1
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Pauling CD, Finke DL, Anderson DM. Interrelationship of soil moisture and temperature to sylvatic plague cycle among prairie dogs in the Western United States. Integr Zool 2021; 16:852-867. [PMID: 34219394 DOI: 10.1111/1749-4877.12567] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Plague, caused by Yersinia pestis, is a flea-borne disease that is endemic in areas throughout the world due to its successful maintenance in a sylvatic cycle, mainly in areas with temperate climates. Burrowing rodents are thought to play a key role in the enzootic maintenance as well as epizootic outbreaks of plague. In the United States, prairie dogs (Cynomys), rodents (Muridae), and ground squirrels (Spermophilus) are susceptible to infection and are parasitized by fleas that transmit plague. In particular, prairie dogs can experience outbreaks that rapidly spread, which can lead to extirpation of colonies. A number of ecological parameters, including climate, are associated with these epizootics. In this study, we asked whether soil parameters, primarily moisture and temperature, are associated with outbreaks of plague in black-tailed prairie dogs and Gunnison's prairie dogs in the Western United States, and at what depth these associations were apparent. We collected publicly available county-level information on the occurrence of population declines or colony extirpation, while historical soil data was collected from SCAN and USCRN stations in counties and states where prairie dogs have been located. The analysis suggests that soil moisture at lower depths correlates with colony die-offs, in addition to temperature near the surface, with key differences within the landscape ecology that impact the occurrence of plague. Overall, the model suggests that the burrow environment may play a significant role in the epizootic spread of disease amongst black-tailed and Gunnison's prairie dogs.
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Affiliation(s)
- Cassandra D Pauling
- Department of Veterinary Pathobiology, University of Missouri, Columbia, Missouri, USA
| | - Deborah L Finke
- Division of Plant Sciences, University of Missouri, Columbia, Missouri, USA
| | - Deborah M Anderson
- Department of Veterinary Pathobiology, University of Missouri, Columbia, Missouri, USA
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2
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Krauer F, Viljugrein H, Dean KR. The influence of temperature on the seasonality of historical plague outbreaks. Proc Biol Sci 2021; 288:20202725. [PMID: 34255997 PMCID: PMC8277479 DOI: 10.1098/rspb.2020.2725] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Accepted: 06/04/2021] [Indexed: 01/13/2023] Open
Abstract
Modern plague outbreaks exhibit a distinct seasonal pattern. By contrast, the seasonality of historical outbreaks and its drivers has not been studied systematically. Here, we investigate the seasonal pattern, the epidemic peak timing and growth rates, and the association with latitude, temperature, and precipitation using a large, novel dataset of plague- and all-cause mortality during the Second Pandemic in Europe and the Mediterranean. We show that epidemic peak timing followed a latitudinal gradient, with mean annual temperature negatively associated with peak timing. Based on modern temperature data, the predicted epidemic growth of all outbreaks was positive between 11.7°C and 21.5°C with a maximum around 17.3°C. Hence, our study provides evidence that the growth of plague epidemics across the whole study region depended on similar absolute temperature thresholds. Here, we present a systematic analysis of the seasonality of historical plague in the Northern Hemisphere, and we show consistent evidence for a temperature-related process influencing the epidemic peak timing and growth rates of plague epidemics.
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Affiliation(s)
- Fabienne Krauer
- Centre for Ecological and Evolutionary Synthesis CEES, University of Oslo, Norway
- Centre for Mathematical Modelling of Infectious Diseases CMMID, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK
| | - Hildegunn Viljugrein
- Centre for Ecological and Evolutionary Synthesis CEES, University of Oslo, Norway
- Norwegian Veterinary Institute, Ås, Norway
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3
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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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4
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Barbieri R, Drancourt M, Raoult D. The role of louse-transmitted diseases in historical plague pandemics. THE LANCET. INFECTIOUS DISEASES 2020; 21:e17-e25. [PMID: 33035476 DOI: 10.1016/s1473-3099(20)30487-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 04/21/2020] [Accepted: 04/21/2020] [Indexed: 11/25/2022]
Abstract
The rodent-murine ectoparasite-human model of plague transmission does not correspond with historical details around plague pandemics in Europe. New analysis of ancient genomes reveal that Yersinia pestis was unable to be transmitted by rat fleas until around 4000 Before Present, which challenges the rodent-murine ectoparasite-human model of plague transmission and historical details around plague pandemics in Europe. In this Review, we summarise data regarding Y pestis transmission by human lice in the context of genomic evolution and co-transmission of other major epidemic deadly pathogens throughout human history, with the aim of broadening our view of plague transmission. Experimental models support the efficiency of human lice as plague vectors through infected faeces, which suggest that Y pestis could be a louse-borne disease, similar to Borrelia recurrentis, Rickettsia prowazekii, and Bartonella quintana. Studies have shown that louse-borne outbreaks often involve multiple pathogens, and several cases of co-transmission of Y pestis and B quintana have been reported. Furthermore, an exclusive louse-borne bacterium, namely B recurrentis, was found to be circulating in northern Europe during the second plague pandemic (14th-18th century). Current data make it possible to attribute large historical pandemics to multiple bacteria, and suggests that human lice probably played a preponderant role in the interhuman transmission of plague and pathogen co-transmission during previous large epidemics, including plague pandemics.
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Affiliation(s)
- Rémi Barbieri
- Aix-Marseille Université, Institut de Recherche pour le Développement, Microbes, Evolution, Phylogénie et Infection, Institut Hospitalo-Universitaire Méditerranée Infection, Marseille, France; Aix-Marseille Université, Centre National de la Recherche Scientifique, Établissement Français du Sang, Anthropologie Bio-culturelle, Droit, Éthique et Santé, Marseille, France; Fondation Méditerranée Infection, Marseille, France
| | - Michel Drancourt
- Aix-Marseille Université, Institut de Recherche pour le Développement, Microbes, Evolution, Phylogénie et Infection, Institut Hospitalo-Universitaire Méditerranée Infection, Marseille, France
| | - Didier Raoult
- Aix-Marseille Université, Institut de Recherche pour le Développement, Microbes, Evolution, Phylogénie et Infection, Institut Hospitalo-Universitaire Méditerranée Infection, Marseille, France; Fondation Méditerranée Infection, Marseille, France.
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5
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Tennant WSD, Tildesley MJ, Spencer SEF, Keeling MJ. Climate drivers of plague epidemiology in British India, 1898-1949. Proc Biol Sci 2020; 287:20200538. [PMID: 32517609 PMCID: PMC7341932 DOI: 10.1098/rspb.2020.0538] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 05/19/2020] [Indexed: 01/14/2023] Open
Abstract
Plague, caused by Yersinia pestis infection, continues to threaten low- and middle-income countries throughout the world. The complex interactions between rodents and fleas with their respective environments challenge our understanding of human plague epidemiology. Historical long-term datasets of reported plague cases offer a unique opportunity to elucidate the effects of climate on plague outbreaks in detail. Here, we analyse monthly plague deaths and climate data from 25 provinces in British India from 1898 to 1949 to generate insights into the influence of temperature, rainfall and humidity on the occurrence, severity and timing of plague outbreaks. We find that moderate relative humidity levels of between 60% and 80% were strongly associated with outbreaks. Using wavelet analysis, we determine that the nationwide spread of plague was driven by changes in humidity, where, on average, a one-month delay in the onset of rising humidity translated into a one-month delay in the timing of plague outbreaks. This work can inform modern spatio-temporal predictive models for the disease and aid in the development of early-warning strategies for the deployment of prophylactic treatments and other control measures.
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Affiliation(s)
- Warren S. D. Tennant
- The Zeeman Institute: SBIDER, University of Warwick, Coventry CV4 7AL, UK
- Mathematics Institute, University of Warwick, Coventry CV4 7AL, UK
| | - Mike J. Tildesley
- The Zeeman Institute: SBIDER, University of Warwick, Coventry CV4 7AL, UK
- Mathematics Institute, University of Warwick, Coventry CV4 7AL, UK
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK
| | - Simon E. F. Spencer
- The Zeeman Institute: SBIDER, University of Warwick, Coventry CV4 7AL, UK
- Department of Statistics, University of Warwick, Coventry CV4 7AL, UK
| | - Matt J. Keeling
- The Zeeman Institute: SBIDER, University of Warwick, Coventry CV4 7AL, UK
- Mathematics Institute, University of Warwick, Coventry CV4 7AL, UK
- School of Life Sciences, University of Warwick, Coventry CV4 7AL, UK
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6
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Xu L, Stige LC, Leirs H, Neerinckx S, Gage KL, Yang R, Liu Q, Bramanti B, Dean KR, Tang H, Sun Z, Stenseth NC, Zhang Z. Historical and genomic data reveal the influencing factors on global transmission velocity of plague during the Third Pandemic. Proc Natl Acad Sci U S A 2019; 116:11833-11838. [PMID: 31138696 PMCID: PMC6584904 DOI: 10.1073/pnas.1901366116] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Quantitative knowledge about which natural and anthropogenic factors influence the global spread of plague remains sparse. We estimated the worldwide spreading velocity of plague during the Third Pandemic, using more than 200 years of extensive human plague case records and genomic data, and analyzed the association of spatiotemporal environmental factors with spreading velocity. Here, we show that two lineages, 2.MED and 1.ORI3, spread significantly faster than others, possibly reflecting differences among strains in transmission mechanisms and virulence. Plague spread fastest in regions with low population density and high proportion of pasture- or forestland, findings that should be taken into account for effective plague monitoring and control. Temperature exhibited a nonlinear, U-shaped association with spread speed, with a minimum around 20 °C, while precipitation showed a positive association. Our results suggest that global warming may accelerate plague spread in warm, tropical regions and that the projected increased precipitation in the Northern Hemisphere may increase plague spread in relevant regions.
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Affiliation(s)
- Lei Xu
- State Key Laboratory of Integrated Management on Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, 100101 Beijing, China
- Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, N-0316 Oslo, Norway
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, 102206 Beijing, China
- Ministry of Education Key Laboratory for Earth System Modeling, Department of Earth System Science, Tsinghua University, 100084 Beijing, China
| | - Leif C Stige
- Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, N-0316 Oslo, Norway
| | - Herwig Leirs
- Evolutionary Ecology Group, Department of Biology, University of Antwerp, 2020 Antwerp, Belgium
| | - Simon Neerinckx
- Evolutionary Ecology Group, Department of Biology, University of Antwerp, 2020 Antwerp, Belgium
| | - Kenneth L Gage
- Bacterial Diseases Branch, Division of Vector-Borne Disease, Centers for Disease Control and Prevention, Fort Collins, CO 80523
| | - Ruifu Yang
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, 100071 Beijing, China
| | - Qiyong Liu
- State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, 102206 Beijing, China
| | - Barbara Bramanti
- Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, N-0316 Oslo, Norway
| | - Katharine R Dean
- Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, N-0316 Oslo, Norway
| | - Hui Tang
- Department of Geosciences, University of Oslo, N-0316 Oslo, Norway
| | - Zhe Sun
- Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, N-0316 Oslo, Norway
- Ministry of Education Key Laboratory for Earth System Modeling, Department of Earth System Science, Tsinghua University, 100084 Beijing, China
| | - Nils Chr Stenseth
- Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, N-0316 Oslo, Norway;
- Ministry of Education Key Laboratory for Earth System Modeling, Department of Earth System Science, Tsinghua University, 100084 Beijing, China
| | - Zhibin Zhang
- State Key Laboratory of Integrated Management on Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, 100101 Beijing, China;
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7
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Russell RE, Abbott RC, Tripp DW, Rocke TE. Local factors associated with on-host flea distributions on prairie dog colonies. Ecol Evol 2018; 8:8951-8972. [PMID: 30271558 PMCID: PMC6157659 DOI: 10.1002/ece3.4390] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 06/01/2018] [Accepted: 06/14/2018] [Indexed: 11/07/2022] Open
Abstract
Outbreaks of plague, a flea-vectored bacterial disease, occur periodically in prairie dog populations in the western United States. In order to understand the conditions that are conducive to plague outbreaks and potentially predict spatial and temporal variations in risk, it is important to understand the factors associated with flea abundance and distribution that may lead to plague outbreaks. We collected and identified 20,041 fleas from 6,542 individual prairie dogs of four different species over a 4-year period along a latitudinal gradient from Texas to Montana. We assessed local climate and other factors associated with flea prevalence and abundance, as well as the incidence of plague outbreaks. Oropsylla hirsuta, a prairie dog specialist flea, and Pulex simulans, a generalist flea species, were the most common fleas found on our pairs. High elevation pairs in Wyoming and Utah had distinct flea communities compared with the rest of the study pairs. The incidence of prairie dogs with Yersinia pestis detections in fleas was low (n = 64 prairie dogs with positive fleas out of 5,024 samples from 4,218 individual prairie dogs). The results of our regression models indicate that many factors are associated with the presence of fleas. In general, flea abundance (number of fleas on hosts) is higher during plague outbreaks, lower when prairie dogs are more abundant, and reaches peak levels when climate and weather variables are at intermediate levels. Changing climate conditions will likely affect aspects of both flea and host communities, including population densities and species composition, which may lead to changes in plague dynamics. Our results support the hypothesis that local conditions, including host, vector, and environmental factors, influence the likelihood of plague outbreaks, and that predicting changes to plague dynamics under climate change scenarios will have to consider both host and vector responses to local factors.
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Affiliation(s)
- Robin E. Russell
- U.S. Geological SurveyNational Wildlife Health CenterMadisonWisconsin
| | - Rachel C. Abbott
- U.S. Geological SurveyNational Wildlife Health CenterMadisonWisconsin
| | - Daniel W. Tripp
- Colorado Division of Parks and WildlifeWildlife Health ProgramFort CollinsColorado
| | - Tonie E. Rocke
- U.S. Geological SurveyNational Wildlife Health CenterMadisonWisconsin
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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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9
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Du HW, Wang Y, Zhuang DF, Jiang XS. Temporal and spatial distribution characteristics in the natural plague foci of Chinese Mongolian gerbils based on spatial autocorrelation. Infect Dis Poverty 2017; 6:124. [PMID: 28780908 PMCID: PMC5545858 DOI: 10.1186/s40249-017-0338-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Accepted: 07/20/2017] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND The nest flea index of Meriones unguiculatus is a critical indicator for the prevention and control of plague, which can be used not only to detect the spatial and temporal distributions of Meriones unguiculatus, but also to reveal its cluster rule. This research detected the temporal and spatial distribution characteristics of the plague natural foci of Mongolian gerbils by body flea index from 2005 to 2014, in order to predict plague outbreaks. METHODS Global spatial autocorrelation was used to describe the entire spatial distribution pattern of the body flea index in the natural plague foci of typical Chinese Mongolian gerbils. Cluster and outlier analysis and hot spot analysis were also used to detect the intensity of clusters based on geographic information system methods. The quantity of M. unguiculatus nest fleas in the sentinel surveillance sites from 2005 to 2014 and host density data of the study area from 2005 to 2010 used in this study were provided by Chinese Center for Disease Control and Prevention. RESULTS The epidemic focus regions of the Mongolian gerbils remain the same as the hot spot regions relating to the body flea index. High clustering areas possess a similar pattern as the distribution pattern of the body flea index indicating that the transmission risk of plague is relatively high. In terms of time series, the area of the epidemic focus gradually increased from 2005 to 2007, declined rapidly in 2008 and 2009, and then decreased slowly and began trending towards stability from 2009 to 2014. For the spatial change, the epidemic focus regions began moving northward from the southwest epidemic focus of the Mongolian gerbils from 2005 to 2007, and then moved from north to south in 2007 and 2008. CONCLUSIONS The body flea index of Chinese gerbil foci reveals significant spatial and temporal aggregation characteristics through the employing of spatial autocorrelation. The diversity of temporary and spatial distribution is mainly affected by seasonal variation, the human activity and natural factors.
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Affiliation(s)
- Hai-Wen Du
- State Key Laboratory of Resources and Environmental Information Systems, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, 11A Datun Road, Chaoyang District, Beijing, 100101, China.,College of Resources and Environmental Science, Nanjing Agricultural University, No.6 Tongwei Road, Nangjing, 210095, China
| | - Yong Wang
- State Key Laboratory of Resources and Environmental Information Systems, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, 11A Datun Road, Chaoyang District, Beijing, 100101, China.
| | - Da-Fang Zhuang
- State Key Laboratory of Resources and Environmental Information Systems, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, 11A Datun Road, Chaoyang District, Beijing, 100101, China
| | - Xiao-San Jiang
- College of Resources and Environmental Science, Nanjing Agricultural University, No.6 Tongwei Road, Nangjing, 210095, China.
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10
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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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11
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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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Yang R, Cui Y, Bi Y. Perspectives on Yersinia pestis: A Model for Studying Zoonotic Pathogens. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 918:377-391. [PMID: 27722871 DOI: 10.1007/978-94-024-0890-4_14] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Yersinia pestis is a typical zoonotic bacterial pathogen. The following reasons make this pathogen a model for studying zoonotic pathogens: (1) Its unique lifestyle makes Y. pestis an ideal model for studying host-vector-environment-pathogen interactions; (2) population diversity characters in Y. pestis render it a model species for studying monomorphic bacterial evolution; (3) the pathogenic features of bacteria provide us with good opportunities to study human immune responses; (4) typical animal and vector models of Y. pestis infection create opportunities for experimental studies on pathogenesis and evolution; and (5) repeated pandemics and local outbreaks provide us with clues about the infectious disease outbreaks that have occurred in human history.
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Affiliation(s)
- Ruifu Yang
- Beijing Institute of Microbiology and Epidemiology, No. 20, Dongdajie, Fengtai, Beijing, 100071, China.
| | - Yujun Cui
- Beijing Institute of Microbiology and Epidemiology, No. 20, Dongdajie, Fengtai, Beijing, 100071, China
| | - Yujing Bi
- Beijing Institute of Microbiology and Epidemiology, No. 20, Dongdajie, Fengtai, Beijing, 100071, China
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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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Climate-driven introduction of the Black Death and successive plague reintroductions into Europe. Proc Natl Acad Sci U S A 2015; 112:3020-5. [PMID: 25713390 DOI: 10.1073/pnas.1412887112] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The Black Death, originating in Asia, arrived in the Mediterranean harbors of Europe in 1347 CE, via the land and sea trade routes of the ancient Silk Road system. This epidemic marked the start of the second plague pandemic, which lasted in Europe until the early 19th century. This pandemic is generally understood as the consequence of a singular introduction of Yersinia pestis, after which the disease established itself in European rodents over four centuries. To locate these putative plague reservoirs, we studied the climate fluctuations that preceded regional plague epidemics, based on a dataset of 7,711 georeferenced historical plague outbreaks and 15 annually resolved tree-ring records from Europe and Asia. We provide evidence for repeated climate-driven reintroductions of the bacterium into European harbors from reservoirs in Asia, with a delay of 15 ± 1 y. Our analysis finds no support for the existence of permanent plague reservoirs in medieval Europe.
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Pumhom P, Morand S, Tran A, Jittapalapong S, Desquesnes M. Trypanosoma from rodents as potential source of infection in human-shaped landscapes of South-East Asia. Vet Parasitol 2014; 208:174-80. [PMID: 25613476 DOI: 10.1016/j.vetpar.2014.12.027] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Revised: 12/18/2014] [Accepted: 12/18/2014] [Indexed: 10/24/2022]
Abstract
Reports of atypical human cases of Trypanosoma lewisi or T. lewisi-like and Trypanosoma evansi infections have increased in South-East Asia, urging to investigate the possible links between humans, animal reservoirs and habitats. We tested how habitat structure affects the infection by Trypanosoma species of common murine rodents, inhabiting human-dominated landscapes in South East Asia. For this, we used geo-referenced data of rodents investigated for Trypanosoma infection and land cover maps produced for seven study sites in Thailand, Cambodia and Lao PDR. High prevalence of infection by T. lewisi was observed in rodents living near human settlement and in areas with high cover of built-up habitat, while the infection of rodents by T. evansi was explained by increased landscape patchiness and high cover of rain-fed agriculture lands. These results suggest a likely role of wild rodents as reservoir and possible source of atypical human infection by animal trypanosomes.
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Affiliation(s)
- Pornpan Pumhom
- Center for Agricultural Biotechnology, Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom, Thailand; Center of Excellence on Agricultural Biotechnology (AG-BIO/PERDO-CHE), Bangkok, Thailand; Department of Parasitology, Faculty of Veterinary Medicine, Kasetsart University, Bangkok, Thailand
| | - Serge Morand
- CIRAD, UPR Animal et Gestion Intégrée des Risques, F-34398 Montpellier, France; CNRS-CIRAD, Centre d'Infectiologie Christophe Mérieux du Laos, Vientiane, Lao Democratic People's Republic
| | - Annelise Tran
- CIRAD, UPR Animal et Gestion Intégrée des Risques, F-34398 Montpellier, France; CIRAD, UMR Territoires Environnement Télédétection et Information Spatiale, F-34093 Montpellier, France
| | - Sathaporn Jittapalapong
- Center of Excellence on Agricultural Biotechnology (AG-BIO/PERDO-CHE), Bangkok, Thailand; Department of Parasitology, Faculty of Veterinary Medicine, Kasetsart University, Bangkok, Thailand.
| | - Marc Desquesnes
- Department of Parasitology, Faculty of Veterinary Medicine, Kasetsart University, Bangkok, Thailand; CIRAD-Bios, UMR17 InterTryp, Montpellier F-34000, France
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Andrianaivoarimanana V, Kreppel K, Elissa N, Duplantier JM, Carniel E, Rajerison M, Jambou R. Understanding the persistence of plague foci in Madagascar. PLoS Negl Trop Dis 2013; 7:e2382. [PMID: 24244760 PMCID: PMC3820717 DOI: 10.1371/journal.pntd.0002382] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Plague, a zoonosis caused by Yersinia pestis, is still found in Africa, Asia, and the Americas. Madagascar reports almost one third of the cases worldwide. Y. pestis can be encountered in three very different types of foci: urban, rural, and sylvatic. Flea vector and wild rodent host population dynamics are tightly correlated with modulation of climatic conditions, an association that could be crucial for both the maintenance of foci and human plague epidemics. The black rat Rattus rattus, the main host of Y. pestis in Madagascar, is found to exhibit high resistance to plague in endemic areas, opposing the concept of high mortality rates among rats exposed to the infection. Also, endemic fleas could play an essential role in maintenance of the foci. This review discusses recent advances in the understanding of the role of these factors as well as human behavior in the persistence of plague in Madagascar.
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Affiliation(s)
- Voahangy Andrianaivoarimanana
- Unité Peste, Institut Pasteur de Madagascar, Antananarivo, Madagascar
- Unité d'Immunologie, Institut Pasteur de Madagascar, Antananarivo, Madagascar
| | - Katharina Kreppel
- Department of Veterinary Clinical Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Nohal Elissa
- Unité d'Entomologie, Institut Pasteur de Madagascar, Antananarivo, Madagascar
| | | | | | | | - Ronan Jambou
- Unité d'Immunologie, Institut Pasteur de Madagascar, Antananarivo, Madagascar
- * E-mail:
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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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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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