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Yasuko Rikihisa - One of the best experts on this subject based on the ideXlab platform.
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Subversion of RAB5-regulated autophagy by the intracellular pathogen Ehrlichia Chaffeensis.
Small GTPases, 2017Co-Authors: Yasuko RikihisaAbstract:ABSTRACTIntracellular pathogens often exploit RAB functions to establish a safe haven in which to survive and proliferate. Ehrlichia Chaffeensis, an obligatory intracellular bacterium, resides in specialized membrane-bound inclusions that have early endosome–like characteristics, e.g., resident RAB5 GTPase and RAB5 effectors, including VPS34 (the catalytic subunit of class III phosphatidylinositol 3-kinase), but the inclusions lack late endosomal or lysosomal markers. Within inclusions, Ehrlichia obtains host-derived nutrients by inducing RAB5-regulated autophagy using Ehrlichia translocated factor-1 deployed by its type IV secretion system. This manipulation of RAB5 by a bacterial molecule offers a simple strategy for Ehrlichia to avoid destruction in lysosomes and obtain nutrients, membrane components, and a homeostatic intra-host-cell environment in which to grow.
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Molecular Pathogenesis of Ehrlichia Chaffeensis Infection.
Annual review of microbiology, 2015Co-Authors: Yasuko RikihisaAbstract:Ehrlichia Chaffeensis is an obligatory intracellular and cholesterol-dependent bacterium that has evolved special proteins and functions to proliferate inside leukocytes and cause disease. E. Chaffeensis has a multigene family of major outer membrane proteins with porin activity and induces infectious entry using its entry-triggering protein to bind the human cell surface protein DNase X. During intracellular replication, three functional pairs of two-component systems are sequentially expressed to regulate metabolism, aggregation, and the development of stress-resistance traits for transmission. A type IV secretion effector of E. Chaffeensis blocks mitochondrion-mediated host cell apoptosis. Several type I secretion proteins are secreted at the Ehrlichia-host interface. E. Chaffeensis strains induce strikingly variable inflammation in mice. The central role of MyD88, but not Toll-like receptors, suggests that Ehrlichia species have unique inflammatory molecules. A recent report about transient targeted mutagenesis and random transposon mutagenesis suggests that stable targeted knockouts may become feasible in Ehrlichia.
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Penicillin-binding protein of Ehrlichia Chaffeensis: cytokine induction through MyD88-dependent pathway
The Journal of infectious diseases, 2012Co-Authors: Mohd. Akhlakur Rahman, Zhihui Cheng, Junji Matsuo, Yasuko RikihisaAbstract:Background. Human monocytic ehrlichiosis is one of the most prevalent tick-borne zoonoses caused by infection with Ehrlichia Chaffeensis. Although E. Chaffeensis lacks entire lipopolysaccharide and most peptidoglycan biosynthesis genes, it induces inflammatory cytokines and chemokines. Ehrlichia Chaffeensis components that induce inflammation and the responsive host cell pathway are not known. Methods. Expression of penicillin-binding protein (PBP) in E. Chaffeensis was analyzed by reverse-transcription polymerase chain reaction and Bocillin FL binding assay. Next, recombinant PBP, which was high-pressure liquid chromatography purified, and native PBP of E. Chaffeensis were investigated for their ability to induce proinflammatory cytokines in the human monocytic leukemia cell line THP-1 and bone marrow–derived macrophages (BMDMs) from wild-type and MyD88 knockout mice. Results. Expression of PBP by E. Chaffeensis was upregulated during its intracellular life cycle. PBP induced interleukin 8 or CXCL2, tumor necrosis factor α, interleukin 1β, and interleukin 10 in THP-1 cells and BMDMs. Cytokine induction by PBP was MyD88-dependent. Removal of PBP from E. Chaffeensis lysate using penicillin affinity column and a complementation assay confirmed cytokine-inducing activity of native PBP. Conclusions. The cytokine-inducing activity by E. Chaffeensis PBP provides novel insights into pathogenassociated molecular patterns and pathogenesis of E. Chaffeensis infection.
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Anaplasma phagocytophilum and Ehrlichia Chaffeensis : subversive manipulators of host cells
Nature reviews. Microbiology, 2010Co-Authors: Yasuko RikihisaAbstract:Anaplasma spp. and Ehrlichia spp. cause several emerging human infectious diseases. Anaplasma phagocytophilum and Ehrlichia Chaffeensis are transmitted between mammals by blood-sucking ticks and replicate inside mammalian white blood cells and tick salivary-gland and midgut cells. Adaptation to a life in eukaryotic cells and transmission between hosts has been assisted by the deletion of many genes that are present in the genomes of free-living bacteria (including genes required for the biosynthesis of lipopolysaccharide and peptidoglycan), by the acquisition of a cholesterol uptake pathway and by the expansion of the repertoire of genes encoding the outer-membrane porins and type IV secretion system. Here, I review the specialized properties and other adaptations of these intracellular bacteria.
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Anaplasma phagocytophilum and Ehrlichia Chaffeensis : subversive manipulators of host cells
Nature Reviews Microbiology, 2010Co-Authors: Yasuko RikihisaAbstract:Anaplasma phagocytophilum and Ehrlichia Chaffeensis cause the emerging zoonoses human granulocytic anaplasmosis and human monocytic ehrlichiosis, respectively, which are among the most prevalent life-threatening tick-borne zoonoses in the United States. Yasuko Rikihisa reviews the adaptations of these obligate intracellular bacteria that allow them to subvert and manipulate host cells.
Susan E. Little - One of the best experts on this subject based on the ideXlab platform.
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Co-infection of white-tailed deer with multiple strains of Ehrlichia Chaffeensis.
Vector borne and zoonotic diseases (Larchmont N.Y.), 2006Co-Authors: Andrea S. Varela-stokes, William R. Davidson, John V. Stokes, Susan E. LittleAbstract:We investigated the effect of exposing deer to multiple strains of Ehrlichia Chaffeensis that differed in number of tandem repeats in either the variable-length PCR target (VLPT) gene or 120 kDa antigen gene. We hypothesized that infection with one strain would provide immunity to infection with other strains of E. Chaffeensis. All deer initially exposed to strain A (604-2) became PCR and culture positive by 10 days post-infection (DPI). Three deer infected with strain A and subsequently inoculated with strain B (623-4) became infected with strain B. Two deer infected with strain A and subsequently inoculated with strain C (125B) became infected with strain C. Of three deer, each infected with strain B and subsequently inoculated with strain C, one was PCR positive for strain C. Of three deer previously inoculated with both strains A and B, and subsequently inoculated with strain C, one showed delayed evidence of strain C. Western blot analysis demonstrated that deer sera reacted differently to antigens f...
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Primary and secondary infection with Ehrlichia Chaffeensis in white-tailed deer (Odocoileus virginianus).
Vector borne and zoonotic diseases (Larchmont N.Y.), 2005Co-Authors: Andrea S. Varela, William R. Davidson, David E. Stallknecht, Elizabeth W. Howerth, Michael J Yabsley, Victor A. Moore, Susan E. LittleAbstract:White-tailed deer (Odocoileus virginianus) are the principal reservoir host for Ehrlichia Chaffeensis, causative agent of human monocytic ehrlichiosis (HME). Because white-tailed deer maintain a long-term infection with E. Chaffeensis and because deer can be naturally exposed to multiple strains of E. Chaffeensis, we evaluated the response to secondary infection of E. Chaffeensis in deer. For primary infection, six white-tailed deer were injected with 5.4 × 106 DH82 cells infected with the Arkansas strain of E. Chaffeensis (Ark) and two control deer were injected with noninfected DH82 cells. On post-infection day 54, three E. Chaffeensis (Ark) infected deer and one naive deer were injected with 4.2 × 106 cells infected with strain WTD-6045B E. Chaffeensis, which differs from the Arkansas strain by number of nucleotide repeats in the variable length PCR target (VLPT) gene; three other Arkansas strain infected deer were injected with noninfected DH82 cells. All animals were monitored for 31 additional days....
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Attempted experimental infection of domestic goats with Ehrlichia Chaffeensis.
Vector borne and zoonotic diseases (Larchmont N.Y.), 2004Co-Authors: Vivien G. Dugan, David E. Stallknecht, Andrea S. Varela, Colin C. Hurd, Susan E. LittleAbstract:Although white-tailed deer (WTD; Odocoileus virginianus ) are considered the primary natural reservoir host for Ehrlichia Chaffeensis, the causative agent of human monocytotropic ehrlichiosis, the potential role of other vertebrates as reservoir hosts has not been fully explored. Because domestic goats are naturally infected in areas where E. Chaffeensis is endemic in deer, we evaluated the susceptibility of domestic goats to experimental infection with E. Chaffeensis. A total of 12 goats were inoculated with E. Chaffeensis (15B-WTD-GA or Ark strain)-infected DH82 cells by one of three routes: intravenously, subcutaneously, or intradermally. White-tailed deer simultaneously inoculated with the same dose, route, and inoculum served as positive controls; additional goats and WTD were included as negative controls. Evidence of E. Chaffeensis infection was evaluated in all animals by indirect fluorescent antibody assay, PCR, and cell culture isolation techniques. All goats exposed to E. Chaffeensis seroconverted by 14 days post-infection (DPI), and E. Chaffeensis was isolated from one goat on 3 DPI; however, molecular or cell culture evidence of active infection was not detected in goats later than 3 DPI. White-tailed deer exhibited serologic and molecular evidence of E. Chaffeensis infection throughout both trials, and E. Chaffeensis was reisolated in cell culture from all infected WTD on numerous days post-infection. Our results suggest that despite the occurrence of natural infection in goats, this animal may not be susceptible to experimental infection and thus may not serve as a suitable model of E. Chaffeensis reservoir host infection.
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Experimental infection of white-tailed deer (Odocoileus virginianus) with Ehrlichia Chaffeensis by different inoculation routes.
Journal of wildlife diseases, 2003Co-Authors: Andrea S. Varela, William R. Davidson, David E. Stallknecht, Michael J Yabsley, Victor A. Moore, Susan E. LittleAbstract:The infection dynamics of the tick-transmitted organism Ehrlichia Chaffeensis were investigated in white-tailed deer (Odocoileus virginianus) using different routes of inoculation. Six deer were each inoculated with 5.4×106 DH82 cells infected with E. Chaffeensis (Arkansas strain) by three different routes: intravenous (n=2), subcutaneous (n=2), and intradermal (n=2). Two control deer were inoculated with uninfected cells. Infections were monitored for 54 days and were continued in one deer from each E. Chaffeensis inoculated group for an additional 31 days. All deer inoculated with E. Chaffeensis seroconverted (≥1: 64) and became 16S rDNA polymerase chain reaction and/or cell culture positive by post-inoculation day 15. There was no apparent difference in susceptibility to infection between deer inoculated by different routes for the first 50 days based on detection of E. Chaffeensis infection by PCR assay of blood or culture isolation. These results demonstrate infection of deer by intradermal and subcu...
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Natural infection of domestic goats with Ehrlichia Chaffeensis.
Journal of clinical microbiology, 2000Co-Authors: Vivien G. Dugan, David E. Stallknecht, Susan E. Little, Ashley D. BeallAbstract:Thirty-eight domestic goats from an area of Ehrlichia Chaffeensis endemicity were tested for antibodies reactive to E. Chaffeensis and for E. Chaffeensis-specific 16S rRNA gene fragments by an indirect fluorescent antibody test and a nested PCR assay, respectively. Twenty-eight of 38 (73.7%) goats had antibodies reactive to E. Chaffeensis (≥1:128), and 6 of 38 (15.8%) goats were positive by diagnostic PCR; E. Chaffeensis was isolated in cell culture from one goat. Our data indicate that goats in areas of endemicity are naturally exposed to and infected with E. Chaffeensis.
David H. Walker - One of the best experts on this subject based on the ideXlab platform.
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Predominance of Ehrlichia Chaffeensis in Rhipicephalus sanguineus ticks from kennel-confined dogs in Limbe, Cameroon.
Experimental & applied acarology, 2009Co-Authors: Lucy M. Ndip, David H. Walker, Roland N. Ndip, Seraphine N. Esemu, Jere W. McbrideAbstract:Rhipicephalus sanguineus ticks (n = 63) collected from five dogs (two adults and three puppies) housed in a kennel were screened for Ehrlichial agents (Ehrlichia canis, E. Chaffeensis, and E. ewingii) using a species-specific multicolor real-time TaqMan PCR amplification of the disulphide bond formation protein (dsb) gene. Ehrlichia Chaffeensis DNA was detected in 33 (56%) ticks, E. canis DNA was detected in four (6%) ticks, and one tick was coinfected. The E. Chaffeensis and E. canis nucleotide sequences of the amplified dsb gene (374 bp) obtained from the Cameroonian R. sanguineus ticks were identical to the North American genotypes.
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Molecular and clinical evidence of Ehrlichia Chaffeensis infection in Cameroonian patients with undifferentiated febrile illness.
Annals of tropical medicine and parasitology, 2009Co-Authors: Lucy M. Ndip, David H. Walker, Roland N. Ndip, Marcelo B. Labruna, Jere W. McbrideAbstract:In the U.S.A., human monocytotropic ehrlichiosis (HME) caused by Ehrlichia Chaffeensis is an emerging tick-transmitted zoonosis. In Cameroon, where E. canis, E. Chaffeensis and E. ewingii have recently been detected in dogs and/or ticks (Rhipicephalus sanguineus), the potential exists for human infections. Patients from the coastal region of Cameroon who had acute fevers of unknown aetiology were therefore checked for Ehrlichial infection, using a real-time PCR that amplifies part of a genus-specific gene (dsb) that codes for a disulphide-bond formation protein. Ehrlichial blood was detected in the peripheral blood from 12 (10%) of the 118 patients investigated by PCR. When the 12 amplicons from the positive cases were sequenced, they were found to be identical to each other and to the corresponding dsb sequence of an Arkansas strain of E. Chaffeensis. The 12 patients who were PCR-positive for E. Chaffeensis suffered from fever (100%), headache (67%), myalgia (42%), arthralgia (58%), pulmonary involvement (17%) and/or a diffuse rash (17%).
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The developmental cycle of Ehrlichia Chaffeensis in vertebrate cells
Cellular microbiology, 2006Co-Authors: Jianzhi Zhang, Vsevolod L. Popov, Si Gao, David H. WalkerAbstract:Ehrlichia Chaffeensis, an obligatory intracellular bacterium, has two forms in mammalian cells: small dense-cored cells (DC) with dense nucleoid and larger reticulate cells (RC) with uniformly dispersed nucleoid. We have determined by electron microscopy that DC but not RC attaches to and enters into the host cells and RC but not DC multiples inside the host cells. Analysis of outer membrane protein expression by confocal microscopy showed that RC expressed the 28 kDa outer membrane protein (p28), the intermediate form, which were transforming from RC to DC, expressed both gp120 and p28, and the mature DC expressed gp120 only. The TCID50 of DC is 6 log10 higher than RC. We conclude that E. Chaffeensis has a developmental cycle, in which the DC attaches to and enters into the host cells, and transforms into RC and the RC multiplies by binary fission for 48 h and then matures into DC at 72 h.
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Ehrlichia Chaffeensis: a prevalent, life-threatening, emerging pathogen.
Transactions of the American Clinical and Climatological Association, 2004Co-Authors: David H. Walker, Jere W. Mcbride, Nahed Ismail, Juan P. Olano, Hui Min FengAbstract:Ehrlichia Chaffeensis are small, obligately intracellular, endosomal bacteria with tropism for macrophages. Persistent infection in reservoir white-tailed deer is transmitted by lone star ticks. Flu-like illness can progress to severe multisystem disease with toxic shock-like syndrome, meningitis, or ARDS. The case-fatality rate is 2.7%. Leukopenia and thrombocytopenia are diagnostically useful. Granulomas are associated with control of the infection. Ehrlichial proteins and glycoproteins have been sequenced and expressed for diagnostic serology and vaccine development. Mouse models (mild disease and persistent infection with E. muris and fatal monocytotropic ehrlichiosis with a Japanese tick isolate) revealed that CD4 and CD8 T type 1 lymphocyte responses, IFN-gamma, TNF-alpha, and antibodies play roles in protective immunity, while a weak CD4 T-helper response, overproduction of TNF-alpha, and very high IL-10 are associated with toxic shock-like mortality. Protection against fatal ehrlichiosis was achieved by prior infection with low virulence E. muris. Acute clinical diagnosis is difficult except by PCR. Response to doxycycline is dramatic.
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Sequence and characterization of an Ehrlichia Chaffeensis gene encoding 314 amino acids highly homologous to the NAD A enzyme.
FEMS microbiology letters, 1997Co-Authors: David H. WalkerAbstract:DNA sequence analysis of the nadA gene of Ehrlichia Chaffeensis revealed a 942 bp open reading frame with the capacity to encode 314 amino acids. The amino acid sequence of the E. Chaffeensis quinolinate synthetase A (NAD A) has 53.6% identity and 82% similarity to the NAD A of the cyanelle of Cyanophora paradoxa. Portions of the homologous genes of E. canis and E. muris were also sequenced. The amino acid sequences of the NAD A of E. canis and E. muris have 89.2% and 93.2% homology, respectively, to the NAD A of E. Chaffeensis. We propose that the nadA gene may be an excellent candidate for a genetic tool for the phylogenetic study of Ehrlichiae.
David E. Stallknecht - One of the best experts on this subject based on the ideXlab platform.
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Primary and secondary infection with Ehrlichia Chaffeensis in white-tailed deer (Odocoileus virginianus).
Vector borne and zoonotic diseases (Larchmont N.Y.), 2005Co-Authors: Andrea S. Varela, William R. Davidson, David E. Stallknecht, Elizabeth W. Howerth, Michael J Yabsley, Victor A. Moore, Susan E. LittleAbstract:White-tailed deer (Odocoileus virginianus) are the principal reservoir host for Ehrlichia Chaffeensis, causative agent of human monocytic ehrlichiosis (HME). Because white-tailed deer maintain a long-term infection with E. Chaffeensis and because deer can be naturally exposed to multiple strains of E. Chaffeensis, we evaluated the response to secondary infection of E. Chaffeensis in deer. For primary infection, six white-tailed deer were injected with 5.4 × 106 DH82 cells infected with the Arkansas strain of E. Chaffeensis (Ark) and two control deer were injected with noninfected DH82 cells. On post-infection day 54, three E. Chaffeensis (Ark) infected deer and one naive deer were injected with 4.2 × 106 cells infected with strain WTD-6045B E. Chaffeensis, which differs from the Arkansas strain by number of nucleotide repeats in the variable length PCR target (VLPT) gene; three other Arkansas strain infected deer were injected with noninfected DH82 cells. All animals were monitored for 31 additional days....
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Attempted experimental infection of domestic goats with Ehrlichia Chaffeensis.
Vector borne and zoonotic diseases (Larchmont N.Y.), 2004Co-Authors: Vivien G. Dugan, David E. Stallknecht, Andrea S. Varela, Colin C. Hurd, Susan E. LittleAbstract:Although white-tailed deer (WTD; Odocoileus virginianus ) are considered the primary natural reservoir host for Ehrlichia Chaffeensis, the causative agent of human monocytotropic ehrlichiosis, the potential role of other vertebrates as reservoir hosts has not been fully explored. Because domestic goats are naturally infected in areas where E. Chaffeensis is endemic in deer, we evaluated the susceptibility of domestic goats to experimental infection with E. Chaffeensis. A total of 12 goats were inoculated with E. Chaffeensis (15B-WTD-GA or Ark strain)-infected DH82 cells by one of three routes: intravenously, subcutaneously, or intradermally. White-tailed deer simultaneously inoculated with the same dose, route, and inoculum served as positive controls; additional goats and WTD were included as negative controls. Evidence of E. Chaffeensis infection was evaluated in all animals by indirect fluorescent antibody assay, PCR, and cell culture isolation techniques. All goats exposed to E. Chaffeensis seroconverted by 14 days post-infection (DPI), and E. Chaffeensis was isolated from one goat on 3 DPI; however, molecular or cell culture evidence of active infection was not detected in goats later than 3 DPI. White-tailed deer exhibited serologic and molecular evidence of E. Chaffeensis infection throughout both trials, and E. Chaffeensis was reisolated in cell culture from all infected WTD on numerous days post-infection. Our results suggest that despite the occurrence of natural infection in goats, this animal may not be susceptible to experimental infection and thus may not serve as a suitable model of E. Chaffeensis reservoir host infection.
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Experimental infection of white-tailed deer (Odocoileus virginianus) with Ehrlichia Chaffeensis by different inoculation routes.
Journal of wildlife diseases, 2003Co-Authors: Andrea S. Varela, William R. Davidson, David E. Stallknecht, Michael J Yabsley, Victor A. Moore, Susan E. LittleAbstract:The infection dynamics of the tick-transmitted organism Ehrlichia Chaffeensis were investigated in white-tailed deer (Odocoileus virginianus) using different routes of inoculation. Six deer were each inoculated with 5.4×106 DH82 cells infected with E. Chaffeensis (Arkansas strain) by three different routes: intravenous (n=2), subcutaneous (n=2), and intradermal (n=2). Two control deer were inoculated with uninfected cells. Infections were monitored for 54 days and were continued in one deer from each E. Chaffeensis inoculated group for an additional 31 days. All deer inoculated with E. Chaffeensis seroconverted (≥1: 64) and became 16S rDNA polymerase chain reaction and/or cell culture positive by post-inoculation day 15. There was no apparent difference in susceptibility to infection between deer inoculated by different routes for the first 50 days based on detection of E. Chaffeensis infection by PCR assay of blood or culture isolation. These results demonstrate infection of deer by intradermal and subcu...
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Persistent Ehrlichia Chaffeensis infection in white-tailed deer.
Journal of wildlife diseases, 2001Co-Authors: William R. Davidson, J. Mitchell Lockhart, David E. Stallknecht, Elizabeth W. Howerth, Jacqueline E. Dawson, Yigal RechavAbstract:Four white-tailed deer (Odocoileus virginianus) were inoculated intravenously with a deer-origin isolate (15B-WTD-GA) of Ehrlichia Chaffeensis. The course of infection was monitored using indirect fluorescent antibody (IFA), polymerase chain reaction (PCR), and culture over a 9 m period. All deer became rickettsemic within 24 days post inoculation (DPI), and all developed antibody titers >1:64 to E. Chaffeensis by 17 DPI. Titers in all deer fell below 1:64 during 87 to 143 DPI. One deer exhibited a second period of seropositivity (peak titer of 1:256) from 207 to 271 DPI but was culture and PCR negative during this period. Rickettsemia was confirmed by reisolation of E. Chaffeensis as late as 73 to 108 DPI in three deer. Positive PCR results were obtained from femur bone marrow of one deer and from rumenal lymph node of another deer at 278 DPI. None of the deer developed clinical signs, hematologic abnormalities, or gross or microscopic lesions attributable to E. Chaffeensis. Two uninoculated control deer...
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Natural infection of domestic goats with Ehrlichia Chaffeensis.
Journal of clinical microbiology, 2000Co-Authors: Vivien G. Dugan, David E. Stallknecht, Susan E. Little, Ashley D. BeallAbstract:Thirty-eight domestic goats from an area of Ehrlichia Chaffeensis endemicity were tested for antibodies reactive to E. Chaffeensis and for E. Chaffeensis-specific 16S rRNA gene fragments by an indirect fluorescent antibody test and a nested PCR assay, respectively. Twenty-eight of 38 (73.7%) goats had antibodies reactive to E. Chaffeensis (≥1:128), and 6 of 38 (15.8%) goats were positive by diagnostic PCR; E. Chaffeensis was isolated in cell culture from one goat. Our data indicate that goats in areas of endemicity are naturally exposed to and infected with E. Chaffeensis.
Jacqueline E. Dawson - One of the best experts on this subject based on the ideXlab platform.
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Persistent Ehrlichia Chaffeensis infection in white-tailed deer.
Journal of wildlife diseases, 2001Co-Authors: William R. Davidson, J. Mitchell Lockhart, David E. Stallknecht, Elizabeth W. Howerth, Jacqueline E. Dawson, Yigal RechavAbstract:Four white-tailed deer (Odocoileus virginianus) were inoculated intravenously with a deer-origin isolate (15B-WTD-GA) of Ehrlichia Chaffeensis. The course of infection was monitored using indirect fluorescent antibody (IFA), polymerase chain reaction (PCR), and culture over a 9 m period. All deer became rickettsemic within 24 days post inoculation (DPI), and all developed antibody titers >1:64 to E. Chaffeensis by 17 DPI. Titers in all deer fell below 1:64 during 87 to 143 DPI. One deer exhibited a second period of seropositivity (peak titer of 1:256) from 207 to 271 DPI but was culture and PCR negative during this period. Rickettsemia was confirmed by reisolation of E. Chaffeensis as late as 73 to 108 DPI in three deer. Positive PCR results were obtained from femur bone marrow of one deer and from rumenal lymph node of another deer at 278 DPI. None of the deer developed clinical signs, hematologic abnormalities, or gross or microscopic lesions attributable to E. Chaffeensis. Two uninoculated control deer...
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Lack of Seroreactivity to Ehrlichia Chaffeensis Among Rodent Populations
Journal of wildlife diseases, 1998Co-Authors: J. Mitchell Lockhart, William R. Davidson, David E. Stallknecht, Jacqueline E. DawsonAbstract:A retrospective serosurvey for antibodies to Ehrlichia Chaffeensis was conducted on eight species of wild rodents (Mus musculus, Oryzomys palustris, Peromysctts leucopns, Rattus norvegicus, Reithrodontomys humulis, Sciurus carolinensis, Sciurus niger, and Sigmodon hispidus) from the southeastern United States. Serum samples (n = 281) collected between 1973 and 1993 were evaluated using an indirect fluorescent antibody test. All samples, screened at a dilution of 1:32, were negative for antibodies to E. Chaffeensis. Sixty-three percent of the rodents tested were from areas where E. Chaffeensis has been confirmed or is strongly suspected to be endemic. These data suggest limited or no involvement of rodents in the epidemiology of E. Chaffeensis.
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persistent infection of c3h hej mice by Ehrlichia Chaffeensis
Veterinary Microbiology, 1996Co-Authors: Sam R. Telford, Jacqueline E. DawsonAbstract:Abstract Description of the pathobiology of the recently described zoonotic agent of human ehrlichiosis ( Ehrlichia Chaffeensis ) would be greatly facilitated by the availability of a convenient experimental animal model of infection. We determined whether C3H/HeJ mice could sustain persistent infection by this predominantly monocyte-inhabiting rickettsia. Such mice rapidly produced an intense specific IgG response upon inoculation of Ehrlichiae, and high titers were demonstrable for more than 6 months thereafter. Ehrlichiae were reisolated from the peripheral blood and spleen of 1 mouse at day 11 after inoculation. DNA of E. Chaffeensis was more frequently detected within these tissues by polymerase chain reaction. Other candidate rodent models appeared to be poor hosts for this pathogen. About half of intact and virtually all splenectomized white-footed mice that were inoculated seroconverted. Sera from inoculated voles and hamsters did not react to antigens of E. Chaffeensis . The C3H/HeJ mouse becomes persistently infected by this rickettsia, and may serve as a useful model for studies of the immune response to the agent of human ehrlichiosis.
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Persistent infection of C3H/HeJ mice by Ehrlichia Chaffeensis
Veterinary microbiology, 1996Co-Authors: Sam R. Telford, Jacqueline E. DawsonAbstract:Abstract Description of the pathobiology of the recently described zoonotic agent of human ehrlichiosis ( Ehrlichia Chaffeensis ) would be greatly facilitated by the availability of a convenient experimental animal model of infection. We determined whether C3H/HeJ mice could sustain persistent infection by this predominantly monocyte-inhabiting rickettsia. Such mice rapidly produced an intense specific IgG response upon inoculation of Ehrlichiae, and high titers were demonstrable for more than 6 months thereafter. Ehrlichiae were reisolated from the peripheral blood and spleen of 1 mouse at day 11 after inoculation. DNA of E. Chaffeensis was more frequently detected within these tissues by polymerase chain reaction. Other candidate rodent models appeared to be poor hosts for this pathogen. About half of intact and virtually all splenectomized white-footed mice that were inoculated seroconverted. Sera from inoculated voles and hamsters did not react to antigens of E. Chaffeensis . The C3H/HeJ mouse becomes persistently infected by this rickettsia, and may serve as a useful model for studies of the immune response to the agent of human ehrlichiosis.
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Experimental transmission of Ehrlichia Chaffeensis (Rickettsiales: Ehrlichieae) among white-tailed deer by Amblyomma americanum (Acari: Ixodidae)
Journal of medical entomology, 1995Co-Authors: Sidney A. Ewing, Jacqueline E. Dawson, A. Alan Kocan, R. W. Barker, Cynthia K. Warner, Roger J. Panciera, J. C. Fox, Katherine M. Kocan, Edmour F. BlouinAbstract:Ehrlichia Chaffeensis Anderson, Dawson & Wilson, causative agent of human (predominantly monocytic) ehrlichiosis, was successfully transmitted experimentally by Amblyomma americanum (L.) to white-tailed deer, Odocoileus virginianus (Zimmerman). Deer were needle-exposed intravenously to E. Chaffeensis in tissue-culture canine macrophage (DH82) cells, and 11 d later were exposed to laboratory-reared A. americanum larvae, nymphs, and adults for acquisition feeding. Three months after this feeding, naive deer and dogs were exposed to recently molted nymphs and adults. Attempted reisolation of the pathogen by way of tissue culture was successful from one needle-exposed deer but not from the tick-exposed deer or dogs. Based on serologic evidence and polymerase chain reaction data, both nymphal and adult ticks transmitted E. Chaffeensis to naive deer but not to dogs.