Molecular, physiological and behavioral responses of honey bee (Apis mellifera) drones to infection with microsporidian parasites.

Susceptibility to pathogens and parasites often varies between sexes due to differences in life history traits and selective pressures. Nosema apis and Nosema ceranae are damaging intestinal pathogens of European honey bees (Apis mellifera). Nosema pathology has primarily been characterized in female workers where infection is energetically costly and accelerates worker behavioral maturation. Few studies, however, have examined infection costs in male honey bees (drones) to determine if Nosema similarly affects male energetic status and sexual maturation. We infected newly emerged adult drones with Nosema spores and conducted a series of molecular, physiological, and behavioral assays to characterize Nosema etiology in drones. We found that infected drones starved faster than controls and exhibited altered patterns of flight activity in the field, consistent with energetic distress or altered rates of sexual maturation. Moreover, expression of candidate genes with metabolic and/or hormonal functions, including members of the insulin signaling pathway, differed by infection status. Of note, while drone molecular responses generally tracked predictions based on worker studies, several aspects of infected drone flight behavior contrasted with previous observations of infected workers. While Nosema infection clearly imposed energetic costs in males, infection had no impact on drone sperm numbers and had only limited effects on antennal responsiveness to a major queen sex pheromone component (9-ODA). We compare Nosema pathology in drones with previous studies describing symptoms in workers and discuss ramifications for drone and colony fitness.

Unity in defence: honeybee workers exhibit conserved molecular responses to diverse pathogens.

BACKGROUND: Organisms typically face infection by diverse pathogens, and hosts are thought to have developed specific responses to each type of pathogen they encounter. The advent of transcriptomics now makes it possible to test this hypothesis and compare host gene expression responses to multiple pathogens at a genome-wide scale. Here, we performed a meta-analysis of multiple published and new transcriptomes using a newly developed bioinformatics approach that filters genes based on their expression profile across datasets. Thereby, we identified common and unique molecular responses of a model host species, the honey bee (Apis mellifera), to its major pathogens and parasites: the Microsporidia Nosema apis and Nosema ceranae, RNA viruses, and the ectoparasitic mite Varroa destructor, which transmits viruses. RESULTS: We identified a common suite of genes and conserved molecular pathways that respond to all investigated pathogens, a result that suggests a commonality in response mechanisms to diverse pathogens. We found that genes differentially expressed after infection exhibit a higher evolutionary rate than non-differentially expressed genes. Using our new bioinformatics approach, we unveiled additional pathogen-specific responses of honey bees; we found that apoptosis appeared to be an important response following microsporidian infection, while genes from the immune signalling pathways, Toll and Imd, were differentially expressed after Varroa/virus infection. Finally, we applied our bioinformatics approach and generated a gene co-expression network to identify highly connected (hub) genes that may represent important mediators and regulators of anti-pathogen responses. CONCLUSIONS: Our meta-analysis generated a comprehensive overview of the host metabolic and other biological processes that mediate interactions between insects and their pathogens. We identified key host genes and pathways that respond to phylogenetically diverse pathogens, representing an important source for future functional studies as well as offering new routes to identify or generate pathogen resilient honey bee stocks. The statistical and bioinformatics approaches that were developed for this study are broadly applicable to synthesize information across transcriptomic datasets. These approaches will likely have utility in addressing a variety of biological questions.

Approaches and Challenges to Managing Nosema (Microspora: Nosematidae) Parasites in Honey Bee (Hymenoptera: Apidae) Colonies.

UNLABELLED: The microsporidia Nosema apis (Zander) and Nosema ceranae (Fries) are common intestinal parasites in honey bee (Apis mellifera L.) colonies. Though globally prevalent, there are mixed reports of Nosema infection costs, with some regions reporting high parasite virulence and colony losses, while others REPORT: high Nosema prevalence but few costs. Basic and applied studies are urgently needed to help beekeepers effectively manage Nosema spp., ideally through an integrated pest management approach that allows beekeepers to deploy multiple strategies to control Nosema when Nosema is likely to cause damage to the colonies, rather than using prophylactic treatments. Beekeepers need practical and affordable technologies that facilitate disease diagnosis and science-backed guidelines that recommend when, if at all, to treat infections. In addition, new treatment methods are needed, as there are several problems associated with the chemical use of fumagillin (the only currently extensively studied, but not globally available treatment) to control Nosema parasites. Though selective breeding of Nosema-resistant or tolerant bees may offer a long-term, sustainable solution to Nosema management, other treatments are needed in the interim. Furthermore, the validation of alternative treatment efficacy in field settings is needed along with toxicology assays to ensure that treatments do not have unintended, adverse effects on honey bees or humans. Finally, given variation in Nosema virulence, development of regional management guidelines, rather than universal guidelines, may provide optimal and cost-effective Nosema management, though more research is needed before regional plans can be developed.

Chronic parasitization by Nosema microsporidia causes global expression changes in core nutritional, metabolic and behavioral pathways in honey bee workers (Apis mellifera).

BACKGROUND: Chronic infections can profoundly affect the physiology, behavior, fitness and longevity of individuals, and may alter the organization and demography of social groups. Nosema apis and Nosema ceranae are two microsporidian parasites which chronically infect the digestive tract of honey bees (Apis mellifera). These parasites, in addition to other stressors, have been linked to increased mortality of individual workers and colony losses in this key pollinator species. Physiologically, Nosema infection damages midgut tissue, is energetically expensive and alters expression of immune genes in worker honey bees. Infection also accelerates worker transition from nursing to foraging behavior (termed behavioral maturation). Here, using microarrays, we characterized global gene expression patterns in adult worker honey bee midgut and fat body tissue in response to Nosema infection. RESULTS: Our results indicate that N. apis infection in young workers (1 and 2 days old) disrupts midgut development. At 2 and 7 days post-infection in the fat body tissue, N. apis drives metabolic changes consistent with energetic costs of infection. A final experiment characterizing gene expression in the fat bodies of 14 day old workers parasitized with N. apis and N. ceranae demonstrated that Nosema co-infection specifically alters conserved nutritional, metabolic and hormonal pathways, including the insulin signaling pathway, which is also linked to behavioral maturation in workers. Interestingly, in all experiments, Nosema infection did not appear to significantly regulate overall expression of canonical immune response genes, but infection did alter expression of acute immune response genes identified in a previous study. Comparative analyses suggest that changes in nutritional/metabolic processes precede changes in behavioral maturation and immune processes. CONCLUSIONS: These genome-wide studies of expression patterns can help us disentangle the direct and indirect effects of chronic infection, and understand the molecular pathways that regulate disease symptoms.

Effects of immunostimulation on social behavior, chemical communication and genome-wide gene expression in honey bee workers (Apis mellifera).

BACKGROUND: Social insects, such as honey bees, use molecular, physiological and behavioral responses to combat pathogens and parasites. The honey bee genome contains all of the canonical insect immune response pathways, and several studies have demonstrated that pathogens can activate expression of immune effectors. Honey bees also use behavioral responses, termed social immunity, to collectively defend their hives from pathogens and parasites. These responses include hygienic behavior (where workers remove diseased brood) and allo-grooming (where workers remove ectoparasites from nestmates). We have previously demonstrated that immunostimulation causes changes in the cuticular hydrocarbon profiles of workers, which results in altered worker-worker social interactions. Thus, cuticular hydrocarbons may enable workers to identify sick nestmates, and adjust their behavior in response. Here, we test the specificity of behavioral, chemical and genomic responses to immunostimulation by challenging workers with a panel of different immune stimulants (saline, Sephadex beads and Gram-negative bacteria E. coli). RESULTS: While only bacteria-injected bees elicited altered behavioral responses from healthy nestmates compared to controls, all treatments resulted in significant changes in cuticular hydrocarbon profiles. Immunostimulation caused significant changes in expression of hundreds of genes, the majority of which have not been identified as members of the canonical immune response pathways. Furthermore, several new candidate genes that may play a role in cuticular hydrocarbon biosynthesis were identified. Effects of immune challenge expression of several genes involved in immune response, cuticular hydrocarbon biosynthesis, and the Notch signaling pathway were confirmed using quantitative real-time PCR. Finally, we identified common genes regulated by pathogen challenge in honey bees and other insects. CONCLUSIONS: These results demonstrate that honey bee genomic responses to immunostimulation are substantially broader than the previously identified canonical immune response pathways, and may mediate the behavioral changes associated with social immunity by orchestrating changes in chemical signaling. These studies lay the groundwork for future research into the genomic responses of honey bees to native honey bee parasites and pathogens.

Medical decision-making among Hispanics and non-Hispanic Whites with chronic back and knee pain: a qualitative study.

BACKGROUND: Musculoskeletal disorders affect all racial and ethnic groups, including Hispanics. Because these disorders are not life-threatening, decision-making is generally preference-based. Little is known about whether Hispanics in the U.S. differ from non-Hispanic Whites with respect to key decision making preferences. METHODS: We assembled six focus groups of Hispanic and non-Hispanic White patients with chronic back or knee pain at an urban medical center to discuss management of their conditions and the roles they preferred in medical decision-making. Hispanic groups were further stratified by socioeconomic status, using neighborhood characteristics as proxy measures. Discussions were led by a moderator, taped, transcribed and analyzed using a grounded theory approach. RESULTS: The analysis revealed ethnic differences in several areas pertinent to medical decision-making. Specifically, Hispanic participants were more likely to permit their physician to take the predominant role in making health decisions. Also, Hispanics of lower socioeconomic status generally preferred to use non-internet sources of health information to make medical decisions and to rely on advice obtained by word of mouth. Hispanics emphasized the role of faith and religion in coping with musculoskeletal disability. The analysis also revealed broad areas of concordance across ethnic strata including the primary role that pain and achieving pain relief play in patients' experiences and decisions. CONCLUSIONS: These findings suggest differences between Hispanics and non-Hispanic Whites in preferred information sources and decision-making roles. These findings are hypothesis-generating. If confirmed in further research, they may inform the development of interventions to enhance preference-based decision-making among Hispanics.

Impact of obesity and knee osteoarthritis on morbidity and mortality in older Americans.

BACKGROUND: Obesity and knee osteoarthritis are among the most frequent chronic conditions affecting Americans aged 50 to 84 years. OBJECTIVE: To estimate quality-adjusted life-years lost due to obesity and knee osteoarthritis and health benefits of reducing obesity prevalence to levels observed a decade ago. DESIGN: The U.S. Census and obesity data from national data sources were combined with estimated prevalence of symptomatic knee osteoarthritis to assign persons aged 50 to 84 years to 4 subpopulations: nonobese without knee osteoarthritis (reference group), nonobese with knee osteoarthritis, obese without knee osteoarthritis, and obese with knee osteoarthritis. The Osteoarthritis Policy Model, a computer simulation model of knee osteoarthritis and obesity, was used to estimate quality-adjusted life-year losses due to knee osteoarthritis and obesity in comparison with the reference group. SETTING: United States. PARTICIPANTS: U.S. population aged 50 to 84 years. MEASUREMENTS: Quality-adjusted life-years lost owing to knee osteoarthritis and obesity. RESULTS: Estimated total losses of per-person quality-adjusted life-years ranged from 1.857 in nonobese persons with knee osteoarthritis to 3.501 for persons affected by both conditions, resulting in a total of 86.0 million quality-adjusted life-years lost due to obesity, knee osteoarthritis, or both. Quality-adjusted life-years lost due to knee osteoarthritis and/or obesity represent 10% to 25% of the remaining quality-adjusted survival of persons aged 50 to 84 years. Hispanic and black women had disproportionately high losses. Model findings suggested that reversing obesity prevalence to levels seen 10 years ago would avert 178,071 cases of coronary heart disease, 889,872 cases of diabetes, and 111,206 total knee replacements. Such a reduction in obesity would increase the quantity of life by 6,318,030 years and improve life expectancy by 7,812,120 quality-adjusted years in U.S. adults aged 50 to 84 years. LIMITATIONS: Comorbidity incidences were derived from prevalence estimates on the basis of life expectancy of the general population, potentially resulting in conservative underestimates. Calibration analyses were conducted to ensure comparability of model-based projections and data from external sources. CONCLUSION: The number of quality-adjusted life-years lost owing to knee osteoarthritis and obesity seems to be substantial, with black and Hispanic women experiencing disproportionate losses. Reducing mean body mass index to the levels observed a decade ago in this population would yield substantial health benefits. PRIMARY FUNDING SOURCE: The National Institutes of Health and the Arthritis Foundation.

Cost-effectiveness of total knee arthroplasty in the United States: patient risk and hospital volume.

BACKGROUND: Total knee arthroplasty (TKA) relieves pain and improves quality of life for persons with advanced knee osteoarthritis. However, to our knowledge, the cost-effectiveness of TKA and the influences of hospital volume and patient risk on TKA cost-effectiveness have not been investigated in the United States. METHODS: We developed a Markov, state-transition, computer simulation model and populated it with Medicare claims data and cost and outcomes data from national and multinational sources. We projected lifetime costs and quality-adjusted life expectancy (QALE) for different risk populations and varied TKA intervention and hospital volume. Cost-effectiveness of TKA was estimated across all patient risk and hospital volume permutations. Finally, we conducted sensitivity analyses to determine various parameters' influences on cost-effectiveness. RESULTS: Overall, TKA increased QALE from 6.822 to 7.957 quality-adjusted life years (QALYs). Lifetime costs rose from $37,100 (no TKA) to $57 900 after TKA, resulting in an incremental cost-effectiveness ratio of $18,300 per QALY. For high-risk patients, TKA increased QALE from 5.713 to 6.594 QALY, yielding a cost-effectiveness ratio of $28,100 per QALY. At all risk levels, TKA was more costly and less effective in low-volume centers than in high-volume centers. Results were insensitive to variations of key input parameters within policy-relevant, clinically plausible ranges. The greatest variations were seen for the quality of life gain after TKA and the cost of TKA. CONCLUSIONS: Total knee arthroplasty appears to be cost-effective in the US Medicare-aged population, as currently practiced across all risk groups. Policy decisions should be made on the basis of available local options for TKA. However, when a high-volume hospital is available, TKAs performed in a high-volume hospital confer even greater value per dollar spent than TKAs performed in low-volume centers.