Innate type 2 immunity controls hair follicle commensalism by Demodex mites.

Demodex mites are commensal parasites of hair follicles (HFs). Normally asymptomatic, inflammatory outgrowth of mites can accompany malnutrition, immune dysfunction, and aging, but mechanisms restricting Demodex outgrowth are not defined. Here, we show that control of mite HF colonization in mice required group 2 innate lymphoid cells (ILC2s), interleukin-13 (IL-13), and its receptor, IL-4Ra-IL-13Ra1. HF-associated ILC2s elaborated IL-13 that attenuated HFs and epithelial proliferation at anagen onset; in their absence, Demodex colonization led to increased epithelial proliferation and replacement of gene programs for repair by aberrant inflammation, leading to the loss of barrier function and HF exhaustion. Humans with rhinophymatous acne rosacea, an inflammatory condition associated with Demodex, had increased HF inflammation with decreased type 2 cytokines, consistent with the inverse relationship seen in mice. Our studies uncover a key role for skin ILC2s and IL-13, which comprise an immune checkpoint that sustains cutaneous integrity and restricts pathologic infestation by colonizing HF mites.

Phylogenomics resolves the higher-level phylogeny of herbivorous eriophyoid mites (Acariformes: Eriophyoidea).

BACKGROUND: Eriophyoid mites (Eriophyoidea) are among the largest groups in the Acariformes; they are strictly phytophagous. The higher-level phylogeny of eriophyoid mites, however, remains unresolved due to the limited number of available morphological characters-some of them are homoplastic. Nevertheless, the eriophyoid mites sequenced to date showed highly variable mitochondrial (mt) gene orders, which could potentially be useful for resolving the higher-level phylogenetic relationships. RESULTS: Here, we sequenced and compared the complete mt genomes of 153 eriophyoid mite species, which showed 54 patterns of rearranged mt gene orders relative to that of the hypothetical ancestor of arthropods. The shared derived mt gene clusters support the monophyly of eriophyoid mites (Eriophyoidea) as a whole and the monophylies of six clades within Eriophyoidea. These monophyletic groups and their relationships were largely supported in the phylogenetic trees inferred from mt genome sequences as well. Our molecular dating results showed that Eriophyoidea originated in the Triassic and diversified in the Cretaceous, coinciding with the diversification of angiosperms. CONCLUSIONS: This study reveals multiple molecular synapomorphies (i.e. shared derived mt gene clusters) at different levels (i.e. family, subfamily or tribe level) from the complete mt genomes of 153 eriophyoid mite species. We demonstrated the use of derived mt gene clusters in unveiling the higher-level phylogeny of eriophyoid mites, and underlines the origin of these mites and their co-diversification with angiosperms.

ICTV Virus Taxonomy Profile: Fimoviridae 2024.

Members of the family Fimoviridae are plant viruses with a multipartite negative-sense enveloped RNA genome (-ssRNA), composed of 4-10 segments comprising 12.3-18.5 kb in total, within quasi-spherical virions. Fimoviruses are transmitted to plants by eriophyid mites and induce characteristic cytopathologies in their host plants, including double membrane-bound bodies in the cytoplasm of virus-infected cells. Most fimoviruses infect dicotyledonous plants, and many cause serious disease epidemics. This is a summary of the ICTV Report on the family Fimoviridae, which is available at ictv.global/report/fimoviridae.

Biomechanical adaptations enable phoretic mite species to occupy distinct spatial niches on host burying beetles.

Niche theory predicts that ecologically similar species coexist by minimizing interspecific competition through niche partitioning. Therefore, understanding the mechanisms of niche partitioning is essential for predicting interactions and coexistence between competing organisms. Here, we study two phoretic mite species, Poecilochirus carabi and Macrocheles nataliae that coexist on the same host burying beetle Nicrophorus vespilloides and use it to 'hitchhike' between reproductive sites. Field observations revealed clear spatial partitioning between species in distinct host body parts. Poecilochirus carabi preferred the ventral side of the thorax, whereas M. nataliae were exclusively found ventrally at the hairy base of the abdomen. Experimental manipulations of mite density showed that each species preferred these body parts, largely regardless of the density of the other mite species on the host beetle. Force measurements indicated that this spatial distribution is mediated by biomechanical adaptations, because each mite species required more force to be removed from their preferred location on the beetle. While P. carabi attached with large adhesive pads to the smooth thorax cuticle, M. nataliae gripped abdominal setae with their chelicerae. Our results show that specialist biomechanical adaptations for attachment can mediate spatial niche partitioning among species sharing the same host.

Structural homology of mite profilins to plant profilins is not indicative of allergic cross-reactivity.

Structural and allergenic characterization of mite profilins has not been previously pursued to a similar extent as plant profilins. Here, we describe structures of profilins originating from Tyrophagus putrescentiae (registered allergen Tyr p 36.0101) and Dermatophagoides pteronyssinus (here termed Der p profilin), which are the first structures of profilins from Arachnida. Additionally, the thermal stabilities of mite and plant profilins are compared, suggesting that the high number of cysteine residues in mite profilins may play a role in their increased stability. We also examine the cross-reactivity of plant and mite profilins as well as investigate the relevance of these profilins in mite inhalant allergy. Despite their high structural similarity to other profilins, mite profilins have low sequence identity with plant and human profilins. Subsequently, these mite profilins most likely do not display cross-reactivity with plant profilins. At the same time the profilins have highly conserved poly(l-proline) and actin binding sites.

Response of the serine/threonine kinase AKT and phosphoinositide-dependent kinase PDK in Frankliniella occidentalis (Thysanoptera: Thripidae) to three kinds of foods and their regulation of reproductive function.

Frankliniella occidentalis (Pergande) is a typical omnivorous insect that feeds on host plants, pollens and mite eggs, and poses a threat to crops worldwide. The insulin signalling pathway (ISP) is a typical nutrient-sensitive pathway that participates in the regulation of various functions in insects. Serine/threonine kinases (AKTs) and phosphoinositide-dependent kinases (PDKs) are key components of the ISP. In this study, the FoAKT and FoPDK genes in F. occidentalis were cloned, and the effects of three foods on their expression were determined. The expression of FoAKT and FoPDK in the thrips fed on kidney bean leaves supplemented with pine pollen or mite eggs was higher than in those primarily fed on leaves alone. Meanwhile, the fecundity of thrips fed on leaves supplemented with pine pollen was highest. In addition, RNA interference-mediated knockdown of FoAKT and FoPDK decreased vitellogenin (Vg) content and Vg expression in females, shortened ovariole length, delayed egg development and reduced fecundity and offspring hatching rates. Furthermore, the synthesis of juvenile hormone (JH) was reduced, and the contents of glucose, trehalose, glycogen and trehalase were affected. These results suggest that FoAKT and FoPDK regulate the reproduction of F. occidentalis by regulating Vg and JH production as well as carbohydrate metabolism.

Clinical Relevance of Lepidoglyphus destructor Sensitisation in Allergic Rhinitis: Nasal Provocation Test as in vivo Assessment.

BACKGROUND: Dust mites are the leading cause of respiratory allergic diseases worldwide. Allergy to storage mites (SMs) has mostly been related to occupational exposures. However, recent studies have shown that sensitisation to SM, such as Lepidoglyphus destructor (Lep d), is of considerable importance also in urban populations, with high prevalence in dust samples of domestic environments. Co-sensitisation between house dust mites (HDMs) and SM is now regarded as very frequent in some regions, and cross-reactivity between them seems to be narrow. Therefore, SM allergenic capacity is increasingly a subject of study. The nasal provocation test (NPT), as an in vivo technique, could be considered the gold standard for the clinical relevance assessment of an allergen, in polysensitised rhinitis patients. OBJECTIVE: The objective of this study was to analyse the clinical relevance of the SM Lep d, by assessing the relationship between in vivo sensitisation and expression of allergic respiratory disease in an urban setting. PATIENTS AND METHODS: In our study, we enrolled a total of 32 allergic patients with rhinitis (with or without asthma) with proven sensitisation by skin prick test (SPT) and specific IgE (sIgE) to HDMs and/or SM. Patients underwent NPT with Lep d using subjective (Lebel Symptom Score Scale) and objective measurements (peak nasal inspiratory flow [PNIF]) for assessment of nasal response. RESULTS: Most of the patients with positive SPT and sIgE to Lep d had a positive NPT (24/27; 89%). True Lep d allergy, assessed by a positive NPT, could be predicted by a SPT wheal size >9.7 mm and a sIgE >0.42 kUA/L, with 100%/95.7% sensitivity and 75.0%/83.3% specificity, respectively. Co-sensitisation between Lep d and Der p was high, 75.0%. Asthma was more frequent in the positive Lep d NPT group (54 vs. 12%, p < 0.05). Significantly more patients from this group reported physical exercise, nonspecific irritants, and respiratory infections as relevant triggers of respiratory symptoms (p < 0.01-p < 0.05). CONCLUSIONS: To our knowledge, this is the first study to show that sensitisation to Lep d may have clinical relevance in a non-occupational setting. In this group, there seems to be a relationship between allergy to Lep d and severity of respiratory disease, with more bronchial inflammation, when comparing with mite-allergic patients sensitised only to HDM. Therefore, the authors consider that sensitisation to Lep d should be considered when assessing and treating allergic respiratory disease in urban environments.

Dispersal-Limited Symbionts Exhibit Unexpectedly Wide Variation in Host Specificity.

A fundamental aspect of symbiotic relationships is host specificity, ranging from extreme specialists associated with only a single host species to generalists associated with many different species. Although symbionts with limited dispersal capabilities are expected to be host specialists, some are able to associate with multiple hosts. Understanding the micro- and macro-evolutionary causes of variations in host specificity is often hindered by sampling biases and the limited power of traditional evolutionary markers. Here, we studied feather mites to address the barriers associated with estimates of host specificity for dispersal-limited symbionts. We sampled feather mites (Proctophyllodidae) from a nearly comprehensive set of North American breeding warblers (Parulidae) to study mite phylogenetic relationships and host-symbiont codiversification. We used pooled-sequencing (Pool-Seq) and short-read Illumina technology to interpret results derived from a traditional barcoding gene (cytochrome c oxidase subunit 1) versus 11 protein-coding mitochondrial genes using concatenated and multispecies coalescent approaches. Despite the statistically significant congruence between mite and host phylogenies, mite-host specificity varies widely, and host switching is common regardless of the genetic marker resolution (i.e., barcode vs. multilocus). However, the multilocus approach was more effective than the single barcode in detecting the presence of a heterogeneous Pool-Seq sample. These results suggest that presumed symbiont dispersal capabilities are not always strong indicators of host specificity or of historical host-symbiont coevolutionary events. A comprehensive sampling at fine phylogenetic scales may help to better elucidate the microevolutionary filters that impact macroevolutionary processes regulating symbioses, particularly for dispersal-limited symbionts. [Codiversification; cophylogenetics; feather mites; host switching; pooled sequencing; species delineation; symbiosis, warblers.].

Transcriptomics of differences in thermal plasticity associated with selection for an exaggerated male sexual trait.

The information about the magnitude of differences in thermal plasticity both between and within populations, as well as identification of the underlying molecular mechanisms are key to understanding the evolution of thermal plasticity. In particular, genes underlying variation in the physiological response to temperature can provide raw material for selection acting on plastic traits. Using RNAseq, we investigate the transcriptional response to temperature in males and females from bulb mite populations selected for the increased frequency of one of two discrete male morphs (fighter- and scrambler-selected populations) that differ in relative fitness depending on temperature. We show that different mechanisms underlie the divergence in thermal response between fighter- and scrambler-selected populations at decreased vs. increased temperature. Temperature decrease to 18 °C was associated with higher transcriptomic plasticity of males with more elaborate armaments, as indicated by a significant selection-by-temperature interaction effect on the expression of 40 genes, 38 of which were upregulated in fighter-selected populations in response to temperature decrease. In response to 28 °C, no selection-by-temperature interaction in gene expression was detected. Hence, differences in phenotypic response to temperature increase likely depended on genes associated with their distinct morph-specific thermal tolerance. Selection of males also drove gene expression patterns in females. These patterns could be associated with temperature-dependent fitness differences between females from fighter- vs. scrambler-selected populations reported in previous studies. Our study shows that selection for divergent male sexually selected morphologies and behaviors has a potential to drive divergence in metabolic pathways underlying plastic response to temperature in both sexes.

Empirically tuned theory reveals why symbiont abundance 'mite' vary across hosts.

Research Highlight: del Mar Labrador, M., Serrano, D., Doña, J., Aguilera, E., Arroyo, J. L., Atiénzar, F., Barba, E., Bermejo, A., Blanco, G., Borràs, A., Calleja, J. A., Cantó, J. L., Cortés, V., de la Puente, J., de Palacio, D., Fernández-González, S., Figuerola, J., Frías, Ó., Fuertes-Marcos, B. Garamszegi, L. Z., Gordo, Ó., Gurpegui, M., Kovács, I., Martínez, J. L., Meléndez, L., Mestre, A., Møller, A. P., Monrós, J. S., Moreno-Opo, R., Navarro, C., Pap, P. L., Pérez-Tris, J., Piculo, R., Ponce, C., Proctor, H., Rodríguez, R., Sallent, Á., Senar, J., Tella, J. L., Vágási, C. I., Vögeli, M., & Jovani, R. (2023). Host space, not energy or symbiont size, constrains feather mite abundance across passerine bird species. Journal of Animal Ecology, https://doi.org/10.1111/1365-2656.14032. Symbionts represent crucial links between species in ecosystems. Consequently, understanding their patterns of abundance is a major goal in the study of symbioses. However, multiple biotic and abiotic factors may regulate symbionts, and disentangling the mechanisms that drive variation in their abundance across host species is challenging. One promising strategy to approach this challenge is to incorporate biologically relevant data into theoretical models. In a recent study, Labrador et al. (2023) used this strategy to investigate the poorly understood symbiosis between feather mites and their avian hosts. They integrate a remarkable amount of empirical data with models based on the metabolic theory of ecology to determine what factors limit feather mite abundance across European passerines. Their quantitative analyses indicate that the number of feather barbs limits mite abundance across host species, suggesting that mite populations are spatially, but not energetically, constrained. These findings not only reveal mechanisms that may drive the variation in feather mite abundances across hosts, but also advance our understanding of the ecology of interspecific interactions more generally.

Host space, not energy or symbiont size, constrains feather mite abundance across passerine bird species.

Comprehending symbiont abundance among host species is a major ecological endeavour, and the metabolic theory of ecology has been proposed to understand what constrains symbiont populations. We parameterized metabolic theory equations to investigate how bird species' body size and the body size of their feather mites relate to mite abundance according to four potential energy (uropygial gland size) and space constraints (wing area, total length of barbs and number of feather barbs). Predictions were compared with the empirical scaling of feather mite abundance across 106 passerine bird species (26,604 individual birds sampled), using phylogenetic modelling and quantile regression. Feather mite abundance was strongly constrained by host space (number of feather barbs) but not by energy. Moreover, feather mite species' body size was unrelated to the body size of their host species. We discuss the implications of our results for our understanding of the bird-feather mite system and for symbiont abundance in general.

Sister predatory mites collectively protect their eggs against predators.

Group-living animals sometimes cooperatively protect their offspring against predators. This behavior is observed in a wide range of taxa but, to the best of our knowledge, this is the first report of its occurrence in arthropods that are not eusocial. Adult female predatory mites Gynaeseius liturivorus protect their eggs against egg predators, the predatory mite species Neoseiulus californicus. In the field, several adult female G. liturivorus were often found on the same plant structures such as folded leaves. We tested whether these females might protect their eggs cooperatively, focusing on kinship between the females. When two adult female G. liturivorus were kept in the absence of egg predators, their reproduction was not affected by their kinship. The presence of egg predators reduced the number of G. liturivorus eggs. However, reproduction of two G. liturivorus sisters was higher than that of two non-sisters. Together, sisters guarded the oviposition site longer than non-sisters. We further tested if non-sisters increased egg guarding by having developed together from eggs to adults and found no such effect. Although it remains unclear how adult female G. liturivorus recognize conspecifics as kin or sisters, our results suggest that G. liturivorus sisters reduced predation on their offspring by cooperatively guarding their eggs.

Lost companions: a new quill mite species and its possible coextinction with the Carolina parakeet.

Investigations of the parasites associated with extinct avian species provide unique insights into the ecology and evolution of both hosts and their parasitic counterparts. In the present paper, a new quill mite species, Peristerophila conuropsis sp. n., belonging to the family Syringophilidae (Prostigmata: Cheyletoidea) is described from the Carolina parakeet Conuropsis carolinensis Linnaeus (Psittaciformes: Psittacidae). This new species was collected from museum dry skin of the Carolina parakeet, the only native representative of the Psittacidae in the United States, which was an abundant resident of the southeastern and midwestern states and has been extinct in the beginning of the 20th century. Comment on the current taxonomic state and host associations of the genus Peristerophila are provided. Based on the host associations and habitats occupied by Peristerophila and related genera on parrots, it is hypothesized with the high probability that P. conuropsis has been extinct along with its host.

Evidence for the Clinical Association between Demodex and Rosacea: A Review.

BACKGROUND: Rosacea is a chronic inflammatory dermatological condition in humans, and its pathogenesis remains unclear. However, the development of rosacea is suspected to be related to Demodex, a microscopic commensal organism that resides in or near hair follicles and sebaceous glands. Although Demodex is known to be a host-specific, obligate commensal organism, it is currently difficult to be cultured in vitro to parasitize and infect other animal hosts. Therefore, direct evidence for a pathogenic role of Demodex in rosacea is currently lacking. SUMMARY: As circumstantial evidence, non-invasive skin-detecting techniques have shown abnormally elevated numbers of Demodex in rosacea patients. Increased cytokine levels such as IL-10, IL-8, and IL-12p70 have been observed in human sebocytes following the Demodex challenge, and acaricides have been found to be effective in rosacea therapy, all point to a close relationship between Demodex and rosacea. Based on these findings, we conducted a comprehensive literature review to summarize the current state of knowledge, research insights, and clinical treatment recommendations for Demodex-associated rosacea, with the ultimate goal of improving patient outcomes.

A Breakthrough in Kitavirids: Genetic Variability, Reverse Genetics, Koch's Postulates, and Transmission of Hibiscus Green Spot Virus 2.

Hibiscus green spot virus 2 (HGSV-2), a member of the genus Higrevirus (family Kitaviridae), is a positive-stranded RNA virus associated with leprosis-like symptoms in citrus and green spots on leaves in hibiscus. HGSV-2 has only been reported in Hawaii, and while it is speculated that mites in the genus Brevipalpus might be responsible for its transmission, proper transmission assays have yet to be conducted. This study characterizes additional citrus and hibiscus isolates of HGSV-2 collected from two Hawaiian Islands. We constructed an infectious cDNA clone from a hibiscus isolate of HGSV-2 collected on Oahu and demonstrated its ability to infect several experimental hosts, including Phaseolus vulgaris, Nicotiana tabacum, and N. benthamiana, as well as natural hosts, Citrus reticulata and Hibiscus arnottianus. Bacilliform virions with varied sizes of 33 to 120 nm (length) and 14 to 70 nm (diameter) were observed in partially purified preparations obtained from agroinoculated leaves. Virus progeny from the infectious cDNA clone was found to be infectious after mechanical transmission to N. benthamiana and to cause local lesions. Finally, an isoline colony of the mite Brevipalpus azores had vector competence to transmit a citrus isolate of HGSV-2 collected from Maui to citrus and hibiscus plants, demonstrating the mite-borne nature of HGSV-2. The infectious cDNA clone developed in this study is the first reverse-genetics system for a kitavirid and will be fundamental to better characterize basic biology of HGSV-2 and its interactions with host plants and mite vectors.

Helper Component-Proteinase of Triticum Mosaic Virus Is a Viral Determinant of Wheat Curl Mite Transmission.

Triticum mosaic virus (TriMV; genus Poacevirus; family Potyviridae) is an economically important virus in the Great Plains region of the United States. TriMV is transmitted by the wheat curl mite (Aceria tosichella) Type 2 genotype but not by Type 1. Helper component-proteinase (HC-Pro) is a vector transmission determinant for several potyvirids, but the role of HC-Pro in TriMV transmission is unknown. In this study, we examined the requirement of the HC-Pro cistron of TriMV for wheat curl mite (Type 2) transmission through deletion and point mutations and constructing TriMV chimeras with heterologous HC-Pros from other potyvirids. TriMV with complete deletion of HC-Pro failed to be transmitted by wheat curl mites at detectable levels. Furthermore, TriMV chimeras with heterologous HC-Pros from aphid-transmitted turnip mosaic virus and tobacco etch virus, or wheat curl mite-transmitted wheat streak mosaic virus, failed to be transmitted by wheat curl mites. These data suggest that heterologous HC-Pros did not complement TriMV for wheat curl mite transmission. A decreasing series of progressive nested in-frame deletions at the N-terminal region of HC-Pro comprising amino acids 3 to 125, 3 to 50, 3 to 25, 3 to 15, 3 to 8, and 3 and 4 abolished TriMV transmission by wheat curl mites. Additionally, mutation of conserved His20, Cys49, or Cys52 to Ala in HC-Pro abolished TriMV transmissibility by wheat curl mites. These data suggest that the N-terminal region of HC-Pro is crucial for TriMV transmission by wheat curl mites. Collectively, these data demonstrate that the HC-Pro cistron of TriMV is a viral determinant for wheat curl mite transmission.

Vitellogenin and its upstream gene TOR play essential roles in the reproduction of Dermanyssus gallinae.

In Dermanyssus gallinae, a hematophagous mite, the initiation of vitellogenesis induced by blood feeding is essential for its reproduction. However, the precise gene structures and physiological functions of Vg in D. gallinae and its upstream gene, Target of Rapamycin (TOR), have not been fully understood. This study revealed the presence of four homologous genes within D. gallinae, named Dg-Vg1, Dg-Vg1-like, Dg-Vg2, and Dg-Vg2-like, especially, Dg-Vg2-like was firstly identified in the mites. The expression levels of all these Vg genes were significantly higher in adult females than other stages. Following blood feeding, the expression levels of these genes increased significantly, followed by a subsequent decrease, aligning with egg production. Silencing Dg-Vgs by RNA interference (RNAi) led to decreased fecundity and egg hatching rates, as well as abnormal embryonic development, suggesting a vital role for Dg-Vgs in both egg formation and embryonic development. Furthermore, the knockdown of Dg-TOR significantly reduced the expression of Dg-Vgs and negatively impacted the reproductive capabilities of PRMs, indicating that TOR influences PRM reproduction by regulating the expression of Dg-Vgs. In summary, these findings demonstrated the crucial roles of Dg-Vgs and Dg-TOR in PRM reproduction, highlighting their potential as targets for pest control.

Effects of weather and air pollution on outpatient visits for insect-and-mite-caused dermatitis: an empirical and predictive analysis.

BACKGROUND: Dermatitis caused by insects and mites, diagnosed as papular urticaria or scabies, is a common skin disease. However, there is still a lack of studies about the effects of weather and air pollution on outpatient visits for this disease. This study aims to explore the impacts of meteorological and environmental factors on daily visits of dermatitis outpatients. METHODS: Analyses are conducted on a total of 43,101 outpatient visiting records during the years 2015-2020 from the largest dermatology specialist hospital in Guangzhou, China. Hierarchical cluster models based on Pearson correlation between risk factors are utilized to select regression variables. Linear regression models are fitted to identify the statistically significant associations between the risk factors and daily visits, taking into account the short-term effects of temperatures. Permutation importance is adopted to evaluate the predictive ability of these factors. RESULTS: Short-term temperatures have positive associations with daily visits and exhibit strong predictive abilities. In terms of total outpatients, the one-day lagged temperature not only has a significant impact on daily visits, but also has the highest median value of permutation importance. This conclusion is robust across most subgroups except for subgroups of summer and scabies, wherein the three-day lagged temperature has a negative effect. By contrast, air pollution has insignificant associations with daily visits and exhibits weak predictive abilities. Moreover, weekdays, holidays and trends have significant impacts on daily visits, but with weak predictive abilities. CONCLUSIONS: Our study suggests that short-term temperatures have positive associations with daily visits and exhibit strong predictive abilities. Nevertheless, air pollution has insignificant associations with daily visits and exhibits weak predictive abilities. The results of this study provide a reference for local authorities to formulate intervention measures and establish an environment-based disease early warning system.

Facultatively ectoparasitic mites as vectors for entomopathogenic bacteria in Drosophila.

Opportunistic bacterial infections are common in insect populations but there is little information on how they are acquired or transmitted. We tested the hypothesis that Macrocheles mites can transmit systemic bacterial infections between Drosophila hosts. We found that 24% of mites acquired detectable levels of bacteria after feeding on infected flies and 87% of infected mites passed bacteria to naïve recipient flies. The probability that a mite could pass Serratia from an infected donor fly to a naïve recipient fly was 27.1%. These data demonstrate that Macrocheles mites are capable of serving as vectors of bacterial infection between insects.

Host switch by honey bee parasitic mites leads to symbiont diversification.

Host-parasite co-evolution is a reciprocal genetic change; however, the parasite may switch to a novel host, deviating from conventional co-evolution. Varroa destructor is a native parasite of the honey bee Apis cerana, and the mite has established infestation in another honey bee, Apis mellifera, causing colony failure. When mites switched to the novel host, they formed a distinct population from mites that remained on the native host. Consequently, this led to divergence in the microbiota associated with mites in two host populations. The microbes were conserved at the species level reflected by alpha diversity, with substantial relative abundance variance. Microbes found in mites were distinct from the bee microbiota. They mainly were pathogenic with antibiotic resistance, while a few bacterial taxa were previously found in honey bees, including Klebsiella pneumoniae and Pseudomanas aeruginosa. These symbionts may transfer between the mites and honey bees.