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1.  Efficacy of a Doxycycline Treatment Regimen Initiated during Three Different Phases of Experimental Ehrlichiosis ▿  
Antimicrobial Agents and Chemotherapy  2010;54(12):5012-5020.
Doxycycline is the treatment of choice for canine monocytic ehrlichiosis (CME), a well-characterized disease and valuable model for tick-borne zoonoses. Conflicting reports of clearance of Ehrlichia canis after treatment with doxycycline suggested that the disease phase during which treatment is initiated influences outcomes of these treatments. The purpose of this study was to evaluate the efficacy of a 28-day doxycycline regimen for clearance of experimental E. canis infections from dogs treated during three phases of the disease. Ten dogs were inoculated with blood from E. canis carriers and treated with doxycycline during acute, subclinical, or chronic phases of CME. Daily rectal temperatures and semiweekly blood samples were monitored from each dog, and Rhipicephalus sanguineus ticks were acquisition fed on each dog for xenodiagnosis. Blood collected from dogs treated during acute or subclinical CME became PCR negative for E. canis as clinical parameters improved, but blood samples collected from dogs treated during chronic CME remained intermittently PCR positive. R. sanguineus ticks fed on dogs after doxycycline treatments became PCR positive for E. canis, regardless of when treatment was initiated. However, fewer ticks became PCR positive after feeding on two persistently infected dogs treated with doxycycline followed by rifampin, suggesting that antibiotic therapy can reduce tick acquisition of E. canis.
doi:10.1128/AAC.01622-09
PMCID: PMC2981254  PMID: 20921310
2.  Experimental infection of dairy calves with Ehrlichia chaffeensis 
Journal of medical microbiology  2007;56(Pt 12):1660-1668.
Human monocytic ehrlichiosis (HME) is a zoonotic emerging tick-borne disease with clinical signs that range from mild symptoms to multiple organ failure and death. Ehrlichia chaffeensis, the aetiologic agent of HME, is reported to infect a divergent range of mammals. Although cattle are common hosts of the primary vector of this pathogen, the susceptibility of this host to E. chaffeensis has not been reported to date. This study was undertaken to determine if cattle could provide a useful infection model of E. chaffeensis. Dairy calves were injected with DH82 cells infected with the Arkansas, St Vincent or 91HE17 strain of E. chaffeensis, and monitored for signs of clinical ehrlichiosis and for infection of peripheral blood and ticks by PCR assay. Splenectomized and spleen-intact calves were injected with cryopreserved stabilates of E. chaffeensis-infected DH82 cells for the first experiment. Mild clinical signs were occasionally observed among these calves, and only two blood samples were PCR-positive, while several ticks fed on each calf tested PCR-positive. The second experiment involved injection of normal calves with active cultures of the same E. chaffeensis strains. Interestingly, three of six calves inoculated with active cultures became recumbent and died or had to be euthanized. All of the surviving calves in this experiment tested PCR-positive on multiple dates, but fewer ticks fed on these calves were PCR-positive. These results suggest that a bovine disease model could facilitate the understanding of factors that affect the severity of HME.
doi:10.1099/jmm.0.47427-0
PMCID: PMC3066168  PMID: 18033836
3.  Antibiotic clearance of Ehrlichia canis from dogs infected by intravenous inoculation of carrier blood 
Ehrlichia canis is the etiologic agent of canine monocytic ehrlichiosis (CME) and is a useful model for tick-borne zoonotic pathogens, many of which infect dogs. The purpose of this study was to evaluate rifampin and doxycycline regimens for clearance of E. canis infections in addition to alleviation of CME. Beagles were infected with E. canis by intravenous inoculation with carrier blood and treated with either rifampin or doxycycline after the acute phase of CME. Improved hematological values demonstrated that both treatments effectively relieved signs of the disease. Peripheral blood from all dogs became PCR-negative after antibiotic treatment, suggesting that these infections were eliminated and that rifampin is an effective alternative chemotherapeutic agent for treatment of CME.
doi:10.1196/annals.1428.087
PMCID: PMC3052985  PMID: 19120226
Ehrlichia canis; Rhipicephalus sanguineus; ehrlichiosis; doxycycline; rifampin
4.  Transstadial and intrastadial experimental transmission of Ehrlichia canis by male Rhipicephalus sanguineus 
Veterinary parasitology  2005;131(1-2):95-105.
The acquisition and transmission of rickettsial pathogens by different tick developmental stages has important epidemiological implications. The purpose of this study was to determine if male Rhipicephalus sanguineus can experimentally acquire and transmit Ehrlichia canis in the absence of female ticks. Two trials were performed where nymphal and male R. sanguineus were simultaneously acquisition fed on the same infected donor hosts, and transstadially or intrastadially exposed male ticks were fed on separate pathogen-free dogs as a test for transmission. A single-step p30-based PCR assay was used to test canine and tick hosts for E. canis infections before and after tick feeding. E. canis was detected after either intrastadial or transstadial passage in male ticks, the organism remained detectable in both tick groups after transmission feeding, and both tick groups transmitted the rickettsia to susceptible dogs. Infection of dogs via tick feeding resulted in milder clinical signs and lower antibody titers than intravenous inoculation of carrier blood, but further investigation is needed to understand the mechanisms responsible for this observation. These results demonstrate that male R. sanguineus can take multiple feedings, and that they can both acquire and transmit E. canis in the absence of female ticks. This tick development stage could be important in transmission of E. canis, and perhaps related pathogens, between vertebrate hosts under natural and experimental conditions.
doi:10.1016/j.vetpar.2005.04.030
PMCID: PMC3052987  PMID: 15941624
Ehrlichia canis; Canine monocytic ehrlichiosis; Tick transmission; Rhipicephalus sanguineus; Metastriata
5.  Host surveys, ixodid tick biology and transmission scenarios as related to the tick-borne pathogen, Ehrlichia canis 
Veterinary parasitology  2008;158(4):256-273.
The ehrlichioses have been subject to increasing interest from veterinary and public health perspectives, but experimental studies of these diseases and their etiologic agents can be challenging. Ehrlichia canis, the primary etiologic agent of canine monocytic ehrlichiosis, is relatively well characterized and offers unique advantages and opportunities to study interactions between a monocytotropic pathogen and both its vertebrate and invertebrate hosts. Historically, advances in tick-borne disease control strategies have typically followed explication of tick-pathogen-vertebrate interactions, thus it is reasonable to expect novel, more sustainable approaches to control of these diseases as the transmission of their associated infections are investigated at the molecular through ecological levels. Better understanding of the interactions between E. canis and its canine and tick hosts would also elucidate similar interactions for other Ehrlichia species as well as the potential roles of canine sentinels, reservoirs and models of tick-borne zoonoses. This article summarizes natural exposure studies and experimental investigations of E. canis in the context of what is understood about biological vectors of tick-borne Anaplasmataceae.
doi:10.1016/j.vetpar.2008.09.013
PMCID: PMC3053144  PMID: 18963493
Ehrlichia canis; canine monocytic ehrlichiosis; host surveys; biological transmission; tick biology; Metastriata; Prostriata
6.  Rapid screening and cultivation of Ehrlichia canis from refrigerated carrier blood 
Improved detection and isolation of rickettsial agents from naturally infected dogs would facilitate understanding the epidemiologic roles of these hosts. In this study, current methods were refined for rapid screening of carrier blood and ticks for Ehrlichia canis, and the feasibility of blood culture after PCR screening was addressed.
doi:10.1111/j.1469-0691.2008.02192.x
PMCID: PMC2901411  PMID: 19438630
Ehrlichia canis; Rhipicephalus sanguineus; blood culture; PCR assay
7.  Validation of a Detailed Scoring Checklist for Use During Advanced Cardiac Life Support Certification 
Introduction
Defining valid, reliable, defensible, and generalizable standards for the evaluation of learner performance is a key issue in assessing both baseline competence and mastery in medical education. However, prior to setting these standards of performance, the reliability of the scores yielding from a grading tool must be assessed. Accordingly, the purpose of this study was to assess the reliability of scores generated from a set of grading checklists used by non-expert raters during simulations of American Heart Association (AHA) MegaCodes.
Methods
The reliability of scores generated from a detailed set of checklists, when used by four non-expert raters, was tested by grading team leader performance in eight MegaCode scenarios. Videos of the scenarios were reviewed and rated by trained faculty facilitators and by a group of non-expert raters. The videos were reviewed “continuously” and “with pauses.” Two content experts served as the reference standard for grading, and four non-expert raters were used to test the reliability of the checklists.
Results
Our results demonstrate that non-expert raters are able to produce reliable grades when using the checklists under consideration, demonstrating excellent intra-rater reliability and agreement with a reference standard. The results also demonstrate that non-expert raters can be trained in the proper use of the checklist in a short amount of time, with no discernible learning curve thereafter. Finally, our results show that a single trained rater can achieve reliable scores of team leader performance during AHA MegaCodes when using our checklist in continuous mode, as measures of agreement in total scoring were very strong (Lin’s Concordance Correlation Coefficient = 0.96; Intraclass Correlation Coefficient = 0.97).
Discussion
We have shown that our checklists can yield reliable scores, are appropriate for use by non-expert raters, and are able to be employed during continuous assessment of team leader performance during the review of a simulated MegaCode. This checklist may be more appropriate for use by Advanced Cardiac Life Support (ACLS) instructors during MegaCode assessments than current tools provided by the AHA.
doi:10.1097/SIH.0b013e3182590b07
PMCID: PMC3467004  PMID: 22863996
simulation; education; checklist; reliability; ACLS
8.  Tick Acquisition of Ehrlichia canis from Dogs Treated with Doxycycline Hyclate▿  
Doxycycline generally alleviates clinical monocytic ehrlichiosis, but its efficacy in the control of monocytotropic ehrlichial pathogens requires further investigation. In this study, Ehrlichia canis was detected in dogs treated with doxycycline for 14 days and in ticks fed on these dogs, suggesting that treated dogs can remain reservoirs for E. canis.
doi:10.1128/AAC.00358-07
PMCID: PMC2043173  PMID: 17606682

Results 1-8 (8)