Evaluation of a prototype Ehrlichia chaffeensis surveillance system using white-tailed deer (Odocoileus virginianus) as natural sentinels

The natural history of Ehrlichia chaffeensis, the causative agent of human monocytotropic ehrlichiosis, includes the lone star tick (LST, Amblyomma americanum) as a vector and white-tailed deer (WTD; Odocoileus virginianus) as both a natural reservoir of E. chaffeensis and a major host of LST. The goal of the current study was to implement and evaluate a prototype surveillance system to delineate the geographic distribution of E. chaffeensis using WTD as natural sentinels. To accomplish this goal, serologic testing using the indirect immunofluorescent antibody (IFA) test was performed on WTD serum samples, and to confirm serologic results, polymerase chain reaction (PCR) assays and culture isolation were conducted. Considerations relevant to the applicability of a surveillance system utilizing WTD were analyzed (e.g., age and gender relationships to serologic status, adequacy of sample sizes needed to distinguish between uninfected and infected populations, presence of LST, and ability to detect stability and spread of E. chaffeensis in WTD populations). Of 3275 WTD serologically tested, 549 (47%) from 17 of 18 states had antibodies reactive to E. chaffeensis (IFA titer > or = 1:128). No difference between age groups or gender was noted with serologic testing, thus these variables would not be a concern for a surveillance system using WTD. Significantly more deer in younger age groups (< or = 1.5 yr) were PCR and culture positive, and 46% of 122 seropositive WTD populations were confirmed positive by PCR or culture isolation. A significant association between LST infestation and E. chaffeensis seroreactivity was noted. Furthermore, the surveillance system was able to detect stability of E. chaffeensis within WTD populations and also spread to new populations, both of which were associated with LST status. These data clearly demonstrate that WTD are useful as natural sentinels for this emerging human pathogen, and establish a prototypical framework for a WTD surveillance system.     

Primary and secondary infection with Ehrlichia chaffeensis in white-tailed deer (Odocoileus virginianus)

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 x 10(6) 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 x 10(6) 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. All deer in the primary infection became positive by PCR amplification of the 16S rRNA or VLPT genes and/or cell culture by DPI-8. PCR amplification of the VLPT gene on whole blood, cell culture, and tissues detected primary and/or secondary strains in all deer exposed to both primary and secondary strains; in one deer, the primary strain was cultured from the lymph node. Our culture results demonstrated that both strains were present; however, PCR detection suggests that the secondary strain may have been circulating in blood at higher levels. In conclusion, this study provides evidence that primary infection of deer with E. chaffeensis does not protect against subsequent exposure and confirms that deer can be simultaneously coinfected with at least two different strains of E. chaffeensis.     

Attempted experimental infection of domestic goats with Ehrlichia chaffeensis

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.     

Habitat factors influencing distributions of Anaplasma phagocytophilum and Ehrlichia chaffeensis in the Mississippi Alluvial Valley

Human monocytotropic ehrlichiosis (HME), caused by the bacterium Ehrlichia chaffeensis, and human granulocytic anaplasmosis (HGA), caused by the bacterium Anaplasma phagocytophilum, are two emerging tick-borne zoonoses of concern. Factors influencing geographic distributions of these pathogens are not fully understood, especially at varying spatial extents (regional versus landscape) and resolutions (counties versus smaller land units). We used logistic regression to compare influences of physical environment, land cover composition, and landscape heterogeneity on distributions of A. phagocytophilum and E. chaffeensis at multiple spatial extents. Pathogen presence or absence was determined from white-tailed deer (Odocoileus virginianus) serum samples collected from 1981 to 2005. Ecological predictor variables were derived from spatial datasets that represented deer density, elevation, land cover, normalized difference vegetation index (NDVI), hydrology, and soil moisture. We used three strategies (a priori, exploratory, and spatial extent) to develop models. Best fitting models were applied within a geographic information system to create predictive probability surfaces for each bacterium. Ecological predictor variables generally resulted in better fitting models for E. chaffeensis than A. phagocytophilum (90.5% and 68% sensitivity, respectively), possibly as a result of differences in the natural histories of tick vectors. Although alternative model development strategies produced different models, in all cases bacteria presence or absence was affected by a combination of soil moisture or flooding variables (thought to affect primarily tick vectors) and forest cover or NDVI variables (thought to affect primarily mammalian hosts). This research demonstrates the potential for modeling the distributions of microscopic tick-borne pathogens using coarse regional datasets and emphasizes the importance of forest cover and flooding as environmental constraints, as well as the importance of considering ecological variables at multiple spatial extents.     

查菲埃立克体和人单核细胞埃立克体病研究进展

埃立克体病是由埃立克体属微生物引起的一类人兽共患急性传染病,其特征为高热、头疼、贫血、白细胞减少、消瘦和黄疸等。查菲埃立克体是埃立克体属中代表性的蜱媒人畜共患病病原体,对人、畜均有较强致病性,在人体引起人单核细胞埃立克体病（HME）。本文较为全面地总结了查非埃立克体和HME的病原学、流行病学、临床表现、诊断和防治等方面的研究进展。     

Ehrlichia chaffeensis infection in dogs in South Korea

Ehrlichia chaffeensis is one of the causative agents of canine ehrlichiosis and human monocytic ehrlichiosis (HME). Canine ehrlichiosis caused by E. chaffeensis was diagnosed in two dogs in South Korea based on clinical findings, and the diagnosis was confirmed by polymerase chain reaction (PCR) and DNA sequencing. A 5-year-old intact male American Pit bull terrier allowed outdoors was found to be concurrently infected with Babesia gibsoni and E. chaffeensis. The major clinical findings were lethargy and reddish urine, and laboratory analysis revealed severe hematuria and thrombocytopenia. In addition, a 3-year-old neutered male Shih-tzu was also found to be infected with E. chaffeensis. Although this dog was an indoor companion animal, he was frequently allowed outside for exercise. The clinical signs observed in this dog included generalized purpura with petechiae and ecchymoses due to thrombocytopenia. A 390-bp partial portion of E. chaffeensis 16S rRNA gene was amplified in both cases, and nucleotide sequence analysis revealed 99% homology of this fragment with other E. chaffeensis isolates. These findings demonstrate the presence of E. chaffeensis infection in dogs in South Korea, and this is the first report to confirm clinical cases of E. chaffeensis infection in dogs.     

Epidemiology of human ehrlichiosis and anaplasmosis in the United States, 2001-2002

During 2001 through 2002, 1,176 cases of the tick-borne diseases human monocytic ehrlichiosis (HME) and human granulocytic anaplasmosis (HGA) were reported to the Centers for Disease Control and Prevention (CDC) by 32 states through the National Electronic Telecommunications System for Surveillance. The average reported annual incidences for HME and HGA during 2001-2002 were 0.6 and 1.4 cases per million population, respectively; incidence was highest among men > 60 years of age. During this same interval, a total of 883 cases of HME and HGA were reported to CDC through a passive surveillance system of tick-borne disease case report forms (CRFs). The surveillance information retrieved from CRFs has allowed for qualitative evaluation of ehrlichiosis and anaplasmosis risk factors, severity, and diagnostic accuracy. Although these surveillance systems likely substantially under-represent the true burden of ehrlichiosis and anaplasmosis in the United States due to poor recognition and reporting, they represent the first compilation of national data since these diseases were made nationally notifiable. Continued and improved surveillance activities will progressively reinforce our understanding and awareness of these newly recognized zoonotic infections.     

Co-infection of white-tailed deer with multiple strains of Ehrlichia chaffeensis

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 from each exposed strain. A complementary in vitro study demonstrated that exposure to two strains differing in VLPT repeats may lead to co-infection of DH82 cells. These results complement a previous study and further show that deer can become sequentially infected with up to three strains of E. chaffeensis. This suggests that competitive exclusion, a phenomenon described in related organisms such as Anaplasma marginale whereby infection with one strain precludes subsequent infection by a second, distinct strain of the same species, may not occur with E. chaffeensis.     

Evaluation of immunocompetent and immunocompromised mice (Mus musculus) for infection with Ehrlichia chaffeensis and transmission to Amblyomma americanum ticks

Experiments on the natural history of Ehrlichia chaffeensis, the agent of human monocytic ehrlichiosis (HME), would be facilitated by the availability of a laboratory animal model for transmission to vector ticks. Five strains of mice were evaluated for their susceptibility to infection with E. chaffeensis and transmission competence: C57BL/6 mice, inducible nitric oxide synthase (iNOS) deficient mice, MHC I deficient (beta2m /) mice, MHC II deficient mice (Abb /), and B and T cell deficient (Rag1 /) mice. Mice were inoculated with a low passage isolate of E. chaffeensis, and infection and morbidity were monitored for 57 days. Three xenodiagnostic infestations with A. americanum nymphs were performed 1, 8, and 15 days following inoculation. C57BL/6 mice cleared the organism in less than 17 days, with no indication of morbidity, and mounted a rapid, strong antibody response. Transmission to feeding A. americanum nymphs was seen in 1/30 nymphs fed on C57BL/6 mice immediately after inoculation. In MHC I and iNOS deficient mice, pathogen DNA was detected up to 17 or 24 days, respectively, after inoculation. Persistent infection for the duration of the experiment (57 days) was observed in MHC II deficient mice. However, E. chaffeensis was not detected in ticks fed on iNOS, MHC I, or MHC II deficient mice. Susceptibility to infection was greatest in Rag1 knockout mice, with significant morbidity and mortality within 24 days after inoculation. E. chaffeensis DNA was detected in up to 55% of replete nymphs that fed on Rag1 mice. However, E. chaffeensis was not detected in molted adult ticks from the same cohorts.     

山东省首例实验室诊断人单核细胞埃立克体病调查

目的 报告山东省首例人单核细胞埃立克体病的发现、诊治经过及其实验室检测.方法 对该疑似病例开展流行病学调查并填写个案调查表,采集其血标本,套式-PCR技术检测血液中嗜吞噬细胞无形体和查菲埃立克体特异性16S rRNA基因.结果 患者为不明原因发热,伴WBC和PLT减少.嗜吞噬细胞无形体特异性核酸检测阴性,查菲埃立克体特异性核酸检测阳性.PCR扩增阳性产物进行测序并与GenBank中注册的已知序列进行比较分析,显示与查菲埃立克体的同源性＞99％.结论 山东省存在查菲埃立克体感染病例,进一步开展自然疫源地调查十分必要.     

Tissue diagnosis of Ehrlichia chaffeensis in patients with fatal ehrlichiosis by use of immunohistochemistry, in situ hybridization, and polymerase chain reaction.

In the United States, human ehrlichiosis is a complex of emerging tick-borne diseases caused by 3 distinct Ehrlichia species: Ehrlichia chaffeensis, Ehrlichia ewingii, and the human granulocytotropic ehrlichiosis agent. Ehrlichioses are characterized by a mild to severe illness, and approximately 4% of cases are fatal. Because these obligate intracellular bacteria are difficult to resolve with routine histologic techniques, their distribution in tissues has not been well described. To facilitate the visualization and detection of ehrlichiae, immunohistochemistry (IHC), in situ hybridization (ISH), and polymerase chain reaction (PCR) assays were developed by use of tissues from 4 fatal cases of E. chaffeensis infection. Evidence of E. chaffeensis via IHC, ISH, and PCR was documented in all 4 cases. Abundant immunostaining and in situ nucleic acid hybridization were observed in spleen and lymph node from all 4 patients. Significantly, in 2 of these patients, serologic evidence of infection was absent. Use of IHC, ISH, and PCR to visualize and detect Ehrlichia in tissues can facilitate diagnosis of ehrlichial infections.     

Increasing incidence of Ehrlichia chaffeensis and Anaplasma phagocytophilum in the United States, 2000-2007

Ehrlichia chaffeensis causes human monocytic ehrlichiosis, and Anaplasma phagocytophilum causes human granulocytic anaplasmosis. These related tick-borne rickettsial organisms can cause severe and fatal illness. During 2000-2007, the reported incidence rate of E. chaffeensis increased from 0.80 to 3.0 cases/million persons/year. The case-fatality rate was 1.9%, and the hospitalization rate was 49%. During 2000-2007, the reported incidence of A. phagocytophilum increased from 1.4 to 3.0 cases/million persons/year. The case-fatality rate was 0.6%, and the hospitalization rate was 36%. Rates among female patients were lower than among male patients for ehrlichiosis (rate ratio = 0.68) and anaplasmosis (rate ratio = 0.70). Most (80%) ehrlichiosis and anaplasmosis cases met only a probable case definition, although, use of a polymerase chain reaction to confirm infections increased during 2000-2007. Heightened reporting of these diseases will likely continue with improving recognition, changing surveillance practices, and appropriate application of diagnostic assays.     

Infection rates of Amblyomma americanum and Dermacentor variabilis by Ehrlichia chaffeensis and Ehrlichia ewingii in southwest Missouri

Both Ehrlichia chaffeensis and Ehrlichia ewingii are causative agents of human ehrlichiosis. Both pathogens are transmitted to humans through the bite of an infected lone star tick (Amblyomma americanum). Since Missouri has a high incidence of human monocytic ehrlichiosis, we investigated the prevalence of E. chaffeensis- and E. ewingii-infected A. americanum and Dermacentor variabilis (American dog tick) ticks to help assess the relative risk for humans exposed to these vectors. We used a nested polymerase chain reaction assay for the detection of ehrlichial DNA in the collected ticks. Infection rates for both ehrlichial species were calculated from the assay results for each of the tick species. E. chaffeensis was found to be present in 9.8% of adult A. americanum ticks (57 of 579) and 6.7% of D. variabilis ticks (eight of 120). E. ewingii DNA was present at an infection rate of 5.4% in adult A. americanum (31 of 579) and 3.3% of D. variabilis ticks (four of 120). A minimum infection rate for nymph pools of A. americanum was 1.7% for E. chaffeensis and 0.6% for E. ewingii.     

Predicting the emergence of tick-borne infections based on climatic changes in Korea

Granulocytic anaplasmosis (GA) and monocytic ehrlichiosis (ME) are maintained in wild rodent reservoirs and tick vectors in the Republic of Korea. This study investigated the prevalence of 2 tick-borne pathogens, Anaplasma phagocytophilum and Ehrlichia chaffeensis, in wild rodents and ticks in central Korea to identify any significant associations with existing or changing climatic conditions. Specifically, the goal of this study was to develop simple models for the probability of occurrence of an epidemic of GA or ME as a function of climate in an area in a given year. Climatic data from 2 regions, Munsan and Dongducheon, Gyeonggi, in central Korea (between the Demilitarized Zone and Seoul, latitude between 37 degrees N-38 degrees N and longitude between 127 degrees E-128 degrees E), were analyzed with respect to the prevalence of GA and ME in Paju, Yoncheon, Pocheon, and Dongducheon for the period from 2001 to 2005. Rates of A. phagocytophilum and E. chaffeensis decreased as the total yearly precipitation levels and daily humidity increased, and as the daily mean sunshine hours decreased. Rates of A. phagocytophilum and E. chaffeensis from rodent ticks and rodents increased in the fall season. Linear regression analyses evaluating the numbers of positive samples by sample type found that rodent ticks were 6.64 times more likely to be actively infected with A. phagocytophilum than grass ticks or rodents, though the likelihood of any samples testing positive for this pathogen decreased by 0.17 as the annual mean level of precipitation increased by 1 mm. For E. chaffeensis, rodents were 15.67 times more likely to be infected than ticks. Logistic regression analyses evaluating each sample separately found that the odds of infection with A. phagocytophilum were nearly 5 times greater for rodents than ticks. In these analyses, precipitation was one potential factor to account for the prevalence of tickborne diseases.     

一种基于洪水信息的血吸虫病风险预警系统的构建

目的 利用气象数据建立模型,预测洪水季节血吸虫病风险区域,为血吸虫病监测预警提供参考.方法 基于开源R软件,建立交互式血吸虫病预警系统.以血吸虫病传播指数为基础参数,根据累积降雨量及气温数据拟合钉螺物种分布模型,预测钉螺分布概率,判断洪涝灾害期间血吸虫病传播风险区域.结果 基于R软件Shiny包构建网页框架,成功建立了...     

Tick-borne diseases in North Carolina: is "Rickettsia amblyommii" a possible cause of rickettsiosis reported as Rocky Mountain spotted fever?

Cases of Rocky Mountain spotted fever (RMSF) in North Carolina have escalated markedly since 2000. In 2005, we identified a county in the Piedmont region with high case numbers of RMSF. We collected ticks and examined them for bacterial pathogens using molecular methods to determine if a novel tick vector or spotted fever group rickettsiae (SFGR) might be emerging. Amblyomma americanum, the lone star tick, comprised 99.6% of 6,502 specimens collected in suburban landscapes. In contrast, Dermacentor variabilis, the American dog tick, a principal vector of Rickettsia rickettsii, comprised < 1% of the ticks collected. Eleven of 25 lone star tick pools tested were infected with "Rickettsia amblyommii," an informally named SFGR. Sera from patients from the same county who were presumptively diagnosed by local physicians with a tick-borne illness were tested by an indirect immunofluorescence antibody (IFA) assay to confirm clinical diagnoses. Three of six patients classified as probable RMSF cases demonstrated a fourfold or greater rise in IgG class antibody titers between paired acute and convalescent sera to "R. amblyommii" antigens, but not to R. rickettsii antigens. White-tailed deer, Odocoileus virginianus, are preferred hosts of lone star ticks. Blood samples collected from hunter-killed deer from the same county were tested by IFA test for antibodies to Ehrlichia chaffeensis and "R. amblyommii." Twenty-eight (87%) of 32 deer were positive for antibodies to E. chaffeensis, but only 1 (3%) of the deer exhibited antibodies to "R. amblyommii," suggesting that deer are not the source of "R. amblyommii" infection for lone star ticks. We propose that some cases of rickettsiosis reported as RMSF may have been caused by "R. amblyommii" transmitted through the bite of A. americanum.     

Ehrlichia species in Rhipicephalus sanguineus ticks in Cameroon

Ehrlichia and Anaplasma species are tick-transmitted obligately intracellular bacteria that commonly cause disease in dogs worldwide. In addition to causing disease in canines, Ehrlichia chaffeensis, Ehrlichia ewingii, and Anaplasma phagocytophilum are responsible for emerging and life-threatening human zoonoses in the United States. We previously reported a high prevalence of E. canis infection in Cameroonian dogs based on serologic and molecular evidence. This study was undertaken to determine the Ehrlichia species (E. canis, E. chaffeensis, E. ewingii) present in Rhipicephalus sanguineus ticks (n = 92) collected from those dogs (n = 51). Ehrlichial DNA was detected by real-time polymerase chain reaction (PCR) in 28 (30%) unengorged R. sanguineus ticks attached to dogs. E. canis, the causative agent of canine monocytic ehrlichiosis, was detected in 19 (21%) ticks from 15 dogs, E. ewingii was detected in six (6%) ticks from 6 dogs, and E. chaffeensis, the etiologic agent of human monocytotropic ehrlichiosis, was detected in 4 (4%) ticks. Notably, 2 ticks were coinfected with E. chaffeensis and E. canis, one tick with E. canis and E. ewingii, and one tick with E. chaffeensis and E. ewingii. These findings further support our previous conclusion that multiple Ehrlichia species are present in Cameroon and identify R. sanguineus ticks primarily infected with E. canis, but suggest that they may be infected with and transmit other ehrlichial agents in Cameroon, potentially to humans.     

用查菲埃立克体P28融合蛋白作免疫印迹诊断犬埃立克体感染

目的 建立以查菲埃立克体P28融合蛋白为抗原的诊断犬埃立克体感染的免疫印迹。方法 诱导PinPoint^TMXa-3/P28重组质粒在E coli细胞内高效表达查菲埃立克体P28融全蛋白,以该重组蛋白作抗原与犬血清行免疫印迹。结果 P28融合蛋白与书籍的3份犬埃立克体感染血清呈阳性反应,与正常犬血清反应为阴性,在165份来自犬埃立克体病疫区的待检犬血清中有43份（26%）与P28反应阳性。结论 查菲埃立克体P28融合蛋白可作为犬埃立克体感染的特异性诊断抗原,以其建立的免疫印迹可用于犬埃立克体病的诊断。     

Evidence of tick-borne organisms in mule deer (Odocoileus hemionus) from the western United States

Free-ranging mule deer (MD; Odocoileus hemionus) from Arizona and California were tested for evidence of infection with several tick-borne pathogens, including species of Ehrlichia, Anaplasma, Babesia, and Borrelia. Of 125 mule deer tested from Arizona, 29 (23%) and 11 (9%) had antibodies reactive to E. chaffeensis and A. phagocytophilum by indirect immunofluorescent antibody testing, respectively; none of the six MD tested from California were seropositive. Using a commercial competitive ELISA kit, antibodies reactive to Anaplasma spp. were detected in 19 (15%) MD from Arizona and four of six (67%) MD from California. Polymerase chain reaction (PCR) testing for tick-borne pathogens was conducted on blood samples from 29 MD from Arizona and 11 MD from California. Twenty-two of 29 (75.9%) MD from Arizona had PCR evidence of infection with at least one tick-borne pathogen. We detected an Anaplasma sp. in 19 of 29 (65.5%) MD and a Babesia sp. in 10 of 29 (34%) MD. Sequencing of these amplicons indicated that the Anaplasma sp. was the same that had previously been detected in MD from California and the Babesia sp. was similar to one previously detected in a reindeer (Rangifer tarandus tarandus) from California. All of the California MD had evidence of infection with a tick-borne pathogen. Two different species of Anaplasma spp. were detected in MD from California, eight of of 11 MD were infected with an Anaplasma sp., and three of 11 MD were infected with A. ovis. This is the first report of a mule deer naturally infected with A. ovis. Ten of 11 MD from California were infected with a Babesia-like organism previously associated with human disease, and a single MD was PCR positive for Borrelia coriaceae, which has been associated with epizootic bovine abortion. Together, these data suggest that MD in northern Arizona and eastern California are exposed to several pathogens of human and veterinary importance.     

The incidence of ehrlichial and rickettsial infection in patients with unexplained fever and recent history of tick bite in central North Carolina.

We examined the clinical and laboratory findings of a consecutive series of patients from central North Carolina presenting with fever and a history of tick bite within the preceding 14 days. Evidence of a tick-transmitted pathogen was detected in 16 of 35 patients enrolled over a 2-year period. Nine patients were infected with Ehrlichia chaffeensis, and 6 were infected with a spotted fever group rickettsia; 1 patient had evidence of coinfection with E. chaffeensis and a spotted fever group rickettsia. Four patients had detectable antibodies against the human granulocytic ehrlichiosis agent; however, only 2 had a 4-fold antibody titer rise without detectable antibodies against E. chaffeensis. The other 2 were thought to have cross-reacting antibodies to E. chaffeensis. We conclude that ehrlichial infections may be as common as spotted fever group rickettsial infections in febrile patients from central North Carolina with a recent history of tick bite.