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Hill JE, Miller ML, Helton JL, Chipman RB, Gilbert AT, Beasley JC, Dharmarajan G, Rhodes OE. Raccoon spatial ecology in the rural southeastern United States. PLoS One 2023; 18:e0293133. [PMID: 37943745 PMCID: PMC10635488 DOI: 10.1371/journal.pone.0293133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Accepted: 10/06/2023] [Indexed: 11/12/2023] Open
Abstract
The movement ecology of raccoons varies widely across habitats with important implications for the management of zoonotic diseases such as rabies. However, the spatial ecology of raccoons remains poorly understood in many regions of the United States, particularly in the southeast. To better understand the spatial ecology of raccoons in the southeastern US, we investigated the role of sex, season, and habitat on monthly raccoon home range and core area sizes in three common rural habitats (bottomland hardwood, upland pine, and riparian forest) in South Carolina, USA. From 2018-2022, we obtained 264 monthly home ranges from 46 raccoons. Mean monthly 95% utilization distribution (UD) sizes ranged from 1.05 ± 0.48 km2 (breeding bottomland females) to 5.69 ± 3.37 km2 (fall riparian males) and mean monthly 60% UD sizes ranged from 0.25 ± 0.15 km2 (breeding bottomland females) to 1.59 ± 1.02 km2 (summer riparian males). Males maintained home range and core areas ~2-5 times larger than females in upland pine and riparian habitat throughout the year, whereas those of bottomland males were only larger than females during the breeding season. Home ranges and core areas of females did not vary across habitats, whereas male raccoons had home ranges and core areas ~2-3 times larger in upland pine and riparian compared to bottomland hardwood throughout much of the year. The home ranges of males in upland pine and riparian are among the largest recorded for raccoons in the United States. Such large and variable home ranges likely contribute to elevated risk of zoonotic disease spread by males in these habitats. These results can be used to inform disease mitigation strategies in the southeastern United States.
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Affiliation(s)
- Jacob E. Hill
- Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, United States of America
| | - Madison L. Miller
- Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, United States of America
| | - James L. Helton
- Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, United States of America
- Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, United States of America
| | - Richard B. Chipman
- National Rabies Management Program, USDA, APHIS, Wildlife Services, Concord, NH, United States of America
| | - Amy T. Gilbert
- National Wildlife Research Center, USDA, APHIS, Wildlife Services, Fort Collins, CO, United States of America
| | - James C. Beasley
- Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, United States of America
- Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, United States of America
| | - Guha Dharmarajan
- Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, United States of America
| | - Olin E. Rhodes
- Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, United States of America
- Odum School of Ecology, University of Georgia, Athens, GA, United States of America
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Bernasconi DA, Miller ML, Hill JE, Gupta P, Chipman R, Gilbert AT, Rhodes OE, Dharmarajan G. RACCOONS (PROCYON LOTOR) SHOW HIGHER TRYPANOSOMA CRUZI DETECTION RATES THAN VIRGINIA OPOSSUMS (DIDELPHIS VIRGINIANA) IN SOUTH CAROLINA, USA. J Wildl Dis 2023; 59:673-683. [PMID: 37846907 DOI: 10.7589/jwd-d-22-00174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 05/01/2023] [Indexed: 10/18/2023]
Abstract
Chagas disease, a significant public health concern in the Americas, is caused by a protozoan parasite, Trypanosoma cruzi. The life cycle of T. cruzi involves kissing bugs (Triatoma spp.) functioning as vectors and mammalian species serving as hosts. Raccoons (Procyon lotor) and opossums (Didelphis virginiana) have been identified as important reservoir species in the life cycle of T. cruzi, but prevalence in both species in the southeastern US is currently understudied. We quantified T. cruzi prevalence in these two key reservoir species across our study area in South Carolina, US, and identified factors that may influence parasite detection. We collected whole blood from 183 raccoons and 126 opossums and used PCR to detect the presence of T. cruzi. We then used generalized linear models with parasite detection status as a binary response variable and predictor variables of land cover, distance to water, sex, season, and species. Our analysis indicated that raccoons experienced significantly higher parasite detection rates than Virginia opossums, with T. cruzi prevalence found to be 26.5% (95% confidence interval [CI], 20.0-33.8) in raccoons and 10.5% (95% CI, 5.51-17.5) in opossums. Overall, our results concur with previous studies, in that T. cruzi is established in reservoir host populations in natural areas of the southeastern US.
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Affiliation(s)
- David A Bernasconi
- Idaho Department of Fish and Game, 15950 North Gate Boulevard, Nampa, Idaho 83687, USA
| | - Madison L Miller
- Division of Sciences, School of Interwoven Arts and Sciences, Krea University, 5655 Central Expressway, Sri City, Andhra Pradesh 517646, India
| | - Jacob E Hill
- Savannah River Ecology Laboratory, University of Georgia, Building 737-A Aiken, South Carolina 29802, USA
| | - Pooja Gupta
- Utah Public Health Laboratory, Utah Department of Health and Human Services, 4431 South 2700 West, Taylorsville, Salt Lake City, Utah 84129, USA
| | - Richard Chipman
- National Rabies Management Program, US Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services, 59 Chenell Drive, Suite 2, Concord, New Hampshire 03301, USA
| | - Amy T Gilbert
- National Wildlife Research Center, US Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services, 4101 LaPorte Avenue, Fort Collins, Colorado 80521, USA
| | - Olin E Rhodes
- Savannah River Ecology Laboratory, University of Georgia, Building 737-A Aiken, South Carolina 29802, USA
| | - Guha Dharmarajan
- Division of Sciences, School of Interwoven Arts and Sciences, Krea University, 5655 Central Expressway, Sri City, Andhra Pradesh 517646, India
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Hill JE, Helton JL, Chipman RB, Gilbert AT, Beasley JC, Dharmarajan G, Rhodes OE. Spatial ecology of translocated raccoons. Sci Rep 2023; 13:10447. [PMID: 37369730 DOI: 10.1038/s41598-023-37323-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Accepted: 06/20/2023] [Indexed: 06/29/2023] Open
Abstract
Raccoons (Procyon lotor) are routinely translocated both legally and illegally to mitigate conflicts with humans, which has contributed to the spread of rabies virus across eastern North America. The movement behavior of translocated raccoons has important ramifications for disease transmission yet remains understudied and poorly quantified. To examine the spatial ecology of raccoons following experimental translocation, we performed reciprocal 16 km-distance translocations of 30 raccoons between habitats of high and low raccoon density (bottomland hardwood and upland pine, respectively) across the Savannah River Site (SRS) in Aiken, South Carolina, USA (2018-2019). Translocation influenced patterns of raccoon space use, with translocated animals exhibiting a 13-fold increase in 95% utilization distributions (UDs) post- compared to pre-translocation (mean 95% UD 35.8 ± 36.1 km2 vs 1.96 ± 1.17 km2). Raccoons originating from upland pine habitats consistently had greater space use and larger nightly movement distances post-translocation compared to raccoons moved from bottomland hardwood habitats, whereas these differences were generally not observed prior to translocation. Estimated home ranges of male raccoons were twice the area as estimated for female raccoons, on average, and this pattern was not affected by translocation. After a transient period lasting on average 36.5 days (SD = 30.0, range = 3.25-92.8), raccoons often resumed pre-experiment movement behavior, with 95% UD sizes not different from those prior to translocation (mean = 2.27 ± 1.63km2). Most animals established new home ranges after translocation, whereas three raccoons moved > 16 km from their release point back to the original capture location. Four animals crossed a 100-m wide river within the SRS post-translocation, but this behavior was not documented among collared raccoons prior to translocation. Large increases in space use combined with the crossing of geographic barriers such as rivers may lead to elevated contact rates with conspecifics, which can heighten disease transmission risks following translocation. These results provide additional insights regarding the potential impacts of raccoon translocation towards population level risks of rabies outbreaks and underscore the need to discourage mesocarnivore translocations to prevent further spread of wildlife rabies.
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Affiliation(s)
- Jacob E Hill
- Savannah River Ecology Laboratory, University of Georgia, PO Drawer E, Aiken, SC, 29802, USA.
| | - James L Helton
- Savannah River Ecology Laboratory, University of Georgia, PO Drawer E, Aiken, SC, 29802, USA
- Warnell School of Forestry and Natural Resources, University of Georgia, 180 E Green St, Athens, GA, 30602, USA
| | - Richard B Chipman
- National Rabies Management Program, USDA, APHIS, Wildlife Services, Concord, NH, 03301, USA
| | - Amy T Gilbert
- National Wildlife Research Center, USDA, APHIS, Wildlife Services, 4101 Laporte Ave, Fort Collins, CO, 80521, USA
| | - James C Beasley
- Savannah River Ecology Laboratory, University of Georgia, PO Drawer E, Aiken, SC, 29802, USA
- Warnell School of Forestry and Natural Resources, University of Georgia, 180 E Green St, Athens, GA, 30602, USA
| | - Guha Dharmarajan
- Savannah River Ecology Laboratory, University of Georgia, PO Drawer E, Aiken, SC, 29802, USA
| | - Olin E Rhodes
- Savannah River Ecology Laboratory, University of Georgia, PO Drawer E, Aiken, SC, 29802, USA
- Odum School of Ecology, University of Georgia, 140 E Green St, Athens, GA, 30602, USA
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Frederick JC, Thompson AT, Sharma P, Dharmarajan G, Ronai I, Pesapane R, Smith RC, Sundstrom KD, Tsao JI, Tuten HC, Yabsley MJ, Glenn TC. Phylogeography of the blacklegged tick (Ixodes scapularis) throughout the USA identifies candidate loci for differences in vectorial capacity. Mol Ecol 2023; 32:3133-3149. [PMID: 36912202 DOI: 10.1111/mec.16921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 02/25/2023] [Accepted: 03/08/2023] [Indexed: 03/14/2023]
Abstract
The blacklegged tick (Ixodes scapularis (Journal of the Academy of Natural Sciences of Philadelphia, 1821, 2, 59)) is a vector of Borrelia burgdorferi sensu stricto (s.s.) (International Journal of Systematic Bacteriology, 1984, 34, 496), the causative bacterial agent of Lyme disease, part of a slow-moving epidemic of Lyme borreliosis spreading across the northern hemisphere. Well-known geographical differences in the vectorial capacity of these ticks are associated with genetic variation. Despite the need for detailed genetic information in this disease system, previous phylogeographical studies of these ticks have been restricted to relatively few populations or few genetic loci. Here we present the most comprehensive phylogeographical study of genome-wide markers in I. scapularis, conducted by using 3RAD (triple-enzyme restriction-site associated sequencing) and surveying 353 ticks from 33 counties throughout the species' range. We found limited genetic variation among populations from the Northeast and Upper Midwest, where Lyme disease is most common, and higher genetic variation among populations from the South. We identify five spatially associated genetic clusters of I. scapularis. In regions where Lyme disease is increasing in frequency, the I. scapularis populations genetically group with ticks from historically highly Lyme-endemic regions. Finally, we identify 10 variable DNA sites that contribute the most to population differentiation. These variable sites cluster on one of the chromosome-scale scaffolds for I. scapularis and are within identified genes. Our findings illuminate the need for additional research to identify loci causing variation in the vectorial capacity of I. scapularis and where additional tick sampling would be most valuable to further understand disease trends caused by pathogens transmitted by I. scapularis.
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Affiliation(s)
- Julia C Frederick
- Department of Environmental Health Science, University of Georgia, Athens, Georgia, 30602, USA
| | - Alec T Thompson
- Southeastern Cooperative Wildlife Disease Study, Department of Population Health, College of Veterinary Medicine, University of Georgia, Athens, Georgia, 30602, USA
- Center for the Ecology of Infectious Diseases, Odom School of Ecology, University of Georgia, Athens, Georgia, 30602, USA
| | - Prisha Sharma
- Department of Environmental Health Science, University of Georgia, Athens, Georgia, 30602, USA
| | - Guha Dharmarajan
- Savannah River Ecology Laboratory, University of Georgia, Aiken, South Carolina, 29808, USA
- Division of Sciences, School of Interwoven Arts and Sciences, Krea University, Sri City, Andhra Pradesh, India
| | - Isobel Ronai
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, 02138, USA
| | - Risa Pesapane
- Department of Veterinary Preventive Medicine, The Ohio State University, Columbus, Ohio, 43210, USA
- School of Environment and Natural Resources, The Ohio State University, Columbus, Ohio, 43210, USA
| | - Ryan C Smith
- Department of Plant Pathology, Entomology, and Microbiology, Iowa State University, Ames, Iowa, 50011, USA
| | - Kellee D Sundstrom
- Department of Veterinary Pathobiology, College of Veterinary Medicine, Oklahoma State University, Stillwater, Oklahoma, 74078, USA
| | - Jean I Tsao
- Department of Wildlife and Fisheries, Michigan State University, East Lansing, Michigan, 48824, USA
| | - Holly C Tuten
- Illinois Natural History Survey, University of Illinois Urbana-Champaign, Champaign, Illinois, 61820, USA
| | - Michael J Yabsley
- Southeastern Cooperative Wildlife Disease Study, Department of Population Health, College of Veterinary Medicine, University of Georgia, Athens, Georgia, 30602, USA
- Center for the Ecology of Infectious Diseases, Odom School of Ecology, University of Georgia, Athens, Georgia, 30602, USA
- Warnell School of Forestry and Natural Resources, University of Georgia, Athens, Georgia, 30602, USA
| | - Travis C Glenn
- Department of Environmental Health Science, University of Georgia, Athens, Georgia, 30602, USA
- Institute of Bioinformatics, University of Georgia, Athens, Georgia, 30602, USA
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Helton JL, Hill JE, Bernasconi DA, Dixon WC, Chipman RB, Gilbert AT, Beasley JC, Dharmarajan G, Rhodes OE. Assessment of habitat‐specific competition for oral rabies vaccine baits between raccoons and opossums. J Wildl Manage 2023. [DOI: 10.1002/jwmg.22398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/07/2023]
Affiliation(s)
- James L. Helton
- Savannah River Ecology Laboratory, Warnell School of Forestry and Natural Resources University of Georgia, Drawer E Aiken SC 29802 USA
| | - Jacob E. Hill
- Savannah River Ecology Laboratory University of Georgia, Drawer E Aiken SC 29802 USA
| | - David A. Bernasconi
- Savannah River Ecology Laboratory, Warnell School of Forestry and Natural Resources University of Georgia, Drawer E Aiken SC 29802 USA
| | - Wesley C. Dixon
- Savannah River Ecology Laboratory, Warnell School of Forestry and Natural Resources University of Georgia, Drawer E Aiken SC 29802 USA
| | - Richard B. Chipman
- National Rabies Management Program, USDA, APHIS, Wildlife Services Concord NH 03301 USA
| | - Amy T. Gilbert
- National Wildlife Research Center, USDA, APHIS, Wildlife Services Fort Collins CO 80521 USA
| | - James C. Beasley
- Savannah River Ecology Laboratory, Warnell School of Forestry and Natural Resources University of Georgia, Drawer E Aiken SC 29802 USA
| | - Guha Dharmarajan
- School of Interwoven Arts and Sciences Krea University Sri City AP India
| | - Olin E. Rhodes
- Savannah River Ecology Laboratory, Odum School of Ecology University of Georgia, Drawer E Aiken SC 29802 USA
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Bernasconi DA, Dixon WC, Hamilton MT, Helton JL, Chipman RB, Gilbert AT, Beasley JC, Rhodes OE, Dharmarajan G. Influence of landscape attributes on Virginia opossum density. J Wildl Manage 2022. [DOI: 10.1002/jwmg.22280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- David A. Bernasconi
- Savannah River Ecology Laboratory, Warnell School of Forestry and Natural Resources University of Georgia, Drawer E Aiken SC 29802 USA
| | - Wesley C. Dixon
- Savannah River Ecology Laboratory, Warnell School of Forestry and Natural Resources University of Georgia, Drawer E Aiken SC 29802 USA
| | - Matthew T. Hamilton
- Department of Forestry and Natural Resources Purdue University West Lafayette IN 47907 USA
| | - James L. Helton
- Savannah River Ecology Laboratory, Warnell School of Forestry and Natural Resources University of Georgia, Drawer E Aiken SC 29802 USA
| | - Richard B. Chipman
- National Rabies Management Program, USDA, APHIS, Wildlife Services Concord NH 03301 USA
| | - Amy T. Gilbert
- National Wildlife Research Center, USDA, APHIS, Wildlife Services Fort Collins CO 80521 USA
| | - James C. Beasley
- Savannah River Ecology Laboratory, Warnell School of Forestry and Natural Resources University of Georgia, Drawer E Aiken SC 29802 USA
| | - Olin E. Rhodes
- Savannah River Ecology Laboratory, Odum School of Ecology, University of Georgia, Drawer E Aiken SC 29802 USA
| | - Guha Dharmarajan
- Division of Sciences, School of Interwoven Arts and Sciences, Krea University, Sri City Andhra Pradesh India
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Street GM, Potts JR, Börger L, Beasley JC, Demarais S, Fryxell JM, McLoughlin PD, Monteith KL, Prokopenko CM, Ribeiro MC, Rodgers AR, Strickland BK, Beest FM, Bernasconi DA, Beumer LT, Dharmarajan G, Dwinnell SP, Keiter DA, Keuroghlian A, Newediuk LJ, Oshima JEF, Rhodes O, Schlichting PE, Schmidt NM, Vander Wal E. Solving the sample size problem for resource selection functions. Methods Ecol Evol 2021. [DOI: 10.1111/2041-210x.13701] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Garrett M. Street
- Department of Wildlife, Fisheries, and Aquaculture Mississippi State University Mississippi State MS USA
- Quantitative Ecology and Spatial Technologies Laboratory Mississippi State University Mississippi State MS USA
| | - Jonathan R. Potts
- School of Mathematics and Statistics University of Sheffield Sheffield UK
| | - Luca Börger
- Department of Biosciences Swansea University Swansea UK
- Centre for Biomathematics Swansea University Swansea UK
| | - James C. Beasley
- Savannah River Ecology Laboratory University of Georgia Aiken SC USA
| | - Stephen Demarais
- Department of Wildlife, Fisheries, and Aquaculture Mississippi State University Mississippi State MS USA
| | - John M. Fryxell
- Department of Integrative Biology University of Guelph Guelph ON Canada
| | | | - Kevin L. Monteith
- Haub School of Environment and Natural Resources University of Wyoming Laramie WY USA
| | | | - Miltinho C. Ribeiro
- Instituto de Biosciências Universidad Estadual Paulista Rio Claro, São Paulo Brazil
| | - Arthur R. Rodgers
- Centre for Northern Forest Ecosystem Research Ontario Ministry of Natural Resources and Forestry ON Canada
| | - Bronson K. Strickland
- Department of Wildlife, Fisheries, and Aquaculture Mississippi State University Mississippi State MS USA
| | | | | | | | - Guha Dharmarajan
- Savannah River Ecology Laboratory University of Georgia Aiken SC USA
| | - Samantha P. Dwinnell
- Wyoming Cooperative Fish and Wildlife Research Unit University of Wyoming Laramie WY USA
| | - David A. Keiter
- Savannah River Ecology Laboratory University of Georgia Aiken SC USA
| | | | - Levi J. Newediuk
- Department of Biology Memorial University of Newfoundland St. John’s NL Canada
| | - Júlia Emi F. Oshima
- Instituto de Biosciências Universidad Estadual Paulista Rio Claro, São Paulo Brazil
| | - Olin Rhodes
- Savannah River Ecology Laboratory University of Georgia Aiken SC USA
| | | | | | - Eric Vander Wal
- Department of Biology Memorial University of Newfoundland St. John’s NL Canada
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Abstract
Researchers worldwide are repeatedly warning us against future zoonotic diseases resulting from humankind's insurgence into natural ecosystems. The same zoonotic pathogens that cause severe infections in a human host frequently fail to produce any disease outcome in their natural hosts. What precise features of the immune system enable natural reservoirs to carry these pathogens so efficiently? To understand these effects, we highlight the importance of tracing the evolutionary basis of pathogen tolerance in reservoir hosts, while drawing implications from their diverse physiological and life-history traits, and ecological contexts of host-pathogen interactions. Long-term co-evolution might allow reservoir hosts to modulate immunity and evolve tolerance to zoonotic pathogens, increasing their circulation and infectious period. Such processes can also create a genetically diverse pathogen pool by allowing more mutations and genetic exchanges between circulating strains, thereby harboring rare alive-on-arrival variants with extended infectivity to new hosts (i.e., spillover). Finally, we end by underscoring the indispensability of a large multidisciplinary empirical framework to explore the proposed link between evolved tolerance, pathogen prevalence, and spillover in the wild.
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Affiliation(s)
| | - Guha Dharmarajan
- Savannah River Ecology Laboratory, University of GeorgiaAikenUnited States
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Dharmarajan G, Gupta P, Vishnudas CK, Robin VV. Cover Image. Ecol Lett 2021. [DOI: 10.1111/ele.13556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Abstract
The COVID-19 pandemic, caused by the novel coronavirus SARS-CoV-2, has been characterized by unprecedented rates of spatio-temporal spread. Here, we summarize the main events in the pandemic's timeline and evaluate what has been learnt by the public health community. We also discuss the implications for future public health policy and, specifically, the practice of epidemic control. We critically analyze this ongoing pandemic's timeline and contrast it with the 2002-2003 SARS outbreak. We identify specific areas (e.g., pathogen identification and initial reporting) wherein the international community learnt valuable lessons from the SARS outbreak. However, we also identify the key areas where international public health policy failed leading to the exponential spread of the pandemic. We outline a clear agenda for improved pandemic control in the future.
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Affiliation(s)
- Nils Chr. Stenseth
- Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, Oslo, Norway
| | - Guha Dharmarajan
- Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, United States
| | - Ruiyun Li
- Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, Oslo, Norway
| | - Zheng-Li Shi
- CAS Key Laboratory of Special Pathogens, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Ruifu Yang
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing, China
| | - George F. Gao
- CAS Key Laboratory of Pathogen Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- Chinese Center for Disease Control and Prevention, Beijing, China
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Dharmarajan G, Gupta P, Vishnudas CK, Robin VV. Anthropogenic disturbance favours generalist over specialist parasites in bird communities: Implications for risk of disease emergence. Ecol Lett 2021; 24:1859-1868. [PMID: 34120404 DOI: 10.1111/ele.13818] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 04/10/2021] [Accepted: 05/03/2021] [Indexed: 11/27/2022]
Abstract
Niche theory predicts specialists which will be more sensitive to environmental perturbation compared to generalists, a hypothesis receiving broad support in free-living species. Based on their niche breadth, parasites can also be classified as specialists and generalists, with specialists infecting only a few and generalists a diverse array of host species. Here, using avian haemosporidian parasites infecting wild bird populations inhabiting the Western Ghats, India as a model system, we elucidate how climate, habitat and human disturbance affects parasite prevalence both directly and indirectly via their effects on host diversity. Our data demonstrate that anthropogenic disturbance acts to reduce the prevalence of specialist parasite lineages, while increasing that of generalist lineages. Thus, as in free-living species, disturbance favours parasite communities dominated by generalist versus specialist species. Because generalist parasites are more likely to cause emerging infectious diseases, such biotic homogenisation of parasite communities could increase disease emergence risk in the Anthropocene.
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Affiliation(s)
- Guha Dharmarajan
- Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, USA.,Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India
| | - Pooja Gupta
- Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, USA.,Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India
| | - C K Vishnudas
- Indian Institute of Science Education and Research Tirupati, Tirupati, Andhra Pradesh, India
| | - V V Robin
- Indian Institute of Science Education and Research Tirupati, Tirupati, Andhra Pradesh, India
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Gupta P, Vishnudas CK, Robin VV, Dharmarajan G. Correction to: Host phylogeny matters: Examining sources of variation in infection risk by blood parasites across a tropical montane bird community in India. Parasit Vectors 2021; 14:99. [PMID: 33557916 PMCID: PMC7869506 DOI: 10.1186/s13071-020-04508-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Pooja Gupta
- Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, USA. .,Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, 30602, USA. .,Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, 741246, India.
| | - C K Vishnudas
- Indian Institute of Science Education and Research Tirupati, Mangalam, Tirupati, 517507, India
| | - V V Robin
- Indian Institute of Science Education and Research Tirupati, Mangalam, Tirupati, 517507, India
| | - Guha Dharmarajan
- Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, USA.,Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, 741246, India
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Neff E, Dharmarajan G. The direct and indirect effects of copper on vector-borne disease dynamics. Environ Pollut 2021; 269:116213. [PMID: 33302085 DOI: 10.1016/j.envpol.2020.116213] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 10/25/2020] [Accepted: 11/30/2020] [Indexed: 06/12/2023]
Abstract
Metal pollution is a growing concern that affects the health of humans and animals globally. Copper is an essential insect micronutrient required for respiration, pigmentation and oxidative stress protection but can also act as a potentially toxic trace element. While several studies have focused on the negative fitness effects of copper on the aquatic larvae of mosquitoes, the effects of larval copper exposure on adult mosquito fitness (i.e., survival and fecundity) and their ability to transmit parasites (i.e., vector competence) remains unclear. Here, using a well-studied model vector-parasite system, the mosquito Aedes aegypti and parasite Dirofilaria immitis, we show that sublethal copper exposure in larval mosquitoes alters adult female fecundity and vector competence. Specifically, mosquitoes exposed to copper had a hormetic fecundity response and mosquitoes exposed to 600 μg/L of copper had significantly fewer infective parasite larvae than control mosquitoes not exposed to copper. Thus, exposure of mosquito larvae to copper levels far below EPA-mandated safe drinking water limits (1300 μg/L) can impact vector-borne disease dynamics not only by reducing mosquito abundance (through increased larval mortality), but also by reducing parasite transmission risk. Our results also demonstrated that larval copper is retained through metamorphosis to adulthood in mosquitoes, indicating that these insects could transfer copper from aquatic to terrestrial foodwebs, especially in urban areas where they are abundant. To our knowledge this is the first study to directly link metal exposure with vector competence (i.e., ability to transmit parasites) in any vector-parasite system. Additionally, it also demonstrates unequivocally that mosquitoes can transfer contaminants from aquatic to terrestrial ecosystems. These results have broad implications for public health because they directly linking contaminants and vector-borne disease dynamics, as well as linking mosquitoes and contaminant dynamics.
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Affiliation(s)
- Erik Neff
- Savannah River Ecology Lab, University of Georgia, Aiken, SC, 29801, USA; Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, 30602, USA.
| | - Guha Dharmarajan
- Savannah River Ecology Lab, University of Georgia, Aiken, SC, 29801, USA
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Neff E, Evans CC, Jimenez Castro PD, Kaplan RM, Dharmarajan G. Drug Resistance in Filarial Parasites Does Not Affect Mosquito Vectorial Capacity. Pathogens 2020; 10:2. [PMID: 33375024 PMCID: PMC7822010 DOI: 10.3390/pathogens10010002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Revised: 12/15/2020] [Accepted: 12/18/2020] [Indexed: 12/19/2022] Open
Abstract
Parasite drug resistance presents a major obstacle to controlling and eliminating vector-borne diseases affecting humans and animals. While vector-borne disease dynamics are affected by factors related to parasite, vertebrate host and vector, research on drug resistance in filarial parasites has primarily focused on the parasite and vertebrate host, rather than the mosquito. However, we expect that the physiological costs associated with drug resistance would reduce the fitness of drug-resistant vs. drug-susceptible parasites in the mosquito wherein parasites are not exposed to drugs. Here we test this hypothesis using four isolates of the dog heartworm (Dirofilaria immitis)-two drug susceptible and two drug resistant-and two vectors-the yellow fever mosquito (Aedes aegypti) and the Asian tiger mosquito (Ae. albopictus)-as our model system. Our data indicated that while vector species had a significant effect on vectorial capacity, there was no significant difference in the vectorial capacity of mosquitoes infected with drug-resistant vs. drug-susceptible parasites. Consequently, contrary to expectations, our data indicate that drug resistance in D. immitis does not appear to reduce the transmission efficiency of these parasites, and thus the spread of drug-resistant parasites in the vertebrate population is unlikely to be mitigated by reduced fitness in the mosquito vector.
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Affiliation(s)
- Erik Neff
- Savannah River Ecology Laboratory, University of Georgia, Drawer E, Aiken, SC 29802, USA
| | - Christopher C. Evans
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA; (C.C.E.); (P.D.J.C.); (R.M.K.)
| | - Pablo D. Jimenez Castro
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA; (C.C.E.); (P.D.J.C.); (R.M.K.)
- Grupo de Parasitología Veterinaria, Universidad Nacional de Colombia, Bogotá 11001000, Colombia
| | - Ray M. Kaplan
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA; (C.C.E.); (P.D.J.C.); (R.M.K.)
| | - Guha Dharmarajan
- Savannah River Ecology Laboratory, University of Georgia, Drawer E, Aiken, SC 29802, USA
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Gupta P, Vishnudas CK, Robin VV, Dharmarajan G. Host phylogeny matters: Examining sources of variation in infection risk by blood parasites across a tropical montane bird community in India. Parasit Vectors 2020; 13:536. [PMID: 33115505 PMCID: PMC7594458 DOI: 10.1186/s13071-020-04404-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 10/14/2020] [Indexed: 11/10/2022] Open
Abstract
Background Identifying patterns and drivers of infection risk among host communities is crucial to elucidate disease dynamics and predict infectious disease risk in wildlife populations. Blood parasites of the genera Plasmodium and Haemoproteus are a diverse group of vector-borne protozoan parasites that affect bird populations globally. Despite their widespread distribution and exceptional diversity, factors underlying haemosporidian infection risk in wild bird communities remain poorly understood. While some studies have examined variation in avian haemosporidian risk, researchers have primarily focused on host ecological traits without considering host phylogenetic relationships. In this study, we employ a phylogenetically informed approach to examine the association between host ecological traits and haemosporidian infection risk in endemic bird communities in the Western Ghats Sky Islands. Methods We used parasite sequence data based on partial mitochondrial cytochrome b gene, that was amplified from genomic DNA extracted from 1177 birds (28 species) across the Western Ghats to assess infection of birds with haemosporidian parasites. We employed a Bayesian phylogenetic mixed effect modelling approach to test whether haemosporidian infection risk was affected by seven species-specific and four individual-level ecological predictors. We also examined the effect of host phylogenetic relationships on the observed patterns of variation in haemosporidian infection risk by estimating phylogenetic signal. Results Our study shows that host ecological traits and host phylogeny differentially influence infection risk by Plasmodium (generalist parasite) and Haemoproteus (specialist parasite). For Plasmodium, we found that sociality, sexual dimorphism and foraging strata were important ecological predictors. For Haemoproteus, patterns of infection risk among host species were associated with sociality, species elevation and individual body condition. Interestingly, variance in infection risk explained by host phylogeny was higher for Haemoproteus parasites compared to Plasmodium. Conclusions Our study highlights that while host ecological traits promoting parasite exposure and host susceptibility are important determinants of infection risk, host phylogeny also contributes substantially to predicting patterns of haemosporidian infection risk in multi-host communities. Importantly, infection risk is driven by joint contributions of host ecology and host phylogeny and studying these effects together could increase our ability to better understand the drivers of infection risk and predict future disease threats. Graphical abstract ![]()
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Affiliation(s)
- Pooja Gupta
- Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, USA. .,Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, 30602, USA. .,Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, 741246, India.
| | - C K Vishnudas
- Indian Institute of Science Education and Research Tirupati, Mangalam, Tirupati, 517507, India
| | - V V Robin
- Indian Institute of Science Education and Research Tirupati, Mangalam, Tirupati, 517507, India
| | - Guha Dharmarajan
- Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, USA.,Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, 741246, India
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16
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Rhodes OE, Bréchignac F, Bradshaw C, Hinton TG, Mothersill C, Arnone JA, Aubrey DP, Barnthouse LW, Beasley JC, Bonisoli-Alquati A, Boring LR, Bryan AL, Capps KA, Clément B, Coleman A, Condon C, Coutelot F, DeVol T, Dharmarajan G, Fletcher D, Flynn W, Gladfelder G, Glenn TC, Hendricks S, Ishida K, Jannik T, Kapustka L, Kautsky U, Kennamer R, Kuhne W, Lance S, Laptyev G, Love C, Manglass L, Martinez N, Mathews T, McKee A, McShea W, Mihok S, Mills G, Parrott B, Powell B, Pryakhin E, Rypstra A, Scott D, Seaman J, Seymour C, Shkvyria M, Ward A, White D, Wood MD, Zimmerman JK. Integration of ecosystem science into radioecology: A consensus perspective. Sci Total Environ 2020; 740:140031. [PMID: 32559536 DOI: 10.1016/j.scitotenv.2020.140031] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 06/04/2020] [Accepted: 06/04/2020] [Indexed: 06/11/2023]
Abstract
In the Fall of 2016 a workshop was held which brought together over 50 scientists from the ecological and radiological fields to discuss feasibility and challenges of reintegrating ecosystem science into radioecology. There is a growing desire to incorporate attributes of ecosystem science into radiological risk assessment and radioecological research more generally, fueled by recent advances in quantification of emergent ecosystem attributes and the desire to accurately reflect impacts of radiological stressors upon ecosystem function. This paper is a synthesis of the discussions and consensus of the workshop participant's responses to three primary questions, which were: 1) How can ecosystem science support radiological risk assessment? 2) What ecosystem level endpoints potentially could be used for radiological risk assessment? and 3) What inference strategies and associated methods would be most appropriate to assess the effects of radionuclides on ecosystem structure and function? The consensus of the participants was that ecosystem science can and should support radiological risk assessment through the incorporation of quantitative metrics that reflect ecosystem functions which are sensitive to radiological contaminants. The participants also agreed that many such endpoints exit or are thought to exit and while many are used in ecological risk assessment currently, additional data need to be collected that link the causal mechanisms of radiological exposure to these endpoints. Finally, the participants agreed that radiological risk assessments must be designed and informed by rigorous statistical frameworks capable of revealing the causal inference tying radiological exposure to the endpoints selected for measurement.
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Affiliation(s)
- Olin E Rhodes
- Savannah River Ecology Lab, Drawer E, Aiken, SC 29802, United States of America.
| | - Francois Bréchignac
- Institut de Radioprotection et de Sûreté Nucléaire, International Union of Radioecology, Center of Cadarache, Bldg 159, BP 1, 13115 St Paul-lez-Durance cedex, France
| | - Clare Bradshaw
- Department of Ecology, Environment and Plant Sciences, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Thomas G Hinton
- Institute of Environmental Radioactivity, 1 Kanayagawa, Fukushima University, Fukushima 960-1296, Japan
| | | | - John A Arnone
- Division of Earth and Ecosystem Sciences Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512, United States of America
| | - Doug P Aubrey
- Savannah River Ecology Lab, Warnell School of Forestry and Natural Resources, Drawer E, Aiken, SC 29802, United States of America
| | - Lawrence W Barnthouse
- LWB Environmental Services, Inc., 1620 New London Rd., Hamilton, OH 45013, United States of America
| | - James C Beasley
- Savannah River Ecology Lab, Warnell School of Forestry and Natural Resources, Drawer E, Aiken, SC 29802, United States of America
| | - Andrea Bonisoli-Alquati
- Department of Biological Sciences, California State Polytechnic University, Pomona, Pomona, CA 91768, United States of America
| | - Lindsay R Boring
- Joseph W. Jones Ecological Research Center, #988 Jones Center Dr., Newton, GA 39870, United States of America
| | - Albert L Bryan
- Savannah River Ecology Lab, Drawer E, Aiken, SC 29802, United States of America
| | - Krista A Capps
- Savannah River Ecology Lab, Drawer E, Aiken, SC 29802, United States of America; Odum School of Ecology, University of Georgia, Athens, GA 30602, United States of America
| | - Bernard Clément
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, ENTPE, UMR5023 LEHNA, F-69518, rue Maurice Audin, Vaulx-en-Velin, France
| | - Austin Coleman
- Savannah River Ecology Lab, Drawer E, Aiken, SC 29802, United States of America
| | - Caitlin Condon
- School of Nuclear Science and Engineering, 100 Radiation Center, Oregon State University, Corvallis, OR 97331, United States of America
| | - Fanny Coutelot
- Environmental Engineering and Earth Sciences, 342 Computer Ct., Clemson University, Clemson, SC 29625, United States of America
| | - Timothy DeVol
- Environmental Engineering and Earth Sciences, 342 Computer Ct., Clemson University, Anderson, SC 29625-6510, United States of America
| | - Guha Dharmarajan
- Savannah River Ecology Lab, Drawer E, Aiken, SC 29802, United States of America
| | - Dean Fletcher
- Savannah River Ecology Lab, Drawer E, Aiken, SC 29802, United States of America
| | - Wes Flynn
- Department of Forestry and Natural Resources, Purdue University, 715 W State Street, West Lafayette, IN 47907, United States of America
| | - Garth Gladfelder
- School of Nuclear Science and Engineering, 100 Radiation Center, Oregon State University, Corvallis, OR 97331, United States of America
| | - Travis C Glenn
- Department of Environmental Health Science, Institute of Bioinformatics, University of Georgia, Athens, GA 30602, United States of America
| | - Susan Hendricks
- Hancock Biological Station, 561 Emma Dr., Murray State University, Murray, KY 42071, United States of America
| | - Ken Ishida
- The University of Tokyo, Yokoze, 6632-12, Yokoze-town, Chichibu-gun, 368-0072, Japan
| | - Tim Jannik
- Savannah River National Laboratory, SRS Bldg. 999-W, Room 312, Aiken, SC 29808, United States of America
| | - Larry Kapustka
- LK Consultancy, P.O Box 373, 100 202 Blacklock Way SW, Turner Valley, Alberta T0L 2A0, Canada
| | - Ulrik Kautsky
- Svensk Kärnbränslehantering AB, PO Box 3091, SE-169 03 Solna, Sweden
| | - Robert Kennamer
- Savannah River Ecology Lab, Drawer E, Aiken, SC 29802, United States of America
| | - Wendy Kuhne
- Savannah River National Laboratory, 735-A, B-102, Aiken, SC 29808, United States of America
| | - Stacey Lance
- Savannah River Ecology Lab, Drawer E, Aiken, SC 29802, United States of America
| | - Gennadiy Laptyev
- Ukrainian HydroMeteorological Institute, 37 Prospekt Nauki, Kiev 02038, Ukraine
| | - Cara Love
- Savannah River Ecology Lab, Drawer E, Aiken, SC 29802, United States of America
| | - Lisa Manglass
- Environmental Engineering and Earth Sciences, 342 Computer Ct., Clemson University, Anderson, SC 29625-6510, United States of America
| | - Nicole Martinez
- Environmental Engineering and Earth Sciences, 342 Computer Ct., Clemson University, Anderson, SC 29625-6510, United States of America
| | - Teresa Mathews
- Oak Ridge National Laboratory, One Bethel Valley Rd., Oak Ridge, TN 37831, United States of America
| | - Arthur McKee
- Flathead Lake Biological Station, 32125 Bio Station Lane, Polson, MT 59860, United States of America
| | - William McShea
- Smithsonian's Conservation Biology Institute, 1500 Remount Rd., Front Royal, VA 22630, United States of America
| | - Steve Mihok
- Canadian Nuclear Safety Commission, P.O. Box 1046, Station B, 280 Slater St., Ottawa, Ontario K1P 5S9, Canada
| | - Gary Mills
- Savannah River Ecology Lab, Drawer E, Aiken, SC 29802, United States of America
| | - Ben Parrott
- Savannah River Ecology Lab, Drawer E, Aiken, SC 29802, United States of America
| | - Brian Powell
- Department of Environmental Engineering and Earth Sciences, 342 Computer Ct., Clemson University, Clemson, SC 29625, United States of America; Savannah River National Laboratory, Aiken, SC 29808, United States of America
| | - Evgeny Pryakhin
- Urals Research Center for Radiation Medicine, Vorovsky Str., 68a, Chelyabinsk 454141, Russia
| | - Ann Rypstra
- Ecology Research Center, Miami University, Oxford, OH 45056, United States of America
| | - David Scott
- Savannah River Ecology Lab, Drawer E, Aiken, SC 29802, United States of America
| | - John Seaman
- Savannah River Ecology Lab, Drawer E, Aiken, SC 29802, United States of America
| | - Colin Seymour
- Dept. of Biology, McMaster University, Hamilton, Ontario, Canada
| | - Maryna Shkvyria
- Kyiv zoological park of national importance, prosp. Peremohy, 32, Kyiv 04116, Ukraine
| | - Amelia Ward
- Department of Biological Sciences, PO Box 870344, University of Alabama, Tuscaloosa, AL 35487, United States of America
| | - David White
- Hancock Biological Station, 561 Emma Dr., Murray State University, Murray, KY 42071, United States of America
| | - Michael D Wood
- School of Science, Engineering & Environment, University of Salford, Salford M5 4WT. United Kingdom
| | - Jess K Zimmerman
- University of Puerto Rico, #17 Ave Universidad, San Juan 00925, Puerto Rico
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Sanchez J, Dharmarajan G, George MM, Pulaski C, Wolstenholme AJ, Gilleard JS, Kaplan RM. Using population genetics to examine relationships of Dirofilaria immitis based on both macrocyclic lactone-resistance status and geography. Vet Parasitol 2020; 283:109125. [PMID: 32535487 DOI: 10.1016/j.vetpar.2020.109125] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 03/24/2020] [Accepted: 04/25/2020] [Indexed: 12/18/2022]
Abstract
Prevention of infection with canine heartworm (Dirofilaria immitis) is based on the compliant administration of macrocyclic lactone (ML) drugs. Resistance to ML drugs is well documented in D. immitis; however, there remains a paucity of information on the spatial distribution and prevalence of resistant isolates. This project aims to improve understanding of ML-resistance by using a population genetic approach. We developed a large panel of microsatellite loci and identified 12 novel highly polymorphic markers. These 12, and five previously published markers were used to screen pools of microfilariae from 16 confirmed drug-susceptible, 25 confirmed drug-resistant, and from 10 suspected drug-resistant field isolates. In isolates where microfilarial suppression testing indicated resistance, Spatial Principal Component Analysis (sPCoA), Neighbor Joining Trees and Bayesian clustering all revealed high genetic similarity between pre- and post-treatment samples. Somewhat surprisingly, the Neighbor Joining tree and sPCoA generated using pairwise Nei's distances did not reveal clustering for resistant isolates, nor did it reveal state-level geographic clustering from samples collected in Georgia, Louisiana or Mississippi. In contrast, Discriminant Analysis of Principle Components was able to discriminate between susceptible, suspected-resistant and resistant samples. However, no resistance-associated markers were detected, and this clustering was driven by the combined effects of multiple alleles across multiple loci. Additionally, we measured unexpectedly large genetic distances between different passages of laboratory strains that originated from the same source infection. This finding strongly suggests that the genetic makeup of laboratory isolates can change substantially with each passage, likely due to genetic bottlenecking. Taken together, these data suggest greater than expected genetic variability in the resistant isolates, and in D. immitis overall. Our results also suggest that microsatellite genotyping lacks the sensitivity to detect a specific genetic signature for resistance. Future investigations using genomic analyses will be required to elucidate the genetic relationships of ML-resistant isolates.
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Affiliation(s)
- Julie Sanchez
- University of Georgia College of Veterinary Medicine, Department of Infectious Diseases, Athens, GA, United States
| | - Guha Dharmarajan
- Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, United States
| | - Melissa M George
- University of Georgia College of Veterinary Medicine, Department of Infectious Diseases, Athens, GA, United States
| | - Cassan Pulaski
- University of Georgia College of Veterinary Medicine, Department of Infectious Diseases, Athens, GA, United States
| | - Adrian J Wolstenholme
- University of Georgia College of Veterinary Medicine, Department of Infectious Diseases, Athens, GA, United States
| | - John S Gilleard
- Faculty of Veterinary Medicine, University of Calgary, Alberta, Canada
| | - Ray M Kaplan
- University of Georgia College of Veterinary Medicine, Department of Infectious Diseases, Athens, GA, United States.
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18
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Dharmarajan G, Walker KD, Lehmann T. Variation in Tolerance to Parasites Affects Vectorial Capacity of Natural Asian Tiger Mosquito Populations. Curr Biol 2019; 29:3946-3952.e5. [PMID: 31679930 PMCID: PMC6956842 DOI: 10.1016/j.cub.2019.09.047] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Revised: 05/10/2019] [Accepted: 09/18/2019] [Indexed: 12/11/2022]
Abstract
Globally, diseases transmitted by arthropod vectors, such as mosquitoes, remain a major cause of morbidity and mortality [1]. The defense responses of mosquito and other arthropod vectors against parasites are important for understanding disease transmission dynamics and for the development of novel disease-control strategies. Consequently, the mechanisms by which mosquitoes resist parasitic infection (e.g., immune-mediated killing) have long been studied [2, 3]. However, the ability of mosquitoes to ameliorate the negative fitness consequences of infection through tolerance mechanisms (e.g., tissue repair) has been virtually ignored (but see [4, 5]). Ignoring parasite tolerance is especially taxing in vector biology because unlike resistance, which typically reduces vectorial capacity, tolerance is expected to increase vectorial capacity by reducing parasite-mediated mortality without killing parasites [6], contributing to the recurrent emergence of vector-borne diseases and its stabilization and exacerbation. Despite its importance, there is currently no evidence for the evolution of tolerance in natural mosquito populations. Here, we use a common-garden experimental framework to measure variation in resistance and tolerance to dog heartworm (Dirofilaria immitis) between eight natural Aedes albopictus mosquito populations representing areas of low and high transmission intensity. We find significant inter-population variation in tolerance and elevated tolerance where transmission intensity is high. Additionally, as expected, we find that increased tolerance is associated with higher vectorial capacity. Consequently, our results indicate that high transmission intensity can lead to the evolution of more competent disease vectors, which can feed back to impact disease risk.
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Affiliation(s)
- Guha Dharmarajan
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12735 Twinbrook Parkway, Rockville, MD 20852, USA; University of Georgia, Savannah River Ecology Lab, Savannah River Site, Building 737-A, Aiken, SC 29808, USA.
| | - Kathryne D Walker
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12735 Twinbrook Parkway, Rockville, MD 20852, USA; Walter Reed Army Institute of Research, Department of Vector and Parasite Biology, 503 Robert Grant Road, Silver Spring, MD 20910, USA
| | - Tovi Lehmann
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12735 Twinbrook Parkway, Rockville, MD 20852, USA
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19
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Gupta P, Vishnudas CK, Ramakrishnan U, Robin VV, Dharmarajan G. Geographical and host species barriers differentially affect generalist and specialist parasite community structure in a tropical sky-island archipelago. Proc Biol Sci 2019; 286:20190439. [PMID: 31161909 DOI: 10.1098/rspb.2019.0439] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Understanding why some parasites emerge in novel host communities while others do not has broad implications for human and wildlife health. In the case of haemosporidian blood parasites, epidemic wild bird mortalities on oceanic islands have been linked to Plasmodium spp., but not genera like Haemoproteus. Indeed, Haemoproteus is absent from many oceanic islands. By contrast, birds on continental islands share long coevolutionary histories with both Plasmodium and Haemoproteus, and are thus ideal model systems to elucidate eco-evolutionary endpoints associated with these parasites in oceanic islands. Here, we examine eco-evolutionary dynamics of avian haemosporidian in the Shola sky-island archipelago of the Western Ghats, India. Our analyses reveal that compared to Plasmodium, Haemoproteus lineages were highly host-specific and diversified via co-speciation with their hosts. We show that community structure of host-generalist Plasmodium was primarily driven by geographical factors (e.g. biogeographic barriers), while that of host-specialist Haemoproteus was driven by host species barriers (e.g. phylogenetic distance). Consequently, a few host species can harbour a high diversity of Plasmodium lineages which, in turn, are capable of infecting multiple host species. These two mechanisms can act in concert to increase the risk of introduction, establishment, and emergence of novel Plasmodium lineages in island systems.
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Affiliation(s)
- Pooja Gupta
- 1 Savannah River Ecology Laboratory, University of Georgia , Aiken, SC , USA.,2 Warnell School of Forestry and Natural Resources, University of Georgia , Athens, GA 30602 , USA
| | - C K Vishnudas
- 3 Indian Institute of Science Education and Research Tirupati , Mangalam, Tirupati 517507 , India
| | - Uma Ramakrishnan
- 4 National Centre for Biological Sciences, TIFR , Bangalore 560065 , India
| | - V V Robin
- 3 Indian Institute of Science Education and Research Tirupati , Mangalam, Tirupati 517507 , India
| | - Guha Dharmarajan
- 1 Savannah River Ecology Laboratory, University of Georgia , Aiken, SC , USA
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20
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Neff E, Coleman AL, Maness RW, Tanelus M, Xu X, Dharmarajan G. Effects of methylmercury on mosquito oviposition behavior: Maladaptive response to non-toxic exposure. Sci Total Environ 2019; 667:248-254. [PMID: 30831364 DOI: 10.1016/j.scitotenv.2019.02.314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 02/10/2019] [Accepted: 02/20/2019] [Indexed: 06/09/2023]
Abstract
Animals can modulate their own exposure to environmental contaminants through behavioral plasticity such as diet and habitat choice. However, it remains unclear if behavior also has cascading effects on contaminant exposure across multiple generations. In insects, oviposition site selection is an important behavior females can use to modify offspring contaminant exposure risk. In this study, we use the yellow fever mosquito, Aedes aegypti, to test how methylmercury (MeHg) affects oviposition site selection. We found that mosquito larval development rate and survival were negatively affected at MeHg concentrations ≥100 ppb. Adult females not exposed to MeHg as larvae avoided oviposition sites with high MeHg concentrations (>50 ppb), but MeHg exposure at the larval stage significantly affected this oviposition site selection. Specifically, females raised from larvae exposed to non-toxic MeHg levels (i.e., five-50 ppb) showed a significant increase in preference for oviposition sites contaminated with toxic MeHg concentrations (≥500 ppb), compared to unexposed controls. This maladaptive behavioral response could be because, when conditioned with non-toxic MeHg concentrations, MeHg-associated olfactory cues act as a "supernormal" stimulus during oviposition site selection. Importantly, however, this maladaptive behavioral response is eliminated in female mosquitoes raised from larvae exposed to toxic MeHg concentrations (i.e. 100 ppb), and these mosquitoes showed a significant increase in preference for MeHg uncontaminated oviposition sites, compared to unexposed controls. Thus, in mosquitoes, the magnitude of MeHg exposure in one generation can impact MeHg exposure in subsequent generations by altering oviposition site selection behavior. Our results have broad implications for our understanding of how contaminant-mediated behavioral modifications can feedback on contaminant exposure risk across multiple generations, and consequently how behavior can affect the evolutionary trajectory of organisms inhabiting a heterogeneously contaminated environment.
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Affiliation(s)
- Erik Neff
- Savannah River Ecology Lab, University of Georgia, Aiken, SC 29801, USA.
| | - Austin L Coleman
- Savannah River Ecology Lab, University of Georgia, Aiken, SC 29801, USA
| | | | - Manette Tanelus
- University of South Carolina Upstate, Spartanburg, SC 29303, USA
| | - Xiaoyu Xu
- Savannah River Ecology Lab, University of Georgia, Aiken, SC 29801, USA
| | - Guha Dharmarajan
- Savannah River Ecology Lab, University of Georgia, Aiken, SC 29801, USA
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Crispell G, Commins SP, Archer-Hartman SA, Choudhary S, Dharmarajan G, Azadi P, Karim S. Discovery of Alpha-Gal-Containing Antigens in North American Tick Species Believed to Induce Red Meat Allergy. Front Immunol 2019; 10:1056. [PMID: 31156631 PMCID: PMC6533943 DOI: 10.3389/fimmu.2019.01056] [Citation(s) in RCA: 96] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Accepted: 04/24/2019] [Indexed: 01/01/2023] Open
Abstract
Development of specific IgE antibodies to the oligosaccharide galactose-α-1, 3-galactose (α-gal) following tick bites has been shown to be the source of red meat allergy. In this study, we investigated the presence of α-gal in four tick species: the lone-star tick (Amblyomma americanum), the Gulf-Coast tick (Amblyomma maculatum), the American dog tick (Dermacentor variabilis), and the black-legged tick (Ixodes scapularis) by using a combination of immunoproteomic approach and, carbohydrate analysis. Anti-α-gal antibodies identified α-gal in the salivary glands of both Am. americanum and Ix. scapularis, while Am. maculatum and De. variabilis appeared to lack the carbohydrate. PNGase F treatment confirmed the deglycosylation of N-linked α-gal-containing proteins in tick salivary glands. Immunolocalization of α-gal moieties to the salivary secretory vesicles of the salivary acini also confirmed the secretory nature of α-gal-containing antigens in ticks. Am. americanum ticks were fed on human blood (lacks α-gal) using a silicone membrane system to determine the source of the α-gal. N-linked glycan analysis revealed that Am. americanum and Ix. scapularis have α-gal in their saliva and salivary glands, but Am. maculatum contains no detectable quantity. Consistent with the glycan analysis, salivary samples from Am. americanum and Ix. scapularis stimulated activation of basophils primed with plasma from α-gal allergic subjects. Together, these data support the idea that bites from certain tick species may specifically create a risk for the development of α-gal-specific IgE and hypersensitivity reactions in humans. Alpha-Gal syndrome challenges the current food allergy paradigm and broadens opportunities for future research.
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Affiliation(s)
- Gary Crispell
- Department of Cell and Molecular Biology, School of Biological, Environment, and Earth Sciences, The University of Southern Mississippi, Hattiesburg, MS, United States
| | - Scott P Commins
- Department of Medicine and Pediatrics, University of North Carolina, Chapel Hill, NC, United States
| | | | - Shailesh Choudhary
- Department of Medicine and Pediatrics, University of North Carolina, Chapel Hill, NC, United States
| | - Guha Dharmarajan
- Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, United States
| | - Parastoo Azadi
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, United States
| | - Shahid Karim
- Department of Cell and Molecular Biology, School of Biological, Environment, and Earth Sciences, The University of Southern Mississippi, Hattiesburg, MS, United States
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Dharmarajan G, Beasley JC, Beatty WS, Olson ZH, Fike JA, Rhodes OE. Genetic co‐structuring in host‐parasite systems: Empirical data from raccoons and raccoon ticks. Ecosphere 2016. [DOI: 10.1002/ecs2.1269] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Affiliation(s)
- Guha Dharmarajan
- Department of Forestry and Natural ResourcesPurdue University West Lafayette Indiana 47907 USA
- Department of Biological SciencesIndian Institute of Science Education and Research – Kolkata Mohanpur West Bengal 741246 India
| | - James C. Beasley
- Department of Forestry and Natural ResourcesPurdue University West Lafayette Indiana 47907 USA
- Savannah River Ecology LaboratoryWarnell School of Forestry and Natural ResourcesUniversity of Georgia Drawer E Aiken South Carolina 29802 USA
| | - William S. Beatty
- Department of Forestry and Natural ResourcesPurdue University West Lafayette Indiana 47907 USA
- Alaska Science CenterUnited States Geological Survey Anchorage Alaska 99508 USA
| | - Zachary H. Olson
- Department of Forestry and Natural ResourcesPurdue University West Lafayette Indiana 47907 USA
- University of New England Biddeford Maine 04005 USA
| | - Jennifer A. Fike
- Department of Forestry and Natural ResourcesPurdue University West Lafayette Indiana 47907 USA
- Fort Collins Science Center Fort Collins Colorado 80526 USA
| | - Olin E. Rhodes
- Department of Forestry and Natural ResourcesPurdue University West Lafayette Indiana 47907 USA
- Savannah River Ecology LaboratoryOdum School of EcologyUniversity of Georgia Drawer E Aiken South Carolina 29802 USA
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Sarkissian CA, Campbell SK, Dharmarajan G, Jacquot J, Page LK, Graham DH. Microgeographic Population Genetic Structure of Baylisascaris procyonis (Nematoda: Ascaroidae) in Western Michigan Indicates the Grand River Is a Barrier to Gene Flow. J Parasitol 2015; 101:671-6. [DOI: 10.1645/15-767] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Affiliation(s)
| | | | | | | | | | - Douglas H. Graham
- Department of Biomedical Sciences, Grand Valley State University, 1 Campus Dr., Allendale, Michigan 49401. Correspondence should be sent to:
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Dharmarajan G. Inbreeding in stochastic subdivided mating systems: the genetic consequences of host spatial structure, aggregated transmission dynamics and life history characteristics in parasite populations. J Genet 2015; 94:43-53. [PMID: 25846876 DOI: 10.1007/s12041-015-0488-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Inbreeding in parasite populations can have important epidemiological and evolutionary implications. However, theoretical models have predominantly focussed on the evolution of parasite populations under strong selection or in epidemic situations, and our understanding of neutral gene dynamics in parasite populations at equilibrium has been limited to verbal arguments or conceptual models. This study focusses on how host-parasite population dynamics affects observed levels of inbreeding in a random sample of parasites from an infinite population of hosts by bridging traditional genetic and parasitological processes utilizing a backward-forward branching Markov process embedded within a flexible statistical framework, the logarithmic-poisson mixture model. My results indicate that levels of inbreeding in parasites are impacted by demographic and/or transmission dynamics (subdivided mating, aggregated transmission dynamics and host spatial structure), and that this inbreeding is poorly estimated by 'equilibrium' levels of inbreeding calculated assuming regular systems of mating. Specifically, the model reveals that at low levels of inbreeding (F ≤ 0.1), equilibrium levels of inbreeding are lower than those observed, while at high levels of inbreeding the opposite pattern occurs. The model also indicates that inbreeding could have important epidemiological implications (e.g., the spread of recessive drug resistance genes) by directly impacting the observed frequency of rare homozygotes in parasite populations. My results indicate that frequencies of rare homozygotes are affected by aggregated transmission dynamics and host spatial structure, and also that an increase in the frequency of rare homozygotes can be caused by a decrease in effective population size solely due to the presence of a subdivided breeding system.
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Affiliation(s)
- Guha Dharmarajan
- Department of Biological Sciences, Indian Institute of Science Education and Research - Kolkata, Mohanpur 741 246, India.
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Beasley JC, Dharmarajan G, Rhodes OE. Melding kin structure and demography to elucidate source and sink habitats in fragmented landscapes. Ecosphere 2015. [DOI: 10.1890/es14-00274.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- J. C. Beasley
- Department of Forestry and Natural Resources, 195 Marsteller Street, Purdue University, West Lafayette, Indiana 47907 USA
| | - G. Dharmarajan
- Department of Forestry and Natural Resources, 195 Marsteller Street, Purdue University, West Lafayette, Indiana 47907 USA
| | - O. E. Rhodes
- Department of Forestry and Natural Resources, 195 Marsteller Street, Purdue University, West Lafayette, Indiana 47907 USA
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Tan CG, Dharmarajan G, Beasley J, Rhodes O, Moore G, Wu CC, Lin TL. Neglected leptospirosis in raccoons (Procyon lotor) in Indiana, USA. Vet Q 2014; 34:1-10. [DOI: 10.1080/01652176.2014.909960] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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Dharmarajan G, Beasley JC, Fike JA, Rhodes OE. Effects of landscape, demographic and behavioral factors on kin structure: testing ecological predictions in a mesopredator with high dispersal capability. Anim Conserv 2013. [DOI: 10.1111/acv.12086] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- G. Dharmarajan
- Department of Forestry and Natural Resources; Purdue University; West Lafayette IN USA
- Indian Institute of Science Education and Research - Kolkata; Mohanpur West Bengal India
| | - J. C. Beasley
- Department of Forestry and Natural Resources; Purdue University; West Lafayette IN USA
- Savannah River Ecology Laboratory; Aiken SC USA
| | - J. A. Fike
- Department of Forestry and Natural Resources; Purdue University; West Lafayette IN USA
- Fort Collins Science Center; Fort Collins CO USA
| | - O. E. Rhodes
- Department of Forestry and Natural Resources; Purdue University; West Lafayette IN USA
- Savannah River Ecology Laboratory; Aiken SC USA
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Abstract
Anthropogenic changes in land use and the extirpation of apex predators have facilitated explosive growth of mesopredator populations. Consequently, many species have been subjected to extensive control throughout portions of their range due to their integral role as generalist predators and reservoirs of zoonotic disease. Yet, few studies have monitored the effects of landscape composition or configuration on the demographic or behavioral response of mesopredators to population manipulation. During 2007 we removed 382 raccoons (Procyon lotor) from 30 forest patches throughout a fragmented agricultural ecosystem to test hypotheses regarding the effects of habitat isolation on population recovery and role of range expansion and dispersal in patch colonization of mesopredators in heterogeneous landscapes. Patches were allowed to recolonize naturally and demographic restructuring of patches was monitored from 2008-2010 using mark-recapture. An additional 25 control patches were monitored as a baseline measure of demography. After 3 years only 40% of experimental patches had returned to pre-removal densities. This stagnant recovery was driven by low colonization rates of females, resulting in little to no within-patch recruitment. Colonizing raccoons were predominantly young males, suggesting that dispersal, rather than range expansion, was the primary mechanism driving population recovery. Contrary to our prediction, neither landscape connectivity nor measured local habitat attributes influenced colonization rates, likely due to the high dispersal capability of raccoons and limited role of range expansion in patch colonization. Although culling is commonly used to control local populations of many mesopredators, we demonstrate that such practices create severe disruptions in population demography that may be counterproductive to disease management in fragmented landscapes due to an influx of dispersing males into depopulated areas. However, given the slow repopulation rates observed in our study, localized depopulation may be effective at reducing negative ecological impacts of mesopredators in fragmented landscapes at limited spatial and temporal scales.
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Affiliation(s)
- James C Beasley
- Savannah River Ecology Laboratory, University of Georgia, Aiken, South Carolina, United States of America.
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Dharmarajan G, Beatty WS, Rhodes OE. Heterozygote deficiencies caused by a Wahlund effect: Dispelling unfounded expectations. J Wildl Manage 2012. [DOI: 10.1002/jwmg.458] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Dharmarajan G, Beasley JC, Fike JA, Raizman EA, Wu CC, Pogranichniy RM, Rhodes OE. Effects of kin-structure on disease dynamics in raccoons (Procyon lotor) inhabiting a fragmented landscape. Basic Appl Ecol 2012. [DOI: 10.1016/j.baae.2012.08.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Beatty WS, Beasley JC, Dharmarajan G, Rhodes OE. Genetic structure of a Virginia opossum (Didelphis virginiana) population inhabiting a fragmented agricultural ecosystem. CAN J ZOOL 2012. [DOI: 10.1139/z11-119] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Fragmentation has drastically altered the quality of habitats throughout numerous ecosystems, often leading to dramatic changes in the composition of wildlife communities. The ecology and associated movement behavior of a species may also be modified as a result of forest fragmentation, resulting in changes in genetic composition of the affected species. In this research, we evaluated the genetic structure of the Virginia opossum ( Didelphis virginiana Kerr, 1792) at the landscape and local scales in a fragmented, agricultural ecosystem in northern Indiana using 13 microsatellite loci. We examined 290 samples from opossums inhabiting 28 discrete habitat patches, and evaluated partitioning of genetic variation of opossums among and within habitat patches. We observed low but significant levels of genetic structure (FST = 0.005) overall, and pairwise comparisons of FST values among habitat patches also were relatively low. Relatedness within patches was highly variable (–0.077 ≤ rxy ≤ 0.060), with a few patches exhibiting significantly higher levels of relatedness than random expectations, and we detected no evidence of sex-biased natal dispersal. These results contrast with previous field studies that documented male-biased dispersal in the Virginia opossum, indicating dispersal in this species is plastic and dependent upon local environmental conditions.
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Affiliation(s)
- William S. Beatty
- Department of Forestry and Natural Resources, Purdue University, 195 Marsteller Street, West Lafayette, IN 47907, USA
| | - James C. Beasley
- Department of Forestry and Natural Resources, Purdue University, 195 Marsteller Street, West Lafayette, IN 47907, USA
| | - Guha Dharmarajan
- Department of Forestry and Natural Resources, Purdue University, 195 Marsteller Street, West Lafayette, IN 47907, USA
| | - Olin E. Rhodes
- Department of Forestry and Natural Resources, Purdue University, 195 Marsteller Street, West Lafayette, IN 47907, USA
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Dharmarajan G, Rhodes OE. Evaluating levels of PCR efficiency and genotyping error in DNA extracted from engorged and non-engorged female Dermacentor variabilis ticks. Med Vet Entomol 2011; 25:109-112. [PMID: 20704654 DOI: 10.1111/j.1365-2915.2010.00903.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Polymerase chain reaction (PCR)-based methods are increasingly used to elucidate tick biology. However, DNA extracted from ticks may provide poor PCR templates as a result of PCR inhibition by mammalian blood or contamination by male DNA (in fertilized females). In this study, the effects of removing the bloodmeal and reproductive organs were evaluated through paired DNA extractions in engorged and non-engorged Dermacentor variabilis (Say) (Acari: Ixodidae), prior to PCR amplification at 12 microsatellites. The first extraction utilized only mouthparts and legs ('mouthpart' samples) and the second utilized tick bodies ('body' samples). The results indicated that contamination by male DNA was an unlikely source of genotyping error in mouthpart and body samples. Engorged females showed higher levels of PCR inhibition in body vs. mouthpart samples, with a 29% decrease in amplification success rates per PCR and a 10-fold increase in levels of missing genotypes in body samples. By contrast, non-engorged females showed little difference in amplification success rates or numbers of missing genotypes in body vs. mouthpart samples. We discuss analytical concerns related to this systematic bias in PCR problems and recommend the removal of the bloodmeal and reproductive organs prior to DNA extraction, especially in engorged female ticks.
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Affiliation(s)
- G Dharmarajan
- Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907, USA.
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Dharmarajan G, Beasley JC, Rhodes OE. Heterozygote deficiencies in parasite populations: an evaluation of interrelated hypotheses in the raccoon tick, Ixodes texanus. Heredity (Edinb) 2010; 106:253-60. [PMID: 20606689 DOI: 10.1038/hdy.2010.84] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Population genetics is increasingly being used to study the biology of parasites at the scales of both the host (infrapopulation, IP) and host population (component population, CP). In this study we tested three mechanistic hypotheses that could explain deviations from Hardy-Weinberg equilibrium (HWE) expectations due to heterozygote deficits (HDs) at the CP scale in raccoon ticks (Ixodes texanus; n=718) collected from raccoons (Procyon lotor; n=91) and genotyped at 11 microsatellite loci. These hypotheses were presence of technical issues (for example, null alleles), hierarchical structure (for example, host demography) and cryptic structure (for example, kin structure). Although statistical support for null alleles existed, their presence would also be expected to lead to an underestimation in levels of relatedness, and thus kin structure. However, we found the opposite pattern: significant HD at the IP scale being more likely in CPs with significant vs non-significant levels of kin structure. Our analyses revealed that pooling of kin groups could lead to highly variable levels of F(IS) among loci, a pattern usually suggestive of null alleles. We used Monte-Carlo (MC) simulations to show that the existence of subdivided breeding groups and high variance in individual reproductive success could adequately explain deviations from HWE in I. texanus. Thus, our results indicate that biological factors can lead to patterns that have usually been interpreted as technical issues (for example, null alleles), and that it is important to take such factors into consideration because loci deviating from HWE likely reflect the effects of real biological processes.
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Affiliation(s)
- G Dharmarajan
- Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907, USA.
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Dharmarajan G, Beasley JC, Rhodes OE. Spatial and temporal factors affecting parasite genotypes encountered by hosts: empirical data from American dog ticks (Dermacentor variabilis) parasitising raccoons (Procyon lotor). Int J Parasitol 2010; 40:787-95. [PMID: 20060394 DOI: 10.1016/j.ijpara.2009.12.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2009] [Revised: 12/02/2009] [Accepted: 12/03/2009] [Indexed: 11/18/2022]
Abstract
The American dog tick (Dermacentor variabilis) is an important vector of numerous pathogens of humans and animals. In this study, we analysed population genetic patterns in D. variabilis at scales of the host individual (infrapopulation) and population (component population) to elucidate fine-scale spatial and temporal factors influencing transmission dynamics. We genotyped D. variabilis collected from raccoons (Procyon lotor) trapped in two habitat patches (located in Indiana, USA) which were spatially proximate (5.9 km) and limited in size (10.48 Ha and 25.47 Ha, respectively). Despite the fine spatial sampling scale, our analyses revealed significant genetic differentiation amongst component populations and infrapopulations (within each component population), indicating a non-random pattern of encountering tick genotypes by raccoons at both scales evaluated. We found evidence for male-biased dispersal in the ticks themselves (in one component population) and an age-bias in spatial scales at which raccoons encountered ticks in the environment. At the scale of the component population, our analyses revealed that raccoons encountered ticks from a limited number of D. variabilis family groups, likely due to high reproductive variance amongst individual ticks. Finally, we found evidence for a temporal effect with raccoons encountering ticks in the environment as "clumps" of related individuals. While the genetic structure of parasite populations are increasingly being investigated at small spatial scales (e.g. the infrapopulation), our data reveal that genetic structuring can originate at scales below that of the infrapopulation, due to the interaction between temporal and biological factors affecting the encounter of parasites by individual hosts. Ultimately, our data indicate that genetic structure in parasites must be viewed as a consequence of both spatial and temporal variance in host-parasite interactions, which in turn are driven by demographic factors related to both the host and parasite.
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Affiliation(s)
- G Dharmarajan
- Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907, USA.
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Dharmarajan G, Beasley JC, Fike JA, Rhodes OE. Population genetic structure of raccoons (Procyon lotor) inhabiting a highly fragmented landscape. CAN J ZOOL 2009. [DOI: 10.1139/z09-072] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The raccoon ( Procyon lotor (L., 1758)), a generalist mesocarnivore, has thrived in anthropogenically fragmented landscapes. In this study we utilized 13 microsatellites to analyze the population genetic structure in raccoons occupying an agriculturally fragmented habitat. Our analyses revealed low, but significant, levels of genetic structure (FST = 0.022, P < 0.001) among 645 raccoons inhabiting 29 spatially distinct habitat patches (neighborhoods). We found no evidence for the presence of either isolation by distance or barriers. However, spatial autocorrelation revealed evidence for social structure at the raccoon-neighborhood scale. About 30% of the variance in levels of social structure among raccoon neighborhoods was explained by effects of habitat-patch size and the percentage of land cover represented by forest around the individual habitat patch. We found strong evidence of sex-biased dispersal using direct (parentage analysis) and indirect (relatedness and assignment indices) genetic estimators. However, our analysis revealed that among dispersing raccoons there was no difference in dispersal distance between sexes and that dispersal events are randomly distributed with respect to distance. Our study provides evidence that demographic and behavioral processes affecting raccoon spatial organization may be most critical at very fine scales of biological organization, such as within individual habitat patches.
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Affiliation(s)
- Guha Dharmarajan
- Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907, USA
| | - James C. Beasley
- Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907, USA
| | - Jennifer A. Fike
- Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907, USA
| | - Olin E. Rhodes
- Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907, USA
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Latch EK, Dharmarajan G, Glaubitz JC, Rhodes OE. Relative performance of Bayesian clustering software for inferring population substructure and individual assignment at low levels of population differentiation. CONSERV GENET 2006. [DOI: 10.1007/s10592-005-9098-1] [Citation(s) in RCA: 317] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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