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Thoroughgood JT, Chilton NB. Comparison of flea diversity in the burrows of Richardson's ground squirrels ( Urocitellus richardsonii) in urban and rural sites in central Saskatchewan, Canada. JOURNAL OF VECTOR ECOLOGY : JOURNAL OF THE SOCIETY FOR VECTOR ECOLOGY 2024; 49:R61-R69. [PMID: 39315965 DOI: 10.52707/1081-1710-49.2.r61] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2024] [Accepted: 07/15/2024] [Indexed: 09/25/2024]
Abstract
Spatial and temporal differences in the relative abundance of arthropod vectors are important factors that influence the risk of disease for mammalian hosts. Seasonal changes in the diversity and abundance of fleas (Siphonaptera) in Richardson's ground squirrel (Urocitellus richardsonii) burrows were studied at two sites in central Saskatchewan. A total of 225 fleas (151 at an urban site and 74 at a rural site) were collected. Flea prevalence differed among seasons at the urban site but not at the rural site. Of the nine flea species detected (eight at the urban site and six at the rural site), Oropsylla rupestris, O. bruneri, O. labis, O. tuberculata, and Aetheca wagneri are vectors of Yersinia pestis, the causative agent of plague. The presence and abundance of some fleas differed between sites and seasons. Neopsylla inopina and O. rupestris were the most abundant species at the urban site during the spring and summer, respectively, while O. bruneri was the most abundant species at the rural site. Our findings may have implications for the management of the black-tailed prairie dogs (Cynomys ludovicianus) in southwestern Saskatchewan because they coexist with U. richardsonii, are hosts for Oropsylla, and are at great risk of plague exposure/infection.
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Affiliation(s)
| | - Neil B Chilton
- Department of Biology, University of Saskatchewan, Saskatoon, SK, S7N 5E2 Canada,
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Eads DA, Livieri TM, Dobesh P, Hughes JP, Fly J, Redmond H, Childers E, Schwarz MS, Biggins DE. Plague mitigation for prairie dog and black-footed ferret conservation: Degree and duration of flea control with 0.005% fipronil grain bait. CURRENT RESEARCH IN PARASITOLOGY & VECTOR-BORNE DISEASES 2023; 3:100124. [PMID: 37305434 PMCID: PMC10250916 DOI: 10.1016/j.crpvbd.2023.100124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 05/11/2023] [Accepted: 05/15/2023] [Indexed: 06/13/2023]
Abstract
Sylvatic plague, a primarily flea-borne zoonosis, is a significant threat to prairie dogs (Cynomys spp., PDs) and their specialized predators, endangered black-footed ferrets (Mustela nigripes, BFFs). Host-fed fipronil baits have proven effective in controlling fleas on PDs for the purposes of plague mitigation and BFF conservation. Currently, annual treatments are the norm. We tested the long-term efficacy of fipronil bait treatments with black-tailed PDs (C. ludovicianus, BTPDs) and BFFs in South Dakota, USA. During 2018-2020, we provided BTPDs on 21 sites with grain bait formula, laced with 0.005% fipronil (50 mg/kg); 18 non-treated sites functioned as baselines. In 2020-2022, we live-trapped, anesthetized, and combed BTPDs for fleas. Flea control was significant for at least 639-885 days. Flea abundance on the treated sites was < 0.5 fleas/BTPD for ∼750 days. During 2020-2022, we sampled BFFs for fleas on 4 BTPD colonies treated with fipronil grain bait and 8 non-treated colonies. Flea control was significant with BFFs, but flea abundance began to rebound within ∼240 days post-treatment. When feasible, the combination of insecticide treatments, such as fipronil baits, and BFF vaccination against plague provide a "two-pronged" protection approach for these endangered carnivores. If fipronil bait treatments are less effective with predatory BFFs than PDs, as found herein, the "two-pronged" approach might be used to protect BFFs and biennial fipronil bait treatments might be used to protect PDs. If BFF vaccination is not possible, or few BFFs can be vaccinated, annual fipronil bait treatments might be used as a precaution to protect BFFs. Flea densities might be surveyed to determine when/where more frequent treatments seem useful.
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Affiliation(s)
- David A. Eads
- U. S. Geological Survey, Fort Collins Science Center, Fort Collins, CO, USA
| | | | - Phillip Dobesh
- U. S. Forest Service, Wall Ranger District, Wall, SD, USA
| | - John P. Hughes
- U. S. Fish and Wildlife Service, National Black-footed Ferret Conservation Center, Carr, CO, USA
| | - Jason Fly
- U. S. Geological Survey, Fort Collins Science Center, Fort Collins, CO, USA
| | - Holly Redmond
- U. S. Geological Survey, Fort Collins Science Center, Fort Collins, CO, USA
| | - Eddie Childers
- National Park Service, Badlands National Park, Interior, SD, USA
| | - Matthew S. Schwarz
- U. S. Fish and Wildlife Service, South Dakota Field Office, Pierre, SD, USA
| | - Dean E. Biggins
- U. S. Geological Survey, Fort Collins Science Center, Fort Collins, CO, USA
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3
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Mitchell CL, Schwarzer AR, Miarinjara A, Jarrett CO, Luis AD, Hinnebusch BJ. A Role for Early-Phase Transmission in the Enzootic Maintenance of Plague. PLoS Pathog 2022; 18:e1010996. [PMID: 36520713 PMCID: PMC9754260 DOI: 10.1371/journal.ppat.1010996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 11/10/2022] [Indexed: 12/23/2022] Open
Abstract
Yersinia pestis, the bacterial agent of plague, is enzootic in many parts of the world within wild rodent populations and is transmitted by different flea vectors. The ecology of plague is complex, with rodent hosts exhibiting varying susceptibilities to overt disease and their fleas exhibiting varying levels of vector competence. A long-standing question in plague ecology concerns the conditions that lead to occasional epizootics among susceptible rodents. Many factors are involved, but a major one is the transmission efficiency of the flea vector. In this study, using Oropsylla montana (a ground squirrel flea that is a major plague vector in the western United States), we comparatively quantified the efficiency of the two basic modes of flea-borne transmission. Transmission efficiency by the early-phase mechanism was strongly affected by the host blood source. Subsequent biofilm-dependent transmission by blocked fleas was less influenced by host blood and was more efficient. Mathematical modeling predicted that early-phase transmission could drive an epizootic only among highly susceptible rodents with certain blood characteristics, but that transmission by blocked O. montana could do so in more resistant hosts irrespective of their blood characteristics. The models further suggested that for most wild rodents, exposure to sublethal doses of Y. pestis transmitted during the early phase may restrain rapid epizootic spread by increasing the number of immune, resistant individuals in the population.
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Affiliation(s)
- Cedar L. Mitchell
- Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Ashley R. Schwarzer
- Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Adélaïde Miarinjara
- Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Clayton O. Jarrett
- Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Angela D. Luis
- Department of Ecosystem and Conservation Sciences, University of Montana, Missoula, Montana, United States of America
| | - B. Joseph Hinnebusch
- Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
- * E-mail:
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Samuel MD, Poje JE, Rocke TE, Metzger ME. Potential Effects of Environmental Conditions on Prairie Dog Flea Development and Implications for Sylvatic Plague Epizootics. ECOHEALTH 2022; 19:365-377. [PMID: 36125583 DOI: 10.1007/s10393-022-01615-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 06/24/2022] [Indexed: 06/15/2023]
Abstract
Fleas are common ectoparasites of vertebrates worldwide and vectors of many pathogens causing disease, such as sylvatic plague in prairie dog colonies. Development of fleas is regulated by environmental conditions, especially temperature and relative humidity. Development rates are typically slower at low temperatures and faster at high temperatures, which are bounded by lower and upper thresholds where development is reduced. Prairie dogs and their associated fleas (mostly Oropsylla spp) live in burrows that moderate outside environmental conditions, remaining cooler in summer and warmer in winter. We found burrow microclimates were characterized by stable daily temperatures and high relative humidity, with temperatures increasing from spring through summer. We previously showed temperature increases corresponded with increasing off-host flea abundance. To evaluate how changes in temperature could affect future prairie dog flea development and abundance, we used development rates of O. montana (a species related to prairie dog fleas), determined how prairie dog burrow microclimates are affected by ambient weather, and combined these results to develop a predictive model. Our model predicts burrow temperatures and flea development rates will increase during the twenty-first century, potentially leading to higher flea abundance and an increased probability of plague epizootics if Y. pestis is present.
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Affiliation(s)
- Michael D Samuel
- Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI, 53706, USA.
| | - Julia E Poje
- Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Tonie E Rocke
- U.S. Geological Survey, National Wildlife Health Center, Madison, WI, 53711, USA
| | - Marco E Metzger
- Department of Entomology, University of California, Riverside, CA, 92521, USA
- Vector-Borne Disease Section, Division of Communicable Disease Control, Center for Infectious Diseases, California Department of Public Health, Ontario, CA, 91764, USA
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5
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Mou W, Li B, Wang X, Wang Y, Liao P, Zhang X, Gui Y, Baokaixi G, Luo Y, Aihemaijiang M, Wang Q, Liu F. Flea index predicts plague epizootics among great gerbils (Rhombomys opimus) in the Junggar Basin China plague focus. Parasit Vectors 2022; 15:214. [PMID: 35715846 PMCID: PMC9205042 DOI: 10.1186/s13071-022-05330-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 05/20/2022] [Indexed: 11/10/2022] Open
Abstract
Background The Junggar Basin plague focus was the most recently identified natural plague focus in China. Through extensive field investigations, great gerbils (Rhombomys opimus) have been confirmed as the main host in this focus, and the community structure of their parasitic fleas is associated with the intensity of plague epizootics. The aim of this study is to provide an indicator that can be surveyed to evaluate the risk of plague epizootics. Methods Between 2005 and 2016, rodents and fleas were collected in the Junggar Basin plague focus. The parasitic fleas on great gerbils were harvested, and anti-F1 antibody in the serum or heart infusion of great gerbils was detected through indirect hemagglutination assay. Yersinia pestis (Y. pestis) was isolated from the liver and spleen of great gerbils and their parasitic fleas using Luria-Bertani plates. Receiver-operating characteristic (ROC) curve was used to evaluate the predictive value of flea index. Results Between 2005 and 2016, 98 investigations were performed, and 6778 great gerbils and 68,498 fleas were collected. Twenty-seven rodents were positive for Y. pestis isolation with a positivity rate of 0.4%; 674 rodents were positive for anti-F1 antibody with a positivity rate of 9.9%. Among these 98 investigations, plague epizootics were confirmed in 13 instances by Y. pestis-positive rodents and in 59 instances by anti-F1 antibody-positive rodents. We observed a higher flea index among rodents with confirmed plague epizootic compared to the negative ones (P = 0.001, 0.002), with an AUC value of 0.659 (95% CI: 0.524–0.835, P = 0.038) for Y. pestis-positive rodents and an AUC value of 0.718 (95% CI: 0.687–0.784, P < 0.001) for anti-F1 antibody-positive rodents. Conclusions Significantly higher flea index was associated with confirmed plague epizootic cases among great gerbils and could be used to predict plague epizootics in this focus. Graphical Abstract ![]()
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Affiliation(s)
- Wenting Mou
- Microbiological Laboratory, Urumqi Center for Disease Control and Prevention, Urumqi, China
| | - Bo Li
- Department of Emergency Response and Plague Control, Xinjiang Center for Disease Control and Prevention, Urumqi, China
| | - Xiaojun Wang
- Department of Emergency Response and Plague Control, Xinjiang Center for Disease Control and Prevention, Urumqi, China
| | - Ying Wang
- Department of Human Resource, Xinjiang Center for Disease Control and Prevention, Urumqi, China
| | - Peihua Liao
- Department of Science and Education, Xinjiang Center for Disease Control and Prevention, Urumqi, China
| | - Xiaobing Zhang
- Department of Emergency Response and Plague Control, Xinjiang Center for Disease Control and Prevention, Urumqi, China
| | - Youjun Gui
- Department of Emergency Response and Plague Control, Xinjiang Center for Disease Control and Prevention, Urumqi, China
| | - Guliayi Baokaixi
- Department of Emergency Response and Plague Control, Xinjiang Center for Disease Control and Prevention, Urumqi, China
| | - Yongjun Luo
- Department of Emergency Response and Plague Control, Xinjiang Center for Disease Control and Prevention, Urumqi, China
| | - Mukedaisi Aihemaijiang
- Department of Emergency Response and Plague Control, Xinjiang Center for Disease Control and Prevention, Urumqi, China
| | - Qiguo Wang
- Department of Emergency Response and Plague Control, Xinjiang Center for Disease Control and Prevention, Urumqi, China.
| | - Feng Liu
- Department of Emergency Response and Plague Control, Xinjiang Center for Disease Control and Prevention, Urumqi, China.
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6
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Miarinjara A, Eads DA, Bland DM, Matchett MR, Biggins DE, Hinnebusch BJ. Reevaluation of the Role of Blocked Oropsylla hirsuta Prairie Dog Fleas (Siphonaptera: Ceratophyllidae) in Yersinia pestis (Enterobacterales: Enterobacteriaceae) Transmission. JOURNAL OF MEDICAL ENTOMOLOGY 2022; 59:1053-1059. [PMID: 35380675 PMCID: PMC9113170 DOI: 10.1093/jme/tjac021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Indexed: 05/17/2023]
Abstract
Prairie dogs in the western United States experience periodic epizootics of plague, caused by the flea-borne bacterial pathogen Yersinia pestis. An early study indicated that Oropsylla hirsuta (Baker), often the most abundant prairie dog flea vector of plague, seldom transmits Y. pestis by the classic blocked flea mechanism. More recently, an alternative early-phase mode of transmission has been proposed as the driving force behind prairie dog epizootics. In this study, using the same flea infection protocol used previously to evaluate early-phase transmission, we assessed the vector competence of O. hirsuta for both modes of transmission. Proventricular blockage was evident during the first two weeks after infection and transmission during this time was at least as efficient as early-phase transmission 2 d after infection. Thus, both modes of transmission likely contribute to plague epizootics in prairie dogs.
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Affiliation(s)
- Adélaïde Miarinjara
- Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, NIH, Hamilton, MT, USA
- Department of Environmental Sciences, Emory University, Atlanta, GA, USA
| | - David A Eads
- U.S. Geological Survey, Fort Collins Science Center, Fort Collins, CO, USA
| | - David M Bland
- Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, NIH, Hamilton, MT, USA
| | | | - Dean E Biggins
- U.S. Geological Survey, Fort Collins Science Center, Fort Collins, CO, USA
| | - B Joseph Hinnebusch
- Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, NIH, Hamilton, MT, USA
- Corresponding author, e-mail:
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7
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Enscore RE, Bai Y, Osikowicz LM, Sexton C, O'Leary DR. Evaluation of a liquid carbaryl formulation to control burrow fleas following a die-off of black-tailed prairie dogs ( Cynomys ludovicianus) caused by plague ( Yersinia pestis) in Converse County, Wyoming. JOURNAL OF VECTOR ECOLOGY : JOURNAL OF THE SOCIETY FOR VECTOR ECOLOGY 2021; 46:230-232. [PMID: 35230028 DOI: 10.52707/1081-1710-46.2.230] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Affiliation(s)
- Russell E Enscore
- Bacterial Diseases Branch, Division of Vector-Borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO,
| | - Ying Bai
- Bacterial Diseases Branch, Division of Vector-Borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO
| | - Lynn M Osikowicz
- Bacterial Diseases Branch, Division of Vector-Borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO
| | - Christopher Sexton
- Bacterial Diseases Branch, Division of Vector-Borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO
| | - Daniel R O'Leary
- Infectious Disease Epidemiology Unit, Public Health Division, Wyoming Department of Health, Cheyenne, WY
- Career Epidemiology Field Officer Program, Field Assignee Services Branch, Division of State and Local Readiness, Center for Preparedness and Response, Centers for Disease Control and Prevention, Atlanta, GA
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8
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Matchett MR, Stanley TR, Mccollister MF, Eads DA, Boulerice JT, Biggins DE. Oral Sylvatic Plague Vaccine Does Not Adequately Protect Prairie Dogs ( Cynomys spp.) for Endangered Black-Footed Ferret ( Mustela nigripes) Conservation. Vector Borne Zoonotic Dis 2021; 21:921-940. [PMID: 34757815 PMCID: PMC8742283 DOI: 10.1089/vbz.2021.0049] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The plague bacterium Yersinia pestis is lethal to endangered black-footed ferrets (Mustela nigripes, BFF) and the prairie dogs (Cynomys spp., PD) on which they depend for habitat and prey. We assessed the effectiveness of an oral sylvatic plague vaccine delivered in baits to black-tailed PD (Cynomys ludovicianus, BTPD) from 2013 to 2017 on the Charles M. Russell National Wildlife Refuge (CMR) in northcentral Montana. We permanently marked BTPD on four paired vaccine (N = 1,349 individuals) and placebo plots (N = 926; 7,027 total captures). We analyzed capture–recapture data under a Cormack–Jolly–Seber model to estimate annual apparent survival. Overall, survival averaged 0.05 lower on vaccine plots than on paired placebo plots. Immediately before noticeable die-offs and detecting plague on pairs CMR1 and CMR2, 89% of BTPD sampled on vaccine plots had consumed at least one bait and the immune systems of 40% were likely boosted by consuming baits over multiple years. Survival to the following year was 0.16 and 0.05 on the vaccine plots and 0.19 and 0.06 on the placebo plots for pairs CMR1 and CMR2, respectively. These rates were markedly lower than 0.63, the overall average estimate on those same plots during the previous 3 years. PD populations subjected to such large die-offs would not be expected to sustain a BFF population. An overriding limitation to achieving sufficient protection rests with vaccine delivery constraints. Late summer/fall bait distribution results in the highest bait uptake rates. However, the PD birth pulse each spring can double the size of populations in most years, greatly reducing the proportion of vaccinates in populations and diminishing potential herd immunity benefits. In addition to nonvaccinated juveniles and PD that do not consume bait, incomplete vaccine protection and time required for immunity to develop leaves a large majority of PD populations vulnerable to plague for 6–7 months or more each year.
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Affiliation(s)
- Marc R Matchett
- Charles M. Russell National Wildlife Refuge, U.S. Fish and Wildlife Service, Lewistown, Montana, USA
| | - Thomas R Stanley
- Fort Collins Science Center, U.S. Geological Survey, Fort Collins, Colorado, USA
| | - Matthew F Mccollister
- Charles M. Russell National Wildlife Refuge, U.S. Fish and Wildlife Service, Lewistown, Montana, USA
| | - David A Eads
- Fort Collins Science Center, U.S. Geological Survey, Fort Collins, Colorado, USA
| | | | - Dean E Biggins
- Fort Collins Science Center, U.S. Geological Survey, Fort Collins, Colorado, USA
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Eads DA, Matchett MR, Poje JE, Biggins DE. Comparison of Flea Sampling Methods and Yersinia pestis Detection on Prairie Dog Colonies. Vector Borne Zoonotic Dis 2021; 21:753-761. [PMID: 34388354 DOI: 10.1089/vbz.2021.0025] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Scientists collect fleas (Siphonaptera) to survey for Yersinia pestis, the bacterial agent of plague. When studying fleas parasitizing prairie dogs (Cynomys spp.), two primary methods are used: (1) combing fleas from live-trapped prairie dogs and (2) swabbing fleas from burrows with cloth swabs attached to metal cables. Ideally, burrow swabbing, the cheaper and easier method, would explain flea burdens on prairie dogs and provide reliable information on plague prevalence. In a linear regression analysis of data from 1-month intervals (June-August 2010-2011) on 13 colonies of black-tailed prairie dogs (Cynomys ludovicianus, BTPDs) in New Mexico, flea abundance on swabs explained 0-26% of variation in BTPD flea burdens. In an analysis of data (May-August 2016) from six colonies of BTPDs in Montana, flea abundance on swabs explained 2% of variation in BTPD flea burdens. In an analysis of data from a short-term interval (July 23-27, 2019) on four colonies of BTPDs in Montana, flea abundance on swabs explained 0.1% of variation in BTPD flea burdens. In an analysis of data from 1-week intervals (August-October 2000) on four colonies of white-tailed prairie dogs (Cynomys leucurus, WTPD) in Utah, swabbing data explained 0.1% of variation in WTPD flea burdens. Pools of fleas from two WTPD colonies were tested for Y. pestis by mouse inoculation and isolation; 65% from WTPDs tested positive, whereas 4% from burrows tested positive. Data herein also show that results from burrow swabbing can misrepresent flea species composition and phenology on prairie dogs. Burrow swabbing is useful for some purposes, but limitations should be acknowledged, and accumulated data should be interpreted with caution.
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Affiliation(s)
- David A Eads
- U.S. Geological Survey, Fort Collins Science Center, Fort Collins, Colorado, USA
| | - Marc R Matchett
- U.S. Fish and Wildlife Service, Charles M. Russell National Wildlife Refuge, Lewistown, Montana, USA
| | - Julia E Poje
- Department of Epidemiology, University of Iowa, Iowa City, Iowa, USA
| | - Dean E Biggins
- U.S. Geological Survey, Fort Collins Science Center, Fort Collins, Colorado, USA
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10
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Miarinjara A, Bland DM, Belthoff JR, Hinnebusch BJ. Poor vector competence of the human flea, Pulex irritans, to transmit Yersinia pestis. Parasit Vectors 2021; 14:317. [PMID: 34112224 PMCID: PMC8194109 DOI: 10.1186/s13071-021-04805-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 05/25/2021] [Indexed: 11/10/2022] Open
Abstract
Background The human flea, Pulex irritans, is widespread globally and has a long association with humans, one of its principal hosts. Its role in plague transmission is still under discussion, although its high prevalence in plague-endemic regions and the presence of infected fleas of this species during plague outbreaks has led to proposals that it has been a significant vector in human-to-human transmission in some historical and present-day epidemiologic situations. However, based on a limited number of studies, P. irritans is considered to be a poor vector and receives very little attention from public health policymakers. In this study we examined the vector competence of P. irritans collected from foxes and owls in the western United States, using a standard protocol and artificial infection system. Methods Wild-caught fleas were maintained in the laboratory and infected by allowing them to feed on human or rat blood containing 2 × 108 to 1 × 109Y. pestis/ml. The fleas were then monitored periodically for infection rate and bacterial load, mortality, feeding rate, bacterial biofilm formation in the foregut (proventricular blockage), and ability to transmit Y. pestis after their single infectious blood meal. Results P. irritans were susceptible to infection, with more than 30% maintaining high bacterial loads for up to 20 days. Transmission during this time was infrequent and inefficient, however. Consistent with previous studies, a low level of early-phase transmission (3 days after the infectious blood meal) was detected in some trials. Transmission at later time points was also sporadic, and the incidence of proventricular blockage, required for this mode of transmission, was low in fleas infected using rat blood and never occurred in fleas infected using human blood. The highest level of blockage and transmission was seen in fleas infected using rat blood and allowed to feed intermittently rather than daily, indicating that host blood and feeding frequency influence vector competence. Conclusions Our results affirm the reputation of P. irritans as a feeble vector compared to rodent flea species examined similarly, and its vector competence may be lower when infected by feeding on bacteremic human blood. Graphic abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s13071-021-04805-3.
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Affiliation(s)
- Adélaïde Miarinjara
- Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, NIH, Hamilton, MT, USA
| | - David M Bland
- Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, NIH, Hamilton, MT, USA
| | - James R Belthoff
- Department of Biological Sciences, Boise State University, Boise, ID, USA
| | - B Joseph Hinnebusch
- Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, NIH, Hamilton, MT, USA.
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11
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Russell RE, Walsh DP, Samuel MD, Grunnill MD, Rocke TE. Space matters: host spatial structure and the dynamics of plague transmission. Ecol Modell 2021. [DOI: 10.1016/j.ecolmodel.2021.109450] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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12
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Thoroughgood JT, Armstrong JS, White B, Anstead CA, Galloway TD, Lindsay LR, Shury TK, Lane JE, Chilton NB. Molecular Differentiation of Four Species of Oropsylla (Siphonaptera: Ceratophyllidae) Using PCR-Based Single Strand Conformation Polymorphism Analyses and DNA Sequencing. JOURNAL OF MEDICAL ENTOMOLOGY 2021; 58:241-245. [PMID: 33432353 DOI: 10.1093/jme/tjaa161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Indexed: 06/12/2023]
Abstract
It is often difficult to distinguish morphologically between closely related species of fleas (Siphonaptera). Morphological identification of fleas often requires microscopic examination of internal structures in specimens cleared using caustic solutions. This process degrades DNA and/or inhibits DNA extraction from specimens, which limits molecular-based studies on individual fleas and their microbiomes. Our objective was to distinguish between Oropsylla rupestris (Jordan), Oropsylla tuberculata (Baker), Oropsylla bruneri (Baker), and Oropsylla labis (Jordan & Rothschild) (Ceratophyllidae) using PCR-based single strand conformation polymorphism (SSCP) analyses and DNA sequencing. A 446 bp region of the nuclear 28S ribosomal RNA (rRNA) gene was used as the genetic marker. The results obtained for 36 reference specimens (i.e., fleas that were morphologically identified to species) revealed no intraspecific variation in DNA sequence, whereas the DNA sequences of the four species of Oropsylla differed from one another at two to six nucleotide positions. Each flea species also had a unique SSCP banding pattern. SSCP analyses were then used to identify another 84 fleas that had not been identified morphologically. DNA sequencing data confirmed the species identity of fleas subjected to SSCP. This demonstrates that PCR-SSCP combined with DNA sequencing of the 28S rRNA gene is a very effective approach for the delineation of four closely related species of flea.
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Affiliation(s)
| | - James S Armstrong
- Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Brandon White
- Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Clare A Anstead
- Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Terry D Galloway
- Department of Entomology, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2
| | - L Robbin Lindsay
- National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada R3T 2R2
| | - Todd K Shury
- National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada R3T 2R2
- Parks Canada Agency, Department of Veterinary Pathology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5B4
| | - Jeffery E Lane
- Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Neil B Chilton
- Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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13
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Barbieri R, Signoli M, Chevé D, Costedoat C, Tzortzis S, Aboudharam G, Raoult D, Drancourt M. Yersinia pestis: the Natural History of Plague. Clin Microbiol Rev 2020; 34:e00044-19. [PMID: 33298527 PMCID: PMC7920731 DOI: 10.1128/cmr.00044-19] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The Gram-negative bacterium Yersinia pestis is responsible for deadly plague, a zoonotic disease established in stable foci in the Americas, Africa, and Eurasia. Its persistence in the environment relies on the subtle balance between Y. pestis-contaminated soils, burrowing and nonburrowing mammals exhibiting variable degrees of plague susceptibility, and their associated fleas. Transmission from one host to another relies mainly on infected flea bites, inducing typical painful, enlarged lymph nodes referred to as buboes, followed by septicemic dissemination of the pathogen. In contrast, droplet inhalation after close contact with infected mammals induces primary pneumonic plague. Finally, the rarely reported consumption of contaminated raw meat causes pharyngeal and gastrointestinal plague. Point-of-care diagnosis, early antibiotic treatment, and confinement measures contribute to outbreak control despite residual mortality. Mandatory primary prevention relies on the active surveillance of established plague foci and ectoparasite control. Plague is acknowledged to have infected human populations for at least 5,000 years in Eurasia. Y. pestis genomes recovered from affected archaeological sites have suggested clonal evolution from a common ancestor shared with the closely related enteric pathogen Yersinia pseudotuberculosis and have indicated that ymt gene acquisition during the Bronze Age conferred Y. pestis with ectoparasite transmissibility while maintaining its enteric transmissibility. Three historic pandemics, starting in 541 AD and continuing until today, have been described. At present, the third pandemic has become largely quiescent, with hundreds of human cases being reported mainly in a few impoverished African countries, where zoonotic plague is mostly transmitted to people by rodent-associated flea bites.
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Affiliation(s)
- R Barbieri
- Aix-Marseille University, IRD, MEPHI, IHU Méditerranée Infection, Marseille, France
- Aix-Marseille University, CNRS, EFS, ADES, Marseille, France
- Fondation Méditerranée Infection, Marseille, France
| | - M Signoli
- Aix-Marseille University, CNRS, EFS, ADES, Marseille, France
| | - D Chevé
- Aix-Marseille University, CNRS, EFS, ADES, Marseille, France
| | - C Costedoat
- Aix-Marseille University, CNRS, EFS, ADES, Marseille, France
| | - S Tzortzis
- Ministère de la Culture, Direction Régionale des Affaires Culturelles de Provence-Alpes-Côte d'Azur, Service Régional de l'Archéologie, Aix-en-Provence, France
| | - G Aboudharam
- Aix-Marseille University, IRD, MEPHI, IHU Méditerranée Infection, Marseille, France
- Aix-Marseille University, Faculty of Odontology, Marseille, France
| | - D Raoult
- Aix-Marseille University, IRD, MEPHI, IHU Méditerranée Infection, Marseille, France
- Fondation Méditerranée Infection, Marseille, France
| | - M Drancourt
- Aix-Marseille University, IRD, MEPHI, IHU Méditerranée Infection, Marseille, France
- Fondation Méditerranée Infection, Marseille, France
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14
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Poje JE, Rocke TE, Samuel MD. Impacts of environmental conditions on fleas in black-tailed prairie dog burrows. JOURNAL OF VECTOR ECOLOGY : JOURNAL OF THE SOCIETY FOR VECTOR ECOLOGY 2020; 45:356-365. [PMID: 33207046 DOI: 10.1111/jvec.12405] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 09/05/2020] [Indexed: 05/17/2023]
Abstract
Sylvatic plague, caused by the bacterium Yersinia pestis and transmitted by fleas, occurs in prairie dogs of the western United States. Outbreaks can devastate prairie dog communities, often causing nearly 100% mortality. Three competent flea vectors, prairie dog specialists Oropsylla hirsuta and O. tuberculata, and generalist Pulex simulans, are found on prairie dogs and in their burrows. Fleas are affected by climate, which varies across the range of black-tailed prairie dogs (Cynomys ludovicianus), but these effects may be ameliorated somewhat due to the burrowing habits of prairie dogs. Our goal was to assess how temperature and precipitation affect off-host flea abundance and whether relative flea abundance varied across the range of black-tailed prairie dogs. Flea abundance was measured by swabbing 300 prairie dog burrows at six widely distributed sites in early and late summer of 2016 and 2017. Relative abundance of flea species varied among sites and sampling sessions. Flea abundance and prevalence increased with monthly mean high temperature and declined with higher winter precipitation. Predicted climate change in North America will likely influence flea abundance and distribution, thereby impacting plague dynamics in prairie dog colonies.
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Affiliation(s)
- Julia E Poje
- Department of Forest and Wildlife Ecology, University of Wisconsin, Madison, WI, 53706, U.S.A
| | - Tonie E Rocke
- U.S. Geological Survey National Wildlife Health Center, Madison, WI, 53711, U.S.A
| | - Michael D Samuel
- Department of Forest and Wildlife Ecology, University of Wisconsin, Madison, WI, 53706, U.S.A
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15
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Liccioli S, Stephens T, Wilson SC, McPherson JM, Keating LM, Antonation KS, Bollinger TK, Corbett CR, Gummer DL, Lindsay LR, Galloway TD, Shury TK, Moehrenschlager A. Enzootic maintenance of sylvatic plague in Canada's threatened black‐tailed prairie dog ecosystem. Ecosphere 2020. [DOI: 10.1002/ecs2.3138] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Affiliation(s)
- Stefano Liccioli
- Grasslands National Park Parks Canada Agency P.O. Box 150 Val Marie Saskatchewan S0N2T0 Canada
| | - Tara Stephens
- Centre for Conservation Research Calgary Zoological Society 1300 Zoo Road N.E. Calgary Alberta T2E 7V6 Canada
| | - Sian C. Wilson
- Centre for Conservation Research Calgary Zoological Society 1300 Zoo Road N.E. Calgary Alberta T2E 7V6 Canada
| | - Jana M. McPherson
- Centre for Conservation Research Calgary Zoological Society 1300 Zoo Road N.E. Calgary Alberta T2E 7V6 Canada
| | - Laura M. Keating
- Centre for Conservation Research Calgary Zoological Society 1300 Zoo Road N.E. Calgary Alberta T2E 7V6 Canada
| | - Kym S. Antonation
- Bioforensics Assay Development and Diagnostics National Microbiology Laboratory Public Health Agency of Canada 1015 Arlington Street Winnipeg Manitoba R3E 3R2 Canada
| | - Trent K. Bollinger
- Department of Veterinary Pathology Canadian Wildlife Health Cooperative 52 Campus Drive Saskatoon Saskatchewan S7N 5B4 Canada
| | - Cindi R. Corbett
- Bioforensics Assay Development and Diagnostics National Microbiology Laboratory Public Health Agency of Canada 1015 Arlington Street Winnipeg Manitoba R3E 3R2 Canada
| | - David L. Gummer
- Natural Resource Management Branch Parks Canada Agency 720 – 220 4 Avenue SE Calgary Alberta T2G 4X3 Canada
| | - L. Robbin Lindsay
- Zoonotic Diseases and Special Pathogens National Microbiology Laboratory Public Health Agency of Canada 1015 Arlington Street Winnipeg Manitoba R3E 3R2 Canada
| | - Terry D. Galloway
- Department of Entomology Faculty of Agricultural and Food Sciences University of Manitoba 12 Dafoe Road Winnipeg Manitoba R3T 2N2 Canada
| | - Todd K. Shury
- Parks Canada Agency 52 Campus Drive Saskatoon Saskatchewan S7N 5B4 Canada
| | - Axel Moehrenschlager
- Centre for Conservation Research Calgary Zoological Society 1300 Zoo Road N.E. Calgary Alberta T2E 7V6 Canada
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16
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FLEA PARASITISM AND HOST SURVIVAL IN A PLAGUE-RELEVANT SYSTEM: THEORETICAL AND CONSERVATION IMPLICATIONS. J Wildl Dis 2019; 56:378-387. [PMID: 31880988 DOI: 10.7589/2019-08-201] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Plague is a bacterial zoonosis of mammalian hosts and flea vectors. The disease is capable of ravaging rodent populations and transforming ecosystems. Because plague mortality is likely to be predicted by flea parasitism, it is critical to understand vector dynamics. It has been hypothesized that paltry precipitation and reduced vegetative production predispose herbivorous rodents to malnourishment and flea parasitism, and flea parasitism varies directly with plague mortality. We evaluated these hypotheses on five colonies of Utah prairie dogs (UPDs; Cynomys parvidens), on the Awapa Plateau, Utah, US, in 2013-16. Ten flea species were identified among 3,257 fleas from UPDs. These 10 flea species parasitize prairie dogs, mice, rats, voles, ground squirrels, chipmunks, and marmots, all known hosts of plague. The abundance of fleas on individual UPDs (1,198 observations) varied inversely with UPD body condition; fleas were most abundant on lightweight, malnourished UPDs. Flea abundance on UPDs was highest in dry years that were preceded by wet years. Increased precipitation and soil moisture in the prior year might generate humid microclimates in UPD burrows (that could facilitate flea survival and reproduction) and paltry precipitation in the current year could predispose UPDs to malnourishment and flea parasitism. Annual re-encounter rates for UPDs (1,072 observations) were reduced in wetter years preceded by drier years; reduced precipitation and vegetative production might kill UPDs, and increased flea densities in drier years could provide conditions for plague transmission (and UPD mortality) when moisture returns. Re-encounter rates were reduced for UPDs carrying at least one flea compared to UPDs with no detected fleas. These results support the hypothesis that reduced precipitation in the current year predisposes UPDs to flea parasitism. Our results also suggest a link between flea parasitism and UPD mortality. Given documented connections between flea parasitism and plague transmission, our results point toward an effect of flea parasitism on plague-related deaths for individual UPDs, a phenomenon rarely investigated in nature.
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17
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Russell RE, Tripp DW, Rocke TE. Differential plague susceptibility in species and populations of prairie dogs. Ecol Evol 2019; 9:11962-11971. [PMID: 31695901 PMCID: PMC6822031 DOI: 10.1002/ece3.5684] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Revised: 08/28/2019] [Accepted: 09/02/2019] [Indexed: 11/24/2022] Open
Abstract
Laboratory trials conducted over the past decade at U.S. Geological Survey National Wildlife Health Center indicate that wild populations of prairie dogs (Cynomys spp.) display different degrees of susceptibility to experimental challenge with fully virulent Yersinia pestis, the causative agent of plague. We evaluated patterns in prairie dog susceptibility to plague to determine whether the historical occurrence of plague at location of capture was related to survival times of prairie dogs challenged with Y. pestis. We found that black-tailed prairie dogs (Cynomys ludovicianus) from South Dakota (captured prior to the detection of plague in the state), Gunnison's prairie dogs (Cynomys gunnisoni) from Colorado, and Utah prairie dogs (Cynomys parvidens) from Utah were most susceptible to plague. Though the susceptibility of black-tailed prairie dogs in South Dakota compared with western locations supports our hypothesis regarding historical exposure, both Colorado and Utah prairie dogs have a long history of exposure to plague. It is possible that for these populations, genetic isolation/bottle necks have made them more susceptible to plague outbreaks.
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Affiliation(s)
- Robin E. Russell
- National Wildlife Health CenterU.S. Geological SurveyMadisonWIUSA
| | - Daniel W. Tripp
- Wildlife Health ProgramColorado Parks and WildlifeFort CollinsCOUSA
| | - Tonie E. Rocke
- National Wildlife Health CenterU.S. Geological SurveyMadisonWIUSA
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18
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Jones SD, Atshabar B, Schmid BV, Zuk M, Amramina A, Stenseth NC. Living with plague: Lessons from the Soviet Union's antiplague system. Proc Natl Acad Sci U S A 2019; 116:9155-9163. [PMID: 31061115 PMCID: PMC6511024 DOI: 10.1073/pnas.1817339116] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Zoonoses, such as plague, are primarily animal diseases that spill over into human populations. While the goal of eradicating such diseases is enticing, historical experience validates abandoning eradication in favor of ecologically based control strategies (which reduce morbidity and mortality to a locally accepted risk level). During the 20th century, one of the most extensive plague-eradication efforts in recorded history was undertaken to enable large-scale changes in land use in the former Soviet Union (including vast areas of central Asia). Despite expending tremendous resources in its attempt to eradicate plague, the Soviet antiplague response gradually abandoned the goal of eradication in favor of plague control linked with developing basic knowledge of plague ecology. Drawing from this experience, we combine new gray-literature sources, historical and recent research, and fieldwork to outline best practices for the control of spillover from zoonoses while minimally disrupting wildlife ecosystems, and we briefly compare the Soviet case with that of endemic plague in the western United States. We argue for the allocation of sufficient resources to maintain ongoing local surveillance, education, and targeted control measures; to incorporate novel technologies selectively; and to use ecological research to inform developing landscape-based models for transmission interruption. We conclude that living with emergent and reemergent zoonotic diseases-switching to control-opens wider possibilities for interrupting spillover while preserving natural ecosystems, encouraging adaptation to local conditions, and using technological tools judiciously and in a cost-effective way.
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Affiliation(s)
- Susan D Jones
- Department of Ecology, Evolution & Behavior, University of Minnesota, St. Paul, MN 55108;
- Program in History of Science & Technology, University of Minnesota, St. Paul, MN 55108
| | - Bakyt Atshabar
- M. Aikimbayev's Kazakh Scientific Centre for Quarantine and Zoonotic Diseases, Ministry of Public Health, Almaty 480074, Republic of Kazakhstan
| | - Boris V Schmid
- Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, N-01316 Oslo, Norway
| | - Marlene Zuk
- Department of Ecology, Evolution & Behavior, University of Minnesota, St. Paul, MN 55108
| | - Anna Amramina
- Program in History of Science & Technology, University of Minnesota, St. Paul, MN 55108
| | - Nils Chr Stenseth
- Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, N-01316 Oslo, Norway;
- Ministry of Education Key Laboratory for Earth System Modeling, Department of Earth System Science, Tsinghua University, Beijing 100084, China
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19
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Biggins DE, Eads DA. Prairie Dogs, Persistent Plague, Flocking Fleas, and Pernicious Positive Feedback. Front Vet Sci 2019; 6:75. [PMID: 30984769 PMCID: PMC6447679 DOI: 10.3389/fvets.2019.00075] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2018] [Accepted: 02/21/2019] [Indexed: 01/21/2023] Open
Abstract
Plague (caused by the bacterium Yersinia pestis) is a deadly flea-borne disease that remains a threat to public health nearly worldwide and is particularly disruptive ecologically where it has been introduced. We review hypotheses regarding maintenance and transmission of Y. pestis, emphasizing recent data from North America supporting maintenance by persistent transmission that results in sustained non-epizootic (but variable) rates of mortality in hosts. This maintenance mechanism may facilitate periodic epizootic eruptions "in place" because the need for repeated reinvasion from disjunct sources is eliminated. Resulting explosive outbreaks that spread rapidly in time and space are likely enhanced by synergistic positive feedback (PFB) cycles involving flea vectors, hosts, and the plague bacterium itself. Although PFB has been implied in plague literature for at least 50 years, we propose this mechanism, particularly with regard to flea responses, as central to epizootic plague rather than a phenomenon worthy of just peripheral mention. We also present new data on increases in flea:host ratios resulting from recreational shooting and poisoning as possible triggers for the transition from enzootic maintenance to PFB cycles and epizootic explosions. Although plague outbreaks have received much historic attention, PFB cycles that result in decimation of host populations lead to speculation that epizootic eruptions might not be part of the adaptive evolutionary strategy of Y. pestis but might instead be a tolerated intermittent cost of its modus operandi. We also speculate that there may be mammal communities where epizootics, as we define them, are rare or absent. Absence of plague epizootics might translate into reduced public health risk but does not necessarily equate to inconsequential ecologic impact.
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Affiliation(s)
- Dean E. Biggins
- United States Geological Survey, Fort Collins Science Center, Fort Collins, CO, United States
| | - David A. Eads
- United States Geological Survey, Fort Collins Science Center, Fort Collins, CO, United States
- Department of Biology, Colorado State University, Fort Collins, CO, United States
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20
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Eads DA, Biggins DE, Bowser J, McAllister JC, Griebel RL, Childers E, Livieri TM, Painter C, Krank LS, Bly K. RESISTANCE TO DELTAMETHRIN IN PRAIRIE DOG ( CYNOMYS LUDOVICIANUS) FLEAS IN THE FIELD AND IN THE LABORATORY. J Wildl Dis 2018; 54:745-754. [PMID: 29723100 PMCID: PMC6710209 DOI: 10.7589/2017-10-250] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Sylvatic plague poses a substantial risk to black-tailed prairie dogs ( Cynomys ludovicianus) and their obligate predator, the black-footed ferret ( Mustela nigripes). The effects of plague on prairie dogs and ferrets are mitigated using a deltamethrin pulicide dust that reduces the spread of plague by killing fleas, the vector for the plague bacterium. In portions of Conata Basin, Buffalo Gap National Grassland, and Badlands National Park, South Dakota, US, 0.05% deltamethrin has been infused into prairie dog burrows on an annual basis since 2005. We aimed to determine if fleas ( Oropsylla hirsuta) in portions of the Conata Basin and Badlands National Park have evolved resistance to deltamethrin. We assessed flea prevalence, obtained by combing prairie dogs for fleas, as an indirect measure of resistance. Dusting was ineffective in two colonies treated with deltamethrin for >8 yr; flea prevalence rebounded within 1 mo of dusting. We used a bioassay that exposed fleas to deltamethrin to directly evaluate resistance. Fleas from colonies with >8 yr of exposure to deltamethrin exhibited survival rates that were 15% to 83% higher than fleas from sites that had never been dusted. All fleas were paralyzed or dead after 55 min. After removal from deltamethrin, 30% of fleas from the dusted colonies recovered, compared with 1% of fleas from the not-dusted sites. Thus, deltamethrin paralyzed fleas from colonies with long-term exposure to deltamethrin, but a substantial number of those fleas was resistant and recovered. Flea collections from live-trapped prairie dogs in Thunder Basin National Grassland, Wyoming, US, suggest that, in some cases, fleas might begin to develop a moderate level of resistance to deltamethrin after 5-6 yr of annual treatments. Restoration of black-footed ferrets and prairie dogs will rely on an adaptive, integrative approach to plague management, for instance involving the use of vaccines and rotating applications of insecticidal products with different active ingredients.
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Affiliation(s)
- David A. Eads
- Department of Biology, Colorado State University, Campus Delivery 1878, Fort Collins, Colorado 80523, USA
- Corresponding author ()
| | - Dean E. Biggins
- US Geological Survey, Fort Collins Science Center, 2150 Centre Avenue Building C, Fort Collins, Colorado 80526, USA
| | - Jonathan Bowser
- US Geological Survey, Fort Collins Science Center, 2150 Centre Avenue Building C, Fort Collins, Colorado 80526, USA
| | - Janet C. McAllister
- Centers for Disease Control and Prevention, Fort Collins, Colorado 80521, USA
| | - Randall L. Griebel
- US Forest Service, Wall Ranger District, 710 Main Street, Wall, South Dakota 57790, USA
| | - Eddie Childers
- National Park Service, Badlands National Park, 25216 Ben Reifel Road, Interior, South Dakota 57750, USA
| | - Travis M. Livieri
- Prairie Wildlife Research, PO Box 308, Wellington, Colorado 80549, USA
| | - Cristi Painter
- US Forest Service, Thunder Basin National Grassland, 2250 E Richards Street, Douglas, Wyoming 82633, USA
| | - Lindsey Sterling Krank
- The Humane Society of the United States, Prairie Dog Coalition, 2525 Arapahoe #E4-527, Boulder, Colorado 80302, USA
| | - Kristy Bly
- World Wildlife Fund, Northern Great Plains Program, 458 Saddle Ridge Road, Hamilton, Montana 59840, USA
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Hinnebusch BJ, Jarrett CO, Bland DM. "Fleaing" the Plague: Adaptations of Yersinia pestis to Its Insect Vector That Lead to Transmission. Annu Rev Microbiol 2018; 71:215-232. [PMID: 28886687 DOI: 10.1146/annurev-micro-090816-093521] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Interest in arthropod-borne pathogens focuses primarily on how they cause disease in humans. How they produce a transmissible infection in their arthropod host is just as critical to their life cycle, however. Yersinia pestis adopts a unique life stage in the digestive tract of its flea vector, characterized by rapid formation of a bacterial biofilm that is enveloped in a complex extracellular polymeric substance. Localization and adherence of the biofilm to the flea foregut is essential for transmission. Here, we review the molecular and genetic mechanisms of these processes and present a comparative evaluation and updated model of two related transmission mechanisms.
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Affiliation(s)
- B Joseph Hinnebusch
- Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana 59840;
| | - Clayton O Jarrett
- Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana 59840;
| | - David M Bland
- Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana 59840;
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Cassin Sackett L. Does the host matter? Variable influence of host traits on parasitism rates. Int J Parasitol 2018; 48:27-39. [DOI: 10.1016/j.ijpara.2017.07.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 06/28/2017] [Accepted: 07/03/2017] [Indexed: 11/28/2022]
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23
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Eads DA, Biggins DE. Paltry past-precipitation: Predisposing prairie dogs to plague? J Wildl Manage 2017. [DOI: 10.1002/jwmg.21281] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- David A. Eads
- Department of Biology, Colorado State University; U.S. Geological Survey, Fort Collins Science Center; 2150 Centre Avenue, Building C Fort Collins CO 80526 USA
| | - Dean E. Biggins
- U.S. Geological Survey; Fort Collins Science Center; 2150 Centre Avenue, Building C Fort Collins CO 80526 USA
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24
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FLEAS OF BLACK-FOOTED FERRETS (MUSTELA NIGRIPES) AND THEIR POTENTIAL ROLE IN THE MOVEMENT OF PLAGUE. J Wildl Dis 2017; 53:521-531. [DOI: 10.7589/2016-09-202] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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25
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Eads DA, Hoogland JL. Precipitation, Climate Change, and Parasitism of Prairie Dogs by Fleas that Transmit Plague. J Parasitol 2017; 103:309-319. [PMID: 28359175 DOI: 10.1645/16-195] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Fleas (Insecta: Siphonaptera) are hematophagous ectoparasites that can reduce the fitness of vertebrate hosts. Laboratory populations of fleas decline under dry conditions, implying that populations of fleas will also decline when precipitation is scarce under natural conditions. If precipitation and hence vegetative production are reduced, however, then herbivorous hosts might suffer declines in body condition and have weakened defenses against fleas, so that fleas will increase in abundance. We tested these competing hypotheses using information from 23 yr of research on 3 species of colonial prairie dogs in the western United States: Gunnison's prairie dog (Cynomys gunnisoni, 1989-1994), Utah prairie dog (Cynomys parvidens, 1996-2005), and white-tailed prairie dog (Cynomys leucurus, 2006-2012). For all 3 species, flea-counts per individual varied inversely with the number of days in the prior growing season with >10 mm of precipitation, an index of the number of precipitation events that might have caused a substantial, prolonged increase in soil moisture and vegetative production. Flea-counts per Utah prairie dog also varied inversely with cumulative precipitation of the prior growing season. Furthermore, flea-counts per Gunnison's and white-tailed prairie dog varied inversely with cumulative precipitation of the just-completed January and February. These results complement research on black-tailed prairie dog (Cynomys ludovicianus) and might have important ramifications for plague, a bacterial disease transmitted by fleas that devastates populations of prairie dogs. In particular, our results might help to explain why, at some colonies, epizootics of plague, which can kill >95% of prairie dogs, are more likely to occur during or shortly after periods of reduced precipitation. Climate change is projected to increase the frequency of droughts in the grasslands of western North America. If so, then climate change might affect the occurrence of plague epizootics among prairie dogs and other mammalian species that associate with them.
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Affiliation(s)
- David A Eads
- Department of Biology, Colorado State University, Fort Collins, Colorado 80523. Correspondence should be sent to David A. Eads at:
| | - John L Hoogland
- Department of Biology, Colorado State University, Fort Collins, Colorado 80523. Correspondence should be sent to David A. Eads at:
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Bahrndorff S, de Jonge N, Skovgård H, Nielsen JL. Bacterial Communities Associated with Houseflies (Musca domestica L.) Sampled within and between Farms. PLoS One 2017; 12:e0169753. [PMID: 28081167 PMCID: PMC5232358 DOI: 10.1371/journal.pone.0169753] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Accepted: 12/21/2016] [Indexed: 11/18/2022] Open
Abstract
The housefly feeds and reproduces in animal manure and decaying organic substances and thus lives in intimate association with various microorganisms including human pathogens. In order to understand the variation and association between bacteria and the housefly, we used 16S rRNA gene amplicon sequencing to describe bacterial communities of 90 individual houseflies collected within and between ten dairy farms in Denmark. Analysis of gene sequences showed that the most abundant classes of bacteria found across all sites included Bacilli, Clostridia, Actinobacteria, Flavobacteria, and all classes of Proteobacteria and at the genus level the most abundant genera included Corynebacterium, Lactobacillus, Staphylococcus, Vagococcus, Weissella, Lactococcus, and Aerococcus. Comparison of the microbiota of houseflies revealed a highly diverse microbiota compared to other insect species and with most variation in species richness and diversity found between individuals, but not locations. Our study is the first in-depth amplicon sequencing study of the housefly microbiota, and collectively shows that the microbiota of single houseflies is highly diverse and differs between individuals likely to reflect the lifestyle of the housefly. We suggest that these results should be taken into account when addressing the transmission of pathogens by the housefly and assessing the vector competence variation under natural conditions.
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Affiliation(s)
- Simon Bahrndorff
- Department of Chemistry and Bioscience, Aalborg University, Aalborg East, Denmark
| | - Nadieh de Jonge
- Department of Chemistry and Bioscience, Aalborg University, Aalborg East, Denmark
| | - Henrik Skovgård
- Department of Agroecology, University of Aarhus, Slagelse, Denmark
| | - Jeppe Lund Nielsen
- Department of Chemistry and Bioscience, Aalborg University, Aalborg East, Denmark
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Hinnebusch BJ, Bland DM, Bosio CF, Jarrett CO. Comparative Ability of Oropsylla montana and Xenopsylla cheopis Fleas to Transmit Yersinia pestis by Two Different Mechanisms. PLoS Negl Trop Dis 2017; 11:e0005276. [PMID: 28081130 PMCID: PMC5230758 DOI: 10.1371/journal.pntd.0005276] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 12/21/2016] [Indexed: 11/19/2022] Open
Abstract
Background Transmission of Yersinia pestis by flea bite can occur by two mechanisms. After taking a blood meal from a bacteremic mammal, fleas have the potential to transmit the very next time they feed. This early-phase transmission resembles mechanical transmission in some respects, but the mechanism is unknown. Thereafter, transmission occurs after Yersinia pestis forms a biofilm in the proventricular valve in the flea foregut. The biofilm can impede and sometimes completely block the ingestion of blood, resulting in regurgitative transmission of bacteria into the bite site. In this study, we compared the relative efficiency of the two modes of transmission for Xenopsylla cheopis, a flea known to become completely blocked at a high rate, and Oropsylla montana, a flea that has been considered to rarely develop proventricular blockage. Methodology/Principal findings Fleas that took an infectious blood meal containing Y. pestis were maintained and monitored for four weeks for infection and proventricular blockage. The number of Y. pestis transmitted by groups of fleas by the two modes of transmission was also determined. O. montana readily developed complete proventricular blockage, and large numbers of Y. pestis were transmitted by that mechanism both by it and by X. cheopis, a flea known to block at a high rate. In contrast, few bacteria were transmitted in the early phase by either species. Conclusions A model system incorporating standardized experimental conditions and viability controls was developed to more reliably compare the infection, proventricular blockage and transmission dynamics of different flea vectors, and was used to resolve a long-standing uncertainty concerning the vector competence of O. montana. Both X. cheopis and O. montana are fully capable of transmitting Y. pestis by the proventricular biofilm-dependent mechanism. The ecology of plague is complex and its epidemiology is enigmatic. Many different flea species are able to transmit Yersinia pestis, the plague bacillus, and they can transmit in two different ways. Early-phase transmission can occur during the first week after a flea has fed on a diseased animal. Thereafter, transmission occurs only as bacterial growth in the flea foregut interferes with and eventually blocks blood feeding. Comparisons of the relative ability of different flea vectors to transmit have been problematic, and contradictory results have been reported for the ability of the ground squirrel flea Oropsylla montana to transmit beyond the early phase. Our results show that O. montana readily develops foregut blockage, and transmission by that mechanism was as good as or better than observed for Xenopsylla cheopis, a flea known to block at a high rate. In contrast, very few bacteria were transmitted in the early phase by either of these fleas compared to later times after infection, suggesting that early-phase transmission is pertinent only to highly susceptible animals. Improved characterization of the transmission patterns of different flea vectors will aid in modeling plague incidence in its various natural settings.
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Affiliation(s)
- B. Joseph Hinnebusch
- Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
- * E-mail:
| | - David M. Bland
- Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Christopher F. Bosio
- Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Clayton O. Jarrett
- Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, United States of America
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Eads DA, Hoogland JL. Factors that affect parasitism of black‐tailed prairie dogs by fleas. Ecosphere 2016. [DOI: 10.1002/ecs2.1372] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Affiliation(s)
- David A. Eads
- Fort Collins Science Center U.S. Geological Survey Fort Collins Colorado 80526 USA
- Department of Biology Colorado State University Fort Collins Colorado 80523 USA
| | - John L. Hoogland
- Appalachian Laboratory University of Maryland Center for Environmental Science Frostburg Maryland 21532 USA
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SEASON OF DELTAMETHRIN APPLICATION AFFECTS FLEA AND PLAGUE CONTROL IN WHITE-TAILED PRAIRIE DOG (CYNOMYS LEUCURUS) COLONIES, COLORADO, USA. J Wildl Dis 2016; 52:553-61. [DOI: 10.7589/2015-10-290] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Boegler KA, Graham CB, Johnson TL, Montenieri JA, Eisen RJ. Infection Prevalence, Bacterial Loads, and Transmission Efficiency in Oropsylla montana (Siphonaptera: Ceratophyllidae) One Day After Exposure to Varying Concentrations of Yersinia pestis in Blood. JOURNAL OF MEDICAL ENTOMOLOGY 2016; 53:674-680. [PMID: 26843450 PMCID: PMC6555412 DOI: 10.1093/jme/tjw004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 01/12/2016] [Indexed: 05/28/2023]
Abstract
Unblocked fleas can transmit Yersinia pestis, the bacterium that causes plague, shortly (≤4 d) after taking an infectious bloodmeal. Investigators have measured so-called early-phase transmission (EPT) efficiency in various fleas following infection with highly bacteremic blood (≥108 cfu/ml). To date, no one has determined the lower limit of bacteremia required for fleas to acquire and transmit infection by EPT, though knowing this threshold is central to determining the length of time a host may be infectious to feeding fleas. Here, we evaluate the ability of Oropsylla montana (Baker) to acquire and transmit Y. pestis after feeding on blood containing 103 to 109 cfu/ml. We evaluated the resulting infection prevalence, bacterial loads, and transmission efficiency within the early-phase time period at 1 d postinfection. Fleas acquired infection from bacteremic blood across a wide range of concentrations, but transmission was observed only when fleas ingested highly bacteremic blood.
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Affiliation(s)
- Karen A Boegler
- Centers for Disease Control and Prevention - Division of Vector-Borne Diseases, 3156 Rampart Rd., Fort Collins, CO 80521 (; ; ; ; ) and
| | - Christine B Graham
- Centers for Disease Control and Prevention - Division of Vector-Borne Diseases, 3156 Rampart Rd., Fort Collins, CO 80521 (; ; ; ; ) and
| | - Tammi L Johnson
- Centers for Disease Control and Prevention - Division of Vector-Borne Diseases, 3156 Rampart Rd., Fort Collins, CO 80521 (; ; ; ; ) and
| | - John A Montenieri
- Centers for Disease Control and Prevention - Division of Vector-Borne Diseases, 3156 Rampart Rd., Fort Collins, CO 80521 (; ; ; ; ) and
| | - Rebecca J Eisen
- Centers for Disease Control and Prevention - Division of Vector-Borne Diseases, 3156 Rampart Rd., Fort Collins, CO 80521 (; ; ; ; ) and
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Brown LD, Banajee KH, Foil LD, Macaluso KR. Transmission mechanisms of an emerging insect-borne rickettsial pathogen. Parasit Vectors 2016; 9:237. [PMID: 27117813 PMCID: PMC4847369 DOI: 10.1186/s13071-016-1511-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Accepted: 04/14/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Vector-borne pathogens must overcome arthropod infection and escape barriers (e.g. midgut and salivary glands) during the extrinsic incubation period (EIP) before subsequent transmission to another host. This particular timespan is undetermined for the etiological agent of flea-borne spotted fever (Rickettsia felis). Artificial acquisition of R. felis by blood-feeding cat fleas revealed dissemination to the salivary glands after seven days; however, this length of time is inconsistent with co-feeding studies that produced infectious cat fleas within 24 h of infection. In the current study, we demonstrated that an alternative mechanism is responsible for the early-phase transmission that typifies flea-borne R. felis spread. METHODS Co-feeding transmission bioassays were constructed to assess temporal dynamics of R. felis amongst cat fleas, including exposure time to produce infectious fleas and association time to transmit infection to naïve fleas. Additional experiments examined the proportion of R. felis-exposed cat fleas with contaminated mouthparts, as well as the likelihood for cat fleas to release R. felis from their mouthparts following exposure to an infectious bloodmeal. The potential for mechanical transmission of R. felis by co-feeding cat fleas was further examined using fluorescent latex beads, as opposed to a live pathogen, which would not require a biological mechanism to achieve transmission. RESULTS Analyses revealed that R. felis-infected cat fleas were infectious to naïve fleas less than 24 h after exposure to the pathogen, but showed no rickettsial dissemination to the salivary glands during this early-phase transmission. Additionally, the current study revealed that R. felis-infected cat fleas must co-feed with naïve fleas for more than 12 h in order for early-phase transmission to occur. Further evidence supported that contaminated flea mouthparts may be the source of the bacteria transmitted early, and demonstrated that R. felis is released from the mouthparts during brief probing events. Moreover, the use of fluorescent latex beads supports the notion that early-phase transmission of R. felis is a mechanical mechanism. CONCLUSIONS Determination of the transmission mechanisms utilized by R. felis is essential to fully understand the vulnerability of susceptible vertebrate hosts, including humans, to this pathogen.
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Affiliation(s)
- Lisa D. Brown
- />Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Skip Bertman Drive, SVM-3213, Baton Rouge, LA 70803 USA
| | - Kaikhushroo H. Banajee
- />Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Skip Bertman Drive, SVM-3213, Baton Rouge, LA 70803 USA
| | - Lane D. Foil
- />Department of Entomology, Louisiana State University Agricultural Center, LSB-413, Baton Rouge, LA 70803 USA
| | - Kevin R. Macaluso
- />Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Skip Bertman Drive, SVM-3213, Baton Rouge, LA 70803 USA
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Graham CB, Eisen RJ, Belthoff JR. Detecting Burrowing Owl Bloodmeals in Pulex irritans (Siphonaptera: Pulicidae). JOURNAL OF MEDICAL ENTOMOLOGY 2016; 53:446-450. [PMID: 26545716 PMCID: PMC5572895 DOI: 10.1093/jme/tjv177] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 10/19/2015] [Indexed: 06/05/2023]
Abstract
Pulex irritans L. is a cosmopolitan flea species that infests a wide variety of hosts. In North America it generally parasitizes large wild mammals, but in the Pacific Northwest an association has emerged between P. irritans and the western burrowing owl (Athene cunicularia hypugaea). While investigators have recognized this association for decades, it has not been clear if P. irritans feeds on burrowing owls, or if the owls serve exclusively as phoretic hosts. Here we describe using a real-time assay that was originally developed to identify bloodmeals in Ugandan cat fleas (Ctenocephalides felis Bouché) to detect burrowing owl DNA in P. irritans collected from burrowing owls in southern Idaho. Of 50 fleas tested, 12 had no detectable vertebrate bloodmeal. The remaining 38 (76%) contained burrowing owl DNA. The assay did not detect vertebrate DNA in unfed fleas exposed to owl or mouse pelts and is therefore unlikely to detect DNA in fleas from vertebrates that have served exclusively as phoretic hosts. We conclude that P. irritans feeds on burrowing owls. We discuss the potential implications of this finding for burrowing owl conservation and enzootic plague dynamics.
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Affiliation(s)
- Christine B Graham
- Bacterial Diseases Branch, Division of Vector-Borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, 3156 Rampart Rd., Fort Collins, CO 80521 (; ),
| | - Rebecca J Eisen
- Bacterial Diseases Branch, Division of Vector-Borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, 3156 Rampart Rd., Fort Collins, CO 80521 (; )
| | - James R Belthoff
- Department of Biological Sciences and Raptor Research Center, Boise State University, 1910 University Dr., Boise, ID 83725
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Mize EL, Britten HB. Detections of Yersinia pestis East of the Known Distribution of Active Plague in the United States. Vector Borne Zoonotic Dis 2016; 16:88-95. [PMID: 26771845 DOI: 10.1089/vbz.2015.1825] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We examined fleas collected from black-tailed prairie dog (Cynomys ludovicianus) burrows from 2009 through 2011 in five national park units east of the known distribution of active plague across the northern Great Plains for the presence of Yersinia pestis. Across all national park units, Oropsylla tuberculata and Oropsylla hirsuta were the most common fleas collected from prairie dog burrows, 42.4% and 56.9%, respectively, of the 3964 fleas collected from burrow swabbing. Using a nested PCR assay, we detected 200 Y. pestis-positive fleas from 3117 assays. In total, 6.4% of assayed fleas were Y. pestis positive and 13.9% of prairie dog burrows swabbed contained Y. pestis-positive fleas. Evidence of the presence of Y. pestis was observed at all national park units except Devils Tower National Monument in Wyoming. We detected the presence of Y. pestis without large die-offs, i.e., enzootic sylvatic plague, east of the known distribution of active plague and near the eastern edge of the present distribution of black-tailed prairie dogs. This study, in combination with previous work suggests that sylvatic plague likely occurs across the range of black-tailed prairie dogs and should now be treated as endemic across this range.
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Affiliation(s)
- Erica L Mize
- Department of Biology, University of South Dakota , Vermillion, South Dakota
| | - Hugh B Britten
- Department of Biology, University of South Dakota , Vermillion, South Dakota
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Salkeld DJ, Stapp P, Tripp DW, Gage KL, Lowell J, Webb CT, Brinkerhoff RJ, Antolin MF. Ecological Traits Driving the Outbreaks and Emergence of Zoonotic Pathogens. Bioscience 2016; 66:118-129. [PMID: 32287347 PMCID: PMC7109792 DOI: 10.1093/biosci/biv179] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Infectious diseases that are transmitted from wildlife hosts to humans, such as the Ebola virus and MERS virus, can be difficult to understand because the pathogens emerge from complex multifaceted ecological interactions. We use a wildlife–pathogen system—prairie dogs (Cynomys ludovicianus) and the plague bacterium (Yersinia pestis)—to describe aspects of disease ecology that apply to many cases of emerging infectious disease. We show that the monitoring and surveillance of hosts and vectors during the buildup to disease outbreaks are crucial for understanding pathogen-transmission dynamics and that a community-ecology framework is important to identify reservoir hosts. Incorporating multidisciplinary approaches and frameworks may improve wildlife–pathogen surveillance and our understanding of seemingly sporadic and rare pathogen outbreaks.
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Affiliation(s)
- Daniel J Salkeld
- Dan Salkeld is an ecologist and epidemiologist affiliated with the Department of Biology at Colorado State University. Paul Stapp is a professor in the Department of Biological Science at California State University, in Fullerton. Dan Tripp is a biologist at the Colorado Division of Parks and Wildlife, in Fort Collins. Ken Gage is the chief of the Flea-Borne Diseases Laboratory, of CDC's Bacterial Zoonoses Branch, Division of Vector-Borne Infectious Diseases, in Fort Collins, Colorado. Jen Lowell is a professor of Health Sciences at Carroll College, in Helena, Montana. Colleen Webb and Michael Antolin are professors in the Department of Biology at Colorado State University, with interests in disease ecology and evolution. Jory Brinkerhoff is a professor at the Department of Biology at the University of Richmond, in Virginia
| | - Paul Stapp
- Dan Salkeld is an ecologist and epidemiologist affiliated with the Department of Biology at Colorado State University. Paul Stapp is a professor in the Department of Biological Science at California State University, in Fullerton. Dan Tripp is a biologist at the Colorado Division of Parks and Wildlife, in Fort Collins. Ken Gage is the chief of the Flea-Borne Diseases Laboratory, of CDC's Bacterial Zoonoses Branch, Division of Vector-Borne Infectious Diseases, in Fort Collins, Colorado. Jen Lowell is a professor of Health Sciences at Carroll College, in Helena, Montana. Colleen Webb and Michael Antolin are professors in the Department of Biology at Colorado State University, with interests in disease ecology and evolution. Jory Brinkerhoff is a professor at the Department of Biology at the University of Richmond, in Virginia
| | - Daniel W Tripp
- Dan Salkeld is an ecologist and epidemiologist affiliated with the Department of Biology at Colorado State University. Paul Stapp is a professor in the Department of Biological Science at California State University, in Fullerton. Dan Tripp is a biologist at the Colorado Division of Parks and Wildlife, in Fort Collins. Ken Gage is the chief of the Flea-Borne Diseases Laboratory, of CDC's Bacterial Zoonoses Branch, Division of Vector-Borne Infectious Diseases, in Fort Collins, Colorado. Jen Lowell is a professor of Health Sciences at Carroll College, in Helena, Montana. Colleen Webb and Michael Antolin are professors in the Department of Biology at Colorado State University, with interests in disease ecology and evolution. Jory Brinkerhoff is a professor at the Department of Biology at the University of Richmond, in Virginia
| | - Kenneth L Gage
- Dan Salkeld is an ecologist and epidemiologist affiliated with the Department of Biology at Colorado State University. Paul Stapp is a professor in the Department of Biological Science at California State University, in Fullerton. Dan Tripp is a biologist at the Colorado Division of Parks and Wildlife, in Fort Collins. Ken Gage is the chief of the Flea-Borne Diseases Laboratory, of CDC's Bacterial Zoonoses Branch, Division of Vector-Borne Infectious Diseases, in Fort Collins, Colorado. Jen Lowell is a professor of Health Sciences at Carroll College, in Helena, Montana. Colleen Webb and Michael Antolin are professors in the Department of Biology at Colorado State University, with interests in disease ecology and evolution. Jory Brinkerhoff is a professor at the Department of Biology at the University of Richmond, in Virginia
| | - Jennifer Lowell
- Dan Salkeld is an ecologist and epidemiologist affiliated with the Department of Biology at Colorado State University. Paul Stapp is a professor in the Department of Biological Science at California State University, in Fullerton. Dan Tripp is a biologist at the Colorado Division of Parks and Wildlife, in Fort Collins. Ken Gage is the chief of the Flea-Borne Diseases Laboratory, of CDC's Bacterial Zoonoses Branch, Division of Vector-Borne Infectious Diseases, in Fort Collins, Colorado. Jen Lowell is a professor of Health Sciences at Carroll College, in Helena, Montana. Colleen Webb and Michael Antolin are professors in the Department of Biology at Colorado State University, with interests in disease ecology and evolution. Jory Brinkerhoff is a professor at the Department of Biology at the University of Richmond, in Virginia
| | - Colleen T Webb
- Dan Salkeld is an ecologist and epidemiologist affiliated with the Department of Biology at Colorado State University. Paul Stapp is a professor in the Department of Biological Science at California State University, in Fullerton. Dan Tripp is a biologist at the Colorado Division of Parks and Wildlife, in Fort Collins. Ken Gage is the chief of the Flea-Borne Diseases Laboratory, of CDC's Bacterial Zoonoses Branch, Division of Vector-Borne Infectious Diseases, in Fort Collins, Colorado. Jen Lowell is a professor of Health Sciences at Carroll College, in Helena, Montana. Colleen Webb and Michael Antolin are professors in the Department of Biology at Colorado State University, with interests in disease ecology and evolution. Jory Brinkerhoff is a professor at the Department of Biology at the University of Richmond, in Virginia
| | - R Jory Brinkerhoff
- Dan Salkeld is an ecologist and epidemiologist affiliated with the Department of Biology at Colorado State University. Paul Stapp is a professor in the Department of Biological Science at California State University, in Fullerton. Dan Tripp is a biologist at the Colorado Division of Parks and Wildlife, in Fort Collins. Ken Gage is the chief of the Flea-Borne Diseases Laboratory, of CDC's Bacterial Zoonoses Branch, Division of Vector-Borne Infectious Diseases, in Fort Collins, Colorado. Jen Lowell is a professor of Health Sciences at Carroll College, in Helena, Montana. Colleen Webb and Michael Antolin are professors in the Department of Biology at Colorado State University, with interests in disease ecology and evolution. Jory Brinkerhoff is a professor at the Department of Biology at the University of Richmond, in Virginia
| | - Michael F Antolin
- Dan Salkeld is an ecologist and epidemiologist affiliated with the Department of Biology at Colorado State University. Paul Stapp is a professor in the Department of Biological Science at California State University, in Fullerton. Dan Tripp is a biologist at the Colorado Division of Parks and Wildlife, in Fort Collins. Ken Gage is the chief of the Flea-Borne Diseases Laboratory, of CDC's Bacterial Zoonoses Branch, Division of Vector-Borne Infectious Diseases, in Fort Collins, Colorado. Jen Lowell is a professor of Health Sciences at Carroll College, in Helena, Montana. Colleen Webb and Michael Antolin are professors in the Department of Biology at Colorado State University, with interests in disease ecology and evolution. Jory Brinkerhoff is a professor at the Department of Biology at the University of Richmond, in Virginia
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Eisen RJ, Dennis DT, Gage KL. The Role of Early-Phase Transmission in the Spread of Yersinia pestis. JOURNAL OF MEDICAL ENTOMOLOGY 2015; 52:1183-92. [PMID: 26336267 PMCID: PMC4636957 DOI: 10.1093/jme/tjv128] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Accepted: 08/01/2015] [Indexed: 05/28/2023]
Abstract
Early-phase transmission (EPT) of Yersinia pestis by unblocked fleas is a well-documented, replicable phenomenon with poorly defined mechanisms. We review evidence demonstrating EPT and current knowledge on its biological and biomechanical processes. We discuss the importance of EPT in the epizootic spread of Y. pestis and its role in the maintenance of plague bacteria in nature. We further address the role of EPT in the epidemiology of plague.
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Affiliation(s)
- Rebecca J Eisen
- Bacterial Diseases Branch, Division of Vectorborne Diseases, National Center for Emerging Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO.
| | | | - Kenneth L Gage
- Bacterial Diseases Branch, Division of Vectorborne Diseases, National Center for Emerging Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO
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Ekanayake AJ, Ekanayake DB. A seasonal SIR metapopulation model with an Allee effect with application to controlling plague in prairie dog colonies. JOURNAL OF BIOLOGICAL DYNAMICS 2014; 9 Suppl 1:262-290. [PMID: 25400201 DOI: 10.1080/17513758.2014.978400] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
For wildlife species living among patchy habitats, disease and the Allee effect (reduced per capita birth rates at low population densities) may together drive a patch's population to extinction, particularly if births are seasonal. Yet local extinction may not be indicative of global extinction, and a patch may become recolonized by migrating individuals. We introduce deterministic and stochastic susceptible, infectious, and immune epidemic models with vector species to study disease in a metapopulation with an Allee effect and seasonal birth and dispersal. We obtain conditions for the existence of a strong Allee effect and existence and stability of a disease-free positive periodic solution. These general models have application to many wildlife diseases. As a case study, we apply them to evaluate dynamics of the sylvatic plague in prairie dog colonies interconnected through dispersal. We further evaluate the effects of control of the vector population and control by immunization on plague eradication.
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Affiliation(s)
- A J Ekanayake
- a Department of Mathematics , Western Illinois University , 1 University Circle, Macomb , IL 61455 , USA
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Johnson TL, Hinnebusch BJ, Boegler KA, Graham CB, MacMillan K, Montenieri JA, Bearden SW, Gage KL, Eisen RJ. Yersinia murine toxin is not required for early-phase transmission of Yersinia pestis by Oropsylla montana (Siphonaptera: Ceratophyllidae) or Xenopsylla cheopis (Siphonaptera: Pulicidae). MICROBIOLOGY-SGM 2014; 160:2517-2525. [PMID: 25187626 DOI: 10.1099/mic.0.082123-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Plague, caused by Yersinia pestis, is characterized by quiescent periods punctuated by rapidly spreading epizootics. The classical 'blocked flea' paradigm, by which a blockage forms in the flea's proventriculus on average 1-2 weeks post-infection (p.i.), forces starving fleas to take multiple blood meals, thus increasing opportunities for transmission. Recently, the importance of early-phase transmission (EPT), which occurs prior to blockage formation, has been emphasized during epizootics. Whilst the physiological and molecular mechanisms of blocked flea transmission are well characterized, the pathogen-vector interactions have not been elucidated for EPT. Within the blocked flea model, Yersinia murine toxin (Ymt) has been shown to be important for facilitating colonization of the midgut within the flea. One proposed mechanism of EPT is the regurgitation of infectious material from the flea midgut during feeding. Such a mechanism would require bacteria to colonize and survive for at least brief periods in the midgut, a process that is mediated by Ymt. Two key bridging vectors of Y. pestis to humans, Oropsylla montana (Siphonaptera: Ceratophyllidae) or Xenopsylla cheopis (Siphonaptera: Pulicidae), were used in our study to test this hypothesis. Fleas were infected with a mutant strain of Y. pestis containing a non-functional ymt that was shown previously to be incapable of colonizing the midgut and were then allowed to feed on SKH-1 mice 3 days p.i. Our results show that Ymt was not required for EPT by either flea species.
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Affiliation(s)
- Tammi L Johnson
- Bacterial Diseases Branch, Division of Vector-borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, USA
| | - B Joseph Hinnebusch
- Laboratory of Zoonotic Pathogens, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA
| | - Karen A Boegler
- Bacterial Diseases Branch, Division of Vector-borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, USA
| | - Christine B Graham
- Bacterial Diseases Branch, Division of Vector-borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, USA
| | - Katherine MacMillan
- Bacterial Diseases Branch, Division of Vector-borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, USA
| | - John A Montenieri
- Bacterial Diseases Branch, Division of Vector-borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, USA
| | - Scott W Bearden
- Bacterial Diseases Branch, Division of Vector-borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, USA
| | - Kenneth L Gage
- Bacterial Diseases Branch, Division of Vector-borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, USA
| | - Rebecca J Eisen
- Bacterial Diseases Branch, Division of Vector-borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, USA
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St Romain K, Tripp DW, Salkeld DJ, Antolin MF. Duration of plague (Yersinia pestis) outbreaks in black-tailed prairie dog (Cynomys ludovicianus) colonies of northern Colorado. ECOHEALTH 2013; 10:241-5. [PMID: 24057801 DOI: 10.1007/s10393-013-0860-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Revised: 06/21/2013] [Accepted: 06/21/2013] [Indexed: 05/24/2023]
Abstract
Plague, caused by the bacterium Yersinia pestis, triggers die-offs in colonies of black-tailed prairie dogs (Cynomys ludovicianus), but the time-frame of plague activity is not well understood. We document plague activity in fleas from prairie dogs and their burrows on three prairie dog colonies that suffered die-offs. We demonstrate that Y. pestis transmission occurs over periods from several months to over a year in prairie dog populations before observed die-offs.
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Affiliation(s)
- Krista St Romain
- Department of Biology, Colorado State University, Fort Collins, CO, 80523, USA
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Jones RT, Vetter SM, Gage KL. Short report: Exposing laboratory-reared fleas to soil and wild flea feces increases transmission of Yersinia pestis. Am J Trop Med Hyg 2013; 89:784-7. [PMID: 23939709 DOI: 10.4269/ajtmh.13-0138] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Laboratory-reared Oropsylla montana were exposed to soil and wild-caught Oropsylla montana feces for 1 week. Fleas from these two treatments and a control group of laboratory-reared fleas were infected with Yersinia pestis, the etiological agent of plague. Fleas exposed to soil transmitted Y. pestis to mice at a significantly greater rate (50.0% of mice were infected) than control fleas (23.3% of mice were infected). Although the concentration of Y. pestis in fleas did not differ among treatments, the minimum transmission efficiency of fleas from the soil and wild flea feces treatments (6.9% and 7.6%, respectively) were more than three times higher than in control fleas (2.2%). Our results suggest that exposing laboratory-reared fleas to diverse microbes alters transmission of Y. pestis.
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Affiliation(s)
- Ryan T Jones
- Division of Vector-Borne Disease, Centers for Disease Control and Prevention, Fort Collins, Colorado
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Williams SK, Schotthoefer AM, Montenieri JA, Holmes JL, Vetter SM, Gage KL, Bearden SW. Effects of low-temperature flea maintenance on the transmission of Yersinia pestis by Oropsylla montana. Vector Borne Zoonotic Dis 2013; 13:468-78. [PMID: 23590319 DOI: 10.1089/vbz.2012.1017] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Yersinia pestis, the causative agent of plague, is primarily a rodent-associated, flea-borne zoonosis maintained in sylvatic foci throughout western North America. Transmission to humans is mediated most commonly by the flea vector Oropsylla montana and occurs predominantly in the southwestern United States. With few exceptions, previous studies showed O. montana to be an inefficient vector at transmitting Y. pestis at ambient temperatures, particularly when such fleas were fed on susceptible hosts more than a few days after ingesting an infectious blood meal. We examined whether holding fleas at subambient temperatures affected the transmissibility of Y. pestis by this vector. An infectious blood meal containing a virulent Y. pestis strain (CO96-3188) was given to colony-reared O. montana fleas. Potentially infected fleas were maintained at different temperatures (6°C, 10°C, 15°C, or 23°C). Transmission efficiencies were tested by allowing up to 15 infectious fleas to feed on each of 7 naïve CD-1 mice on days 1-4, 7, 10, 14, 17, and 21 postinfection (p.i.). Mice were monitored for signs of infection for 21 days after exposure to infectious fleas. Fleas held at 6°C, 10°C, and 15°C were able to effectively transmit at every time point p.i. The percentage of transmission to naïve mice by fleas maintained at low temperatures (46.0% at 6°C, 71.4% at 10°C, 66.7% at 15°C) was higher than for fleas maintained at 23°C (25.4%) and indicates that O. montana fleas efficiently transmit Y. pestis at low temperatures. Moreover, pooled percent per flea transmission efficiencies for flea cohorts maintained at temperatures of 10°C and 15°C (8.67% and 7.87%, respectively) showed a statistically significant difference in the pooled percent per flea transmission efficiency from fleas maintained at 23°C (1.94%). This is the first comprehensive study to demonstrate efficient transmission of Y. pestis by O. montana fleas maintained at temperatures as low as 6°C. Our findings further contribute to the understanding of plague ecology in temperate climates by providing support for the hypothesis that Y. pestis is able to overwinter within the flea gut and potentially cause infection during the following transmission season. The findings also might hold implications for explaining the focality of plague in tropical regions.
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Affiliation(s)
- Shanna K Williams
- Bacterial Diseases Branch, Division of Vector-Borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado, USA
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Restif O, Hayman DTS, Pulliam JRC, Plowright RK, George DB, Luis AD, Cunningham AA, Bowen RA, Fooks AR, O'Shea TJ, Wood JLN, Webb CT. Model-guided fieldwork: practical guidelines for multidisciplinary research on wildlife ecological and epidemiological dynamics. Ecol Lett 2012; 15:1083-94. [PMID: 22809422 PMCID: PMC3466409 DOI: 10.1111/j.1461-0248.2012.01836.x] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Revised: 02/02/2012] [Accepted: 06/20/2012] [Indexed: 12/25/2022]
Abstract
Infectious disease ecology has recently raised its public profile beyond the scientific community due to the major threats that wildlife infections pose to biological conservation, animal welfare, human health and food security. As we start unravelling the full extent of emerging infectious diseases, there is an urgent need to facilitate multidisciplinary research in this area. Even though research in ecology has always had a strong theoretical component, cultural and technical hurdles often hamper direct collaboration between theoreticians and empiricists. Building upon our collective experience of multidisciplinary research and teaching in this area, we propose practical guidelines to help with effective integration among mathematical modelling, fieldwork and laboratory work. Modelling tools can be used at all steps of a field-based research programme, from the formulation of working hypotheses to field study design and data analysis. We illustrate our model-guided fieldwork framework with two case studies we have been conducting on wildlife infectious diseases: plague transmission in prairie dogs and lyssavirus dynamics in American and African bats. These demonstrate that mechanistic models, if properly integrated in research programmes, can provide a framework for holistic approaches to complex biological systems.
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Affiliation(s)
- Olivier Restif
- Disease Dynamics Unit, Department of Veterinary Medicine, University of Cambridge, Cambridge, UK.
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Biofilm-dependent and biofilm-independent mechanisms of transmission of Yersinia pestis by fleas. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 954:237-43. [PMID: 22782769 DOI: 10.1007/978-1-4614-3561-7_30] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Gage KL. Factors Affecting the Spread and Maintenance of Plague. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 954:79-94. [DOI: 10.1007/978-1-4614-3561-7_11] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Schotthoefer AM, Bearden SW, Holmes JL, Vetter SM, Montenieri JA, Williams SK, Graham CB, Woods ME, Eisen RJ, Gage KL. Effects of temperature on the transmission of Yersinia Pestis by the flea, Xenopsylla Cheopis, in the late phase period. Parasit Vectors 2011; 4:191. [PMID: 21958555 PMCID: PMC3195756 DOI: 10.1186/1756-3305-4-191] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Accepted: 09/29/2011] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Traditionally, efficient flea-borne transmission of Yersinia pestis, the causative agent of plague, was thought to be dependent on a process referred to as blockage in which biofilm-mediated growth of the bacteria physically blocks the flea gut, leading to the regurgitation of contaminated blood into the host. This process was previously shown to be temperature-regulated, with blockage failing at temperatures approaching 30°C; however, the abilities of fleas to transmit infections at different temperatures had not been adequately assessed. We infected colony-reared fleas of Xenopsylla cheopis with a wild type strain of Y. pestis and maintained them at 10, 23, 27, or 30°C. Naïve mice were exposed to groups of infected fleas beginning on day 7 post-infection (p.i.), and every 3-4 days thereafter until day 14 p.i. for fleas held at 10°C, or 28 days p.i. for fleas held at 23-30°C. Transmission was confirmed using Y. pestis-specific antigen or antibody detection assays on mouse tissues. RESULTS Although no statistically significant differences in per flea transmission efficiencies were detected between 23 and 30°C, efficiencies were highest for fleas maintained at 23°C and they began to decline at 27 and 30°C by day 21 p.i. These declines coincided with declining median bacterial loads in fleas at 27 and 30°C. Survival and feeding rates of fleas also varied by temperature to suggest fleas at 27 and 30°C would be less likely to sustain transmission than fleas maintained at 23°C. Fleas held at 10°C transmitted Y. pestis infections, although flea survival was significantly reduced compared to that of uninfected fleas at this temperature. Median bacterial loads were significantly higher at 10°C than at the other temperatures. CONCLUSIONS Our results suggest that temperature does not significantly effect the per flea efficiency of Y. pestis transmission by X. cheopis, but that temperature is likely to influence the dynamics of Y. pestis flea-borne transmission, perhaps by affecting persistence of the bacteria in the flea gut or by influencing flea survival. Whether Y. pestis biofilm production is important for transmission at different temperatures remains unresolved, although our results support the hypothesis that blockage is not necessary for efficient transmission.
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Affiliation(s)
- Anna M Schotthoefer
- Bacterial Diseases Branch, Division of Vector Borne Diseases, National Center for Emerging and Zoonotic, Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO 80521, USA
- Marshfield Clinic Research Foundation, 1000 North Oak Avenue, Marshfield, WI 54449, USA
| | - Scott W Bearden
- Bacterial Diseases Branch, Division of Vector Borne Diseases, National Center for Emerging and Zoonotic, Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO 80521, USA
| | - Jennifer L Holmes
- Bacterial Diseases Branch, Division of Vector Borne Diseases, National Center for Emerging and Zoonotic, Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO 80521, USA
| | - Sara M Vetter
- Bacterial Diseases Branch, Division of Vector Borne Diseases, National Center for Emerging and Zoonotic, Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO 80521, USA
- Minnesota Department of Health, P. O. Box 64975, St Paul, MN 55164, USA
| | - John A Montenieri
- Bacterial Diseases Branch, Division of Vector Borne Diseases, National Center for Emerging and Zoonotic, Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO 80521, USA
| | - Shanna K Williams
- Bacterial Diseases Branch, Division of Vector Borne Diseases, National Center for Emerging and Zoonotic, Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO 80521, USA
| | - Christine B Graham
- Bacterial Diseases Branch, Division of Vector Borne Diseases, National Center for Emerging and Zoonotic, Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO 80521, USA
| | - Michael E Woods
- Bacterial Diseases Branch, Division of Vector Borne Diseases, National Center for Emerging and Zoonotic, Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO 80521, USA
- Lawrence Livermore National Laboratory, 7000 East Avenue. L-174, Livermore, CA 94550, USA
| | - Rebecca J Eisen
- Bacterial Diseases Branch, Division of Vector Borne Diseases, National Center for Emerging and Zoonotic, Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO 80521, USA
| | - Kenneth L Gage
- Bacterial Diseases Branch, Division of Vector Borne Diseases, National Center for Emerging and Zoonotic, Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO 80521, USA
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Abstract
Flea-borne zoonoses such as plague (Yersinia pestis) and murine typhus (Rickettsia typhi) caused significant numbers of human cases in the past and remain a public health concern. Other flea-borne human pathogens have emerged recently (e.g., Bartonella henselae, Rickettsia felis), and their mechanisms of transmission and impact on human health are not fully understood. Our review focuses on the ecology and epidemiology of the flea-borne bacterial zoonoses mentioned above with an emphasis on recent advancements in our understanding of how these organisms are transmitted by fleas, maintained in zoonotic cycles, and transmitted to humans. Emphasis is given to plague because of the considerable number of studies generated during the first decade of the twenty-first century that arose, in part, because of renewed interest in potential agents of bioterrorism, including Y. pestis.
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Affiliation(s)
- Rebecca J Eisen
- Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado 30333, USA.
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Buhnerkempe MG, Eisen RJ, Goodell B, Gage KL, Antolin MF, Webb CT. Transmission shifts underlie variability in population responses to Yersinia pestis infection. PLoS One 2011; 6:e22498. [PMID: 21799873 PMCID: PMC3143141 DOI: 10.1371/journal.pone.0022498] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Accepted: 06/28/2011] [Indexed: 11/23/2022] Open
Abstract
Host populations for the plague bacterium, Yersinia pestis, are highly variable in their response to plague ranging from near deterministic extinction (i.e., epizootic dynamics) to a low probability of extinction despite persistent infection (i.e., enzootic dynamics). Much of the work to understand this variability has focused on specific host characteristics, such as population size and resistance, and their role in determining plague dynamics. Here, however, we advance the idea that the relative importance of alternative transmission routes may vary causing shifts from epizootic to enzootic dynamics. We present a model that incorporates host and flea ecology with multiple transmission hypotheses to study how transmission shifts determine population responses to plague. Our results suggest enzootic persistence relies on infection of an off-host flea reservoir and epizootics rely on transiently maintained flea infection loads through repeated infectious feeds by fleas. In either case, early-phase transmission by fleas (i.e., transmission immediately following an infected blood meal) has been observed in laboratory studies, and we show that it is capable of driving plague dynamics at the population level. Sensitivity analysis of model parameters revealed that host characteristics (e.g., population size and resistance) vary in importance depending on transmission dynamics, suggesting that host ecology may scale differently through different transmission routes enabling prediction of population responses in a more robust way than using either host characteristics or transmission shifts alone.
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Affiliation(s)
- Michael G Buhnerkempe
- Department of Biology, Colorado State University, Fort Collins, Colorado, United States of America.
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Jachowski DS, Skipper S, Gompper ME. Field evaluation of imidacloprid as a systemic approach to flea control in black-tailed prairie dogs, Cynomys ludovicianus. JOURNAL OF VECTOR ECOLOGY : JOURNAL OF THE SOCIETY FOR VECTOR ECOLOGY 2011; 36:100-107. [PMID: 21635647 DOI: 10.1111/j.1948-7134.2011.00146.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Epizootic outbreaks of sylvatic plague have dramatically influenced prairie dog (Cynomys sp.) populations across North America. While a great deal of debate surrounds the cause and persistence of plague, flea control can stop the spread of plague epizootic outbreaks and even increase prairie dog survival under non-epizootic conditions. We investigated a newly-developed imidacloprid-treated grain bait that could potentially reduce flea infestations and mitigate the effects of plague on black-tailed prairie dogs (C. ludovicianus). We used a study design involving randomly assigned experimental and control study plots to assess the effectiveness of the systemic flea control product. We observed a significant difference in flea prevalence and abundance between experimental and control sites on three of the four sites treated with a single application of imidacloprid-treated grain bait for up to 90 days post-treatment. We observed an even greater reduction in flea infestations following the double application of treatment bait on two of three additional experimental sites. While we were unable to reduce flea infestations to the extent reported for more commonly used topical insecticides containing deltamethrin, imidacloprid might still be effective at reducing the risk of plague and halting epizootics. In addition, this systemic product can be more rapidly applied than topical insecticides, providing managers with a tool to quickly reduce flea infestations. Future research is needed to evaluate the effectiveness of different application timing and rates, the utility of the product in limiting plague, and the potential effects on non-target species that might also consume the treated bait.
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Affiliation(s)
- David S Jachowski
- U.S. Fish and Wildlife Service, South Dakota Ecological Services Field Office, Pierre, SD 57501, USA
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Hubbart JA, Jachowski DS, Eads DA. Seasonal and among-site variation in the occurrence and abundance of fleas on California ground squirrels (Otospermophilus beecheyi). JOURNAL OF VECTOR ECOLOGY : JOURNAL OF THE SOCIETY FOR VECTOR ECOLOGY 2011; 36:117-123. [PMID: 21635649 DOI: 10.1111/j.1948-7134.2011.00148.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
An improved understanding of the ecology of fleas on California ground squirrels, Otospermophilus beecheyi, is warranted given the role of fleas in the transmission, and perhaps persistence, of the plague-causing bacterium Yersinia pestis. We sampled O. beecheyi on a seasonal basis from three study sites, each representing a different land use type (preserve, pasture, and agriculture) in the San Joaquin Valley, CA. Overall, the abundance of fleas on squirrels was greatest in spring at the preserve site, in summer at the agriculture and pasture sites, and in winter at the pasture site. Hoplopsyllus anomalus, the species most frequently found on squirrels, was most abundant in spring at the preserve site and in summer at the agriculture and pasture sites. Oropsylla montana was most abundant in winter at the pasture site and on adult squirrels. Echidnophaga gallinacea was most abundant in fall on juvenile squirrels at the preserve site. All three flea species we encountered are known to be potential vectors of Y. pestis. Future efforts to predict flea species occurrence and abundance (and plague risk) at sites of concern should consider seasonal microclimatic conditions and the potential influence of human land use practices.
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Affiliation(s)
- Jason A Hubbart
- Department of Forestry and Soils, University of Missouri, Columbia, MO 65211, USA
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Yin JX, Geater A, Chongsuvivatwong V, Dong XQ, Du CH, Zhong YH. Predictors for abundance of host flea and floor flea in households of villages with endemic commensal rodent plague, Yunnan Province, China. PLoS Negl Trop Dis 2011; 5:e997. [PMID: 21468306 PMCID: PMC3066137 DOI: 10.1371/journal.pntd.0000997] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2010] [Accepted: 03/03/2011] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND From 1990 to 2006, fifty-five natural villages experienced at least one plague epidemic in Lianghe County, Yunnan Province, China. This study is aimed to document flea abundance and identify predictors in households of villages with endemic commensal rodent plague in Lianghe County. METHODS Trappings were used to collect fleas and interviews were conducted to gather demography, environmental factors, and other relevant information. Multivariate hurdle negative binomial model was applied to identify predictors for flea abundance. RESULTS A total of 344 fleas were collected on 101 small mammals (94 Rattus flavipectus and 7 Suncus murinus). R. flavipectus had higher flea prevalence and abundance than S. murinus, but the flea intensities did not differ significantly. A total of 315 floor fleas were captured in 104 households. Xenopsylla cheopis and Ctenocephalides felis felis were the predominant flea species on the host and the floor flea, respectively. The presence of small mammal faeces and R. flavipectus increased host flea prevalence odds 2.9- and 10-fold, respectively. Keeping a dog in the house increased floor flea prevalence odds 2-fold. Keeping cattle increased floor flea intensity by 153%. Villages with over 80% of houses raising chickens had increased prevalence odds and intensity of floor flea about 2.9- and 11.6-fold, respectively. The prevalence and intensity of floor flea in brick and wood houses were decreased by 60% and 90%, respectively. Flea prevalences of host and floor flea in the households that were adjacent to other houses were increased 7.4- and 2.2-fold, respectively. Houses with a paddy nearby decreased host flea intensity by 53%, while houses with an outside toilet increased host flea intensity by 125%. CONCLUSION Rodent control alone may not be sufficient to control plague risk in these areas. In order to have successful results, plague control programs should pay attention to ecological and hygiene factors that influence flea populations.
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Affiliation(s)
- Jia-Xiang Yin
- Yunnan Institute of Endemic Disease Control and Prevention, Dali City, Yunnan Province, People's Republic of China.
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Schotthoefer AM, Bearden SW, Vetter SM, Holmes J, Montenieri JA, Graham CB, Woods ME, Eisen RJ, Gage KL. Effects of temperature on early-phase transmission of Yersina pestis by the flea, Xenopsylla cheopis. JOURNAL OF MEDICAL ENTOMOLOGY 2011; 48:411-417. [PMID: 21485382 DOI: 10.1603/me10155] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Sharp declines in human and animal cases of plague, caused by the bacterium Yersinia pestis (Yersin), have been observed when outbreaks coincide with hot weather. Failure of biofilm production, or blockage, to occur in the flea, as temperatures reach 30 degrees C has been suggested as an explanation for these declines. Recent work demonstrating efficient flea transmission during the first few days after fleas have taken an infectious blood meal, in the absence of blockage (e.g., early-phase transmission), however, has called this hypothesis into question. To explore the potential effects of temperature on early-phase transmission, we infected colony-reared Xenopsylla cheopis (Rothchild) fleas with a wild-type strain of plague bacteria using an artificial feeding system, and held groups of fleas at 10, 23, 27, and 30 degrees C. Naive Swiss Webster mice were exposed to fleas from each of these temperatures on days 1-4 postinfection, and monitored for signs of infection for 21 d. Temperature did not significantly influence the rates of transmission observed for fleas held at 23, 27, and 30 degrees C. Estimated per flea transmission efficiencies for these higher temperatures ranged from 2.32 to 4.96% (95% confidence interval [CI]: 0.96-8.74). In contrast, no transmission was observed in mice challenged by fleas held at 10 degrees C (per flea transmission efficiency estimates, 0-1.68%). These results suggest that declines in human and animal cases during hot weather are not related to changes in the abilities of X. cheopis fleas to transmit Y. pestis infections during the early-phase period. By contrast, transmission may be delayed or inhibited at low temperatures, indicating that epizootic spread of Y. pestis by X. cheopis via early-phase transmission is unlikely during colder periods of the year.
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Affiliation(s)
- Anna M Schotthoefer
- Bacterial Diseases Branch, Division of Vector Borne Infectious Diseases, National Center for Emerging and Zoonotic, Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO 80521, USA.
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