Parasitic Mite Research Articles

Allele Frequencies of Genetic Variants Associated with Varroa Drone Brood Resistance (DBR) in Apis mellifera Subspecies across the European Continent.

Implementation of marker-assisted selection (MAS) in modern beekeeping would improve sustainability, especially in breeding programs aiming for resilience against the parasitic mite Varroa destructor. Selecting honey bee colonies for natural resistance traits, such as brood-intrinsic suppression of varroa mite reproduction, reduces the use of chemical acaricides while respecting local adaptation. In 2019, eight genomic variants associated with varroa non-reproduction in drone brood were discovered in a single colony from the Amsterdam Water Dune population in the Netherlands. Recently, a new study tested the applicability of these eight genetic variants for the same phenotype on a population-wide scale in Flanders, Belgium. As the properties of some variants varied between the two studies, one hypothesized that the difference in genetic ancestry of the sampled colonies may underly these contribution shifts. In order to frame this, we determined the allele frequencies of the eight genetic variants in more than 360 Apis mellifera colonies across the European continent and found that variant type allele frequencies of these variants are primarily related to the A. mellifera subspecies or phylogenetic honey bee lineage. Our results confirm that population-specific genetic markers should always be evaluated in a new population prior to using them in MAS programs.

The First Report of a Water Mite Unionicola (Trombidiformes: Unionicolidae) Infection in Filopaludina spp. (Gastropoda: Viviparidae) from Thailand with a Description of a New Species of Unionicola (Polyatax) kasetbangkhenensis sp. nov.

Two species of gastropods, Filopaludina sumatrensis polygramma and F. martensi martensi, were found infested with water mites of the genus Unionicola in Bangkok and Nonthaburi provinces, Thailand. Morphological studies on these water mites, based on the characteristics of their genital acetabular and female genital fields, identified them as a new member of subgenus Polyatax. Unionicola (Polyatax) kasetbangkhenensis sp. nov. was named after the first location where this parasitic water mite was discovered. This species is distinguished from others by the pattern of their female genital field, with their anterior acetabular plates each bearing two acetabula and a short thick spine on the inner margin. Additionally, it differs from other species by the structure of the spines in its pedipalps and legs, as well as in the shapes of its coxal plates.

Varroa destructor economic injury levels and pathogens associated with colony losses in Western Canada

IntroductionThe honey bee parasitic mite, Varroa destructor, is considered the main factor associated with winter colony losses. To control this mite, beekeepers must implement Integrated Pest Management (IPM) strategies. An effective IPM strategy is based on timely monitoring of mite levels to treat the colonies when the mites reach an economic threshold and before they grow to damaging levels (economic injury level). Additionally, concerns have been raised about the possible interaction between V. destructor and other stressors; stressors acting additively or synergistically may lead to high colony mortality.MethodologyVarroa destructor levels were recorded in colonies from five regions of British Columbia, Canada: Lower Mainland, Kootenay, Okanagan, Cariboo, and Peace. Mite levels were analyzed for associations with colony strength and mortality, as well as with other pathogens that were identified using total RNA sequencing.ResultsThe Kootenay and Lower Mainland regions had the highest V. destructor levels in the fall (3.38±0.65 and 2.51±0.57, respectively) followed by the Okanagan (1.54±0.36), Cariboo (1.31±0.39), and Peace (0.66±0.25) regions. The Peace region had a significantly lower proportion of dead colonies than the other regions. Varroa destructor levels in the fall significantly predicted odds of colony mortality in the spring. Colonies with ≥ 1% mite infestation in the fall (August) had a significantly higher mortality rate (p=0.005) compared to colonies with <1% mite levels. Therefore, treatment is recommended above that threshold. Also, deformed wing virus-B levels were 8.4 times higher than those of deformed wing virus-A variant in all the regions and were highest in the Kootenay region, which also had the highest rate of colony losses. Lastly, Malpighamoeba mellificae and Nosema (Vairimorpha) apis transcripts were identified along with other pathogens that deserve further investigation, including Apis mellifera filamentous virus, Apis rhabdovirus, Lake Sinai virus, Varroa tymo-like, and Apis mellifera solinvivirus 1.DiscussionThe dynamic nature of host-pathogen interactions requires frequent pathogen surveillance to determine the prevalence and levels of parasitic mites and associated infectious diseases, and their impact on honey bee health, not only in the regions of this study, but globally. Nevertheless, more studies are needed to determine the nature of the type of interaction between the identified pathogens and V. destructor. Also, more research is needed to evaluate their potential impact on colony survival, to provide accurate mite and disease control recommendations to beekeepers.

A novel spider venom peptide from the predatory mite Neoseiulus barkeri shows lethal effect on phytophagous pests

The long-term use of pesticides in the field, and the high fertility and adaptability of phytophagous mites have led to resistance problems; consequently, novel safe and efficient active substances are necessary to broaden the tools of pest mite control. Natural enemies of arthropods typically secrete substances with paralytic or lethal effects on their prey, and those substances are a resource for future biopesticides. In this study, two putative venom peptide genes were identified in a parasitic mite Neoseiulus barkeri transcriptome. Recombinant venom NbSP2 peptide injected into Tetranychus cinnabarinus mites was significantly more lethal than recombinant NBSP1. NbSP2 was also lethal to Spodoptera litura when injected but not when fed to third instar larvae. The interaction proteins of NbSP2 in T. cinnabarinus and S. litura were identified by affinity chromatography. Among these proteins, ATP synthase subunit β (ATP SSβ) was deduced as a potential target. Four binding sites were predicted between NBSP2 and ATP SSβ of T. cinnabarinus and S. litura. In conclusion, we identified a venom peptide with activity against T. cinnabarinus and S. litura. This study provides a novel component for development of a new biological pesticide.

Podapolipid mites (Acari: Heterostigmata): key to genera, biogeographical history and description of four new Australian species of Eutarsopolipus

Four new species of parasitic mites of the genus Eutarsopolipus (Trombidiformes: Podapolipidae) are described from Australian carabid beetles: E. ampullaceous sp. nov. (ochoai species group) from Lecanomerus niger (Harpalini); E. tripodus sp. nov. (ochoai species group) from Notolestus sulcipennis (Pterostichini); E. vepreculus sp. nov. (leytei species group) from Coleolissus papua (Harpalini); and E. walteri sp. nov. (myzus species group) from Chlaenius ophonoides (Chlaeniini). Keys to the world genera of Podapolipidae and to the Australian species of Eutarsopolipus are provided. We further reviewed the world distribution of Eutarsopolipus species groups and postulated that the Australian representatives could be classified into two distinct faunas: a putatively Gondwanan fauna represented mainly by the ochoai species group and a more recent Laurasian fauna represented by just a few species in the myzus and acanthomus species groups.

Mathematical analysis of transmission dynamics of Acute Bee Paralysis Virus within a hive

In this paper, a mechanistic model of Acute Bee Paralysis Virus (ABPV) transmission is designed and analyzed. The qualitative behavior of honeybee-pathogen and honeybee-pathogen-mite interactions sub-models revealed the existence of backward bifurcation. It is shown that whenever the survivability of a newly hatched egg is guaranteed, both the disease-free and endemic equilibria of the sub-models are globally asymptotically stable. Sensitivity and uncertainty analyses have shown that egg-laying, viral ingestion and deposition rates are the most influential parameters that drive ABPV infection. Suggesting that intervention strategies that focus on how to manage these rates are required for effective control. The combination of disinfection and fumigation of hives, using optimal control analysis, is shown to be the most effective strategy for controlling the spread of ABPV infection. In addition, disinfection alone is found to be the most cost-effective strategy. Finally, an extended model that incorporates mite migration and parasitism is formulated and simulated. The results have shown that mite migration weakens the colony and spacing hives to the farthest distance a forager can reach strengthen the colony. It is also shown that parasitism contributes towards colony collapse, however, fumigation strategy reduces honeybee mortality due to parasitism.

Combined treatment with amitraz and thymol to manage Varroa destructor mites (Acari: Varroidae) in Apis mellifera honey bee colonies (Hymenoptera: Apidae).

The parasitic mite Varroa destructor (Anderson and Trueman) is one of the greatest stressors of Apis mellifera (L.) honey bee colonies. When Varroa infestations reach damaging levels during fall, rapid control is necessary to minimize damage to colonies. We performed a field trial in the US Southeast to determine if a combination of registered treatments (Apivar, amitraz-based; and Apiguard, thymol-based) could provide rapid and effective control of Varroa. We compared colonies that received this combination treatment against colonies that received amitraz-based positive control treatments: (i) Apivar alone; or (ii) amitraz emulsifiable concentrate ("amitraz EC"). While not registered, amitraz EC is used by beekeepers in the United States in part because it is thought to control Varroa more rapidly and effectively than registered products. Based on measurements of Varroa infestation rates of colonies after 21 days of treatment, we found that the combination treatment controlled Varroa nearly as rapidly as the amitraz EC treatment: this or other combinations could be useful for Varroa management. At the end of the 42-day trial, colonies in the amitraz EC group had higher bee populations than those in the Apivar group, which suggests that rapid control helps reduce Varroa damage. Colonies in the combination group had lower bee populations than those in the amitraz EC group, which indicates that the combination treatment needs to be optimized to avoid damage to colonies.

Neonicotinoid exposure increases Varroa destructor (Mesostigmata: Varroidae) mite parasitism severity in honey bee colonies and is not mitigated by increased colony genetic diversity.

Agrochemical exposure is a major contributor to ecological declines worldwide, including the loss of crucial pollinator species. In addition to direct toxicity, field-relevant doses of pesticides can increase species' vulnerabilities to other stressors, including parasites. Experimental field demonstrations of potential interactive effects of pesticides and additional stressors are rare, as are tests of mechanisms via which pollinators tolerate pesticides. Here, we controlled honey bee colony exposure to field-relevant concentrations of 2 neonicotinoid insecticides (clothianidin and thiamethoxam) in pollen and simultaneously manipulated intracolony genetic heterogeneity. We showed that exposure increased rates of Varroa destructor (Anderson and Trueman) parasitism and that while increased genetic heterogeneity overall improved survivability, it did not reduce the negative effect size of neonicotinoid exposure. This study is, to our knowledge, the first experimental field demonstration of how neonicotinoid exposure can increase V. destructor populations in honey bees and also demonstrates that colony genetic diversity cannot mitigate the effects of neonicotinoid pesticides.

Ghosts of parasites past influence current non-consumptive effects in Drosophila nigrospiracula

Parasites can indirectly impact hosts through non-consumptive effects (NCEs) via changes in behaviour, morphology, and/or physiology. These responses can be understood in terms of the ecology of fear (ectoparasites) or the ecology of disgust (endoparasites) framework. We tested the hypothesis that NCEs of parasite exposure (e.g., parasite avoidance and defense) trade off with other important behaviours such as feeding and resting. We predicted that when exposed to parasites (without infection), hosts will increase their defensive behaviors at the expense of feeding. We also posited that history of exposure (without infection), or previous infection would impact the expression of these NCEs. The study system involves a cactophilic fruit fly (Drosophila nigrospiracula) and a naturally occurring parasitic mite (Macrocheles subbadius). First, we assessed how prior mite exposure affected fly behaviour in response to current parasite exposure. Mite presence resulted in increased grooming and movement, but exposure history did not affect these behaviours. However, the interaction between previous and current exposure influenced host feeding and resting behaviours. We found that previously exposed flies increased feeding and decreased resting upon a secondary mite exposure. In a second experiment, we tested the role of infection history on current parasite exposure. Compared with naïve flies, previously infected flies were expected to increase defensive behaviours upon secondary exposure. Flies increased defensive and ambulatory behaviour in the presence of mites, and consequently less time was spent resting but feeding was unaffected. None of the behaviours measured were affected by previous infection status. In general, current parasite exposure resulted in NCEs. Moreover, our results showed that previous exposure (without infection) to parasites may have an even stronger effect upon secondary exposure than infection history. Our study highlights the importance of the ecology of fear and the role that exposure and infection history plays in generating NCEs of parasitism.

Driven apart: fossil parasitic long-legged velvet mite larvae on gall midges represent a long lost parasitic association between mites and dipterans

Driven apart: fossil parasitic long-legged velvet mite larvae on gall midges represent a long lost parasitic association between mites and dipterans

First report of Polyxenidae (Diplopoda: Polyxenida) as a host for Charletonia rocciai Treat & Flechtmann, 1979 (Trombidiformes: Erythraeidae) in Brazil

Reports of mites parasitizing arthropods are common worldwide. However, there hasn't been a single record of mite parasitism by any Erythraeidae species on the millipede Polyxenidae in Brazil. To address this gap, we present a record of the species Charletonia rocciai Treat & Flechtmann, 1979 (Trombidiformes: Erythraeidae), parasitizing a specimen of this millipede family in the country.

Honey bee stressor networks are complex and dependent on crop and region

Honey bees play a major role in crop pollination but have experienced declining health throughout most of the globe. Despite decades of research on key honey bee stressors (e.g., parasitic Varroa destructor mites and viruses), researchers cannot fully explain or predict colony mortality, potentially because it is caused by exposure to multiple interacting stressors in the field. Understanding which honey bee stressors co-occur and have the potential to interact is therefore of profound importance. Here, we used the emerging field of systems theory to characterize the stressor networks found in honey bee colonies after they were placed in fields containing economically valuable crops across Canada. Honey bee stressor networks were often highly complex, with hundreds of potential interactions between stressors. Their placement in crops for the pollination season generally exposed colonies to more complex stressor networks, with an average of 23 stressors and 307 interactions. We discovered that the most influential stressors in a network-those that substantively impacted network architecture-are not currently addressed by beekeepers. Finally, the stressor networks showed substantial divergence among crop systems from different regions, which is consistent with the knowledge that some crops (e.g., highbush blueberry) are traditionally riskier to honey bees than others. Our approach sheds light on the stressor networks that honey bees encounter in the field and underscores the importance of considering interactions among stressors. Clearly, addressing and managing these issues will require solutions that are tailored to specific crops and regions and their associated stressor networks.

Prevalence and clinical findings of feline otitis externa in Midwest Brazil

This study was conducted to evaluate the prevalence of otitis externa (OE) in cats using cytology, direct otoscopic examination, and parasitological examination through swabs and curettage, and to compare the accuracy between collection methods for parasitological examination. Direct otoscopic evaluation of the external auditory canal (right and left), swabs for cytological examination of the external auditory canal, and collection of cerumen for parasitological examination through swabs and curettage of 137 cats from a veterinary hospital care were conducted between March 2021 and March 2022. The influences of age, sex, habitat, street access, and the presence of fleas on OE were evaluated. Cytological evidence of OE was observed in 25.5 % of cats and was statistically associated with flea and mite parasitism. Otodectes cynotis was found in 13.9 % of the cats. Cocci and Bacilli were the secondary factors in 34.3 % and 22.9 % of cats with OE, respectively. The Malassezia genus was a secundary factor in 57.1 % of the cats with OE. The frequency of OE was high in cats receiving hospital care. O. cynotis was a frequent primary cause of OE in cats. The curette sampling method is a great option for diagnosing O. cynotis infestation due to its ease of use.

Population-wide modelling reveals prospects of marker-assisted selection for parasitic mite resistance in honey bees

In 2019, a joint eight-variant model was published in which eight single nucleotide polymorphisms (SNPs) in seven Apis mellifera genes were associated with Varroa destructor drone brood resistance (DBR, i.e. mite non-reproduction in drone brood). As this model was derived from only one Darwinian Black Bee Box colony, it could not directly be applied on a population-overarching scale in the northern part of Belgium (Flanders), where beekeepers prefer the carnica subspecies. To determine whether these eight SNPs remained associated with the DBR trait on a Flemish colony-broad scope, we performed population-wide modelling through sampling of various A. mellifera carnica colonies, DBR scoring of Varroa-infested drone brood and variant genotyping. Novel eight-variant modelling was performed and the classification performance of the eight SNPs was evaluated. Besides, we built a reduced three-variant model retaining only three genetic variants and found that this model classified 76% of the phenotyped drones correctly. To examine the spread of beneficial alleles and predict the DBR probability distribution in Flanders, we determined the allelic frequencies of the three variants in 292 A. mellifera carnica queens. As such, this research reveals prospects of marker-assisted selection for Varroa drone brood resistance in honeybees.

Resolution of Clinical Signs of Sarcoptic Mange in American Black Bears (Ursus americanus), in Ivermectin-Treated and Nontreated Individuals.

The parasitic mite Sarcoptes scabiei causes mange in nearly 150 species of mammals by burrowing under the skin, triggering hypersensitivity responses that can alter animals' behavior and result in extreme weight loss, secondary infections, and even death. Since the 1990s, sarcoptic mange has increased in incidence and geographic distribution in Pennsylvania black bear (Ursus americanus) populations, including expansion into other states. Recovery from mange in free-ranging wildlife has rarely been evaluated. Following the Pennsylvania Game Commission's standard operating procedures at the time of the study, treatment consisted of one subcutaneous injection of ivermectin. To evaluate black bear survival and recovery from mange, from 2018 to 2020 we fitted 61 bears, including 43 with mange, with GPS collars to track their movements and recovery. Bears were collared in triplicates according to sex and habitat, consisting of one bear without mange (healthy control), one scabietic bear treated with ivermectin when collared, and one untreated scabietic bear. Bears were reevaluated for signs of mange during annual den visits, if recaptured during the study period, and after mortality events. Disease status and recovery from mange was determined based on outward gross appearance and presence of S. scabiei mites from skin scrapes. Of the 36 scabietic bears with known recovery status, 81% fully recovered regardless of treatment, with 88% recovered with treatment and 74% recovered without treatment. All bears with no, low, or moderate mite burdens (<16 mites on skin scrapes) fully recovered from mange (n=20), and nearly half of bears with severe mite burden (≥16 mites) fully recovered (n=5, 42%). However, nonrecovered status did not indicate mortality, and mange-related mortality was infrequent. Most bears were able to recover from mange irrespective of treatment, potentially indicating a need for reevaluation of the mange wildlife management paradigm.

Behaviours of honeybees can reduce the probability of deformed wing virus outbreaks in Varroa destructor-infested colonies

Honeybees are important plant pollinators. Unfortunately, there is a growing increase in the loss of honeybee colonies, and this is having a serious economic impact on crop farmers. A major cause of these losses is the parasitic mite Varroadestructor, which is a vector of deformed wing virus (DWV). Some bee species have resistant mechanisms, such as grooming and hygienic behaviours, against Varroa mites. A clear understanding of the effects of these control behaviours on the mites and the viruses they transmit can be important in reducing colony losses. Here, a stochastic model is formulated and analysed to consider the extent to which these control behaviours reduce the probability of an outbreak of DWV in honeybee colonies. Vector and bee-to-bee transmission routes are considered. Using branching process theory, it is shown that without any hygienic or grooming behaviour, a large probability of a DWV outbreak is possible. Also, if bees apply grooming or hygienic behaviour, this can reduce the probability of a virus outbreak, especially in the case of vector transmission, where it can be reduced to zero. Hygienic behaviour is the most significant factor in reducing a DWV outbreak. Thus, bee selection for hygienic behaviour may be important to reduce honeybee colony losses caused by DWV.

The Apian Pharmacopeia

Abstract This article describes the pharmaceuticalization of honeybee health, a process that has accelerated alongside growing beekeeper concerns about unexplained colony losses over the past nearly two decades. Despite their uncertainty about the causes of colony loss and the role of pesticide exposures in rendering bees vulnerable, many entomologists agree that controlling populations of parasitic mites in bee colonies is the key to bees’ survival, making mite infestations a primary target for medical interventions. The pharmaceuticalization of honeybee health means that beekeepers need to track drug administration to prevent toxic interactions, avoid overuse, and reduce resistance. This means not only managing those chemicals intentionally applied, but also those ferried in from outside the colony, notably pesticides and fungicides. Medicalizing a range of husbandry practices like supplemental feeding and mite treatment has become a way to regulate beekeepers’ use of medicine as well as encourage it, making medicalization, paradoxically, a means of encouraging restraint.

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.

Assessment of Efficacy of Algerian Propolis against the Parasitic Mite Varroa destructor and Safety for Honey Bees by Spray Treatment.

Varroa destructor is an ectoparasitic mite and is considered one of the most important causes of honey bee population loss. In the last years, substances of botanical origin have emerged as natural alternatives to diminish the mite population levels. Propolis is a natural product and is used by honey bees for multiple tasks, including protection from pathogens and parasites, and varroacidal activity of propolis extracts has been shown. In this study, we investigated the potential of propolis, collected by native Algerian honey bee subspecies (Apis mellifera intermissa and A. m. sahariensis) in different locations in Algeria and extracted by ultrasound, to control mites of V. destructor and tested the safety for the honey bees. The most important results were that the best propolis extracts at 10% killed 100% of the Varroa mites within 3-4 h in a Petri dish assay. In addition, when we sprayed A. m. intermissa bees infested with Varroa mites with a 10% concentration in a mini-hive setup, we scored a high mite mortality of 85-87% with the best propolis extracts, and importantly, there was no mortality in the bees. Our data demonstrated that propolis extracts in Algeria could be used in honey bee colonies by spraying against Varroa mite infestations, which may develop as an easy method for local beekeepers to control Varroa in their hives. Further research should investigate the mechanism of action.

Stress-induced loss of social resilience in honeybee colonies and its implications on fitness.

Stressors may lead to a shift in the timing of life-history events of species, causing a mismatch with optimal environmental conditions, potentially reducing fitness. In honeybees, the timing of brood rearing and nest emergence in late winter/early spring is critical as colonies need to grow fast after winter to prepare for reproduction. However, the effects of stress on these life-history events in late winter/early spring and the possible consequences are not well understood. Therefore, we tested whether (i) honeybee colonies shift timing of brood rearing and nest emergence as response to stressors, and (ii) if there is a consequent loss of social resilience, reflected in colony fitness (survival, growth and reproduction). We monitored stressed (high load of the parasitic mite Varroa destructor or nutrition restricted) colonies and presumably non-stressed colonies from the beginning of 2020 till spring of 2021. We found that honeybee colonies do not shift the timing of brood rearing and nest emergence in spring as a coping mechanism to stressors. However, we show that there is loss of social resilience in stressed colonies, leading to reduced growth and reproduction. Our study contributes to better understanding the effects of stressors on social resilience in eusocial organisms.