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1.  Emergence of Ixodes scapularis and Borrelia burgdorferi, the Lyme disease vector and agent, in Ohio 
Lyme disease, the most common vector-borne disease in the United States, is caused by a tick-borne infection with Borrelia burgdorferi. Currently, Ohio is considered by the Centers for Disease Control and Prevention (CDC) to be non-endemic for Lyme disease. The low incidence of Lyme disease in this state was largely attributed to the absence of the transmitting vector, Ixodes scapularis, commonly known as the blacklegged tick. However, a tick surveillance program established by Ohio Department of Health indicated that the number of I. scapularis in Ohio had increased sharply in recent years, from 0 - 5 ticks per year during 1983–2008 to 15 in 2009, 40 in 2010, and 184 in 2011. During the fall deer hunting season, examination of deer heads submitted to Ohio Department of Agriculture found 29 I. scapularis from 7 counties in 2010 and 1,830 from 25 counties in 2011. As of 2012, the tick had been found in 57 of the 88 counties of Ohio. In addition, all three active stages (larva, nymph, and adult) of I. scapularis were found in Tiverton Township of Coshocton County, demonstrating the presence of established tick populations at this central Ohio location. Of 530 nymphal or adult I. scapularis analyzed by quantitative polymerase chain reaction (qPCR), 32 (6.1%) tested positive for the B. burgdorferi flaB gene, ranging from 36 to 390,000 copies per tick. Antibodies to B. burgdorferi antigens were detected in 2 of 10 (20%) field-captured Peromyscus leucopus from Tiverton Township, and in 41 of 355 (11.5%) dogs residing in Ohio. Collectively, these data suggest that the enzootic life cycle of B. burgdorferi has become established in Ohio, which poses risk of Lyme disease to people and animals in the area.
PMCID: PMC4044495  PMID: 24926441
Lyme disease; Ohio; Borrelia burgdorferi; Ixodes scapularis; Peromyscus leucopus
2.  Quantitative factors proposed to influence the prevalence of canine tick-borne disease agents in the United States 
Parasites & Vectors  2014;7:417.
The Companion Animal Parasite Council hosted a meeting to identify quantifiable factors that can influence the prevalence of tick-borne disease agents among dogs in North America. This report summarizes the approach used and the factors identified for further analysis with mathematical models of canine exposure to tick-borne pathogens.
PMCID: PMC4167287  PMID: 25185829
Anaplasma; Ehrlichia; Borrelia burgdorferi; Tick-borne infections; Prevalence map factors; Ticks; Ixodidae; Prostriata; Metastriata
3.  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.
PMCID: PMC2981254  PMID: 20921310
4.  Development of a p28-based PCR assay for Ehrlichia chaffeensis 
Molecular and cellular probes  2004;18(2):111-116.
Detection of Ehrlichia chaffeensis is necessary to study interactions between the parasite and its vertebrate and invertebrate hosts. The purpose of this study was to develop a sensitive, specific PCR assay for E. chaffeensis based on the outer membrane protein gene, p28. Candidate primer sets were identified and ranked based on annealing scores, similarities to three major p28 sequence clusters, dissimilarity to E. canis p30, an ortholog of p28, and the proximities of flanking primer sequences for nested PCR. The relative sensitivities of five optimized single-step and two nested PCR assays were determined, and the most sensitive assay was found to be a single-step PCR that was as much as 1000-fold more sensitive than a standard 16S rDNA-based nested PCR assay. This p28-based PCR assay amplified the target amplicon from isolates representative of all three major clusters of known p28 sequences, and this assay did not amplify template prepared from either of the two species most closely related to E. chaffeensis, E. canis and E. muris. These results indicate that this sensitive, specific and isolate-universal single-step PCR assay will be a useful tool in characterizing the transmission of this important zoonotic pathogen.
PMCID: PMC3066156  PMID: 15051120
Ehrlichia chaffeensis; Human monocytic ehrlichiosis; PCR assay
5.  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.
PMCID: PMC3066168  PMID: 18033836
6.  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.
PMCID: PMC3052985  PMID: 19120226
Ehrlichia canis; Rhipicephalus sanguineus; ehrlichiosis; doxycycline; rifampin
7.  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.
PMCID: PMC3052987  PMID: 15941624
Ehrlichia canis; Canine monocytic ehrlichiosis; Tick transmission; Rhipicephalus sanguineus; Metastriata
8.  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.
PMCID: PMC3053144  PMID: 18963493
Ehrlichia canis; canine monocytic ehrlichiosis; host surveys; biological transmission; tick biology; Metastriata; Prostriata
9.  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.
PMCID: PMC2043173  PMID: 17606682
10.  Detection of Ehrlichia canis in Canine Carrier Blood and in Individual Experimentally Infected Ticks with a p30-Based PCR Assay 
Journal of Clinical Microbiology  2002;40(2):540-546.
Detection of vector-borne pathogens is necessary for investigation of their association with vertebrate and invertebrate hosts. The ability to detect Ehrlichia spp. within individual experimentally infected ticks would be valuable for studies to evaluate the relative competence of different vector species and transmission scenarios. The purpose of this study was to develop a sensitive PCR assay based on oligonucleotide sequences from the unique Ehrlichia canis gene, p30, to facilitate studies that require monitoring this pathogen in canine and tick hosts during experimental transmission. Homologous sequences for Ehrlichia chaffeensis p28 were compared to sequences of primers derived from a sequence conserved among E. canis isolates. Criteria for primer selection included annealing scores, identity of the primers to homologous E. chaffeensis sequences, and the availability of similarly optimal primers that were nested within the target template sequence. The p30-based assay was at least 100-fold more sensitive than a previously reported nested 16S ribosomal DNA (rDNA)-based assay and did not amplify the 200-bp target amplicon from E. chaffeensis, the human granulocytic ehrlichiosis agent, or Ehrlichia muris DNA. The assay was used to detect E. canis in canine carrier blood and in experimentally infected Rhipicephalus sanguineus ticks. Optimized procedures for preparing tissues from these hosts for PCR assay are described. Our results indicated that this p30-based PCR assay will be useful for experimental investigations, that it has potential as a routine test, and that this approach to PCR assay design may be applicable to other pathogens that occur at low levels in affected hosts.
PMCID: PMC153401  PMID: 11825969

Results 1-10 (10)