) in width. Spores stained with Giemsa's stain measured 3.11 ± 0.31 μm (3.72-2.41 μm, n = 150) in length and 1.76 ± 0.23 μm (2.16-1.25 μm, n = 150) in width. Spores have an isofilar polar filament with 10-12 coils. An 1110 bp long alignment of the current microsporidium showed an SSU rRNA gene difference of only 0.0009, corresponding to >99.91% sequence similarity with Nosema fumiferanae, while RPB1 gene sequences were 98.03% similar within an alignment of 969 bp. All morphological, ultrastructural and molecular features indicate that the microsporidian pathogen of A. ceratoniae is the new isolate of the N. fumiferanae and is named here as Nosema fumiferanae TY61.