Varroa Mite Infestation Research Articles

On the front line: quantitative virus dynamics in honeybee (Apis mellifera L.) colonies along a new expansion front of the parasite Varroa destructor.

Over the past fifty years, annual honeybee (Apis mellifera) colony losses have been steadily increasing worldwide. These losses have occurred in parallel with the global spread of the honeybee parasite Varroa destructor. Indeed, Varroa mite infestations are considered to be a key explanatory factor for the widespread increase in annual honeybee colony mortality. The host-parasite relationship between honeybees and Varroa is complicated by the mite's close association with a range of honeybee viral pathogens. The 10-year history of the expanding front of Varroa infestation in New Zealand offered a rare opportunity to assess the dynamic quantitative and qualitative changes in honeybee viral landscapes in response to the arrival, spread and level of Varroa infestation. We studied the impact of de novo infestation of bee colonies by Varroa on the prevalence and titres of seven well-characterised honeybee viruses in both bees and mites, using a large-scale molecular ecology approach. We also examined the effect of the number of years since Varroa arrival on honeybee and mite viral titres. The dynamic shifts in the viral titres of black queen cell virus and Kashmir bee virus mirrored the patterns of change in Varroa infestation rates along the Varroa expansion front. The deformed wing virus (DWV) titres in bees continued to increase with Varroa infestation history, despite dropping infestation rates, which could be linked to increasing DWV titres in the mites. This suggests that the DWV titres in mites, perhaps boosted by virus replication, may be a major factor in maintaining the DWV epidemic after initial establishment. Both positive and negative associations were identified for several pairs of viruses, in response to the arrival of Varroa. These findings provide important new insights into the role of the parasitic mite Varroa destructor in influencing the viral landscape that affects honeybee colonies.

Increased tolerance and resistance to virus infections: a possible factor in the survival of Varroa destructor-resistant honey bees (Apis mellifera).

The honey bee ectoparasitic mite, Varroa destructor, has a world-wide distribution and inflicts more damage than all other known apicultural diseases. However, Varroa-induced colony mortality is more accurately a result of secondary virus infections vectored by the mite. This means that honey bee resistance to Varroa may include resistance or tolerance to virus infections. The aim of this study was to see if this is the case for a unique population of mite-resistant (MR) European honey bees on the island of Gotland, Sweden. This population has survived uncontrolled mite infestation for over a decade, developing specific mite-related resistance traits to do so. Using RT-qPCR techniques, we monitored late season virus infections, Varroa mite infestation and honey bee colony population dynamics in the Gotland MR population and compared this to mite-susceptible (MS) colonies in a close by apiary. From summer to autumn the deformed wing virus (DWV) titres increased similarly between the MR and MS populations, while the black queen cell virus (BQCV) and sacbrood virus (SBV) titres decreased substantially in the MR population compared to the MS population by several orders of magnitude. The MR colonies all survived the following winter with high mite infestation, high DWV infection, small colony size and low proportions of autumn brood, while the MS colonies all perished. Possible explanations for these changes in virus titres and their relevance to Varroa resistance and colony winter survival are discussed.

Identification of developmentally-specific kinotypes and mechanisms of Varroa mite resistance through whole-organism, kinome analysis of honeybee.

Recent investigations associate Varroa destructor (Mesostigmata: Varroidae) parasitism and its associated pathogens and agricultural pesticides with negative effects on colony health, resulting in sporadic global declines in domestic honeybee (Apis mellifera) populations. These events have motivated efforts to develop research tools that can offer insight into the causes of declining bee health as well as identify biomarkers to guide breeding programs. Here we report the development of a bee-specific peptide array for characterizing global cellular kinase activity in whole bee extracts. The arrays reveal distinct, developmentally-specific signaling profiles between bees with differential susceptibility to infestation by Varroa mites. Gene ontology analysis of the differentially phosphorylated peptides indicates that the differential susceptibility to Varroa mite infestation does not reflect compromised immunity; rather, there is evidence for mite-mediated immune suppression within the susceptible phenotype that may reduce the ability of these bees to counter secondary viral infections. This hypothesis is supported by the demonstration of more diverse viral infections in mite-infested, susceptible adult bees. The bee-specific peptide arrays are an effective tool for understanding the molecular basis of this complex phenotype as well as for the discovery and utilization of phosphorylation biomarkers for breeding programs.

GENETIC DIFFERENTIATION OF POPULATIONS OF HONEY BEE (Apis mellifera L.) AND DISTRIBUTION OF RNA-CONTAINING VIRUSES AT THE BACKGROUND OF EPIZOOTIA OF Varroa destructor ON THE TERRITORY OF UDMURTIA

GENETIC DIFFERENTIATION OF POPULATIONS OF HONEY BEE (Apis mellifera L.) AND DISTRIBUTION OF RNA-CONTAINING VIRUSES AT THE BACKGROUND OF EPIZOOTIA OF Varroa destructor ON THE TERRITORY OF UDMURTIA Alexander E. Kalashnikov*, Ivan V. Maslennikov**, Ludmila M. Kolbina**, Irina G. Udina* *N.I. Vavilov Institute of General Genetics RAS **Udmurt Research Institute of Agriculture Abstract The bees of dark forest species (Apis mellifera mellifera L.) are winter-hardy. These bees are able to effectively use a short honey harvest. Introgression of southern bee species in the Russia affects ro the economic quality of local northern species of bees. Introgression of species reduces their immunity, thereby It was enhancing susceptibility bees to infection with ectoparasites, as well as distribution of various viral diseases. Varroa destructor mite infestations on bees may predispose to infection by viruses. We have presented data about population differentiation of bees of dark forest species in Udmurtia, which were obtained based on the study using PCR method, morphometric parameters (cubital index of wing) and estimation of variability in intergenic locus of the CO-I-CO-II of mtDNA. Based on the analysis of the mtDNA the hybridization degree in samples of bees from Udmurtia 1UD_S and 5UD_S (maternal line) was 15.4 and 60.0%, respectively. Sample 2D_S-4UD_S meet the standards of dark forest bee species. For all analyzed samples (1UD_S-5UD_S) obtained average rating of cubital index> 0.55. These data confirmed the high probability of belonging of bees of sample data to the dark forest bee species. However, the variability analysis (according to the length of the intergenic locus CO-I-CO-II) with Southern species hybridization was observed only in samples 2UD_S-4UD_S, whereas in the other samples 1UD_S 5UD_S hybridization has occurred. This indicates a greater degree of reliability of molecular techniques in the evaluation of the degree of hybridization when samples of bees were studied. It's interesting that in one of the samples 2UD_S we founded a heteroplasmy PQ/P3*Q. In bees exposed to Varroa destructor defeat was detected deformed wing virus (DWV) (23,3% of families), chronic bee paralysis virus (CBPV) and sacbrood bee virus (SBV) (13, 3%). Keywords honey bee, Apis mellifera L., mitochondrial DNA, cubital index, deformed wing virus, sacbrood virus, chronic paralysis virus, Varroa destructor Introduction The dark forest bee Apis mellifera mellifera L. and related subspecies of Central Russian bee breed was widespread in Russia (1), including Udmurtia (2) and Bashkortostan (3). These bees have winter hardiness, resistance to several diseases, the ability efficiently uses a short honey harvest. The proboscis of these bees is short (6.0-6.4 mm). They have a dark color of the body. For these bees is a characteristic light dry seal of honey. However, these bees are aggressive and have a tendency to increase swarming. The cubital index value of the breed standard of these bees is in the range 0.60-0.65 (4). Under the influence of anthropogenic factor in Russia, like in Western Europe and North America, there was observes a hybridization of A. m. mellifera subspecies with subspecies, which are spread in the more southern latitudes. Integration of the southern subspecies effect on economic quality of the local northern species, as well as have a negative impact on their adaptability to environmental conditions. It also reduces immunity, thereby enhancing susceptibility of bees to infection of ectoparasites and distribution of various diseases, including viral (5). Infection bee mite Varroa destructor bees predispose to infection by viruses (5-7). Mite serves as a reservoir for virus bee mite infestation therefore weaken their immunity and promotes viral infection (8). Six of the studied viruses of the honey bee cause serious consequences if infected, up

Challenges associated with the honey bee (Apis mellifera adansonii) colonies establishment in south western Nigeria

The southwestern part of Nigeria is a tropical rainforest region having many local beekeepers. The se beekeepers have experienced decline in colony establishment in the recent past . A study carried out in Lagos, Ogun and Osun states between December 2009 and September 2011 examined 14 randomly selected commercial bee farms for problems associated with decline in colony establishment . Sampling and treatments were split equally between each apiary and three colonies were selected in each . All the colonies were housed in Tanzania /local top bar hive s. There were 58.34, 44.84 and 40.61 average percentage declines in colony establishment in Lagos, Ogun and Osun States , respectively. Presence of pests and diseases, pesticide poisoning, poor hive and seasonal management, ecological problem and lack of queen rearing were potential problems identified by the beekeepers . All the apiaries had pests like Crickets, Ants ( Companotus pennsylvanicus ), Small Hive beetle ( Aethina tumida ), Termites ( Macrotermes spp ) and Spider ( Lactrodectus mactan ) . Varroa mite infestations were found in 33 (78.57%) of apiaries sampled. There was no significant difference between the levels of Varroa infestation in all the colonies during the dry and wet seasons at confidence interval of 95 percent ( t = 1.542, df = 13, p = 0.147 ( p > 0.05) . Nosema spores were found in 27 (64.29%) colonies examined. The number of spores range from 16 x 10 3 to 30.4 x 10 3 . T here were no significant differences in the infection from colony to colony, apiary to apiary and between dry and wet seasons ( t = - 0.094 df = 11, P = 0.927 (P > 0.05). Diseases like American and European foulbrood were absent while chalkbrood disease was prevalent. Environmental factors of high temperature, high rainfall and high relative and hive humidity enhanced the spread of pests and disease pathogens. Many insecticides were constantly applied by the farmers on the crops in the surrounding farmland. Two of the commonly used insecticides DDVP (Dichlorvos) and Cyperforce (Cypermetrin) were discovered to have increased mortality on worker honey bees with progressively larger doses. It was obvious that insecticide toxicity had a significant effect on the colony. Hence , ecological and management problems had contributed to the decline in colony establishment in this area.

Produtos naturais para o controle do ácaro Varroa destructor em abelhas africanizadas

O objetivo deste trabalho foi avaliar os efeitos do ácido oxálico e de óleos essenciais de plantas no controle da infestação pelo ácaro Varroa destructor em colônias de Apis mellifera africanizadas. O experimento foi realizado em delineamento inteiramente casualizado, em 30 colônias, com seis tratamentos e cinco repetições. As colmeias foram tratadas com óleos essenciais de arruda (Ruta graveolens), eucalipto (Eucalyptus spp.) e hortelã (Mentha piperita), além de timol, ácido oxálico e do tratamento controle sem aplicação de produtos. Foram avaliadas a mortalidade de varroas e as taxas de mortalidade de crias e de infestação de varroas em crias e em abelhas adultas, antes e depois da aplicação de cada produto. O ácido oxálico e os óleos de arruda, timol, eucalipto e de hortelã reduziram a mortalidade de crias parasitadas pelo ácaro em 92,1, 83,3, 81,7, 86,4 e 81,3%, respectivamente. O tratamento com ácido oxálico reduziu em 87,4% a infestação de varroas em abelhas adultas. O uso desses produtos é eficiente na redução da mortalidade de crias de A. mellifera parasitadas por V. destructor.

First detection of four viruses in honey bee (Apis mellifera) workers with and without deformed wings and Varroa destructor in Mexico

SummaryLittle information exists in Mexico about the presence of viral diseases in honey bee (Apis mellifera) colonies and their association with Varroa destructor mites. Here we report the first investigation using molecular techniques, of honey bees and varroa mites tested for viruses in Mexico. Samples of varroa mites, worker pupae, and adult bees were collected from five colonies, four of which had a high proportion of workers with deformed wings. Varroa mite infestation rates were determined in worker brood and in adult bees. Samples were analysed by reverse transcription-PCR (RT-PCR) for sacbrood virus (SBV), deformed wing virus (DWV), acute bee paralysis virus (ABPV), Israeli acute paralysis virus (IAPV), chronic bee paralysis virus (CBPV) and Kashmir bee virus (KBV). Of the six viruses surveyed, four were found in adult bees (DWV, IAPV, ABPV and SBV), two in worker brood (DWV and IAPV) and two in varroa mites (DWV and IAPV). Only KBV and CBPV were not detected. This is the first molecular detection of these four viruses infecting honey bees and varroa mites in Mexico. The association of these viruses with V. destructor is discussed.

Dynamics of persistent and acute deformed wing virus infections in honey bees, Apis mellifera.

The dynamics of viruses are critical to our understanding of disease pathogenesis. Using honey bee Deformed wing virus (DWV) as a model, we conducted field and laboratory studies to investigate the roles of abiotic and biotic stress factors as well as host health conditions in dynamics of virus replication in honey bees. The results showed that temperature decline could lead to not only significant decrease in the rate for pupae to emerge as adult bees, but also an increased severity of the virus infection in emerged bees, partly explaining the high levels of winter losses of managed honey bees, Apis mellifera, around the world. By experimentally exposing adult bees with variable levels of parasitic mite Varroa destructor, we showed that the severity of DWV infection was positively correlated with the density and time period of Varroa mite infestation, confirming the role of Varroa mites in virus transmission and activation in honey bees. Further, we showed that host conditions have a significant impact on the outcome of DWV infection as bees that originate from strong colonies resist DWV infection and replication significantly better than bee originating from weak colonies. The information obtained from this study has important implications for enhancing our understanding of host‑pathogen interactions and can be used to develop effective disease control strategies for honey bees.

Comparative Effectiveness of Some Acaricides used to ControlVarroa destructor(Mesostigmata: Varroidae) in Algeria

In this study the effectiveness of two synthetic (Bayvarol and Apivar) and two natural acaricides (Apiguard and ApiLife Var) against Varroa destructor were evaluated with use of infested colonies of Apis mellifera intermissa, housed in Langstroth standard hives. Each acaricide was tested in five hives, and one group of five hives was left untreated as the control. All acaricides significantly reduced the levels of varroa mite infestation on adult honeybees and worker brood, but the efficacy was higher for Apiguard (93–97 %) and ApiLife Var (94–98 %) compared to Bayvarol (85–90 %) and Apivar (82–88 %). Overall, the data indicated that essential oils like Apiguard and ApiLife Var can be recommended in the control of V. destructor, while synthetic varroacides like Bayvarol and Apivar should be minimized due to increased mite resistance for these products.

TOLERANCE OF HONEY BEE COLONIES TO VARROA DESTRUCTOR (ANDERSON AND TRUEMAN) AND THE ECONOMIC THRESHOLD OF THE PARASITE IN THE CENTRAL REGION OF KINGDOM OF SAUDI ARABIA

Experiments were carried out on honey bee colonies (Apis mellifera) during the winter of 2008 and spring of 2009 using colonies wintered with five levels of varroa infestation (0.0, 3.8, 9.0, 13.1 and 22.9%) in the Central Region of the kingdom of Saudi Arabia. The goal of the present work is to determine varroa treatment thresholds and colony collapse level. Response variables examined included varroa mite infestation level (%), cm2 of brood number of frames of brood, number of frames covered with adult honey bees and mites recovered on sticky boards. The data obtained reveled that no significant differences were noticed in cm2 of brood, number of frames of brood, and number of frames of bees in colonies (range of 0.0 to 9.0% varroa infestation or 0.0 – 0.9 mites/bee). Colonies with 13.1% infestation (0.13 mites/bee) exhibited a significant reduction in all measures of performance. The present results suggested that honey bee colonies can tolerate a level of 9.0% varroa infestation (0.9 mites/bee) during the winter without evidence of colony injury. It also suggested that 13.1% infestation (0.13 mites/bee) is the colony collapse or economic injury threshold in the Central Region of the Kingdom of Saudi Arabia. Also colonies with 12.3 or more mites falling on sticky boards after 48-hour period were likely to have lower populations of bees and brood the following spring.

Disruption of an exotic mutualism can improve management of an invasive plant: varroa mite, honeybees and biological control of Scotch broomCytisus scopariusin New Zealand

Summary 1. A seed-feeding biocontrol agent Bruchidius villosus was released in New Zealand (NZ) to control the invasive European shrub, broom Cytisus scoparius, in 1988 but it was subsequently considered unable to destroy sufficient seed to suppress broom populations. We hypothesized that an invasive mite Varroa destructor, which has caused honeybee decline in NZ, may cause pollinator limitation, so that the additional impact of B. villosus might now reach thresholds for population suppression. 2. We performed manipulative pollination treatments and broad-scale surveys of pollination, seed rain and seed destruction by B. villosus to investigate how pollinator limitation and biocontrol interact throughout the NZ range of broom. 3. The effect of reduced pollination in combination with seed-destruction was explored using a population model parameterized for NZ populations. 4. Broom seed rain ranged from 59 to 21 416 seeds m )2 from 2004 to 2008, and was closely correlated with visitation frequency of honeybees and bumblebees. Infestation of broom seeds by B. villosus is expected to eventually reach 73% (the average rate observed at the localities adjacent to early release sites). 5. The model demonstrated that 73% seed destruction, combined with an absence of honeybee pollination, could cause broom extinction at many sites and, where broom persists, reduce the intensity of treatment required to control broom by conventional means. 6. Nevertheless, seed rain was predicted to be sufficient to maintain broom invasions over many sites in NZ, even in the presence of the varroa mite and B. villosus, largely due to the continued presence of commercial beehives that are treated for varroa mite infestation. 7. Synthesis and applications. Reduced pollination through absence of honeybees can reduce broom seed set to levels at which biocontrol can be more effective. To capitalize on the impact of the varroa mite on feral honeybees, improved management of commercial beehives (for example, withdrawal of licences for beekeepers to locate hives on Department of Conservation land) could be used as part of a successful integrated broom management programme at many sites in NZ.

Varroa destructoris the main culprit for the death and reduced populations of overwintered honey bee (Apis mellifera) colonies in Ontario, Canada

The relative effect of parasite levels, bee population size, and food reserves on winter mortality and post winter populations of honey bee colonies was estimated. More than 400 colonies were monitored throughout three seasons in Ontario, Canada. Most of the colonies were infested with varroa mites during the fall (75.7%), but only 27.9% and 6.1% tested positive to nosema disease and tracheal mites, respectively. Winter colony mortality was 27.2%, and when examined as a fraction of all morbidity factors, fall varroa mite infestations were the leading cause of colony mortality (associated to > 85% of colony deaths), followed by fall bee populations and food reserves. Varroa-infested colonies, with weak populations and low food reserves in the fall, significantly decreased spring colony populations, whereas varroa infestations and Nosema infections in the spring, significantly decreased bee populations by early summer. Overall, results suggest that varroa mites could be the main culprit for the death and reduced populations of overwintered honey bee colonies in northern climates.

Deformed Wing Virus Implicated in Overwintering Honeybee Colony Losses

The worldwide decline in honeybee colonies during the past 50 years has often been linked to the spread of the parasitic mite Varroa destructor and its interaction with certain honeybee viruses. Recently in the United States, dramatic honeybee losses (colony collapse disorder) have been reported; however, there remains no clear explanation for these colony losses, with parasitic mites, viruses, bacteria, and fungal diseases all being proposed as possible candidates. Common characteristics that most failing colonies share is a lack of overt disease symptoms and the disappearance of workers from what appears to be normally functioning colonies. In this study, we used quantitative PCR to monitor the presence of three honeybee viruses, deformed wing virus (DWV), acute bee paralysis virus (ABPV), and black queen cell virus (BQCV), during a 1-year period in 15 asymptomatic, varroa mite-positive honeybee colonies in Southern England, and 3 asymptomatic colonies confirmed to be varroa mite free. All colonies with varroa mites underwent control treatments to ensure that mite populations remained low throughout the study. Despite this, multiple virus infections were detected, yet a significant correlation was observed only between DWV viral load and overwintering colony losses. The long-held view has been that DWV is relatively harmless to the overall health status of honeybee colonies unless it is in association with severe varroa mite infestations. Our findings suggest that DWV can potentially act independently of varroa mites to bring about colony losses. Therefore, DWV may be a major factor in overwintering colony losses.

Uncapping of pupal cells by European bees in the United States as responses to Varroa destructor and Galleria mellonella

SummaryWe investigated the uncapping of pupal cells by honey bees in the United States as responses to infestation with V. destructor and G. mellonella. In a group of 15 colonies, we counted the number of uncapped cells with pupae, and estimated the total sealed brood area. At the same time, the infestation by V. destructor and evidence of wax moth activity were measured in uncapped pupal cells, in cells immediately adjacent (neighbours), and in cells along linear transects. The relative amount of uncapped pupal cells (uncapped pupal cells/total sealed cells) increased with infestation (linear regression R2 = 0.64, slope = 0.16). Varroa mite infestation of uncapped cells (30%) significantly exceeded that of neighbours (14%) and also that of transect cells (12%), but infestations of neighbour and transect cells were similar. The relationship between infestation of uncapped cells and that of other cells (neighbour or transect cells) had a slope significantly higher than one, suggesting that discrimination of infested cells increases with overall colony infestation. Frequencies of wax moth activity (presence of larvae, frass, tunnelling and webbing) were highest in uncapped cells (33%), lower in neighbour cells (21%) and extremely low in transect cells (4%). We followed the opening, removing and resealing of pupal cells every 24 h in a colony with one of the highest infestations with varroa mites and with one of the lowest levels of wax moths, and in a second colony with the opposite infestation levels. Many opened or partly removed cells were found in a different condition, suggesting a dynamic process under conditions of high infestation.

Varroa mite infestations in elevated honey bee brood cells: effects of context and caste.

The Varroa mite infestation level of honey bee, Apis mellifera, worker larvae reared in individual raised cells was 6-fold higher than in the adjacent six cells surrounding them; this differential infestation rate is similar to published values of higher mite infestations of drone cells compared to worker cells. Infestation levels in control cells were the same as in the surrounding cells. In contrast to infestation of these individually raised cells, Varroa mites invaded worker larvae in raised cells along the perimeter of a patch of raised cells (10 by 21 rows) 2.5 times more often than surrounding unraised cells, and similarly ca. 2.5 times more often than in the remaining raised cells (interior) of this patch. In similarly prepared frames of drone comb, Varroa mites invaded individually raised drone cells 3.3-fold more often than the adjacent surrounding cells and control cells. On the other hand, Varroa mites infested drone larvae in the interior of the raised-patch area as often as drones in raised cells along the perimeter of the raised-patch, and this rate was ca. 2.5-fold higher than for drone larvae in unraised cells surrounding the raised-patch and drone larvae in control cells. The higher levels of infestation of raised cells did not come at the expense of the surrounding cells, i.e., the infestation levels of the adjacent surrounding cells were the same as in control cells. For worker larvae, the increased number of mites invading individual raised cells and edge cells of the raised patch were proportional to the number of surrounding nonraised cells. The relationship between raised cell-edges, observations of mite walking behavior on comb surfaces, and larval-to-cell-rim distances are discussed in relation to their possible roles in eliciting mite invasion of honey bee larval cells and contrasted to the putative role of kairomones in larval-host location.

Effect of Varroa jacobsoni (Mesostigmata: Varroidae) on Feral Apis mellifera (Hymenoptera: Apidae) in California

We studied the spread of the newly introduced parasitic mite, Varma jacobsoni Oudemans, within California's population of the feral honey bee, Apis mellifera L., by examining worker bees taken from 208 colonies in 1990, 124 of which were examined again in 1993. The samples taken in 1990 did not contain V. jacobsoni mites. In 1993, 75% of the colonies examined in an area located near Sacramento, CA, no longer existed, and all surviving colonies were infested with V. jacobsoni. In an area located near the Californian central coast, 84% of the nest sites examined were occupied and few colonies contained detectable levels of V. jacobsoni. The probability of survival for colonies that have not survived a winter yet (founder colonies) has been previously reported to be low in areas with a temperate climate. Data collected in an area with a low level of Varroa mite infestation suggest that the probability of founder colony survival is higher in California with a mostly Mediterranean climate. The data collected in areas with a high level of Varroa mite infestation suggest that the parasite reduces the mean life span of feral honey bee colonies in California to go between 6 mo and 1 yr. The parasite was widely spread in areas with a high density of commercial colonies. This suggests that the fast spread of the parasite is caused mostly by migration of commercial colonies. We discuss the consequences of the decline of the feral honey bee population on pollination and on the invasion of California by Africanized bees.