312
views
0
recommends
+1 Recommend
1 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found
      Is Open Access

      Geography, Deer, and Host Biodiversity Shape the Pattern of Lyme Disease Emergence in the Thousand Islands Archipelago of Ontario, Canada

      research-article

      Read this article at

      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          In the Thousand Islands region of eastern Ontario, Canada, Lyme disease is emerging as a serious health risk. The factors that influence Lyme disease risk, as measured by the number of blacklegged tick ( Ixodes scapularis) vectors infected with Borrelia burgdorferi, are complex and vary across eastern North America. Despite study sites in the Thousand Islands being in close geographic proximity, host communities differed and both the abundance of ticks and the prevalence of B. burgdorferi infection in them varied among sites. Using this archipelago in a natural experiment, we examined the relative importance of various biotic and abiotic factors, including air temperature, vegetation, and host communities on Lyme disease risk in this zone of recent invasion. Deer abundance and temperature at ground level were positively associated with tick abundance, whereas the number of ticks in the environment, the prevalence of B. burgdorferi infection, and the number of infected nymphs all decreased with increasing distance from the United States, the presumed source of this new endemic population of ticks. Higher species richness was associated with a lower number of infected nymphs. However, the relative abundance of Peromyscus leucopus was an important factor in modulating the effects of species richness such that high biodiversity did not always reduce the number of nymphs or the prevalence of B. burgdorferi infection. Our study is one of the first to consider the interaction between the relative abundance of small mammal hosts and species richness in the analysis of the effects of biodiversity on disease risk, providing validation for theoretical models showing both dilution and amplification effects. Insights into the B. burgdorferi transmission cycle in this zone of recent invasion will also help in devising management strategies as this important vector-borne disease expands its range in North America.

          Related collections

          Most cited references44

          • Record: found
          • Abstract: found
          • Article: not found

          The ecology of infectious disease: effects of host diversity and community composition on Lyme disease risk.

          The extent to which the biodiversity and community composition of ecosystems affect their functions is an issue that grows ever more compelling as human impacts on ecosystems increase. We present evidence that supports a novel function of vertebrate biodiversity, the buffering of human risk of exposure to Lyme-disease-bearing ticks. We tested the Dilution Effect model, which predicts that high species diversity in the community of tick hosts reduces vector infection prevalence by diluting the effects of the most competent disease reservoir, the ubiquitous white-footed mouse (Peromyscus leucopus). As habitats are degraded by fragmentation or other anthropogenic forces, some members of the host community disappear. Thus, species-poor communities tend to have mice, but few other hosts, whereas species-rich communities have mice, plus many other potential hosts. We demonstrate that the most common nonmouse hosts are relatively poor reservoirs for the Lyme spirochete and should reduce the prevalence of the disease by feeding, but rarely infecting, ticks. By accounting for nearly every host species' contribution to the number of larval ticks fed and infected, we show that as new host species are added to a depauperate community, the nymphal infection prevalence, a key risk factor, declines. We identify important "dilution hosts" (e.g., squirrels), characterized by high tick burdens, low reservoir competence, and high population density, as well as "rescue hosts" (e.g., shrews), which are capable of maintaining high disease risk when mouse density is low. Our study suggests that the preservation of vertebrate biodiversity and community composition can reduce the incidence of Lyme disease.
            Bookmark
            • Record: found
            • Abstract: found
            • Article: not found

            Pangloss revisited: a critique of the dilution effect and the biodiversity-buffers-disease paradigm.

            The twin concepts of zooprophylaxis and the dilution effect originated with vector-borne diseases (malaria), were driven forward by studies on Lyme borreliosis and have now developed into the mantra "biodiversity protects against disease". The basic idea is that by diluting the assemblage of transmission-competent hosts with non-competent hosts, the probability of vectors feeding on transmission-competent hosts is reduced and so the abundance of infected vectors is lowered. The same principle has recently been applied to other infectious disease systems--tick-borne, insect-borne, indirectly transmitted via intermediate hosts, directly transmitted. It is claimed that the presence of extra species of various sorts, acting through a variety of distinct mechanisms, causes the prevalence of infectious agents to decrease. Examination of the theoretical and empirical evidence for this hypothesis reveals that it applies only in certain circumstances even amongst tick-borne diseases, and even less often if considering the correct metric--abundance rather than prevalence of infected vectors. Whether dilution or amplification occurs depends more on specific community composition than on biodiversity per se. We warn against raising a straw man, an untenable argument easily dismantled and dismissed. The intrinsic value of protecting biodiversity and ecosystem function outweighs this questionable utilitarian justification.
              Bookmark
              • Record: found
              • Abstract: found
              • Article: not found

              Climate change and the potential for range expansion of the Lyme disease vector Ixodes scapularis in Canada.

              We used an Ixodes scapularis population model to investigate potential northward spread of the tick associated with climate change. Annual degree-days >0 degrees C limits for I. scapularis establishment, obtained from tick population model simulations, were mapped using temperatures projected for the 2020s, 2050s and 2080s by two Global Climate Models (the Canadian CGCM2 and the UK HadCM3) for two greenhouse gas emission scenario enforcings 'A2'and 'B2' of the Intergovernmental Panel on Climate Change. Under scenario 'A2' using either climate model, the theoretical range for I. scapularis establishment moved northwards by approximately 200 km by the 2020s and 1000 km by the 2080s. Reductions in emissions (scenario 'B2') had little effect on projected range expansion up to the 2050s, but the range expansion projected to occur between the 2050s and 2080s was less than that under scenario 'A2'. When the tick population model was driven by projected annual temperature cycles (obtained using CGCM2 under scenario 'A2'), tick abundance almost doubled by the 2020s at the current northern limit of I. scapularis, suggesting that the threshold numbers of immigrating ticks needed to establish new populations will fall during the coming decades. The projected degrees of theoretical range expansion and increased tick survival by the 2020s, suggest that actual range expansion of I. scapularis may be detectable within the next two decades. Seasonal tick activity under climate change scenarios was consistent with maintenance of endemic cycles of the Lyme disease agent in newly established tick populations. The geographic range of I. scapularis-borne zoonoses may, therefore, expand significantly northwards as a consequence of climate change this century.
                Bookmark

                Author and article information

                Contributors
                Role: Editor
                Journal
                PLoS One
                PLoS ONE
                plos
                plosone
                PLoS ONE
                Public Library of Science (San Francisco, USA )
                1932-6203
                2014
                9 January 2014
                : 9
                : 1
                : e85640
                Affiliations
                [1 ]Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
                [2 ]Parks Canada Agency, Thousand Islands National Park, Mallorytown, Ontario, Canada
                [3 ]Canadian Cooperative Wildlife Health Centre, Guelph, Ontario, Canada
                [4 ]Ontario Ministry of Natural Resources, Peterborough, Ontario, Canada
                [5 ]University of Victoria, Victoria, British Columbia, Canada
                [6 ]Department of Pathology and Microbiology, Faulty of Veterinary Medicine, University of Montréal, Saint-Hyacinthe, Quebec, Canada
                [7 ]Public Health Agency of Canada, Winnipeg, Manitoba, Canada
                The Johns Hopkins University School of Medicine, United States of America
                Author notes

                Competing Interests: The authors have declared that no competing interests exist.

                Conceived and designed the experiments: IKB JB EKG LRL CMJ. Performed the experiments: LW JB EKG LRL CMJ. Analyzed the data: LW IKB PAL CMJ. Contributed reagents/materials/analysis tools: IKB JB EKG PAL LRL CMJ. Wrote the paper: LW IKB JB EKG PAL LRL CMJ. Phylogenetic analysis on species determination for white-footed mice: JB. Species determinations and real time PCR testing on nymphs: LRL.

                Article
                PONE-D-13-14095
                10.1371/journal.pone.0085640
                3887107
                24416435
                3cbd5f51-1ed9-4e73-badd-29e65f5dcfe3
                Copyright @ 2014

                This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

                History
                : 6 April 2013
                : 4 December 2013
                Page count
                Pages: 14
                Funding
                Funding for this study was provided by the University of Guelph (CJ), Canadian Cooperative Wildlife Health Centre (IKB), Ontario Ministry of Natural Resources (JB), Parks Canada Agency (EKG), Public Health Agency of Canada (LRL), Natural Sciences and Engineering and Research Council of Canada (CJ; www.nserc.ca), and an Ontario Graduate Scholarship (LW). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Employees and/or students with all funding agencies assisted with data collection.
                Categories
                Research Article
                Biology
                Ecology
                Biodiversity
                Microbiology
                Vector Biology
                Ticks
                Medicine
                Infectious Diseases
                Bacterial Diseases
                Borrelia Infection
                Lyme Disease
                Vectors and Hosts
                Ticks
                Public Health
                Disease Ecology
                Veterinary Science
                Animal Types
                Wildlife

                Uncategorized
                Uncategorized

                Comments

                Comment on this article