Does Pathogen Spillover from Commercially Reared Bumble Bees Threaten Wild Pollinators?

The conservation of insect pollinators is drawing attention because of reported declines in bee species and the ‘ecosystem services’ they provide. This issue has been brought to a head by recent devastating losses of honey bees throughout North America (so called, ‘Colony Collapse Disorder’); yet, we still have little understanding of the cause(s) of bee declines. Wild bumble bees (Bombus spp.) have also suffered serious declines and circumstantial evidence suggests that pathogen ‘spillover’ from commercially reared bumble bees, which are used extensively to pollinate greenhouse crops, is a possible cause. We constructed a spatially explicit model of pathogen spillover in bumble bees and, using laboratory experiments and the literature, estimated parameter values for the spillover of Crithidia bombi, a destructive pathogen commonly found in commercial Bombus. We also monitored wild bumble bee populations near greenhouses for evidence of pathogen spillover, and compared the fit of our model to patterns of C. bombi infection observed in the field. Our model predicts that, during the first three months of spillover, transmission from commercial hives would infect up to 20% of wild bumble bees within 2 km of the greenhouse. However, a travelling wave of disease is predicted to form suddenly, infecting up to 35–100% of wild Bombus, and spread away from the greenhouse at a rate of 2 km/wk. In the field, although we did not observe a large epizootic wave of infection, the prevalences of C. bombi near greenhouses were consistent with our model. Indeed, we found that spillover has allowed C. bombi to invade several wild bumble bee species near greenhouses. Given the available evidence, it is likely that pathogen spillover from commercial bees is contributing to the ongoing decline of wild Bombus in North America. Improved management of domestic bees, for example by reducing their parasite loads and their overlap with wild congeners, could diminish or even eliminate pathogen spillover

The genomes of two key bumblebee species with primitive eusocial organization

Background: The shift from solitary to social behavior is one of the major evolutionary transitions. Primitively eusocial bumblebees are uniquely placed to illuminate the evolution of highly eusocial insect societies. Bumblebees are also invaluable natural and agricultural pollinators, and there is widespread concern over recent population declines in some species. High-quality genomic data will inform key aspects of bumblebee biology, including susceptibility to implicated population viability threats. Results: We report the high quality draft genome sequences of Bombus terrestris and Bombus impatiens, two ecologically dominant bumblebees and widely utilized study species. Comparing these new genomes to those of the highly eusocial honeybee Apis mellifera and other Hymenoptera, we identify deeply conserved similarities, as well as novelties key to the biology of these organisms. Some honeybee genome features thought to underpin advanced eusociality are also present in bumblebees, indicating an earlier evolution in the bee lineage. Xenobiotic detoxification and immune genes are similarly depauperate in bumblebees and honeybees, and multiple categories of genes linked to social organization, including development and behavior, show high conservation. Key differences identified include a bias in bumblebee chemoreception towards gustation from olfaction, and striking differences in microRNAs, potentially responsible for gene regulation underlying social and other traits. Conclusions: These two bumblebee genomes provide a foundation for post-genomic research on these key pollinators and insect societies. Overall, gene repertoires suggest that the route to advanced eusociality in bees was mediated by many small changes in many genes and processes, and not by notable expansion or depauperation

A depauperate immune repertoire precedes evolution of sociality in bees

Background Sociality has many rewards, but can also be dangerous, as high population density and low genetic diversity, common in social insects, is ideal for parasite transmission. Despite this risk, honeybees and other sequenced social insects have far fewer canonical immune genes relative to solitary insects. Social protection from infection, including behavioral responses, may explain this depauperate immune repertoire. Here, based on full genome sequences, we describe the immune repertoire of two ecologically and commercially important bumblebee species that diverged approximately 18 million years ago, the North American Bombus impatiens and European Bombus terrestris. Results We find that the immune systems of these bumblebees, two species of honeybee, and a solitary leafcutting bee, are strikingly similar. Transcriptional assays confirm the expression of many of these genes in an immunological context and more strongly in young queens than males, affirming Bateman’s principle of greater investment in female immunity. We find evidence of positive selection in genes encoding antiviral responses, components of the Toll and JAK/STAT pathways, and serine protease inhibitors in both social and solitary bees. Finally, we detect many genes across pathways that differ in selection between bumblebees and honeybees, or between the social and solitary clades. Conclusions The similarity in immune complement across a gradient of sociality suggests that a reduced immune repertoire predates the evolution of sociality in bees. The differences in selection on immune genes likely reflect divergent pressures exerted by parasites across social contexts

The incidence of parasitism by conopid and phorid flies and its effects on the behavior of bumble bees(Hymenoptera: Apidae)

Bibliography: p. 124-138

Patterns of parasitism by tracheal mites (Locustacarus buchneri) in natural bumble bee populations

Parasitic mites are among the most destructive enemies of social bees. However, aside from mites of honey bees, virtually nothing is known about the prevalence and effects of parasitic mites in natural bee populations. In this paper, we report on parasitism of bumble bees (Bombus spp.) by the tracheal mite Locustacarus buchneri Stammer in south-western Alberta, Canada. Parasitism of bumble bees by L. buchneri occurred at many sites and in several host species. However, L. buchneri appears to be relatively host-species specific as it was found primarily in bumble bee species belonging to the subgenus Bombus sensu stricto. Furthermore, bumble bees containing tracheal mites had significantly reduced lifespans in the laboratory. Implications of parasitism on bumble bee life history are discussed

Measuring the impact of sea surface temperature on the human incidence of Vibrio sp. infection in British Columbia, Canada, 1992–2017

Background: Vibrio growth in the environment is related to sea surface temperature (SST). The incidence of human Vibrio illness increased sharply in British Columbia (BC) between 2008 and 2015 for unknown reasons, culminating in the largest outbreak of shellfish-associated Vibrio parahaemolyticus (Vp) in Canadian history in 2015. Our objective was to assess the relationship between SST and Vibrio illness in BC, Canada during 1992–2017 and assess the role of SST and other environmental factors in the 2015 Vp outbreak. Methods: Cases of Vibrio infection reported to the BC Centre for Disease Control during 1992–2017 were used. SST data were obtained from NOAA and NASA. We assessed changes in incidence trend of annual Vibrio cases during 1992–2017 using a Poisson regression. We assessed the correlation between annual Vibrio cases and the average annual maximum SST using a Spearman rank-order correlation. We modeled the association between weekly Vp case counts, SST and other environmental factors during 2007–2017 using a Poisson regression. Results: There was a significant increase in Vibrio cases between 2008 and 2015 (annual slope = 0.163, P < 0.001). Increased Vibrio incidence was observed in most El Niño years. There was a significant correlation between annual Vibrio cases and maximum SST from 1992 to 2017 (r = 0.46, P = 0.018). Our model captured observed seasonal variation in shellfish-associated Vp in most years, but underestimated the 2015 Vp outbreak. Conclusions: Vibrio incidence has been increasing concurrently with increasing SST in BC during 2008–2015. The 2015 Vp outbreak was not fully explained by climatic factors and may in part have been associated with other factors. Vp subtyping would be useful in the future to understand the combined effects of SST changes and strain emergence.Medicine, Faculty ofOther UBCPopulation and Public Health (SPPH), School ofReviewedFacult

Identification of spatial and cohort clustering of tuberculosis using surveillance data from British Columbia, Canada, 1990–2013

Since 2000, the global incidence of tuberculosis (TB) has decreased by 1.5% per year, becoming increasingly clustered in key subpopulations in low incidence settings. TB clustering can manifest spatially from recent transmission, or in non-spatial cohort clusters resulting from reactivation of latent infection in populations with shared risk factors. Identifying and interrupting disease clusters is required to eliminate TB in low incidence countries. Here we demonstrate an analytical approach for detecting both spatial and cohort clustering of TB among population subgroups, and describe the value in differentiating these forms of clustering. TB cases in British Columbia meeting the Canadian case definition were geocoded and mapped using Geographic Information Systems (GIS). Incidence rates were calculated for three periods (1990–1997, n = 2556; 1998–2005, n = 2488; 2006–2013, n = 2225) among Canadian born (CB) and foreign-born (FB) populations using denominator data from the Canadian Census. Spatial clusters were identified using a scanning window statistic (SaTScan) and overlaid on provincial incidence maps. Country of birth (cohort) clustering in the FB was identified using Lorenz curves and Gini coefficients. TB incidence in the CB population was generally low, but punctuated with few areas of high incidence; the spatial clusters identified in the CB match previously identified clusters. TB incidence in the FB did not show spatially localized clusters. However, Lorenz curves revealed substantial, and increasing, cohort clustering in the FB in semi-urban and rural regions of British Columbia, and less pronounced, and decreasing, clustering in urban regions. In general, the TB incidence in groups defined by country of birth shifted over time to become increasingly uniform across regions. Our approach, based on spatial analysis and the application of Lorenz curves revealed a complex coexistence of spatial and cohort clustering. Spatial and cohort clusters require differing public health responses, and differentiating types of clustering can inform TB prevention programs. •Tuberculosis cases in British Columbia are clustered spatially and non-spatially.•Spatial clustering is more common in Canadian-born cases.•Non-spatial cohort clustering is more common in foreign-born cases.•Differentiating types of clustering helps to clarify required public health action

Improved DNA Extraction and Illumina Sequencing of DNA Recovered from Aged Rootless Hair Shafts Found in Relics Associated with the Romanov Family.

This study describes an optimized DNA extraction protocol targeting ultrashort DNA molecules from single rootless hairs. It was applied to the oldest samples available to us: locks of hairs that were found in relics associated with the Romanov family. Published mitochondrial DNA genome sequences of Tsar Nicholas II and his wife, Tsarina Alexandra, made these samples ideal to assess this DNA extraction protocol and evaluate the types of genetic information that can be recovered by sequencing ultrashort fragments. Using this method, the mtGenome of the Tsarina's lineage was identified in hairs that were concealed in a pendant made by Karl Fabergé for Alexandra Feodorovna Romanov. In addition, to determine if the lock originated from more than one individual, two hairs from the locket were extracted independently and converted into Illumina libraries for shotgun sequencing on a NextSeq 500 platform. From these data, autosomal SNPs were analyzed to assess relatedness. The results indicated that the two hairs came from a single individual. Genetic testing of hairs that were found in the second artifact, a framed photograph of Louise of Hesse-Kassel, Queen of Denmark and maternal grandmother of Tsar Nicholas II, revealed that the hair belonged to a woman who shared Tsar Nicholas' maternal lineage, including the well-known point heteroplasmy at position 16169

Illicit drug overdose deaths resulting from income assistance payments : analysis of the ‘check effect’ using daily mortality data

Background Although income assistance is an important source of support for low income individuals, there is evidence that adverse outcomes may increase when payments are disbursed on the same day for all recipients. The objective of this study was to assess the temporal patterns and causal relation between population-level illicit drug overdose deaths and income assistance payments using daily mortality data for British Columbia over a period of five years. Methods Retrospective data on daily mortality due to illicit drug overdose, 2009 to 2013, were provided by the BC Coroners Service. These data were analyzed using regression models and time series tests for causality in relation to dates of income assistance payments. Results 1343 deaths due to illicit drug overdose were reported in BC during 2009-2013; 394 occurred during cheque weeks (n=60) and 949 occurred during non-cheque weeks (n=202). Average weekly mortality due to illicit drug overdose was 40% higher during weeks of income assistance payments compared to weeks without payments (P < 0.001). Consistent increases in mortality appeared the day after cheque disbursement and were significantly higher for two days, and marginally higher after 3 days, even when controlling for other temporal trends. Granger causality testing suggests the timing of cheque issue was causally linked to increased drug overdose mortality (P < 0.001). Conclusions Our findings clarify the temporal relation and causal impact of income assistance payments on illicit drug deaths. We estimate 77 avoidable deaths were attributable to the synchronized disbursement of income assistance cheques over the five year period. An important consideration is whether varying the timing of payments among recipients could reduce this excess mortality and the related demands on health and social servicesArts, Faculty ofMedicine, Faculty ofOther UBCNon UBCPopulation and Public Health (SPPH), School ofSociology, Department ofReviewedFacult