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Godfrey EJ, Cameron EZ, Hickling GJ. Social learning in a nocturnal marsupial: is it a possum-ability? Biol Lett 2023; 19:20220460. [PMID: 36651032 PMCID: PMC9845967 DOI: 10.1098/rsbl.2022.0460] [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] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Social learning can reduce the costs associated with trial-and-error learning. There is speculation that social learning could contribute to trap and bait avoidance in invasive species like the common brushtail possum (Trichosurus vulpecula)-a marsupial for which social learning has not previously been investigated. In large outdoor pens, we presented wild-caught 'demonstrator' possums with puzzle devices containing an attractive food reward; 2 of 8 demonstrators accessed the reward the first night the puzzle was presented and another three succeeded on later nights. Meanwhile, 'observer' possums in adjacent pens watched the demonstrators for five nights and then were given the opportunity to solve the puzzle themselves; 15 of 15 succeeded on their first night (a highly significant improvement). This experiment thus provides strong evidence of social learning by common brushtail possums. Future research should investigate whether information about aversive stimuli (such as traps and toxic baits) can similarly be transmitted between possums by social learning; if so, this could have important implications for possum pest control.
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Affiliation(s)
- Emma J. Godfrey
- School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch 8041, New Zealand
| | - Elissa Z. Cameron
- School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch 8041, New Zealand
| | - Graham J. Hickling
- Wildlife Ecology and Management, Manaaki Whenua Landcare Research, PO Box 69040, Lincoln 7640, New Zealand
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2
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Poh KC, Evans JR, Skvarla MJ, Kent CM, Olafson PU, Hickling GJ, Mullinax JM, Machtinger ET. Patterns of deer ked (Diptera: Hippoboscidae) and tick (Ixodida: Ixodidae) infestation on white-tailed deer (Odocoileus virginianus) in the eastern United States. Parasit Vectors 2022; 15:31. [PMID: 35057829 PMCID: PMC8772158 DOI: 10.1186/s13071-021-05148-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Accepted: 12/29/2021] [Indexed: 11/10/2022] Open
Abstract
Abstract
Background
White-tailed deer (Odocoileus virginianus) host numerous ectoparasitic species in the eastern USA, most notably various species of ticks and two species of deer keds. Several pathogens transmitted by ticks to humans and other animal hosts have also been found in deer keds. Little is known about the acquisition and potential for transmission of these pathogens by deer keds; however, tick-deer ked co-feeding transmission is one possible scenario. On-host localization of ticks and deer keds on white-tailed deer was evaluated across several geographical regions of the eastern US to define tick-deer ked spatial relationships on host deer, which may impact the vector-borne disease ecology of these ectoparasites.
Methods
Ticks and deer keds were collected from hunter-harvested white-tailed deer from six states in the eastern US. Each deer was divided into three body sections, and each section was checked for 4 person-minutes. Differences in ectoparasite counts across body sections and/or states were evaluated using a Bayesian generalized mixed model.
Results
A total of 168 white-tailed deer were inspected for ticks and deer keds across the study sites. Ticks (n = 1636) were collected from all surveyed states, with Ixodes scapularis (n = 1427) being the predominant species. Counts of I. scapularis from the head and front sections were greater than from the rear section. Neotropical deer keds (Lipoptena mazamae) from Alabama and Tennessee (n = 247) were more often found on the rear body section. European deer keds from Pennsylvania (all Lipoptena cervi, n = 314) were found on all body sections of deer.
Conclusions
The distributions of ticks and deer keds on white-tailed deer were significantly different from each other, providing the first evidence of possible on-host niche partitioning of ticks and two geographically distinct deer ked species (L. cervi in the northeast and L. mazamae in the southeast). These differences in spatial distributions may have implications for acquisition and/or transmission of vector-borne pathogens and therefore warrant further study over a wider geographic range and longer time frame.
Graphical Abstract
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Ginsberg HS, Hickling GJ, Pang G, Tsao JI, Fitzgerald M, Ross B, Rulison EL, Burke RL. Selective Host Attachment by Ixodes scapularis (Acari: Ixodidae): Tick-Lizard Associations in the Southeastern United States. J Med Entomol 2022; 59:267-272. [PMID: 34718657 DOI: 10.1093/jme/tjab181] [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: 07/22/2021] [Indexed: 06/13/2023]
Abstract
Questing behavior and host associations of immature blacklegged ticks, Ixodes scapularis Say, from the southeastern United States are known to differ from those in the north. To elucidate these relationships we describe host associations of larval and nymphal I. scapularis from 8 lizard species sampled from 5 sites in the southeastern U.S. Larvae and nymphs attached in greater numbers to larger lizards than to smaller lizards, with differential levels of attachment to different lizard species. Blacklegged ticks are generally attached to skinks of the genus Plestiodon in greater numbers per unit lizard weight than to anoles (Anolis) or fence lizards (Sceloporus). The broad-headed skink, Plestiodon laticeps (Schneider), was a particularly important host for immature I. scapularis in our study and in several previous studies of tick-host associations in the southeast. Blacklegged ticks show selective attachment to Plestiodon lizard hosts in the southeast, but whether this results from behavioral host preferences or from ecological factors such as timing or microhabitat distributions of tick questing and host activity remains to be determined.
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Affiliation(s)
- Howard S Ginsberg
- U.S. Geological Survey, Eastern Ecological Science Center, Field Station at the University of Rhode Island, Kingston, RI, USA
| | - Graham J Hickling
- Center for Wildlife Health, University of Tennessee Institute of Agriculture, Knoxville, TN, USA
| | - Genevieve Pang
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI, USA
| | - Jean I Tsao
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI, USA
| | - Meghan Fitzgerald
- Center for Wildlife Health, University of Tennessee Institute of Agriculture, Knoxville, TN, USA
| | - Breann Ross
- Department of Biology, Hofstra University, Hempstead, NY, USA
| | - Eric L Rulison
- Department of Plant Sciences and Entomology, University of Rhode Island, Kingston, RI, USA
| | - Russell L Burke
- Department of Biology, Hofstra University, Hempstead, NY, USA
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4
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Ginsberg HS, Hickling GJ, Burke RL, Ogden NH, Beati L, LeBrun RA, Arsnoe IM, Gerhold R, Han S, Jackson K, Maestas L, Moody T, Pang G, Ross B, Rulison EL, Tsao JI. Correction: Why Lyme disease is common in the northern US, but rare in the south: The roles of host choice, host-seeking behavior, and tick density. PLoS Biol 2021; 19:e3001396. [PMID: 34495954 PMCID: PMC8425571 DOI: 10.1371/journal.pbio.3001396] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
[This corrects the article DOI: 10.1371/journal.pbio.3001066.].
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Tsao JI, Hamer SA, Han S, Sidge JL, Hickling GJ. The Contribution of Wildlife Hosts to the Rise of Ticks and Tick-Borne Diseases in North America. J Med Entomol 2021; 58:1565-1587. [PMID: 33885784 DOI: 10.1093/jme/tjab047] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [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: 11/03/2020] [Indexed: 05/09/2023]
Abstract
Wildlife vertebrate hosts are integral to enzootic cycles of tick-borne pathogens, and in some cases have played key roles in the recent rise of ticks and tick-borne diseases in North America. In this forum article, we highlight roles that wildlife hosts play in the maintenance and transmission of zoonotic, companion animal, livestock, and wildlife tick-borne pathogens. We begin by illustrating how wildlife contribute directly and indirectly to the increase and geographic expansion of ticks and their associated pathogens. Wildlife provide blood meals for tick growth and reproduction; serve as pathogen reservoirs; and can disperse ticks and pathogens-either through natural movement (e.g., avian migration) or through human-facilitated movement (e.g., wildlife translocations and trade). We then discuss opportunities to manage tick-borne disease through actions directed at wildlife hosts. To conclude, we highlight key gaps in our understanding of the ecology of tick-host interactions, emphasizing that wildlife host communities are themselves a very dynamic component of tick-pathogen-host systems and therefore complicate management of tick-borne diseases, and should be taken into account when considering host-targeted approaches. Effective management of wildlife to reduce tick-borne disease risk further requires consideration of the 'human dimensions' of wildlife management. This includes understanding the public's diverse views and values about wildlife and wildlife impacts-including the perceived role of wildlife in fostering tick-borne diseases. Public health agencies should capitalize on the expertise of wildlife agencies when developing strategies to reduce tick-borne disease risks.
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Affiliation(s)
- Jean I Tsao
- Department of Fisheries and Wildlife, Department of Large Animal Clinical Sciences, Michigan State University, East Lansing, MI, USA
| | - Sarah A Hamer
- Department of Veterinary Integrative Biosciences, and Schubot Center for Avian Health, Department of Veterinary Pathology, Texas A&M University, College Station, TX, USA
| | - Seungeun Han
- Department of Disease Control and Epidemiology, National Veterinary Institute (SVA), Uppsala, Sweden
| | - Jennifer L Sidge
- Michigan Department of Agriculture and Rural Development, Lansing, MI, USA
| | - Graham J Hickling
- Center for Wildlife Health, Department of Forestry, Wildlife and Fisheries, University of Tennessee, Knoxville, TN, USA
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Ginsberg HS, Hickling GJ, Burke RL, Ogden NH, Beati L, LeBrun RA, Arsnoe IM, Gerhold R, Han S, Jackson K, Maestas L, Moody T, Pang G, Ross B, Rulison EL, Tsao JI. Why Lyme disease is common in the northern US, but rare in the south: The roles of host choice, host-seeking behavior, and tick density. PLoS Biol 2021; 19:e3001066. [PMID: 33507921 PMCID: PMC7842935 DOI: 10.1371/journal.pbio.3001066] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Accepted: 12/22/2020] [Indexed: 12/28/2022] Open
Abstract
Lyme disease is common in the northeastern United States, but rare in the southeast, even though the tick vector is found in both regions. Infection prevalence of Lyme spirochetes in host-seeking ticks, an important component to the risk of Lyme disease, is also high in the northeast and northern midwest, but declines sharply in the south. As ticks must acquire Lyme spirochetes from infected vertebrate hosts, the role of wildlife species composition on Lyme disease risk has been a topic of lively academic discussion. We compared tick–vertebrate host interactions using standardized sampling methods among 8 sites scattered throughout the eastern US. Geographical trends in diversity of tick hosts are gradual and do not match the sharp decline in prevalence at southern sites, but tick–host associations show a clear shift from mammals in the north to reptiles in the south. Tick infection prevalence declines north to south largely because of high tick infestation of efficient spirochete reservoir hosts (rodents and shrews) in the north but not in the south. Minimal infestation of small mammals in the south results from strong selective attachment to lizards such as skinks (which are inefficient reservoirs for Lyme spirochetes) in the southern states. Selective host choice, along with latitudinal differences in tick host-seeking behavior and variations in tick densities, explains the geographic pattern of Lyme disease in the eastern US. Lyme disease is common in the northeastern United States, but rare in the southeast, even though the tick vector is found in both regions. This study shows that this is largely because the tick vectors attach abundantly to rodents (which are good hosts for the Lyme bacteria) in the north, and to lizards (which are relatively poor hosts for Lyme bacteria) in the south.
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Affiliation(s)
- Howard S. Ginsberg
- US Geological Survey, Patuxent Wildlife Research Center, Woodward-PSE, University of Rhode Island, Kingston, Rhode Island, United States of America
- Department of Plant Sciences and Entomology, University of Rhode Island, Kingston, Rhode Island, United States of America
- * E-mail:
| | - Graham J. Hickling
- Center for Wildlife Health, University of Tennessee Institute of Agriculture, Knoxville, Tennessee, United States of America
| | - Russell L. Burke
- Department of Biology, Hofstra University, Hempstead, New York, United States of America
| | - Nicholas H. Ogden
- Public Health Risk Sciences Division, National Microbiology Laboratory, Public Health Agency of Canada, Ste-Hyacinthe, Quebec, Canada
| | - Lorenza Beati
- US National Tick Collection, Institute for Coastal Plain Science, Georgia Southern University, Statesboro, Georgia, United States of America
| | - Roger A. LeBrun
- Department of Plant Sciences and Entomology, University of Rhode Island, Kingston, Rhode Island, United States of America
| | - Isis M. Arsnoe
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, Michigan, United States of America
| | - Richard Gerhold
- Center for Wildlife Health, University of Tennessee Institute of Agriculture, Knoxville, Tennessee, United States of America
| | - Seungeun Han
- Comparative Medicine and Integrative Biology, Michigan State University, East Lansing, Michigan, United States of America
| | - Kaetlyn Jackson
- Department of Biology, Hofstra University, Hempstead, New York, United States of America
| | - Lauren Maestas
- Center for Wildlife Health, University of Tennessee Institute of Agriculture, Knoxville, Tennessee, United States of America
| | - Teresa Moody
- Center for Wildlife Health, University of Tennessee Institute of Agriculture, Knoxville, Tennessee, United States of America
| | - Genevieve Pang
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, Michigan, United States of America
| | - Breann Ross
- Department of Biology, Hofstra University, Hempstead, New York, United States of America
| | - Eric L. Rulison
- Department of Plant Sciences and Entomology, University of Rhode Island, Kingston, Rhode Island, United States of America
| | - Jean I. Tsao
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, Michigan, United States of America
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Gardner AM, Pawlikowski NC, Hamer SA, Hickling GJ, Miller JR, Schotthoefer AM, Tsao JI, Allan BF. Landscape features predict the current and forecast the future geographic spread of Lyme disease. Proc Biol Sci 2020; 287:20202278. [PMID: 33352074 PMCID: PMC7779494 DOI: 10.1098/rspb.2020.2278] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [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: 09/14/2020] [Accepted: 11/27/2020] [Indexed: 01/02/2023] Open
Abstract
Lyme disease, the most prevalent vector-borne disease in North America, is increasing in incidence and geographic distribution as the tick vector, Ixodes scapularis, spreads to new regions. We re-construct the spatial-temporal invasion of the tick and human disease in the Midwestern US, a major focus of Lyme disease transmission, from 1967 to 2018, to analyse the influence of spatial factors on the geographic spread. A regression model indicates that three spatial factors-proximity to a previously invaded county, forest cover and adjacency to a river-collectively predict tick occurrence. Validation of the predictive capability of this model correctly predicts counties invaded or uninvaded with 90.6% and 98.5% accuracy, respectively. Reported incidence increases in counties after the first report of the tick; based on this modelled relationship, we identify 31 counties where we suspect I. scapularis already occurs yet remains undetected. Finally, we apply the model to forecast tick establishment by 2021 and predict 42 additional counties where I. scapularis will probably be detected based upon historical drivers of geographic spread. Our findings leverage resources dedicated to tick and human disease reporting and provide the opportunity to take proactive steps (e.g. educational efforts) to prevent and limit transmission in areas of future geographic spread.
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Affiliation(s)
- Allison M. Gardner
- School of Biology and Ecology, University of Maine, 5722 Deering Hall, Orono, ME 04469, USA
| | - Natalie C. Pawlikowski
- School of Integrative Biology, University of Illinois, 505 S. Goodwin Avenue, Urbana, IL 61801, USA
| | - Sarah A. Hamer
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX 77843, USA
| | - Graham J. Hickling
- The Center for Wildlife Health, University of Tennessee Institute of Agriculture, Knoxville, TN 37966, USA
| | - James R. Miller
- Department of Natural Resources and Environmental Sciences, University of Illinois, 1102 S. Goodwin Ave, Urbana, IL 61801, USA
| | | | - Jean I. Tsao
- Department of Fisheries and Wildlife and Department of Large Animal Clinical Sciences, Michigan State University, 480 Wilson Rd., East Lansing, MI 48824, USA
| | - Brian F. Allan
- School of Integrative Biology, University of Illinois, 505 S. Goodwin Avenue, Urbana, IL 61801, USA
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Han S, Hickling GJ, Ogden NH, Ginsberg HS, Kobbekaduwa V, Rulison EL, Beati L, Tsao JI. Seasonality of acarological risk of exposure to Borrelia miyamotoi from questing life stages of Ixodes scapularis collected from Wisconsin and Massachusetts, USA. Ticks Tick Borne Dis 2020; 12:101556. [PMID: 33035757 DOI: 10.1016/j.ttbdis.2020.101556] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [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: 03/04/2020] [Revised: 08/29/2020] [Accepted: 08/31/2020] [Indexed: 11/28/2022]
Abstract
Measures of acarological risk of exposure to Ixodes scapularis-borne disease agents typically focus on nymphs; however, the relapsing fever group spirochete Borrelia miyamotoi can be passed transovarially, and I. scapularis larvae are capable of transmitting B. miyamotoi to their hosts. To quantify the larval contribution to acarological risk, relative to nymphs and adults, we collected questing I. scapularis for 3 yr at Fort McCoy, Wisconsin (WI, n = 23,367 ticks), and Cape Cod, Massachusetts (MA, n = 4190) in the United States. Borrelia miyamotoi infection prevalence was estimated for I. scapularis larvae, nymphs, females, and males, respectively, as 0.88, 2.05, 0.63, and 1.22 % from the WI site and 0.33, 2.32, 2.83, and 2.11 % from the MA site. Densities of B. miyamotoi-infected ticks (DIT, per 1000 m2) were estimated for larvae, nymphs, females, and males, respectively, as 0.36, 0.14, 0.01, and 0.03 from the WI site and 0.05, 0.06, 0.03, and 0.02 from the MA site. Thus, although larval infection prevalence with B. miyamotoi was significantly lower than that of nymphs and similar to that of adults, because of their higher abundance, the larval contribution to the overall DIT was similar to that of nymphs and trended towards a greater contribution than adults. Assuming homogenous contact rates with humans, these results suggest that eco-epidemiological investigations of B. miyamotoi disease in North America should include larvae. A fuller appreciation of the epidemiological implications of these results, therefore, requires an examination of the heterogeneity in contact rates with humans among life stages.
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Affiliation(s)
- Seungeun Han
- Comparative Medicine and Integrative Biology program, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824, United States.
| | - Graham J Hickling
- Center for Wildlife Health, University of Tennessee Institute of Agriculture, Knoxville, TN 37996, United States.
| | - Nicholas H Ogden
- Public Health Risk Sciences Division, National Microbiology Laboratory, Public Health Agency of Canada, St-Hyacinthe, QC J2S 2M2, Canada.
| | - Howard S Ginsberg
- U.S. Geological Survey, Patuxent Wildlife Research Center, Kingston, RI 02881, United States.
| | - Vishvapali Kobbekaduwa
- Comparative Medicine and Integrative Biology program, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824, United States.
| | - Eric L Rulison
- California Department of Transportation, Redding, CA 96001, United States.
| | - Lorenza Beati
- Department of Biology, Georgia Southern University, Statesboro, GA 30460, United States.
| | - Jean I Tsao
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI, 48824, United States; Department of Large Animal Clinical Sciences, Michigan State University, East Lansing, MI, 48824, United States.
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Ginsberg HS, Rulison EL, Miller JL, Pang G, Arsnoe IM, Hickling GJ, Ogden NH, LeBrun RA, Tsao JI. Local abundance of Ixodes scapularis in forests: Effects of environmental moisture, vegetation characteristics, and host abundance. Ticks Tick Borne Dis 2019; 11:101271. [PMID: 31677969 DOI: 10.1016/j.ttbdis.2019.101271] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [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: 04/25/2019] [Revised: 07/31/2019] [Accepted: 08/15/2019] [Indexed: 11/29/2022]
Abstract
Ixodes scapularis is the primary vector of Lyme disease spirochetes in eastern and central North America, and local densities of this tick can affect human disease risk. We sampled larvae and nymphs from sites in Massachusetts and Wisconsin, USA, using flag/drag devices and by collecting ticks from hosts, and measured environmental variables to evaluate the environmental factors that affect local distribution and abundance of I. scapularis. Our sites were all forested areas with known I. scapularis populations. Environmental variables included those associated with weather (e.g., temperature and relative humidity), vegetation characteristics (at canopy, shrub, and ground levels), and host abundance (small and medium-sized mammals and reptiles). The numbers of larvae on animals at a given site and season showed a logarithmic relationship to the numbers in flag/drag samples, suggesting limitation in the numbers on host animals. The numbers of nymphs on animals showed no relationship to the numbers in flag/drag samples. These results suggest that only a small proportion of larvae and nymphs found hosts because in neither stage did the numbers of host-seeking ticks decline with increased numbers on hosts. Canopy cover was predictive of larval and nymphal numbers in flag/drag samples, but not of numbers on hosts. Numbers of small and medium-sized mammal hosts the previous year were generally not predictive of the current year's tick numbers, except that mouse abundance predicted log numbers of nymphs on all hosts the following year. Some measures of larval abundance were predictive of nymphal numbers the following year. The mean number of larvae per mouse was well predicted by measures of overall larval abundance (based on flag/drag samples and samples from all hosts), and some environmental factors contributed significantly to the model. In contrast, the mean numbers of nymphs per mouse were not well predicted by environmental variables, only by overall nymphal abundance on hosts. Therefore, larvae respond differently than nymphs to environmental factors. Furthermore, flag/drag samples provide different information about nymphal numbers than do samples from hosts. Flag/drag samples can provide information about human risk of acquiring nymph-borne pathogens because they provide information on the densities of ticks that might encounter humans, but to understand the epizootiology of tick-borne agents both flag/drag and host infestation data are needed.
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Affiliation(s)
- Howard S Ginsberg
- U.S. Geological Survey, Patuxent Wildlife Research Center, Rhode Island Field Station, Woodward Hall-PSE, University of Rhode Island, Kingston, RI 02881, USA; Department of Plant Sciences and Entomology, University of Rhode Island, Kingston, RI 02881, USA.
| | - Eric L Rulison
- Department of Plant Sciences and Entomology, University of Rhode Island, Kingston, RI 02881, USA
| | - Jasmine L Miller
- Department of Plant Sciences and Entomology, University of Rhode Island, Kingston, RI 02881, USA
| | - Genevieve Pang
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI 48824, USA
| | - Isis M Arsnoe
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI 48824, USA
| | - Graham J Hickling
- Center for Wildlife Health, University of Tennessee Institute of Agriculture, Knoxville, TN 37920, USA
| | - Nicholas H Ogden
- Public Health Risk Sciences Division, National Microbiology Laboratory, Public Health Agency of Canada, St-Hyacinthe, QC, Canada
| | - Roger A LeBrun
- Department of Plant Sciences and Entomology, University of Rhode Island, Kingston, RI 02881, USA
| | - Jean I Tsao
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI 48824, USA
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Arsnoe I, Tsao JI, Hickling GJ. Nymphal Ixodes scapularis questing behavior explains geographic variation in Lyme borreliosis risk in the eastern United States. Ticks Tick Borne Dis 2019; 10:553-563. [PMID: 30709659 DOI: 10.1016/j.ttbdis.2019.01.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 01/02/2019] [Accepted: 01/11/2019] [Indexed: 01/21/2023]
Abstract
Most people who contract Lyme borreliosis in the eastern United States (US) acquire infection from the bite of the nymphal life stage of the vector tick Ixodes scapularis, which is present in all eastern states. Yet <5% of Lyme borreliosis cases are reported from outside the north-central and northeastern US. Geographical differences in nymphal questing (i.e., host-seeking behavior) may be epidemiologically important in explaining this latitudinal gradient in Lyme borreliosis incidence. Using field enclosures and a 'common garden' experimental design at two field sites, we directly tested this hypothesis by observing above-litter questing of laboratory-raised nymphal I. scapularis whose parents were collected from 15 locations (= origins) across the species' range. Relative to southern nymphs from origins considered to be of low acarologic risk, northern nymphs from high-risk origins were eight times as likely to quest on or above the surface of the leaf litter. This regional variation in vector behavior (specifically, the propensity of southern nymphs to remain under leaf litter) was highly correlated with Lyme borreliosis incidence in nymphs' counties of origin. We conclude that nymphal host-seeking behavior is a key factor contributing to the low incidence of Lyme borreliosis in southern states. Expansion of northern I. scapularis populations could lead to increased incidence in southern states of Lyme borreliosis and other diseases vectored by this tick, if the 'northern' host-seeking behavior of immigrant nymphs is retained. Systematic surveillance for I. scapularis nymphs questing above the leaf litter in southern states will help predict future geographic change in I. scapularis-borne disease risk.
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Affiliation(s)
- Isis Arsnoe
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI, 48824, USA; Program in Ecology, Evolutionary Biology, and Behavior, Michigan State University, East Lansing, MI, 48933, USA
| | - Jean I Tsao
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI, 48824, USA; Program in Ecology, Evolutionary Biology, and Behavior, Michigan State University, East Lansing, MI, 48933, USA; Department of Large Animal Clinical Sciences, Michigan State University, East Lansing, MI, 48933, USA
| | - Graham J Hickling
- Center for Wildlife Health, University of Tennessee Institute of Agriculture, Knoxville, TN, 37996, USA.
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Ogden NH, Pang G, Ginsberg HS, Hickling GJ, Burke RL, Beati L, Tsao JI. Evidence for Geographic Variation in Life-Cycle Processes Affecting Phenology of the Lyme Disease Vector Ixodes scapularis (Acari: Ixodidae) in the United States. J Med Entomol 2018; 55:1386-1401. [PMID: 29986046 DOI: 10.1093/jme/tjy104] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Indexed: 06/08/2023]
Abstract
The seasonal activity pattern of immature Ixodes scapularis Say (Acari: Ixodidae) varies geographically in the United States, which may affect the efficiency of transmission cycles of pathogens transmitted by this species. To study the factors that determine seasonality, a multiyear study at seven sites across the geographic range of I. scapularis systematically collected questing ticks by flagging/dragging, and feeding ticks by capture of their hosts. The observed phenology patterns were consistent with previous studies reporting geographic variation in seasonal tick activity. Predictions of seasonal activity for each site were obtained from an I. scapularis simulation model calibrated using contemporaneous weather data. A range of scenarios for life-cycle processes-including different regimes of temperature-independent behavioral and developmental diapause, variations in temperature-development rate relationships, and temperature-dependent tick activity-were used in model formulations. These formulations produced a range of simulations of seasonal activity for each site and were compared against the field observed tick data using negative binomial regression models. Best fit scenarios were chosen for each site on the basis of Akaike's information criterion and regression model parameters. This analysis suggests that temperature-independent diapause mechanisms explain some key observed variations in I. scapularis seasonality, and are responsible in part for geographic variations in I. scapularis seasonality in the United States. However, diapause appears to operate in idiosyncratic ways in different regions of the United States, so further studies on populations in different regions will be needed to enable predictive modeling of climatic and climate change effects on I. scapularis seasonal activity and pathogen transmission.
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Affiliation(s)
- Nicholas H Ogden
- Public Health Risk Sciences Division, National Microbiology Laboratory, Public Health Agency of Canada, St-Hyacinthe, QC, Canada
- South African Centre for Epidemiological Modelling and Analysis, Stellenbosch University, Stellenbosch, Western Cape, South Africa
| | - Genevieve Pang
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI
| | - Howard S Ginsberg
- USGS Patuxent Wildlife Research Center Coastal Field Station, Kingston, RI
| | - Graham J Hickling
- Center for Wildlife Health, University of Tennessee Institute of Agriculture, Knoxville, TN
| | | | - Lorenza Beati
- Department of Biology, Georgia Southern University, Statesboro, GA
| | - Jean I Tsao
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI
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Hickling GJ, Kelly JR, Auckland LD, Hamer SA. Increasing Prevalence of Borrelia burgdorferi sensu stricto-Infected Blacklegged Ticks in Tennessee Valley, Tennessee, USA. Emerg Infect Dis 2018; 24:1713-1716. [PMID: 30044211 PMCID: PMC6106412 DOI: 10.3201/eid2409.180343] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
In 2017, we surveyed forests in the upper Tennessee Valley, Tennessee, USA. We found Ixodes scapularis ticks established in 23 of 26 counties, 4 of which had Borrelia burgdorferi sensu stricto–infected ticks. Public health officials should be vigilant for increasing Lyme disease incidence in this region.
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13
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Stromdahl EY, Nadolny RM, Hickling GJ, Hamer SA, Ogden NH, Casal C, Heck GA, Gibbons JA, Cremeans TF, Pilgard MA. Amblyomma americanum (Acari: Ixodidae) Ticks Are Not Vectors of the Lyme Disease Agent, Borrelia burgdorferi (Spirocheatales: Spirochaetaceae): A Review of the Evidence. J Med Entomol 2018; 55:501-514. [PMID: 29394366 PMCID: PMC6459681 DOI: 10.1093/jme/tjx250] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Indexed: 06/02/2023]
Abstract
In the early 1980s, Ixodes spp. ticks were implicated as the key North American vectors of Borrelia burgdorferi (Johnson, Schmid, Hyde, Steigerwalt and Brenner) (Spirocheatales: Spirochaetaceae), the etiological agent of Lyme disease. Concurrently, other human-biting tick species were investigated as potential B. burgdorferi vectors. Rashes thought to be erythema migrans were observed in patients bitten by Amblyomma americanum (L.) (Acari: Ixodidae) ticks, and spirochetes were visualized in a small percentage of A. americanum using fluorescent antibody staining methods, sparking interest in this species as a candidate vector of B. burgdorferi. Using molecular methods, the spirochetes were subsequently described as Borrelia lonestari sp. nov. (Spirocheatales: Spirochaetaceae), a transovarially transmitted relapsing fever Borrelia of uncertain clinical significance. In total, 54 surveys from more than 35 research groups, involving more than 52,000 ticks, have revealed a low prevalence of B. lonestari, and scarce B. burgdorferi, in A. americanum. In Lyme disease-endemic areas, A. americanum commonly feeds on B. burgdorferi-infected hosts; the extremely low prevalence of B. burgdorferi in this tick results from a saliva barrier to acquiring infection from infected hosts. At least nine transmission experiments involving B. burgdorferi in A. americanum have failed to demonstrate vector competency. Advancements in molecular analysis strongly suggest that initial reports of B. burgdorferi in A. americanum across many states were misidentified B. lonestari, or DNA contamination, yet the early reports continue to be cited without regard to the later clarifying studies. In this article, the surveillance and vector competency studies of B. burgdorferi in A. americanum are reviewed, and we conclude that A. americanum is not a vector of B. burgdorferi.
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Affiliation(s)
- Ellen Y. Stromdahl
- Army Public Health Center, Aberdeen Proving Ground, MD 21010-5403
- Corresponding author, ;
| | - Robyn M. Nadolny
- Army Public Health Center, Aberdeen Proving Ground, MD 21010-5403
| | - Graham J. Hickling
- Center for Wildlife Health, The University of Tennessee Institute of Agriculture, Knoxville, TN 37996
| | - Sarah A. Hamer
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX 77843
| | - Nicholas H. Ogden
- Public Health Risk Sciences Division, National Microbiology Laboratory, Public Health Agency of Canada, Quebec, Canada J2S 2M2
| | - Cory Casal
- Army Public Health Center, Aberdeen Proving Ground, MD 21010-5403
| | - Garrett A. Heck
- Army Public Health Center, Aberdeen Proving Ground, MD 21010-5403
- Department of Cell and Molecular Biology, Colorado State University, Fort Collins, CO 80523
| | | | | | - Mark A. Pilgard
- Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, Fort Collins, CO 80521
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14
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Abstract
We compared the prevalence of Borrelia miyamotoi infection in questing and deer-associated adult Ixodes scapularis ticks in Wisconsin, USA. Prevalence among deer-associated ticks (4.5% overall, 7.1% in females) was significantly higher than among questing ticks (1.0% overall, 0.6% in females). Deer may be a sylvatic reservoir for this newly recognized zoonotic pathogen.
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15
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Carter C, Yambem O, Carlson T, Hickling GJ, Collins K, Jacewicz M, Tsao JW. Male tick bite: A rare cause of adult tick paralysis. Neurol Neuroimmunol Neuroinflamm 2016; 3:e243. [PMID: 27218120 PMCID: PMC4864618 DOI: 10.1212/nxi.0000000000000243] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 04/11/2016] [Indexed: 11/18/2022]
Affiliation(s)
- Cynthia Carter
- Departments of Psychiatry (C.C.) and Neurology (O.Y., M.J., J.W.T.), Veterans Administration Medical Center; Departments of Psychiatry (C.C.) and Neurology (O.Y., K.C., M.J., J.W.T.), University of Tennessee Health Science Center, Memphis; Division of Vector Control (T.C.), Shelby County Health Department, Memphis, TN; and Center for Wildlife Health (G.J.H.), The University of Tennessee, Knoxville
| | - Olivia Yambem
- Departments of Psychiatry (C.C.) and Neurology (O.Y., M.J., J.W.T.), Veterans Administration Medical Center; Departments of Psychiatry (C.C.) and Neurology (O.Y., K.C., M.J., J.W.T.), University of Tennessee Health Science Center, Memphis; Division of Vector Control (T.C.), Shelby County Health Department, Memphis, TN; and Center for Wildlife Health (G.J.H.), The University of Tennessee, Knoxville
| | - Ture Carlson
- Departments of Psychiatry (C.C.) and Neurology (O.Y., M.J., J.W.T.), Veterans Administration Medical Center; Departments of Psychiatry (C.C.) and Neurology (O.Y., K.C., M.J., J.W.T.), University of Tennessee Health Science Center, Memphis; Division of Vector Control (T.C.), Shelby County Health Department, Memphis, TN; and Center for Wildlife Health (G.J.H.), The University of Tennessee, Knoxville
| | - Graham J Hickling
- Departments of Psychiatry (C.C.) and Neurology (O.Y., M.J., J.W.T.), Veterans Administration Medical Center; Departments of Psychiatry (C.C.) and Neurology (O.Y., K.C., M.J., J.W.T.), University of Tennessee Health Science Center, Memphis; Division of Vector Control (T.C.), Shelby County Health Department, Memphis, TN; and Center for Wildlife Health (G.J.H.), The University of Tennessee, Knoxville
| | - Kassondra Collins
- Departments of Psychiatry (C.C.) and Neurology (O.Y., M.J., J.W.T.), Veterans Administration Medical Center; Departments of Psychiatry (C.C.) and Neurology (O.Y., K.C., M.J., J.W.T.), University of Tennessee Health Science Center, Memphis; Division of Vector Control (T.C.), Shelby County Health Department, Memphis, TN; and Center for Wildlife Health (G.J.H.), The University of Tennessee, Knoxville
| | - Michael Jacewicz
- Departments of Psychiatry (C.C.) and Neurology (O.Y., M.J., J.W.T.), Veterans Administration Medical Center; Departments of Psychiatry (C.C.) and Neurology (O.Y., K.C., M.J., J.W.T.), University of Tennessee Health Science Center, Memphis; Division of Vector Control (T.C.), Shelby County Health Department, Memphis, TN; and Center for Wildlife Health (G.J.H.), The University of Tennessee, Knoxville
| | - Jack W Tsao
- Departments of Psychiatry (C.C.) and Neurology (O.Y., M.J., J.W.T.), Veterans Administration Medical Center; Departments of Psychiatry (C.C.) and Neurology (O.Y., K.C., M.J., J.W.T.), University of Tennessee Health Science Center, Memphis; Division of Vector Control (T.C.), Shelby County Health Department, Memphis, TN; and Center for Wildlife Health (G.J.H.), The University of Tennessee, Knoxville
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16
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Carter C, Yambem O, Carlson T, Hickling GJ, Collins K, Jacewicz M, Tsao JW. Male tick bite: A rare cause of adult tick paralysis. Neurol Neuroimmunol Neuroinflamm 2016. [PMID: 27218120 DOI: 10.1212/nxi.0000000000000243.] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- Cynthia Carter
- Departments of Psychiatry (C.C.) and Neurology (O.Y., M.J., J.W.T.), Veterans Administration Medical Center; Departments of Psychiatry (C.C.) and Neurology (O.Y., K.C., M.J., J.W.T.), University of Tennessee Health Science Center, Memphis; Division of Vector Control (T.C.), Shelby County Health Department, Memphis, TN; and Center for Wildlife Health (G.J.H.), The University of Tennessee, Knoxville
| | - Olivia Yambem
- Departments of Psychiatry (C.C.) and Neurology (O.Y., M.J., J.W.T.), Veterans Administration Medical Center; Departments of Psychiatry (C.C.) and Neurology (O.Y., K.C., M.J., J.W.T.), University of Tennessee Health Science Center, Memphis; Division of Vector Control (T.C.), Shelby County Health Department, Memphis, TN; and Center for Wildlife Health (G.J.H.), The University of Tennessee, Knoxville
| | - Ture Carlson
- Departments of Psychiatry (C.C.) and Neurology (O.Y., M.J., J.W.T.), Veterans Administration Medical Center; Departments of Psychiatry (C.C.) and Neurology (O.Y., K.C., M.J., J.W.T.), University of Tennessee Health Science Center, Memphis; Division of Vector Control (T.C.), Shelby County Health Department, Memphis, TN; and Center for Wildlife Health (G.J.H.), The University of Tennessee, Knoxville
| | - Graham J Hickling
- Departments of Psychiatry (C.C.) and Neurology (O.Y., M.J., J.W.T.), Veterans Administration Medical Center; Departments of Psychiatry (C.C.) and Neurology (O.Y., K.C., M.J., J.W.T.), University of Tennessee Health Science Center, Memphis; Division of Vector Control (T.C.), Shelby County Health Department, Memphis, TN; and Center for Wildlife Health (G.J.H.), The University of Tennessee, Knoxville
| | - Kassondra Collins
- Departments of Psychiatry (C.C.) and Neurology (O.Y., M.J., J.W.T.), Veterans Administration Medical Center; Departments of Psychiatry (C.C.) and Neurology (O.Y., K.C., M.J., J.W.T.), University of Tennessee Health Science Center, Memphis; Division of Vector Control (T.C.), Shelby County Health Department, Memphis, TN; and Center for Wildlife Health (G.J.H.), The University of Tennessee, Knoxville
| | - Michael Jacewicz
- Departments of Psychiatry (C.C.) and Neurology (O.Y., M.J., J.W.T.), Veterans Administration Medical Center; Departments of Psychiatry (C.C.) and Neurology (O.Y., K.C., M.J., J.W.T.), University of Tennessee Health Science Center, Memphis; Division of Vector Control (T.C.), Shelby County Health Department, Memphis, TN; and Center for Wildlife Health (G.J.H.), The University of Tennessee, Knoxville
| | - Jack W Tsao
- Departments of Psychiatry (C.C.) and Neurology (O.Y., M.J., J.W.T.), Veterans Administration Medical Center; Departments of Psychiatry (C.C.) and Neurology (O.Y., K.C., M.J., J.W.T.), University of Tennessee Health Science Center, Memphis; Division of Vector Control (T.C.), Shelby County Health Department, Memphis, TN; and Center for Wildlife Health (G.J.H.), The University of Tennessee, Knoxville
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17
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Ludwig A, Ginsberg HS, Hickling GJ, Ogden NH. A Dynamic Population Model to Investigate Effects of Climate and Climate-Independent Factors on the Lifecycle of Amblyomma americanum (Acari: Ixodidae). J Med Entomol 2016; 53:99-115. [PMID: 26502753 DOI: 10.1093/jme/tjv150] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [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: 04/17/2015] [Accepted: 09/14/2015] [Indexed: 05/23/2023]
Abstract
The lone star tick, Amblyomma americanum, is a disease vector of significance for human and animal health throughout much of the eastern United States. To model the potential effects of climate change on this tick, a better understanding is needed of the relative roles of temperature-dependent and temperature-independent (day-length-dependent behavioral or morphogenetic diapause) processes acting on the tick lifecycle. In this study, we explored the roles of these processes by simulating seasonal activity patterns using models with site-specific temperature and day-length-dependent processes. We first modeled the transitions from engorged larvae to feeding nymphs, engorged nymphs to feeding adults, and engorged adult females to feeding larvae. The simulated seasonal patterns were compared against field observations at three locations in United States. Simulations suggested that 1) during the larva-to-nymph transition, some larvae undergo no diapause while others undergo morphogenetic diapause of engorged larvae; 2) molted adults undergo behavioral diapause during the transition from nymph-to-adult; and 3) there is no diapause during the adult-to-larva transition. A model constructed to simulate the full lifecycle of A. americanum successfully predicted observed tick activity at the three U.S. study locations. Some differences between observed and simulated seasonality patterns were observed, however, identifying the need for research to refine some model parameters. In simulations run using temperature data for Montreal, deterministic die-out of A. americanum populations did not occur, suggesting the possibility that current climate in parts of southern Canada is suitable for survival and reproduction of this tick.
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Affiliation(s)
- Antoinette Ludwig
- Public Health Agency of Canada, 3200 Sicotte CP5000, St Hyacinthe, QC, Canada J2S 7C6 (; )
| | - Howard S Ginsberg
- USGS Patuxent Wildlife Research Center, Coastal Field Station, Woodward Hall-PSE, University of Rhode Island, Kingston, RI 02881
| | - Graham J Hickling
- The Center for Wildlife Health, Ellington Plant Science Building, The University of Tennessee, Knoxville, TN 37996
| | - Nicholas H Ogden
- Public Health Agency of Canada, 3200 Sicotte CP5000, St Hyacinthe, QC, Canada J2S 7C6 (; )
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18
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Arsnoe IM, Hickling GJ, Ginsberg HS, McElreath R, Tsao JI. Different populations of blacklegged tick nymphs exhibit differences in questing behavior that have implications for human lyme disease risk. PLoS One 2015; 10:e0127450. [PMID: 25996603 PMCID: PMC4440738 DOI: 10.1371/journal.pone.0127450] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Accepted: 04/15/2015] [Indexed: 11/18/2022] Open
Abstract
Animal behavior can have profound effects on pathogen transmission and disease incidence. We studied the questing (= host-seeking) behavior of blacklegged tick (Ixodes scapularis) nymphs, which are the primary vectors of Lyme disease in the eastern United States. Lyme disease is common in northern but not in southern regions, and prior ecological studies have found that standard methods used to collect host-seeking nymphs in northern regions are unsuccessful in the south. This led us to hypothesize that there are behavior differences between northern and southern nymphs that alter how readily they are collected, and how likely they are to transmit the etiological agent of Lyme disease to humans. To examine this question, we compared the questing behavior of I. scapularis nymphs originating from one northern (Lyme disease endemic) and two southern (non-endemic) US regions at field sites in Wisconsin, Rhode Island, Tennessee, and Florida. Laboratory-raised uninfected nymphs were monitored in circular 0.2 m2 arenas containing wooden dowels (mimicking stems of understory vegetation) for 10 (2011) and 19 (2012) weeks. The probability of observing nymphs questing on these stems (2011), and on stems, on top of leaf litter, and on arena walls (2012) was much greater for northern than for southern origin ticks in both years and at all field sites (19.5 times greater in 2011; 3.6-11.6 times greater in 2012). Our findings suggest that southern origin I. scapularis nymphs rarely emerge from the leaf litter, and consequently are unlikely to contact passing humans. We propose that this difference in questing behavior accounts for observed geographic differences in the efficacy of the standard sampling techniques used to collect questing nymphs. These findings also support our hypothesis that very low Lyme disease incidence in southern states is, in part, a consequence of the type of host-seeking behavior exhibited by southern populations of the key Lyme disease vector.
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Affiliation(s)
- Isis M. Arsnoe
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, Michigan, United States of America
| | - Graham J. Hickling
- Center for Wildlife Health, University of Tennessee Institute of Agriculture, Knoxville, Tennessee, United States of America
| | - Howard S. Ginsberg
- United States Geological Survey Patuxent Wildlife Research Center, Rhode Island Field Station, University of Rhode Island, Kingston, Rhode Island, United States of America
| | - Richard McElreath
- Department of Anthropology and Center for Population Biology, University of California Davis, Davis, California, United States of America
| | - Jean I. Tsao
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, Michigan, United States of America
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19
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Harmon JR, Scott MC, Baker EM, Jones CJ, Hickling GJ. Molecular identification of Ehrlichia species and host bloodmeal source in Amblyomma americanum L. from two locations in Tennessee, United States. Ticks Tick Borne Dis 2015; 6:246-52. [PMID: 25682494 DOI: 10.1016/j.ttbdis.2015.01.004] [Citation(s) in RCA: 18] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2014] [Revised: 01/12/2015] [Accepted: 01/15/2015] [Indexed: 11/26/2022]
Abstract
The current status of tick-borne diseases in the southeastern United States is challenging to define due to emerging pathogens, uncertain tick/host relationships, and changing disease case definitions. A golf-oriented retirement community on the Cumberland Plateau in Tennessee experienced an ehrlichiosis outbreak in 1993, prompting efforts to reduce the local tick population using '4-Poster' acaricide devices targeting white-tailed deer (Odocoileus virginianus). In 2009, the prevalence of Ehrlichia spp. in questing ticks was surveyed in the area and compared to a Tennessee state park where acaricide had not been applied. The range of wildlife hosts that immature Amblyomma americanum fed upon and the role that these hosts may play in pathogen dynamics were investigated using a reverse line blot (RLB) bloodmeal analysis technique. Amblyomma americanum was by far the most common tick species in both study areas (>99% of ticks collected). Of 303 adult and nymphal A. americanum tested at the retirement community, six were positive for Ehrlichia chaffeensis (2.0%), 16 were positive for E. ewingii (5.3%), and six were positive for Panola Mountain Ehrlichia (2.0%). This is the first confirmation of Panola Mountain Ehrlichia in A. americanum from the state of Tennessee. The 9.3% prevalence of Ehrlichia spp. in ticks from the retirement community was similar to that detected at the state park site (5.5%), suggesting that the 4-Poster treatment had not been sufficient to reduce Ehrlichia spp. cycling in the tick population. At both study sites, A. americanum fed on a wide range of mammal and bird species, with a minority of detectable bloodmeals coming from deer. Of the Ehrlichia-infected nymphs with positive bloodmeal identification, none fed on deer, indicating that multiple vertebrate species are contributing to sylvatic maintenance of Ehrlichia spp. at these sites. This highlights the difficulty of attempting to reduce the risk of tick-borne disease through host-targeted interventions alone.
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Affiliation(s)
- Jessica R Harmon
- University of Tennessee Institute of Agriculture, Entomology and Plant Pathology Department, United States; University of Tennessee Institute of Agriculture, Center for Wildlife Health, United States.
| | - M Cathy Scott
- University of Tennessee Institute of Agriculture, Center for Wildlife Health, United States
| | - Ellen M Baker
- University of Tennessee Institute of Agriculture, Center for Wildlife Health, United States
| | - Carl J Jones
- University of Tennessee Institute of Agriculture, Entomology and Plant Pathology Department, United States
| | - Graham J Hickling
- University of Tennessee Institute of Agriculture, Center for Wildlife Health, United States
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Stich RW, Blagburn BL, Bowman DD, Carpenter C, Cortinas MR, Ewing SA, Foley D, Foley JE, Gaff H, Hickling GJ, Lash RR, Little SE, Lund C, Lund R, Mather TN, Needham GR, Nicholson WL, Sharp J, Varela-Stokes A, Wang D. Quantitative factors proposed to influence the prevalence of canine tick-borne disease agents in the United States. Parasit Vectors 2014; 7:417. [PMID: 25185829 PMCID: PMC4167287 DOI: 10.1186/1756-3305-7-417] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 08/30/2014] [Indexed: 11/11/2022] Open
Abstract
The Companion Animal Parasite Council hosted a meeting to identify quantifiable factors that can influence the prevalence of tick-borne disease agents among dogs in North America. This report summarizes the approach used and the factors identified for further analysis with mathematical models of canine exposure to tick-borne pathogens.
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Affiliation(s)
- Roger W Stich
- Department of Veterinary Pathobiology, University of Missouri, Columbia, MO, USA.
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21
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Hamer SA, Hickling GJ, Walker ED, Tsao JI. Increased diversity of zoonotic pathogens and Borrelia burgdorferi strains in established versus incipient Ixodes scapularis populations across the Midwestern United States. Infect Genet Evol 2014; 27:531-42. [PMID: 24953506 DOI: 10.1016/j.meegid.2014.06.003] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Revised: 06/02/2014] [Accepted: 06/06/2014] [Indexed: 10/25/2022]
Abstract
The center of origin theory predicts that genetic diversity will be greatest near a specie's geographic origin because of the length of time for evolution. By corollary, diversity will decrease with distance from the origin; furthermore, invasion and colonization are frequently associated with founder effects that reduce genetic variation in incipient populations. The blacklegged tick, Ixodes scapularis, harbors a suite of zoonotic pathogens, and the geographic range of the tick is expanding in the upper Midwestern United States. Therefore, we posited that diversity of I. scapularis-borne pathogens across its Midwestern range should correlate with the rate of the range expansion of this tick as well as subsequent disease emergence. Analysis of 1565 adult I. scapularis ticks from 13 sites across five Midwestern states revealed that tick infection prevalence with multiple microbial agents (Borrelia burgdorferi, Borrelia miyamotoi, Babesia odocoilei, Babesia microti, and Anaplasma phagocytophilum), coinfections, and molecular genetic diversity of B. burgdorferi all were positively correlated with the duration of establishment of tick populations, and therefore generally support the center of origin - pathogen diversity hypothesis. The observed differences across the gradient of establishment, however, were not strong and were nuanced by the high frequency of coinfections in tick populations at both established and recently-invaded tick populations. These results suggest that the invasion of ticks and their associated pathogens likely involve multiple means of pathogen introduction, rather than the conventionally presented scenario whereby infected, invading ticks are solely responsible for introducing pathogens to naïve host populations.
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Affiliation(s)
- Sarah A Hamer
- Texas A&M University, 4458 TAMU, College Station, TX 77843, USA.
| | - Graham J Hickling
- University of Tennessee, 274 Ellington Plant Science Building, Knoxville, TN 37996, USA.
| | - Edward D Walker
- Michigan State University, 13 Natural Resources Building, East Lansing, MI 48823, USA.
| | - Jean I Tsao
- Michigan State University, 13 Natural Resources Building, East Lansing, MI 48823, USA.
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Muller LI, Hackworth AM, Giffen NR, Evans JW, Henning J, Hickling GJ, Allen P. Spatial and temporal relationships between deer harvest and deer-vehicle collisions at Oak Ridge Reservation, Tennessee. WILDLIFE SOC B 2014. [DOI: 10.1002/wsb.446] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Lisa I. Muller
- Department of Forestry; Wildlife and Fisheries, University of Tennessee; Knoxville TN 37996 USA
| | - Amanda M. Hackworth
- Department of Forestry; Wildlife and Fisheries, University of Tennessee; Knoxville TN 37996 USA
| | - Neil R. Giffen
- Environmental Sciences Division; Oak Ridge National Laboratory; Oak Ridge TN 37831-6351 USA
| | - James W. Evans
- Tennessee Wildlife Resources Agency; Oak Ridge TN 37831 USA
| | - Jason Henning
- Department of Forestry; Wildlife and Fisheries, University of Tennessee; Knoxville TN 37996 USA
| | - Graham J. Hickling
- Department of Forestry; Wildlife and Fisheries, University of Tennessee; Knoxville TN 37996 USA
| | - Phillip Allen
- Department of Biosystems Engineering; University of Tennessee; Knoxville TN 37996 USA
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Rulison EL, Kuczaj I, Pang G, Hickling GJ, Tsao JI, Ginsberg HS. Flagging versus dragging as sampling methods for nymphal Ixodes scapularis (Acari: Ixodidae). J Vector Ecol 2013; 38:163-7. [PMID: 23701621 DOI: 10.1111/j.1948-7134.2013.12022.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The nymphal stage of the blacklegged tick, Ixodes scapularis (Acari: Ixodidae), is responsible for most transmission of Borrelia burgdorferi, the etiologic agent of Lyme disease, to humans in North America. From 2010 to fall of 2012, we compared two commonly used techniques, flagging and dragging, as sampling methods for nymphal I. scapularis at three sites, each with multiple sampling arrays (grids), in the eastern and central United States. Flagging and dragging collected comparable numbers of nymphs, with no consistent differences between methods. Dragging collected more nymphs than flagging in some samples, but these differences were not consistent among sites or sampling years. The ratio of nymphs collected by flagging vs dragging was not significantly related to shrub density, so habitat type did not have a strong effect on the relative efficacy of these methods. Therefore, although dragging collected more ticks in a few cases, the numbers collected by each method were so variable that neither technique had a clear advantage for sampling nymphal I. scapularis.
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Affiliation(s)
- Eric L Rulison
- Department of Plant Sciences and Entomology, University of Rhode Island, Kingston, RI 02881, USA
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Rosen ME, Hamer SA, Gerhardt RR, Jones CJ, Muller LI, Scott MC, Hickling GJ. Borrelia burgdorferi not detected in widespread Ixodes scapularis (Acari: Ixodidae) collected from white-tailed deer in Tennessee. J Med Entomol 2012; 49:1473-1480. [PMID: 23270178 DOI: 10.1603/me11255] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Lyme disease (LD), caused by the bacterium Borrelia burgdorferi and transmitted in the eastern United States by blacklegged ticks, Ixodes scapularis Say, is classified as nonendemic in Tennessee and surrounding states in the Southeast. Low incidence of LD in these states has been attributed, in part, to vector ticks being scarce or absent; however, tick survey data for many counties are incomplete or out of date. To improve our knowledge of the distribution, abundance, and Borrelia spp. prevalence of I. scapularis, we collected ticks from 1,018 hunter-harvested white-tailed deer (Odocoileus virginianus (Zimmerman)) from 71 of 95 Tennessee counties in fall 2007 and 2008. In total, 160 deer (15.7%) from 35 counties were infested with adult I. scapularis; 30 of these counties were new distributional records for this tick. The mean number of I. scapularis collected per infested deer was 5.4 +/- 0.6 SE. Of the 883 I. scapularis we removed from deer, none were positive for B. burgdorferi and one tested positive for B. miyamotoi. Deer are not reservoir hosts for B. burgdorferi; nevertheless, past surveys in northern LD-endemic states have readily detected B. burgdoreferi in ticks collected from deer. We conclude that I. scapularis is far more widespread in Tennessee than previously reported. The absence of detectable B. burgdorferi infection among these ticks suggests that the LD risk posed by I. scapularis in the surveyed areas of Tennessee is much lower than in LD-endemic areas of the Northeast and upper Midwest.
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Affiliation(s)
- M E Rosen
- Center for Wildlife Health, University of Tennessee Institute of Agriculture, Knoxville, 37996, USA.
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25
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Hamer SA, Hickling GJ, Keith R, Sidge JL, Walker ED, Tsao JI. Associations of passerine birds, rabbits, and ticks with Borrelia miyamotoi and Borrelia andersonii in Michigan, U.S.A. Parasit Vectors 2012; 5:231. [PMID: 23057837 PMCID: PMC3497883 DOI: 10.1186/1756-3305-5-231] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Accepted: 10/09/2012] [Indexed: 11/16/2022] Open
Abstract
Background Wild birds contribute to maintenance and dissemination of vectors and microbes, including those that impact human, domestic animal, and wildlife health. Here we elucidate roles of wild passerine birds, eastern cottontail rabbits (Sylvilagus floridanus), and Ixodes dentatus ticks in enzootic cycles of two spirochetes, Borrelia miyamotoi and B. andersonii in a region of Michigan where the zoonotic pathogen B. burgdorferi co-circulates. Methods Over a four-year period, wild birds (n = 19,631) and rabbits (n = 20) were inspected for tick presence and ear tissue was obtained from rabbits. Samples were tested for Borrelia spirochetes using nested PCR of the 16S-23S rRNA intergenic spacer region (IGS) and bidirectional DNA sequencing. Natural xenodiagnosis was used to implicate wildlife reservoirs. Results Ixodes dentatus, a tick that specializes on birds and rabbits and rarely bites humans, was the most common tick found, comprising 86.5% of the 12,432 ticks collected in the study. The relapsing fever group spirochete B. miyamotoi was documented for the first time in ticks removed from wild birds (0.7% minimum infection prevalence; MIP, in I. dentatus), and included two IGS strains. The majority of B. miyamotoi-positive ticks were removed from Northern Cardinals (Cardinalis cardinalis). Borrelia andersonii infected ticks removed from birds (1.6% MIP), ticks removed from rabbits (5.3% MIP), and rabbit ear biopsies (5%) comprised twelve novel IGS strains. Six species of wild birds were implicated as reservoirs for B. andersonii. Frequency of I. dentatus larval and nymphal co-feeding on birds was ten times greater than expected by chance. The relatively well-studied ecology of I. scapularis and the Lyme disease pathogen provides a context for understanding how the phenology of bird ticks may impact B. miyamotoi and B. andersonii prevalence and host associations. Conclusions Given the current invasion of I. scapularis, a human biting species that serves as a bridge vector for Borrelia spirochetes, human exposure to B. miyamotoi and B. andersonii in this region may increase. The presence of these spirochetes underscores the ecological complexity within which Borrelia organisms are maintained and the need for diagnostic tests to differentiate among these organisms.
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Affiliation(s)
- Sarah A Hamer
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI 48823, USA.
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26
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Scott MC, Harmon JR, Tsao JI, Jones CJ, Hickling GJ. Reverse line blot probe design and polymerase chain reaction optimization for bloodmeal analysis of ticks from the eastern United States. J Med Entomol 2012; 49:697-709. [PMID: 22679879 DOI: 10.1603/me11162] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Determining the host preference of vector ticks is vital to elucidating the eco-epidemiology of the diseases they spread. Detachment of ticks from captured hosts can provide evidence of feeding on those host species, but only for those species that are feasible to capture. Recently developed, highly sensitive molecular assays show great promise in allowing host selection to be determined from minute traces of host DNA that persist in recently molted ticks. Using methods developed in Europe as a starting-point, we designed 12S rDNA mitochondrial gene probes suitable for use in a reverse line blot (RLB) assay of ticks feeding on common host species in the eastern United States. This is the first study to use the 12S mitochondrial gene in a RLB bloodmeal assay in North America. The assay combines conventional PCR with a biotin-labeled primer and reverse line blots that can be stripped and rehybridized up to 20 times, making the method less expensive and more straightforward to interpret than previous methods of tick bloodmeal identification. Probes were designed that target the species, genus, genus group, family, order, or class of eight reptile, 13 birds, and 32 mammal hosts. After optimization, the RLB assay correctly identified the current hostspecies for 99% of ticks [Amblyomma americanum (L.) and eight other ixodid tick species] collected directly from known hosts. The method identified previous-host DNA for approximately half of all questing ticks assayed. Multiple bloodmeal determinations were obtained in some instances from feeding and questing ticks; this pattern is consistent with previous RLB studies but requires further investigation. Development of this probe library, suitable for eastern U.S. ecosystems, opens new avenues for eco-epidemiological investigations of this region's tick-host systems.
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Affiliation(s)
- M C Scott
- Center for Wildlife Health, The University of Tennessee Institute of Agriculture, 274 Ellington Plant Sciences, Knoxville, TN 37996, USA.
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27
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Diuk-Wasser MA, Hoen AG, Cislo P, Brinkerhoff R, Hamer SA, Rowland M, Cortinas R, Vourc'h G, Melton F, Hickling GJ, Tsao JI, Bunikis J, Barbour AG, Kitron U, Piesman J, Fish D. Human risk of infection with Borrelia burgdorferi, the Lyme disease agent, in eastern United States. Am J Trop Med Hyg 2012; 86:320-7. [PMID: 22302869 PMCID: PMC3269287 DOI: 10.4269/ajtmh.2012.11-0395] [Citation(s) in RCA: 190] [Impact Index Per Article: 15.8] [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: 06/21/2011] [Accepted: 10/09/2011] [Indexed: 11/07/2022] Open
Abstract
The geographic pattern of human risk for infection with Borrelia burgdorferi sensu stricto, the tick-borne pathogen that causes Lyme disease, was mapped for the eastern United States. The map is based on standardized field sampling in 304 sites of the density of Ixodes scapularis host-seeking nymphs infected with B. burgdorferi, which is closely associated with human infection risk. Risk factors for the presence and density of infected nymphs were used to model a continuous 8 km×8 km resolution predictive surface of human risk, including confidence intervals for each pixel. Discontinuous Lyme disease risk foci were identified in the Northeast and upper Midwest, with a transitional zone including sites with uninfected I. scapularis populations. Given frequent under- and over-diagnoses of Lyme disease, this map could act as a tool to guide surveillance, control, and prevention efforts and act as a baseline for studies tracking the spread of infection.
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Harmon JR, Hickling GJ, Scott MC, Jones CJ. Evaluation of 4-poster acaricide applicators to manage tick populations associated with disease risk in a Tennessee retirement community. J Vector Ecol 2011; 36:404-410. [PMID: 22129412 DOI: 10.1111/j.1948-7134.2011.00181.x] [Citation(s) in RCA: 7] [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: 05/31/2023]
Abstract
In 1993, four residents of a retirement community in middle Tennessee were hospitalized with symptoms of ehrlichiosis causing community managers to implement mitigation methods to reduce tick numbers. For the past four years, managers have utilized 4-poster acaricide applicators that aim to reduce disease risk to residents by killing ticks that feed on deer. To determine the efficacy of this technique, we assessed Amblyomma americanum abundance in the vicinity of the devices by dragging 400 m vegetation transects once per month while ticks were active. In 2009, adult tick activity peaked in May, nymphal tick activity peaked in June, and larval activity peaked in September. Close to 4-poster devices, larval, nymphal, and adult tick abundances were reduced by 91%, 68%, and 49%, respectively (larval and nymphal p<0.001, adult p=0.005), relative to nearby untreated areas. No significant reduction in nymphal or adult A. americanum ticks was evident >300 m from 4-poster devices, however a ∼90% reduction in larvae was observed to our sampling limit (400 m). At the low density at which these devices are currently being used (average distance between devices = 6.6 km), we conclude that they will have little large-scale effect on the health risk posed by ticks in this community.
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Affiliation(s)
- Jessica R Harmon
- Entomology and Plant Pathology Department, University of Tennessee, Knoxville, TN 37996-4560, USA
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Hamer SA, Hickling GJ, Sidge JL, Rosen ME, Walker ED, Tsao JI. Diverse Borrelia burgdorferi strains in a bird-tick cryptic cycle. Appl Environ Microbiol 2011; 77:1999-2007. [PMID: 21257811 PMCID: PMC3067335 DOI: 10.1128/aem.02479-10] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [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: 10/20/2010] [Accepted: 01/11/2011] [Indexed: 11/20/2022] Open
Abstract
The blacklegged tick Ixodes scapularis is the primary vector of the most prevalent vector-borne zoonosis in North America, Lyme disease (LD). Enzootic maintenance of the pathogen Borrelia burgdorferi by I. scapularis and small mammals is well documented, whereas its "cryptic" maintenance by other specialist ticks and wildlife hosts remains largely unexplored because these ticks rarely bite humans. We quantified B. burgdorferi infection in a cryptic bird-rabbit-tick cycle. Furthermore, we explored the role of birds in maintaining and moving B. burgdorferi strains by comparing their genetic diversity in this cryptic cycle to that found in cycles vectored by I. scapularis. We examined birds, rabbits, and small mammals for ticks and infection over a 4-year period at a focal site in Michigan, 90 km east of a zone of I. scapularis invasion. We mist netted 19,631 birds that yielded 12,301 ticks, of which 86% were I. dentatus, a bird-rabbit specialist. No resident wildlife harbored I. scapularis, and yet 3.5% of bird-derived ticks, 3.6% of rabbit-derived ticks, and 20% of rabbit ear biopsy specimens were infected with B. burgdorferi. We identified 25 closely related B. burgdorferi strains using an rRNA gene intergenic spacer marker, the majority (68%) of which had not been reported previously. The presence of strains common to both cryptic and endemic cycles strongly implies bird-mediated dispersal. Given continued large-scale expansion of I. scapularis populations, we predict that its invasion into zones of cryptic transmission will allow for bridging of novel pathogen strains to humans and animals.
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Affiliation(s)
- Sarah A Hamer
- Department of Fisheries and Wildlife, 13 Natural Resources Bldg., Michigan State University, East Lansing, MI 48824, USA.
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30
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Caley P, Coleman JD, Hickling GJ. Habitat-related prevalence of macroscopicMycobacterium bovisinfection in brushtail possums (Trichosurus vulpecula), Hohonu Range, Westland, New Zealand. N Z Vet J 2011; 49:82-7. [PMID: 16032168 DOI: 10.1080/00480169.2001.36208] [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: 10/18/2022]
Abstract
AIM To identify broadscale habitat factors influencing the prevalence of macroscopic Mycobacterium bovis infection in brushtail possums (Trichosurus vulpecula) at a site in Westland, New Zealand. METHODS During 1973/74, 1989/90 and 1997, we undertook repeated cross-sectional surveys of M. bovis infection in a possum population on the Hohonu Range , Westland. Data were analysed to determine the influence of site-specific habitat characteristics (land form, aspect, slope, altitude), distance from forest-pasture margin and time since infection on the spatial and temporal prevalence of macroscopic M. bovis infection. RESULTS The prevalence of M. bovis infection was highest in 1973/74 (13.4%), compared with 1989/90 (3.1%) and 1997 (9.4%). The prevalence of macroscopic M. bovis infection was significantly influenced by habitat, as indexed by altitude and slope in this study site. Every 100 m increase in elevation was associated with a 29% decrease in the odds of infection, and every 10 degrees increase in slope was associated with a 20% decrease in the odds of infection. For possums caught in the lowland podocarp forest (altitude 100-200 m, average slope=5.7 degrees ), the odds of infection were nearly 30-fold higher than those for possums caught in high-altitude hardwood forest near the tree line (altitude 900-1000 m, average slope=28 degrees ). Whilst the prevalence of disease fluctuated markedly between surveys, its broadscale spatial distribution changed little over time. Proximity to the forest-pasture margin had no significant influence on the prevalence of disease, once the effect of habitat was taken into account. CONCLUSION The prevalence of macroscopic M. bovis infection in possums was strongly influenced by habitat type, being highest in habitats that supported the highest density of possums, and lowest in habitats where population density was low. There was no evidence of progressive spread of M. bovis infection in possums into forest away from pasture-forest margins over the 24-year period of these surveys.
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Affiliation(s)
- P Caley
- Landcare Research, Palmerston North, New Zealand.
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Scott MC, Rosen ME, Hamer SA, Baker E, Edwards H, Crowder C, Tsao JI, Hickling GJ. High-prevalence Borrelia miyamotoi infection among [corrected] wild turkeys (Meleagris gallopavo) in Tennessee. J Med Entomol 2010; 47:1238-1242. [PMID: 21175079 DOI: 10.1603/me10075] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
During spring and fall 2009, 60 wild turkeys (Meleagris gallopavo) harvested by Tennessee hunters were surveyed for Borrelia spp. by sampling their blood, tissue, and attached ticks. In both seasons, 70% of turkeys were infested with juvenile Amblyomma americanum; one spring turkey hosted an adult female Ixodes brunneus. Polymerase chain reaction assays followed by DNA sequencing indicated that 58% of the turkeys were positive for the spirochete Borrelia miyamotoi, with tissue testing positive more frequently than blood (P = 0.015). Sequencing of the 16S-23S rRNA intergenic spacer indicated > or = 99% similarity to previously published sequences of the North American strain of this spirochete. Positive turkeys were present in both seasons and from all seven middle Tennessee counties sampled. No ticks from the turkeys tested positive for any Borrelia spp. This is the first report of B. miyamotoi in birds; the transmission pathways and epidemiological significance of this high-prevalence spirochetal infection remain uncertain.
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Affiliation(s)
- M C Scott
- Center for Wildlife Health, University of Tennessee, Knoxville, TN 37996, USA.
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Hamer SA, Tsao JI, Walker ED, Hickling GJ. Invasion of the lyme disease vector Ixodes scapularis: implications for Borrelia burgdorferi endemicity. Ecohealth 2010; 7:47-63. [PMID: 20229127 DOI: 10.1007/s10393-010-0287-0] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Revised: 01/23/2010] [Accepted: 01/26/2010] [Indexed: 05/28/2023]
Abstract
Lyme disease risk is increasing in the United States due in part to the spread of blacklegged ticks Ixodes scapularis, the principal vector of the spirochetal pathogen Borrelia burgdorferi. A 5-year study was undertaken to investigate hypothesized coinvasion of I. scapularis and B. burgdorferi in Lower Michigan. We tracked the spatial and temporal dynamics of the tick and spirochete using mammal, bird, and vegetation drag sampling at eight field sites along coastal and inland transects originating in a zone of recent I. scapularis establishment. We document northward invasion of these ticks along Michigan's west coast during the study period; this pattern was most evident in ticks removed from rodents. B. burgdorferi infection prevalences in I. scapularis sampled from vegetation in the invasion zone were 9.3% and 36.6% in nymphs and adults, respectively, with the majority of infection (95.1%) found at the most endemic site. There was no evidence of I. scapularis invasion along the inland transect; however, low-prevalence B. burgdorferi infection was detected in other tick species and in wildlife at inland sites, and at northern coastal sites in years before the arrival of I. scapularis. These infections suggest that cryptic B. burgdorferi transmission by other vector-competent tick species is occurring in the absence of I. scapularis. Other Borrelia spirochetes, including those that group with B. miyamotoi and B. andersonii, were present at a low prevalence within invading ticks and local wildlife. Reports of Lyme disease have increased significantly in the invasion zone in recent years. This rapid blacklegged tick invasion--measurable within 5 years--in combination with cryptic pathogen maintenance suggests a complex ecology of Lyme disease emergence in which wildlife sentinels can provide an early warning of disease emergence.
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Affiliation(s)
- Sarah A Hamer
- Department of Fisheries and Wildlife, Michigan State University, 13 Natural Resources Building, East Lansing, MI 48824, USA.
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Winters AM, Rumbeiha WK, Winterstein SR, Fine AE, Munkhtsog B, Hickling GJ. Residues in Brandt's voles (Microtus brandti) exposed to bromadiolone-impregnated baits in Mongolia. Ecotoxicol Environ Saf 2010; 73:1071-1077. [PMID: 20227761 DOI: 10.1016/j.ecoenv.2010.02.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2009] [Revised: 02/19/2010] [Accepted: 02/20/2010] [Indexed: 05/28/2023]
Abstract
In 2002, hundreds of non-target wildlife deaths occurred in Mongolia following aerial applications of bromadiolone, an anticoagulant rodenticide, to control eruptive Brandt's vole (Microtus brandti) populations. To clarify whether secondary poisoning could have contributed to these deaths, a field study was undertaken in Mongolia to measure bromadiolone residues in voles following exposure to two concentrations (50 and 500 mg/kg) of bromadiolone-treated wheat. The two treatments produced different total burdens (2.65 microg+/-0.53SE and 13.70 microg+/-3.82SE, respectively) and liver burdens (1.74 microg+/-0.33SE and 8.81 microg+/-2.33SE, respectively) of bromadiolone in voles (both p<0.05). Total burdens of bromadiolone in voles found dead above ground were higher than those of live-trapped voles (32.35 microg+/-17.98SE versus 5.18 microg+/-1.40SE, respectively; p<0.05). These results are valuable for future assessments of secondary poisoning risk to scavengers and predators from large-scale bromadiolone poisoning operations of the type undertaken in Mongolia.
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Affiliation(s)
- Ann M Winters
- Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI, USA.
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Fenichel EP, Horan RD, Hickling GJ. Management of infectious wildlife diseases: bridging conventional and bioeconomic approaches. Ecol Appl 2010; 20:903-14. [PMID: 20597279 DOI: 10.1890/09-0446.1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The primary goal of disease ecology is to understand disease systems and then use this information to inform management. The purpose of this paper is to show that conventional disease ecology models are limited in their ability to inform management of systems that are already infected, and to show how such models can be integrated with economic decision models to improve upon management recommendations. Management strategies based solely on disease ecology entail managing infected host populations or reservoir populations below a threshold value based on R0, the basic reproductive ratio of the pathogen, or a multiple-host version of this metric. These metrics measure a pathogen's ability to invade uninfected systems and do not account for postinfection dynamics. Once a pathogen has invaded a population, alternative management criteria are needed. Bioeconomic modeling offers a useful alternative approach to developing management criteria and facilitates the consideration of ecological-economic trade-offs so that diseases are managed in a cost-effective manner. The threshold concept takes on a more profound role under a bioeconomic paradigm: rather than unilaterally determining disease control choices, thresholds inform control choices and are influenced by them.
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Affiliation(s)
- Eli P Fenichel
- School of Life Science, Arizona State University, Box 874501, Tempe, Arizona 85287-4501, USA.
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Hamer SA, Tsao JI, Walker ED, Mansfield LS, Foster ES, Hickling GJ. Use of tick surveys and serosurveys to evaluate pet dogs as a sentinel species for emerging Lyme disease. Am J Vet Res 2009; 70:49-56. [PMID: 19119948 DOI: 10.2460/ajvr.70.1.49] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To evaluate dogs as a sentinel species for emergence of Lyme disease in a region undergoing invasion by Ixodes scapularis. SAMPLE POPULATION 353 serum samples and 78 ticks obtained from dogs brought to 18 veterinary clinics located in the lower peninsula of Michigan from July 15, 2005, through August 15, 2005. PROCEDURES Serum samples were evaluated for specific antibodies against Borrelia burgdorferi by use of 3 serologic assays. Ticks from dogs were subjected to PCR assays for detection of pathogens. RESULTS Of 353 serum samples from dogs in 18 counties in 2005, only 2 (0.6%) contained western blot analysis-confirmed antibodies against B burgdorferi. Ten of 13 dogs with I scapularis were from clinics within or immediately adjacent to the known tick invasion zone. Six of 18 I scapularis and 12 of 60 noncompetent vector ticks were infected with B burgdorferi. No ticks were infected with Anaplasma phagocytophilum, and 3 were infected with Babesia spp. CONCLUSIONS AND CLINICAL RELEVANCE Serosurvey in dogs was found to be ineffective in tracking early invasion dynamics of I scapularis in this area. Tick chemoprophylaxis likely reduces serosurvey sensitivity in dogs. Ticks infected with B burgdorferi were more common and widely dispersed than seropositive dogs. In areas of low tick density, use of dogs as a source of ticks is preferable to serosurvey for surveillance of emerging Lyme disease. IMPACT FOR HUMAN MEDICINE By retaining ticks from dogs for identification and pathogen testing, veterinarians can play an important role in early detection in areas with increasing risk of Lyme disease.
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Affiliation(s)
- Sarah A Hamer
- Department of Fisheries and Wildlife, College of Agricultural and Natural Resources, Michigan State University, East Lansing, MI 48824, USA
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Hamer SA, Tsao JI, Walker ED, Mansfield LS, Foster ES, Hickling GJ. Use of tick surveys and serosurveys to evaluate pet dogs as a sentinel species for emerging Lyme disease. J Am Vet Med Assoc 2009. [DOI: 10.2460/javma.234.2.244] [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: 11/20/2022]
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Fenichel EP, Tsao JI, Jones M, Hickling GJ. Fish pathogen screening and its influence on the likelihood of accidental pathogen introduction during fish translocations. J Aquat Anim Health 2008; 20:19-28. [PMID: 18536499 DOI: 10.1577/h07-005.1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Fish translocations are an important tool in fisheries management, yet translocating fish carries the risk of introducing unwanted pathogens. Although pathogen screening can be a useful tool for managing the risk associated with fish translocations, screening cannot eliminate this risk. This paper addresses these problems by demonstrating that two elements must be considered when designing efficient and effective aquatic pathogen screening programs: (1) how many fish to screen and (2) how long to continue screening programs when repeated testing detects zero infected individuals. The chance that infected fish are translocated despite screening is the joint probability of (1) the failure of the screening to detect infected fish in the sample and (2) the actual presence of infected fish in the translocation batch. Our analysis demonstrates that transfer of an infected fish is most likely to occur at moderately low levels of pathogen prevalence because the probability of detecting at least one infected fish through screening increases as pathogen prevalence increases. Small screening samples (i.e., with a low number of individuals) are most likely to detect infected fish when pathogen prevalence is relatively high (i.e., > 5%). Screening programs should terminate after some number of successive screening events in which no infected individuals have been detected. The number of screening events is a function of the cost of the screening program, the cost of a pathogen translocation, and the probability that an infected fish will be transferred. Furthermore, our analysis indicates that the cost of a disease outbreak has relatively little effect on the length of time the screening program should continue. A more pronounced result is that screening programs that are inexpensive or allow a higher probability of pathogen translocation should be continued longer.
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Affiliation(s)
- Eli P Fenichel
- Department of Fisheries and Wildlife and Quantitative Fisheries Center, Michigan State University, East Lansing, Michigan 48824, USA.
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Affiliation(s)
| | - Pamela L. Roy
- Michigan State University, East Lansing, Michigan, USA
| | | | | | - Erik S. Foster
- Michigan Department of Community Health, East Lansing, Michigan, USA
| | | | - Jean I. Tsao
- Michigan State University, East Lansing, Michigan, USA
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Gray MJ, Rajeev S, Miller DL, Schmutzer AC, Burton EC, Rogers ED, Hickling GJ. Preliminary evidence that American bullfrogs (Rana catesbeiana) are suitable hosts for Escherichia coli O157:H7. Appl Environ Microbiol 2007; 73:4066-8. [PMID: 17449685 PMCID: PMC1932734 DOI: 10.1128/aem.02905-06] [Citation(s) in RCA: 9] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We orally inoculated Rana catesbeiana tadpoles (n=23) and metamorphs (n=24) to test their suitability as hosts for Escherichia coli O157:H7. Tadpoles were housed in flowthrough aquaria and did not become infected. Metamorphs were housed in stagnant aquaria, and 54% tested positive through 14 days postinoculation, suggesting that they are suitable hosts for E. coli O157:H7.
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Affiliation(s)
- Matthew J Gray
- The University of Tennessee, Department of Forestry, Wildlife and Fisheries, Knoxville 37996, USA
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Wehi PM, Barrell GK, Hickling GJ. Hormonal Correlates of Social Rank in an Asocial Species, the Common Brushtail Possum (Trichosurus vulpecula). Ethology 2006. [DOI: 10.1111/j.1439-0310.2005.01185.x] [Citation(s) in RCA: 4] [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: 11/29/2022]
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Abstract
Historical, social and economic factors combined to provide a focus where bovine tuberculosis has become established in free-ranging wildlife in northeastern lower Michigan. White-tailed deer, the primary reservoir and maintenance host of tuberculosis, are highly valued by the public, and particularly hunters, for cultural and economic reasons. Since 1995, significant progress has been made in defining and reducing the reservoir of tuberculosis in deer. As yet, no other wildlife species has been shown to play an epidemiologically important role in the disease cycle. The importance of deer and deer hunting to Michigan has uniquely shaped tuberculosis control policies, and poses ongoing challenges as wildlife managers strive to maintain momentum for broad control strategies, and develop focused strategies that are publicly acceptable. Even if momentum and funding can be maintained, tuberculosis will likely continue to be present for a decade or longer. Thus, cattle producers waiting for tuberculosis to be eradicated from wildlife to eliminate risks to their herds and markets face disappointment for the foreseeable future. Such unrealistic expectations also place Michigan's federal tuberculosis accreditation status at perpetual risk. Accredited free status is unlikely to be regained without accompanying changes in cattle management. In Michigan, management of tuberculosis has clearly demonstrated that social issues and public approval are likely to be the critical limiting factors in control.
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Affiliation(s)
- Daniel J O'brien
- Wildlife Disease Laboratory, Michigan Department of Natural Resources, 4125 Beaumont Road, Room 250, Lansing, MI 48910-8106, USA.
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Schulte-Hostedde AI, Millar JS, Hickling GJ. Intraspecific variation in testis size of small mammals: implications for muscle mass. CAN J ZOOL 2003. [DOI: 10.1139/z03-040] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Intraspecific variation in testis size is usually interpreted in the context of sperm competition, yet an unconsidered consequence of increased testis size may be an increase in the production of testosterone, which can affect the growth of muscle mass. After muscle mass is corrected for body size, male small mammals have more muscle mass than females, which suggests that it may be a sexually selected trait. An enhanced musculature may have fitness consequences with respect to male mate-searching activities and malemale competition for access to females. We tested the prediction that males with large testes have more muscle mass (measured as lean dry mass) by examining testis size and body composition in three species of small mammals (bushy-tailed wood rat (Neotoma cinerea), deer mouse (Peromyscus maniculatus), and red-backed vole (Clethrionomys gapperi)) from the Kananaskis Valley, Alberta. In all three species, males with relatively large testes had relatively more lean dry mass than males with relatively small testes. This suggests that a secondary consequence of relatively large testes may be a relative increase in muscle mass. Further research should investigate alternative effects of intraspecific variation in testis size on individual fitness within wild populations to gain further insight into sexual selection.
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O'Brien DJ, Schmitt SM, Hickling GJ. Comments offered on Michigan bovine TB study. J Am Vet Med Assoc 2002; 221:1380-1; author reply 1381-2. [PMID: 12458600 DOI: 10.2460/javma.2002.221.1380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Reddiex B, Hickling GJ, Norbury GL, Frampton CM. Effects of predation and rabbit haemorrhagic disease on population dynamics of rabbits (Oryctolagus cuniculus) in North Canterbury, New Zealand. Wildl Res 2002. [DOI: 10.1071/wr00088] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The impact of predation and rabbit haemorrhagic disease (RHD) on population dynamics of rabbits, and the survival of juvenile rabbits, was investigated between July 1999 and March 2000 in North Canterbury, New Zealand. Rabbit abundance and pre- and post-emergent rabbit mortality were monitored on four sites, two of which were subject to predator control. RHD spread naturally through all sites from late November to early December. Rabbit densities declined on all sites, but after the RHD epidemic, declines were significantly greater where populations of predators had not been controlled. Survival of rabbit nestlings was lower where predators were not controlled. All post-emergent radio-collared rabbits died at sites where predators were not controlled, whereas 18% of those collared at sites where predators were controlled survived to maturity. In contrast to the results from previous studies, rabbits born at the start of the breeding season had very high rates of post-emergent mortality, as they appeared to be susceptible to the RHD virus later in the breeding season. The age at which juvenile rabbits become susceptible to RHD, the timing of RHD epidemics, and the abundance of predators are likely to be important in determining survival of juvenile rabbits. This study demonstrates that predation can reduce rabbit populations to low levels, but only in combination with other factors, in this case RHD.
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Abstract
Differences in reproductive roles between the sexes may lead to sexual dimorphism in body composition. Body size and composition of three species of small mammals (bushy-tailed wood rats (Neotoma cinerea Ord), deer mice (Peromyscus maniculatus Wagner), and red-backed voles (Clethrionomys gapperi Vigors)) were analyzed to test the predictions that (i) males will have more muscle mass than females and (ii) females will have more fat than males. Results supported the first prediction but not the second. For all three species, males had more lean dry mass relative to body size than females, but females did not have relatively more fat than males. Muscle mass of males may aid in mate-searching and mate-guarding activities, but fat content may not differ between the sexes because female small mammals depend on increased ingestion rates, rather than fat stores, to support reproduction.
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Abstract
Body condition (energy reserves) can have important fitness consequences. Measuring condition of live animals is typically done by regressing body mass on measures of body size and using the residuals as an index of condition. The validity of this condition index was evaluated by determining whether it reflected measured fat content of five species of small mammals (yellow-pine chipmunks (Tamias amoenus Allen), bushy-tailed wood rats (Neotoma cinerea Ord), deer mice (Peromyscus maniculatus Ord), red-backed voles (Clethrionomys gapperi Vigors), and meadow voles (Microtus pennsylvanicus Ord)). We also determined whether body water could predict fat content, enabling the use of hydrogen-isotope dilution for estimating condition. For all five species, condition estimates weakly predicted fat content and more accurately predicted variation in lean dry mass and water content. The relationship between body water and fat content was inconsistent among the five species, discouraging against the general use of isotope dilution in these animals. Although ecologically important, these indices are best interpreted as explaining variation in all constituents of body composition.
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Henderson RJ, Frampton CM, Morgan DR, Hickling GJ. The Efficacy of Baits Containing 1080 for Control of Brushtail Possums. J Wildl Manage 1999. [DOI: 10.2307/3802832] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Caley P, Hickling GJ, Cowan PE, Pfeiffer DU. Effects of sustained control of brushtail possums on levels ofMycobacteriumbovis infection in cattle and brushtail possum populations from Hohotaka, New Zealand. N Z Vet J 1999; 47:133-42. [PMID: 16032090 DOI: 10.1080/00480169.1999.36130] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
AIMS To examine the effect of reducing the abundance of brushtail possums (Trichosurus vulpecula) on the distribution and prevalence of bovine tuberculosis (Mycobacterium bovis, Tb) in possums and the incidence of Tb in domestic cattle on a group of farms in the central North Island, New Zealand. METHODS The cumulative yearly incidence of Tb infection from 12 cattle herds was estimated from annual tuberculin testing and abattoir inspection data over the period 1983-98. Intensive control of possum populations began for six of the herds in 1988, five herds in 1994 and the remaining herd in 1996. The prevalence and distribution of macroscopic M. bovis infection in possums and an index of possum abundance was estimated during yearly cross-sectional surveys from 1988 to 1998. This enabled formal testing of the link between the abundance of tuberculous possums and the incidence of Tb in cattle. RESULTS Before possum control, infected possums were clustered in foci on or adjacent to the farms with the highest annual incidence of tuberculosis in cattle, and had an overall prevalence of macroscopic M. bovis infection of 2.3%. The prevalence of disease declined to zero with ongoing possum control, although infected possums continued to be found during the first 5 years of control. Maintaining the possum population at an average of 22.1% of its pre-control density significantly reduced the odds of the cumulative yearly incidence of Tb in cattle by 77% during the first 5 years of possum control and a further 65% in the second 5-year period. Nine of 11 tuberculous possums identified since the start of possum control were found within the areas where infected possums were clustered during the pre-control survey, suggesting that the persistence of infection within these clusters rather than infected immigrants was the source of ongoing disease. Annual estimates of the prevalence of tuberculous possums broadly followed the predictions of Barlow's possum-Tb model for a controlled possum population. CONCLUSION The results support the hypothesis that tuberculous possums transmit bovine tuberculosis to domestic cattle, and therefore that reducing the abundance of tuberculous possums reduces the incidence of Tb in cattle. If the level of possum culling is sufficient, it appears that M. bovis infection may be eradicated from possum populations. Better information on population density, rate of increase and annual culling rates would have been needed for a truly independent examination of the Barlow possum-Tb model.
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Affiliation(s)
- P Caley
- Landcare Research New Zealand Ltd, Private Bag 11052, Palmerston North, New Zealand
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Forsyth DM, Hickling GJ. Increasing Himalayan tahr and decreasing chamois densities in the eastern Southern Alps, New Zealand: evidence for interspecific competition. Oecologia 1998; 113:377-382. [PMID: 28307822 DOI: 10.1007/s004420050389] [Citation(s) in RCA: 44] [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] [Indexed: 11/27/2022]
Abstract
There is anecdotal evidence that increasing densities of Himalayan tahr (Hemitragus jemlahicus) are associated with declining densities of chamois (Rupicapra rupicapra) in the Southern Alps, New Zealand. To examine this phenomenon, densities of tahr and chamois were measured at 53 sites within their sympatric range in the eastern Southern Alps during 1978-1979. In sites where only one species was present, tahr density was significantly higher than chamois density (P=0.032), probably reflecting species differences in sociality. Chamois density was higher in catchments without tahr than in those with tahr (P=0.012). Similarly, tahr density was significantly higher at sites without chamois than at those with chamois (P=0.033). Sites with both species present (termed sympatric) were significantly larger than those with only chamois or tahr (P<0.001). Following the prohibition of aerial hunting of tahr in 1983, 16 of the 17 sites where tahr and chamois were sympatric during 1978-1979 were recounted during 1991-1996. There was a 6-fold increase in the mean density of tahr between the two counts (P=0.001), whereas chamois density had declined significantly (P=0.006). Chamois persisted at only three sites, two of which had the highest chamois densities in 1978-1979. This is evidence that increasing densities of tahr exclude chamois from all but the `best' habitats. We conclude that intensive aerial hunting of tahr during 1967-1983 reduced tahr densities such that chamois could co-exist with tahr.
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Affiliation(s)
- David M Forsyth
- Department of Entomology and Animal Ecology, P.O. Box 84, Lincoln University, Canterbury, New Zealand Fax: 0064 3 325 3844; e-mail: , , , , , , NZ
| | - Graham J Hickling
- Department of Entomology and Animal Ecology, P.O. Box 84, Lincoln University, Canterbury, New Zealand Fax: 0064 3 325 3844; e-mail: , , , , , , NZ
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