Large pathogen screening reveals first report of Megaselia scalaris (Diptera: Phoridae) parasitizing Apis mellifera intermissa (Hymenoptera: Apidae)

Consequences of microsporidian prior exposure for virus infection outcomes and bumble bee host health

Host-parasite interactions do not occur in a vacuum, but in connected multi-parasite networks that can result in co-exposures and coinfections of individual hosts. These can affect host health and disease ecology, including disease outbreaks. However, many host-parasite studies examine pairwise interactions, meaning we still lack a general understanding of the influence of co-exposures and coinfections. Using the bumble bee Bombus impatiens, we study the effects of larval exposure to a microsporidian Nosema bombi, implicated in bumble bee declines, and adult exposure to Israeli Acute Paralysis Virus (IAPV), an emerging infectious disease from honey bee parasite spillover. We hypothesize that infection outcomes will be modified by co-exposure or coinfection. Nosema bombi is a potentially severe, larval-infecting parasite, and we predict that prior exposure will result in decreased host resistance to adult IAPV infection. We predict double parasite exposure will also reduce host tolerance of infection, as measured by host survival. Although our larval Nosema exposure mostly did not result in viable infections, it partially reduced resistance to adult IAPV infection. Nosema exposure also negatively affected survival, potentially due to a cost of immunity in resisting the exposure. There was a significant negative effect of IAPV exposure on survivorship, but prior Nosema exposure did not alter this survival outcome, suggesting increased tolerance given the higher IAPV infections in the bees previously exposed to Nosema. These results again demonstrate that infection outcomes can be non-independent when multiple parasites are present, even when exposure to one parasite does not result in a substantial infection.

First detection of Lake Sinai virus in the Czech Republic: a potential member of a new species

Lake Sinai virus (LSV) is one of over 20 honey bee viruses. Variants of LSV have been classified as members of two officially recognised species, Lake Sinai virus 1 and Lake Sinai virus 2. However, there are currently a limited number of whole-genome sequences, and the genetic variability of the virus indicates that additional species may need to be established. Extracted nucleic acid of 209 honey bee samples was screened by PCR for 11 honey bee viruses. LSV was the third most abundant virus (36.9% of positive samples), after Apis mellifera filamentous virus (72.2%) and deformed wing virus (52.5%). LSV-positive samples were analyzed further by PCR with primers targeting the region encoding the viral RNA-dependent RNA polymerase. Subsequently, the PCR products were sequenced, and the resulting sequences were used for a first round of phylogenetic analysis. Based on those results, several isolates were selected for whole-genome sequencing, and the complete genome sequences were used for additional phylogenetic analysis. The results indicated the presence of at least three genetically distinct groups of LSV in the Czech Republic, the most prevalent one being related to LSV 2 but too dissimilar to be considered a member of the same species. Two sequences of a major LSV strain cluster native to the Czech Republic were determined, representing the first Czech LSV strains published to date.

Multibiomarker responses after exposure to a sublethal concentration of thiamethoxam in the African honeybee (Apis mellifera intermissa)

Thiamethoxam is an insecticide mainly used in agriculture to control insect pests. However, non-target insect species, such as honeybees, may also be impacted. In this study, adults of Apis mellifera intermissa were orally exposed under laboratory conditions to a sublethal concentration of thiamethoxam (CL₂₅₌ 0.17 ng/μl) for 9 days and the effects were evaluated at the biochemical level, by monitoring specific oxidative stress and neuronal biomarkers. Results showed an increase in the antioxidant enzymes, glutatione-S-transferase (GST), catalase (CAT) and glutathione peroxidase (GPx) and in content of malondialdehyde (MDA). The activity of acetylcholinesterase (AChE) was downregulated as evidence of a neurotoxic action and no significant change was observed in glutathione (GSH). Exposure to the insecticide thiamethoxam induced oxidative stress and defense mechanisms affecting honeybee physiology.

Beekeeping Genetic Resources and Retrieval of Honey Bee Apis mellifera L. Stock in the Russian Federation: A Review

The loss of honey bees has drawn a large amount of attention in various countries. Therefore, the development of efficient methods for recovering honey bee populations has been a priority for beekeepers. Here we present an extended literature review and report on personal communications relating to the characterization of the local and bred stock of honey bees in the Russian Federation. New types have been bred from local colonies (A. mellifera L., A. m. carpatica Avet., A. m. caucasia Gorb.). The main selection traits consist of a strong ability for overwintering, disease resistance and different aptitudes for nectar collection in low and high blooming seasons. These honey bees were certified by several methods: behavioral, morphometric and genetic analysis. We illustrate the practical experience of scientists, beekeepers and breeders in breeding A. mellifera Far East honey bees with Varroa and tracheal mite resistance, which were the initial reasons for breeding the A. mellifera Far Eastern breed by Russian breeders, Russian honey bee in America, the hybrid honey bee in Canada by American breeders, and in China by Chinese beekeepers. The recent achievements of Russian beekeepers may lead to the recovery of beekeeping areas suffering from crossbreeding and losses of honey bee colonies.

Crithidia mellificae infection in different mammalian species in Brazil

Crithidia mellificae, a monoxenous trypanosomatid considered restricted to insects, was recently reported to infect a bat. Herein, C. mellificae has been demonstrated to have a wider range of vertebrate hosts and distribution in Brazilian biomes than once thought. Parasites isolated from haemocultures were characterized using V7V8 SSU rDNA and glyceraldehyde 3-phosphate dehydrogenase genes. Coatis (Nasua nasua) in the Cerrado; marmosets (Callithrix sp.) and bats (Carollia perspicillata, Myotis lavali, M. izecksohni, Artibeus lituratus) in the Atlantic Forest; crab-eating foxes (Cerdocyon thous) and ocelot (Leopardus pardalis) in the Pantanal biomes were infected by trypanosomatids that displayed choanomastigote forms in haemoculture in Giemsa-stained slide smears. Molecular characterization and phylogenetic inference confirmed the infection of C. mellificae in these animals. Moreover, slight differences in C. mellificae sequences were observed. Crithidia mellificae growth curves were counted at 27°C, 36°C and 37°C, and the morphotypes were able to grow and survive for up to 16 days. Serological titers for C. mellificae were observed in nonhuman primates, demonstrating that this parasite is able to induce a humoral immune response in an infected mammal. These results showed that host specificity in trypanosomatids is complex and far from understood.

First Report on Megaselia scalaris Loew (Diptera: Phoridae) Infestation of the Invasive Pest Spodoptera frugiperda Smith (Lepidoptera: Noctuidae) in China

Simple Summary

The invasive pest Spodoptera frugiperda first emerged in China in 2019, and therefore the information on indigenous natural enemies of S. frugiperda has been limited in China. In this study, we reported that a dipteran species was observed to infest S. frugiperda collected from maize fields in four different regions of China. Further morphological and molecular recognition identified all the flies as Megaselia scalaris. The findings of this study will improve our understanding on natural enemies to S. frugiperda and potentially provide new ideas for integrated pest management strategies in China.

Abstract

The invasive pest Spodoptera frugiperda first emerged in China in January 2019 and has, to date, migrated to 29 provinces and municipalities in China, causing heavy crop damage in large areas. As a response to this invasive species from the environment, some indigenous natural enemies have been discovered and reported after S. frugiperda invasion. In this paper, parasitic flies were collected and identified from S. frugiperda collected in the Yunnan, Guangxi, and Henan provinces and the Chongqing municipality in China. By using both conventional and molecular approaches, we were able to show that all the parasitic flies of S. frugiperda identified in the four regions were Megaselia. scalaris, and that they attacked the pest larvae and pupae. This is the first report on an indigenous Chinese Megaselia species that has parasitic ability against the invasive pest S. frugiperda, potentially providing new ideas for pest control in China.

The First Record of Facultative Parasitism of Megaselia Spp. (Diptera: Phoridae) in a Honeybee Colony in Slovakia

The current global climate warming trend leads to a shift in animal-habitats northwards. According to the Slovak Hydrometeorological Institute, summer 2018 was extremely hot and long throughout Slovakia. This was probably the fact that resulted in the detection of the presence of Megaselia spp. (Diptera: Phoridae) in one honeybee colony at the University apiary located in Rozhanovce (48° 46’ 27.24″ N; 21° 22’ 26.01″ E; eastern Slovakia). The first warning signal after opening the hive was the changed odour. During closer inspection, there were observed small parasitoid phorid larvae that emerged from the sealed bee brood; further examination revealed that the parasitized bee larvae and pupae contained emptied body cavities. Vice-versa, parasitisation was not detected in adult honey bees. Our knowledge of Diptera being responsible for parasitizing (even facultative) the honey bee (Apis mellifera) is still incomplete and needs to be investigated further in more details.

Bee Viruses: Routes of Infection in Hymenoptera

Numerous studies have recently reported on the discovery of bee viruses in different arthropod species and their possible transmission routes, vastly increasing our understanding of these viruses and their distribution. Here, we review the current literature on the recent advances in understanding the transmission of viruses, both on the presence of bee viruses in Apis and non-Apis bee species and on the discovery of previously unknown bee viruses. The natural transmission of bee viruses will be discussed among different bee species and other insects. Finally, the research potential of in vivo (host organisms) and in vitro (cell lines) serial passages of bee viruses is discussed, from the perspective of the host-virus landscape changes and potential transmission routes for emerging bee virus infections.

Comparison between Apicystis cryptica sp. n. and Apicystis bombi (Arthrogregarida, Apicomplexa): Gregarine parasites that cause fat body hypertrophism in bees

The molecular divergence, morphology and pathology of a cryptic gregarine that is related to the bee parasite Apicystis bombi Lipa and Triggiani, 1996 is described. The 18S ribosomal DNA gene sequence of the new gregarine was equally dissimilar to that of A. bombi and the closest related genus Mattesia Naville, 1930, although phylogenetic analysis supported a closer relation to A. bombi. Pronounced divergence with A. bombi was found in the ITS1 sequence (69.6% similarity) and seven protein-coding genes (nucleotide 78.05% and protein 90.2% similarity). The new gregarine was isolated from a Bombus pascuorum Scopoli, 1763 female and caused heavy hypertrophism of the fat body tissue in its host. In addition, infected cells of the hypopharyngeal gland tissue, an important excretory organ of the host, were observed. Mature oocysts were navicular in shape and contained four sporozoites, similar to A. bombi oocysts. Given these characteristics, we proposed the name Apicystis cryptica sp. n. Detections so far indicated that distribution and host species occupation of Apicystis spp. overlap at least in Europe, and that historical detections could not discriminate between them. Specific molecular assays were developed that can be implemented in future pathogen screens that aim to discriminate Apicystis spp. in bees.

Systemic Israeli acute paralysis virus (IAPV) infection in bumblebees (Bombus terrestris) through feeding and injection

Israeli acute paralysis virus (IAPV) can cause a systemic infection, resulting in mortality in both Apis and Bombus spp. bees. However, little is known about the virus infection dynamics within bee tissues. Here, we established systemic IAPV infections in reared bumblebee Bombus terrestris workers through feeding and injection and investigated the mortality, tissue tropism and viral localization. Injection of approximately 500 IAPV (IAPV^inj stock) particles resulted in acute infection, viral loads within tissues that were relatively stable from bee to bee, and a distinctive tissue tropism, making this method suitable for studying systemic IAPV infection in bumblebees. Feeding with approximately 1 × 10⁶ particles of the same virus stock did not result in systemic infection. A high-concentration stock of IAPV (IAPV^fed stock) allowed us to feed bumblebees with approximately 1 × 10⁹ viral particles, which induced both chronic and acute infection. We also observed a higher variability in viral titers within tissues and less clear tissue tropism during systemic infection, making feeding with IAPV^fed stock less optimal for studying IAPV systemic infection. Strikingly, both infection methods and stocks with different viral loads gave a similar viral localization pattern in the brain and midgut of bumblebees with an acute infection. The implications of these findings in the study of the local immunity in bees and barriers to oral transmission are discussed. Our data provide useful information on the establishment of a systemic viral infection in bees.