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.

Persistent Ehrlichia chaffeensis infection in white-tailed deer

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 (leer 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 were negative on all tests through 90 DPI at which time they were removed from the study. Herein we confirm that white-tailed deer become persistently infected with E. chaffeensis, have initial rickettsemias of several weeks duration and may experience recrudescence of rickettsemia, which reaffirm the importance of deer in the epidemiology of E. chaffeensis.

A cluster of fulminant myocarditis cases in children, Baltimore, Maryland, 1997

The true incidence of myocarditis in children is difficult to estimate because many mild cases go undetected. This study describes an unusual cluster of myocarditis cases that occurred in young children living in the greater Baltimore area between May and October 1997. A search of multiple comprehensive databases and interviews with area pediatric cardiologists were conducted to identify unreported cases and determine the background rate of myocarditis in the area. Seven cases of myocarditis were found as well as two with a similar clinical picture and myocardial fibrosis on tissue examination. Six case patients with active myocarditis and one child with fibrosis died. The case children were predominantly black (eight of nine) and male (seven of nine), with no identifiable risk factors. The disease was characterized by a fulminant course with malignant arrhythmias. The greatest number of pediatric myocarditis deaths reported in 1 year prior to 1997 was three. Myocardial tissues were examined using immunohistochemistry, in situ hybridization, and polymerase chain reaction but no etiologic agent was identified. This outbreak is unusual because of both the number of cases and the fulminant course of the disease in this group of children.

Influenza A virus infection complicated by fatal myocarditis

Influenza virus typically causes a febrile respiratory illness, but it can present with a variety of other clinical manifestations. We report a fatal case of myocarditis associated with influenza A infection. A previously healthy 11-year-old girl had malaise and fever for approximately 1 week before a sudden, witnessed fatal collapse at home. Autopsy revealed a pericardial effusion, a mixed lymphocytic and neutrophilic myocarditis, a mild lymphocytic interstitial pneumonia, focal bronchial/bronchiolar mucosal necrosis, and histologic changes consistent with asthma. Infection with influenza A (H3N2) was confirmed by virus isolation from a postmortem nasopharyngeal swab. Attempts to isolate virus from heart and lung tissue were unsuccessful. Immunohistochemical tests directed against influenza A antigens and in situ hybridization for influenza A genetic material demonstrated positive staining in bronchial epithelial cells, whereas heart sections were negative. Sudden death is a rare complication of influenza and may be caused by myocarditis. Forensic pathologists should be aware that postmortem nasopharyngeal swabs for viral culture and immunohistochemical or in situ hybridization procedures on lung tissue might be necessary to achieve a diagnosis. Because neither culturable virus nor influenza viral antigen could be identified in heart tissue, the pathogenesis of influenza myocarditis in this case is unlikely to be the result of direct infection of myocardium by the virus. The risk factors for developing myocarditis during an influenza infection are unknown.

Effects of verbal elaborations on memory for sentences in adults with mental retardation

We examined the effects of verbal elaborations on memory for verbal material in adults with mental retardation and a control group of adults of normal intelligence. During acquisition, three types of sentences were presented that differed in elaboration of the subject-adjective relationship: a) non-elaborated base sentences; b) base sentences with arbitrary verbal elaborations; and c) base sentences with explanatory verbal elaborations that clarified the significance of the subject-adjective relationship. At test, we varied the retrieval context by presenting either base sentences alone or base sentences with the verbal elaborations. A three-alternative, forced-choice recognition procedure was used to test memory for the target adjectives. Results yielded a positive effect of retrieval support (elaborations present at study and test) on recognition performance for adults with mental retardation. These data imply that the retrieval context plays an important role in recognition memory for adults with mental retardation.

Novel Ehrlichia organism (Rickettsiales: Ehrlichieae) in white-tailed deer associated with lone star tick (Acari: Ixodidae) parasitism

Polymerase chain reaction (PCR) evidence of a novel Ehrlichia organism was found recently in wild white-tailed deer, Odocoileus virginianus Zimmermann, and lone star ticks, Amblyomma americanum L., from the southeastern United States. To evaluate whether lone star tick parasitism was associated with the presence of this novel Ehrlichia organism in deer, 2 retrospective studies were conducted using specific nested PCR to test archived deer serum samples. The 1st study of 150 serum samples collected from a single deer population over a 15-yr period examined the temporal association between the presence of the Ehrlichia organism in deer and parasitism by lone star ticks. The deer Ehrlichia was not detected in serum samples collected before 1986, when lone star ticks were absent or rare, but was detected in samples collected in 1986 and every year thereafter, when lone star ticks became increasingly abundant. In the 2nd study, serum samples from 120 deer from 24 sites in 14 southeastern states were tested to evaluate if a site-specific, spatial association existed between the presence of the deer Ehrlichia and lone star ticks. All 60 serum samples from the 12 deer populations without evidence of lone star tick infestation were negative for the deer Ehrlichia, whereas 83% of the 12 populations infested by lone star ticks had PCR evidence of infection. These data suggest that lone star ticks may be a vector of the deer Ehrlichia; however, they do not preclude the involvement of other arthropods in maintaining infection with this organism in deer populations.

Serologic evidence of human monocytic and granulocytic ehrlichiosis in Israel

We conducted a retrospective serosurvey of 1,000 persons in Israel who had fever of undetermined cause to look for Ehrlichia chaffeensis antibodies. Four of five cases with antibodies reactive to E. chaffeensis were diagnosed in the summer, when ticks are more active. All patients had influenzalike symptoms with high fever. None of the cases was fatal. Three serum samples were also seroreactive for antibodies to E. canis, and one was also reactive to the human granulocytic ehrlichiosis (HGE) agent. The titer to the HGE agent in this patient was higher than the serum titer to E. chaffeensis, and the Western blot analysis also indicated that the HGE agent was the primary cause of infection. We present the first serologic evidence that the agents of human monocytic ehrlichiosis (HME) and HGE are present in Israel. Therefore, human ehrlichiosis should be included in the differential diagnoses for persons in Israel who have been exposed to ticks and have influenzalike symptoms.

Natural coinfection of a white-tailed deer (Odocoileus virginianus) population with three Ehrlichia spp

The ticks Amblyomma americanum and Ixodes scapularis, strongly implicated vectors of Ehrlichia chaffeensis and the human granulocytic ehrlichiosis (HGE) agent, respectively, commonly are found on white-tailed deer (Odocoileus virginianus). As deer can be infected with E. chaffeensis, the HGE agent, and another Ehrlichia-like organism, a deer population parasitized by both tick species in coastal Georgia was tested for evidence of Ehrlichia spp. infection using serologic, molecular, and culture techniques. Antibodies to both E. chaffeensis (geometric mean titer = 111) and Ehrlichia equi, surrogate antigen for the HGE agent, (geometric mean titer = 1,024) were detected by indirect fluorescent antibody testing. Nested polymerase chain reaction employing species-specific primers demonstrated sequence-confirmed 16S rDNA fragments of 3 distinct Ehrlichia spp. in this population: E. chaffeensis (1/5), the HGE agent (3/5), and an Ehrlichia-like organism previously described from white-tailed deer (5/5). Ehrlichia chaffeensis was isolated in culture from the inguinal lymph node of a single deer. An Ehrlichia-type morula was identified in a neutrophil of 1 deer on examination of blood smears. This work provides the first evidence of the HGE agent in a nonhuman host in the southeastern United States and documents infection with both E. chaffeensis and the HGE agent in a single deer population, thereby supporting the importance of white-tailed deer in the natural history of the human ehrlichioses agents.

An analysis of maladaptive behaviors in persons with autism, PDD-NOS, and mental retardation

In this study, we examined three maladaptive behaviors, self-injurious behavior (SIB), stereotypies, and aggression in adults with autism, pervasive developmental disorder, not otherwise specified (PDD-NOS), and mental retardation. We used a brief functional analysis rating scale. The Questions About Behavioral Functions (QABF), to examine the function of each behavior. Across the three groups, our results indicated that aggression was primarily maintained for attentional reasons and stereotypies for nonsocial reasons. No specific function(s) were found to maintain SIB. These results suggest that the function of a maladaptive behavior may be associated more with the particular maladaptive behavior displayed rather than inclusion in a certain diagnostic group. Implications of findings for assessment and treatment issues are discussed.

A single tissue culture system for the propagation of the agents of the human ehrlichioses

Two newly emergent human diseases found in the United States, human monocytotropic ehrlichiosis (HME) and human granulocytotropic ehrlichiosis (HGE), are caused by pathogens of the genus Ehrlichia. The causative agent of HGE can be propagated in HL-60 human promyelocytic leukemia cells. Herein, we report the development of a method to propagate E. chaffeensis, the causative agent of HME, in HL-60 cells, thus providing a common system for the study of both species. The continuous propagation of E. chaffeensis requires the induction of HL-60 differentiation along the monocytic pathway toward phenotypically mature macrophages by the addition of 25-OH vitamin D3 to the growth medium.

Duration of tick attachment required for transmission of granulocytic ehrlichiosis

Deer tick-transmitted pathogens such as Lyme disease spirochetes and babesiae appear to require a period of reactivation and replication during the tick's blood meal before it is able to infect a host. The duration of nymphal tick attachment that is required for transmission of the agent of human granulocytic ehrlichiosis (HGE) was determined by removing feeding ticks from mice at various time points. As with spirochetes and babesiae, ehrlichiae infected few mice when ticks were removed prior to 36 h of tick attachment. This "grace period" may serve as a modifying factor in the epidemiology of this newly emergent zoonosis and help physicians make informed decisions concerning management of tick bites in HGE-endemic areas.

Lack of seroreactivity to Ehrlichia chaffeensis among rodent populations

A retrospective serosurvey for antibodies to Ehrlichia chaffeensis was conducted on eight species of wild rodents (Mus musculus, Oryzomys palustris, Peromyscus leucopus, 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.

Dogs infected with a human granulocytotropic Ehrlichia spp. (Rickettsiales: Ehrlichieae)

Dogs were found to be susceptible to human granulocytotropic Ehrlichia spp. Infection was produced through the bite of Ixodes scapularis Say (= dammini Spielman, Clifford, Piesman & Corwin) nymphs and adults that acquired infection while feeding as larvae on experimentally infected mice. Dogs were also infected by intravenous injection of mouse blood or dog blood from parasitemic donors. Parasites were demonstrable in neutrophils within 8 or 9 d after nymphs began feeding; prepatent periods were longer when infection was induced by adult tick feeding (18 d) or by transfusion of mouse blood (12 d). The shortest prepatent period observed was 5 d in a dog infected by transfusion of blood from a parasitemic dog. Infections in dogs were mild and apparently transient. Mild thrombocytopenia was the most commonly observed abnormality. Parasites could be detected by light microscopy during the acute phase of infection (4 or 5 d) and parasite DNA by polymerase chain reaction as early as 5 d after exposure but not at 6-9 d after morulae were first observed in neutrophils. Likewise, dog blood was infectious for mice at 2 d but not at 25 d, and for dogs at 3 d but not at 13 d after morulae were first observed in neutrophils. Seroconversion occurred as early as 11 d after onset of tick feeding and persisted until dogs were euthanatized. Gross and histopathologic lesions were similar to those observed in dogs with E. canis (Donatien & Lestoquard), E. chaffeensis Anderson, Dawson & Wilson, and E. ewingii Anderson, Greene, Jones & Dawson infections but were generally milder than any of these. The moderate enlargement of lymphoid organs observed grossly was reflected histologically as mild to moderate reactive hyperplasia, which was largely follicular (B cell).

Natural history of Ehrlichia chaffeensis (Rickettsiales: Ehrlichieae) in the piedmont physiographic province of Georgia

The roles of wild mammals and ticks in the epidemiology of Ehrlichia chaffeensis at a suspected endemic site were investigated using serologic testing, culture, and polymerase chain reaction (PCR) supported by restriction endonuclease analysis and DNA sequencing. Antibodies reactive to E. chaffeensis (> or = 1:64) were detected in 92% of white-tailed deer (Odocoileus virginianus), 21% of raccoons (Procyon lotor), and 8% of opossums (Didelphis virginianus), but not in 8 other species of mammals. Of 7 species of ticks found by host and environmental sampling, Amblyomma americanum was the dominant species, accounting for greater than 99% of all ticks collected. Deer, raccoons, and opossums were the only species parasitized by all life stages of A. americanum, and A. americanum was the only tick parasitizing deer. A nested PCR protocol incorporating E. chaffeensis-specific primers detected E. chaffeensis DNA in blood, lymph nodes, or spleen from 54% of deer examined. The nested PCR detected E. chaffeensis DNA in 6 of 50 (12%) individual adult A. americanum collected from the environment, in 14 of 79 (18%) pools representing 402 adult A. americanum collected from the environment, and in 7 of 25 (28%) pools of mixed stages of A. americanum collected from deer. Although no Ehrlichia spp. were isolated in culture, sequencing of representative amplicons from deer and ticks confirmed PCR products as E. chaffeensis. These data provide strong evidence that white-tailed deer and lone star ticks are the primary reservoir and vector of E. chaffeensis, respectively. The same PCR protocol, incorporating primers specific for an Ehrlichia-like organism of white-tailed deer, detected this organism in blood, lymph nodes, or spleen from 96% of these deer. The Ehrlichia-like organism of deer was detected by PCR from 0 of 50 individual ticks, 7 of 79 (9%) pools, and 1 of 25 (4%) pools of A. americanum collected from deer. Sequencing of representative amplicons from deer and ticks confirmed PCR products as Ehrlichia-like organism of deer. These data suggest that the Ehrlichia-like organism of deer is present in both the deer and lone star ticks populations at this location.

Isolation of Ehrlichia chaffeensis from wild white-tailed deer (Odocoileus virginianus) confirms their role as natural reservoir hosts

Field and experimental studies have implicated white-tailed deer (Odocoileus virginianus) as probable reservoir hosts for Ehrlichia chaffeensis, the causative agent of human monocytic ehrlichiosis, but natural infection in deer has not been confirmed through isolation of E. chaffeensis. Thirty-five white-tailed deer collected from three Amblyomma americanum-infested populations in Georgia were examined for evidence of E. chaffeensis infection by serologic, molecular, cell culture, and xenodiagnostic methods. Twenty-seven deer (77%) had E. chaffeensis-reactive indirect fluorescent-antibody assay titers of > or = 1:64; and the blood, spleens, or lymph nodes of seven (20%) deer were positive in a nested PCR assay with E. chaffeensis-specific primers. E. chaffeensis was isolated in DH82 cell cultures from the blood of five (14%) deer, including two deer that were PCR negative. Combination of culture and PCR results indicated that six (17%) deer were probably rickettsemic and that nine (26%) were probably infected. Restriction digestion of PCR products amplified from deer tissues and cell culture isolates resulted in a banding pattern consistent with the E. chaffeensis 16S rRNA gene sequence. The sequences of all PCR products from deer tissues or cell culture isolates were identical to the sequence of the Arkansas type strain of E. chaffeensis. Xenodiagnosis with C3H mice inoculated intraperitoneally with deer blood, spleen, or lymph node suspensions was unsuccessful. When viewed in the context of previous studies, these findings provide strong evidence that E. chaffeensis is maintained in nature primarily by a tick vector-vertebrate reservoir system consisting of lone star ticks and white-tailed deer.

Fingerprinting of Ehrlichia species by repetitive element polymerase chain reaction

To facilitate identification of ehrlichial pathogens, we developed a new technique based on fingerprints resulting from repetitive element polymerase chain reaction (rep-PCR). This technique uses consensus tRNA primers to generate amplification products that reflect distance polymorphisms between adjacent tRNA genes. Species-specific fingerprint patterns were obtained for seven Ehrlichia spp., as well as the unnamed causative agent of human granulocytotropic ehrlichiosis. Bands ranged in size from approximately 50 to 1,000 base pairs. Banding patterns varied depending on dilution of template DNA, with lower dilutions giving more complex banding patterns. These preliminary data indicate that repetitive-sequence-based PCR appears to be a useful technique for identifying ehrlichial organisms to the species, and perhaps the strain level. Compared with other conventional molecular-biologic methods, rep-PCR offers the advantages of ease of performance and rapid availability of results.

Attempted transmission of human granulocytotropic Ehrlichia (HGE) by Amblyomma americanum and Amblyomma maculatum

Transstadial transmission of human granulocytotrophic Ehrlichia (HGE) was attempted in dogs using Amblyomma americanum (L.) and A. maculatum Koch, two species that, as adults, feed readily on human beings. Larvae and nymphs were acquisition-fed on a dog that was parasitemic with HGE. Two months later, following digestion of the blood meal and subsequent molting to nymphal or adult stage, these ticks were fed to repletion on HGE-naive dogs. None of the dogs developed clinical evidence of ehrlichiosis. Parasites were not observed in blood smears by light microscopy, HGE DNA was not detected by polymerase chain reaction, and none of the dogs seroconverted. Based on this trial, we conclude that, unlike E. chaffeensis, HGE is probably not transmitted from dog to dog by either A. americanum or A. maculatum.

Evaluation of indapamide 1.25 mg once daily in elderly patients with mild to moderate hypertension

The objective of this study was to evaluate the safety and efficacy of indapamide 1.25 mg once daily as monotherapy in elderly patients (65 years and older) with mild to moderate essential hypertension. Two hundred and seventy-nine (279) elderly patients were enrolled in a washout period, during which patients received single-blind placebo for 4 weeks. Patients demonstrating supine diastolic pressures between 95 mm Hg and 114 mm Hg at the end of the 4-week placebo washout period were entered into the 8-week double-blind treatment period. Two hundred and four (204) patients qualified for the study and were randomized to the double-blind treatment; 103 patients received indapamide 1.25 mg and 101 patients received placebo for 8 weeks. Overall, 177 patients (92 indapamide and 85 placebo) completed the study. The primary efficacy criterion was the mean change in supine diastolic blood pressure (DBP) from double-blind baseline to the end of 8 weeks of therapy. By week 8 of the double-blind treatment period, indapamide 1.25 mg produced a statistically significant (P = 0.0037) decrease in supine DBP of 8.2 mm Hg compared to a decrease of 5.3 mm Hg produced in the placebo group. Additionally, indapamide 1.25 mg was statistically (P = 0.0028) more effective than placebo in reducing supine systolic BP (SBP) (-10.1 vs -4.2 mm Hg). The incidence of drug-related adverse events during the double-blind treatment period was similar between the two treatment groups. A low dose of indapamide, 1.25 mg, given once daily for 8 weeks was effective as monotherapy with respect to BP reduction in an elderly population with mild to moderate hypertension. Indapamide 1.25 mg was safe and generally well tolerated in this elderly patient population.

Development and use of specific polymerase reaction for the detection of an organism resembling Ehrlichia sp. in white-tailed deer

The role of white-tailed deer (Odocoileus virginianus) in the epidemiology of Ehrlichia chaffeensis and the agent of human granulocytic ehrlichiosis (HGE) is not fully understood, and diagnostic procedures may be complicated by the recent detection of 16S rDNA sequence from an Ehrlichia sp.-like organism in wild deer. A specific forward primer (DGA) and an Ehrlichia spp. reverse primer (GA1UR) were constructed to amplify this new, distinct Ehrlichia sp.-like 16S rDNA. The DGA primer, a forward primer specific for E. chaffeensis (DCH), and a forward primer specific for the E. phagocytophila genogroup (GE9f) were each used with GA1UR in nested polymerase chain reactions to amplify 16S rDNA sequences from control samples containing the deer Ehrlichia sp.-like organism, E. chaffeensis, or the HGE agent. Primer pairs DGA/GA1UR and DCH/GA1UR specifically amplified 16S rDNA sequences from the corresponding target organism, whereas GE9f/GA1UR amplified 16S rDNA sequence from both the HGE agent and the deer Ehrlichia sp.-like organism. With a nested PCR using DGA/GA1UR and DCH/GA1IUR on DNA extracted from white blood cells from 62 deer from 10 populations in four U.S. states, we observed a high prevalence (65%) of 16S rDNA sequences of the deer Ehrlichia sp.-like organism, and a low prevalence (5%) of the E. chaffeensis sequence. In this field survey, E. chaffeensis-reactive antibodies detected by indirect fluorescence assays were associated (P < 0.001) with PCR evidence of the deer Ehrlichia sp.-like organism, but not E. chaffeensis. Infestations of Amblyomma americanum also were associated (P < 0.001) with PCR evidence of the deer Ehrlichia sp.-like organism. The potential for serologic cross-reactions and non-specific PCR products arising from the deer Ehrlichia sp.-like organism should be considered when evaluating the role of deer and their ticks in the epidemiology of ehrlichial pathogens of humans.

Development and evaluation of a recombinant antigen, monoclonal antibody-based competitive ELISA for heartwater serodiagnosis

Cowdria ruminantium is the etiologic agent of heartwater, a tick-transmitted foreign animal disease with considerable potential for entrance into the USA. A competitive enzyme-linked immunosorbent assay (cELISA) was developed to detect serologic responses to C. ruminantium infection. The cELISA utilized a recombinant form of the C. ruminantium major antigenic protein (MAP-1) as the antigen and an anti-MAP-1 monoclonal antibody as the competing indicator reagent. Experimental antisera to C. ruminantium and a wide variety of related ehrlichial organisms were used to evaluate cELISA reactivity. Only sera against C. ruminantium, Ehrlichia canis, E. chaffeensis, and a recently discovered cervine ehrlichia-like organism reacted positively in the cELISA. Specificity of the cELISA was > or = 99.5% in a survey of 1,774 southeastern US and Puerto Rican slaughter cattle sera but was only 85% in a group of 79 hunter-killed white-tailed deer (Odocoileus virginianus) from the southeastern USA. Reference true-positive and cELISA false-positive sera were further analyzed by end point titrations using the cELISA and by indirect fluorescent antibody (IFA) tests for reactivity with C. ruminantium, E. canis, and E. chaffeensis antigens. True heartwater-positive sera were significantly more reactive using the cELISA and C. ruminantium IFA procedures (P < 0.05), whereas false-positive sera were significantly more reactive with the antigens used in the E. chaffeensis IFA procedure (P < 0.05). A group of sera from 210 field-origin ruminants residing on known or potentially heartwater-endemic Caribbean islands revealed a substantial (12.4%) prevalence of cELISA-positive specimens. The cELISA is a relatively specific serodiagnostic test for heartwater in cattle and could be used to monitor for possible introduction of the disease into the USA. The cELISA may also be an excellent tool for monitoring the success of an ongoing Caribbean Amblyomma tick eradication program designed to eliminate the biological vector responsible for the perpetuation and spread of this dangerous foreign animal disease.

Attempted transmission of Ehrlichia canis by Rhipicephalus sanguineus after passage in cell culture

OBJECTIVES

To compare the transmissibility by the brown dog tick, Rhipicephalus sanguineus, of a recent isolate of Ehrlichia canis (Ebony) with that of another isolate (Oklahoma) that had been passaged in cell culture, and to assess the genetic similarity of the 2 isolates as reflected in the nucleotide (NT) sequence of 16S rDNA.

ANIMALS

13 healthy dogs of various ages and breeds.

PROCEDURE

Larval and nymphal ticks were acquisition fed on acutely infected dogs, and, after molting, they were transmission fed as nymphs and adults, respectively, on Ehrlichia-naive dogs. All dogs were monitored daily by blood smear evaluation for evidence of parasitized leukocytes and by physical examination for clinical signs of ehrlichiosis. Serologic and hematologic values were measured weekly. Using a nested polymerase chain reaction, the 16S rDNA was amplified, and the NT sequence of the template DNA was determined.

RESULTS

The Ebony isolate of E canis was successfully transmitted to dogs by nymphal and adult ticks. In contrast, no ticks that fed on dogs harboring the cell-cultured isolate (Oklahoma) transmitted it to dogs. On the basis of 16S rDNA sequence, the 2 isolates were 99.9% similar, with only 1 NT difference.

CONCLUSIONS

These results reconfirm the vector potential of R sanguineus for E canis. Passage of the Oklahoma isolate of E canis in cell culture apparently adversely affected its transmissibility by ticks, raising the possibility that cell-cultured isolates of this rickettsia may lose their affinity for ticks. Determination of 16S rDNA sequence suggests minor strain variation within the species E canis.

Persistent infection of C3H/HeJ mice by Ehrlichia chaffeensis

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.

Polymerase chain reaction evidence of Ehrlichia chaffeensis, an etiologic agent of human ehrlichiosis, in dogs from southeast Virginia

OBJECTIVE

To ascertain whether dogs are naturally infected with Ehrlichia chaffeensis.

ANIMALS

74 dogs from 5 animal shelters and 1 kennel in 3 cities and 3 counties in southeastern Virginia were tested during June 1991.

PROCEDURE

Blood was drawn from 74 dogs; 73 were tested serologically for antibodies reactive to E chaffeensis and E canis, and 38 were tested for the presence of E chaffeensis, E canis, and E ewingii by polymerase chain reaction (PCR). Serologic testing by indirect fluorescent antibody assay. Nested PCR used Ehrlichia wide outside primers to detect initial products, followed by use of species-specific primers for identification.

RESULTS

28 (38.4%) dogs had a positive test result (minimum titer, > or = 1:64) for antibodies reactive to E chaffeensis, and 28 (38.4%) had a positive reaction to E canis. PCR analysis indicated that 8 (42.1%) dogs were positive for E chaffeensis and 6 dogs (31.6%) were positive for E ewingii. All dogs had negative results of the PCR test for E canis.

CONCLUSION

Dogs are potential reservoirs of E chaffeensis.

CLINICAL RELEVANCE

Canine E chaffeensis infection may be more prevalent than E canis or E ewingii infection in this region of the United States.

A recombinant antigen from the heartwater agent (Cowdria ruminatium) reactive with antibodies in some southeastern United States white-tailed deer (Odocoileus virginianus), but not cattle, sera

Recombinant baculovirus techniques were used to express the 260 amino acid carboxyterminal portion of the 32 kilodalton (kDa) major antigenic protein (MAP 1) of Cowdria ruminantium, the heartwater agent, as a fusion protein. The recombinant MAP 1 was fused to an aminoterminal independently antigenic octapeptide sequence (FLAG peptide). Recombinant MAP 1 was used as an immunoblotting antigen to evaluate numerous reference antisera against organisms of the tribe Ehrlichieae. Monoclonal and polyclonal C. ruminantium antibodies, monoclonal anti-FLAG ascites, and antisera to Ehrlichia canis and Ehrlichia chaffeensis reacted with this antigen. Twelve of 79 sera collected 1980 to 1992 from southeastern U.S. white-tailed deer (Odocoileus virginianus) were also unexpectedly immunoblot-positive to MAP 1. These 12 deer sera had, as a group, significantly (P < 0.01) greater anti-E. chaffeensis titers (previously determined) than the sera from MAP 1 immunoblot-negative deer living in the same areas. None of the 262 sera from cattle living in the same areas were immunoblot-positive to MAP 1. All of an additional 50 cervine sera from Michigan (USA), 72 bovine sera from northern U.S. cattle, and 72 sera from Puerto Rican cattle were also immunoblot-negative to MAP 1. Sera from African sheep which were falsely seropositive to authentic MAP 1 were also immunoblot-positive to the recombinant MAP 1. Unidentified Ehrlichia spp. capable of serologic crossreactivity with the heartwater agent appear to be present in some southeastern U.S. white-tailed deer but not cattle. These or related Ehrlichia spp. may also be found elsewhere in the world in non-cervine species.

Perpetuation of the agent of human granulocytic ehrlichiosis in a deer tick-rodent cycle

A human-derived strain of the agent of human granulocytic ehrlichiosis, a recently described emerging rickettsial disease, has been established by serial blood passage in mouse hosts. Larval deer ticks acquired infection by feeding upon such mice and efficiently transmitted the ehrlichiae after molting to nymphs, thereby demonstrating vector competence. The agent was detected by demonstrating Feulgen-positive inclusions in the salivary glands of the experimentally infected ticks and from field-derived adult deer ticks. White-footed mice from a field site infected laboratory-reared ticks with the agent of human granulocytic ehrlichiosis, suggesting that these rodents serve as reservoirs for ehrlichiae as well as for Lyme disease spirochetes and the piroplasm that causes human babesiosis. About 10% of host-seeking deer ticks were infected with ehrlichiae, and of these, 20% also contained spirochetes. Cotransmission of diverse pathogens by the aggressively human-biting deer tick may have a unique impact on public health in certain endemic sites.

The first isolation, in vitro propagation, and genetic characterization of Ehrlichia canis in Israel

Ehrlichia canis, the etiologic agent of canine ehrlichiosis, was isolated in Israel from a naturally infected dog with acute signs of the disease. The organism designated E. canis 611, was passaged experimentally to a beagle, from which it was propagated in primary canine monocytes. The organism was then grown in vitro in a continuous canine cell line, DH82. Nine beagles subsequently injected with whole E. canis-infected blood all developed typical symptoms of ehrlichiosis. An indirect immunofluorescence antibody test to E. canis was developed and compared with a commercial kit, revealing a good correlation between the two assays. Transmission electron microscopy of DH82 cells infected with the Israeli strain of E. canis (611), revealed organisms similar to those described in the literature: two different forms of morulae appeared, one tightly, the other loosely, packed. The 16S rRNA gene sequence obtained from the Israeli Ehrlichia isolate was compared with other isolates, E. canis Oklahoma and E. canis Florida. The Israeli strain 16S rRNA had three nucleotide differences from the Oklahoma isolate, and four nucleotide differences from the Florida isolate, in addition to one nucleotide gap in each. The Israeli isolate was found to be 0.54% different from the Oklahoma strain, and 0.61% different from the Florida strain. There are the same magnitudes of differences displayed by the other most closely related group in the phylogenetic tree, namely Ehrlichia equi, Ehrlichia phagocytophilia and the human granulocytic ehrlichia.

Ehrlichia-like 16S rDNA sequence from wild white-tailed deer (Odocoileus virginianus)

The reservoir hosts of Ehrlichia chaffeensis, etiologic agent of human ehrlichiosis are unknown. Initially, white-tailed deer (WTD) were serologically implicated as possible reservoirs of E. chaffeensis. Subsequent studies showed that WTD were susceptible to infection with E. chaffeensis and that deer-to-deer transmission by a tick vector, Amblyomma americanum, is possible under experimental conditions. To determine if wild WTD were infected with E. chaffeensis, whole blood was collected from 10 deer from Oklahoma and Georgia. All 10 deer had antibodies reactive to E. chaffeensis. Whereas E. chaffeensis was not isolated, restriction enzyme mapping and sequencing of the 16S rDNA gene revealed that a unique Ehrlichia-like agent was present. All 10 deer appeared to be infected with the same agent. We suspect that A. americanum is the vector of this new agent based upon the previously published temporal association between the appearance of E. chaffeensis seropositive WTD and A. americanum. However, the taxonomic and antigenic relationships, geographic distribution, epidemiology, and zoonotic potential of this agent are yet to be determined.

The interface between research and the diagnosis of an emerging tick-borne disease, human ehrlichiosis due to Ehrlichia chaffeensis

Two new ehrlichial species that cause human disease have recently been identified: Ehrlichia chaffeensis and the currently unnamed agent of human granulocytic ehrlichiosis. Our objective was to review data on the clinical presentation, laboratory and epidemiological findings, therapy, and diagnostic procedures of patients with human ehrlichiosis due to E chaffeensis. From 1986 through 1994, 400 case patients were identified from 30 US states. Most patients had a nonspecific illness, characterized by fever and headache. Severe illness and death occurred, primarily in the elderly. Laboratory findings most commonly included leukopenia, thrombocytopenia, and elevated liver function test results. Antibody response was the basis for diagnosis, although polymerase chain reaction testing has been useful in research settings. Empirical treatment with tetracycline or its analogues should be begun as soon as possible after the onset of symptoms. Clinicians need to be alert for this illness when evaluating febrile patients whose history includes possible recent tick exposure.

Site-specific geographic association between Amblyomma americanum (Acari: Ixodidae) infestations and Ehrlichia chaffeensis-reactive (Rickettsiales: Ehrlichieae) antibodies in white-tailed deer

Serum samples from white-tailed deer, Odocoileus virginianus Zimmermann, collected from 1982 through 1992 from the southeastern United States were tested for antibodies reactive to Ehrlichia chaffeensis Anderson, Dawson, Jones, & Wilson, the causative agent of human ehrlichiosis. Results were compared between areas based on known infestations of the lone star tick, Amblyomma americanum L., a suspected vector of E. chaffeensis. One hundred and twenty-five of 300 (41.7%) deer tested positive (> or = 1:128) for E. chaffeensis-reactive antibodies by fluorescent antibody analysis. Thirty of 30 (100%) collection areas known to be lone star tick infested contained deer that tested positive for E. chaffeensis-reactive antibodies, corresponding to 121/150 (80.7%) of deer examined. A few deer, 4/150 (2.7%) of those examined, from 2 of 30 (6.7%) areas where lone star ticks were not detected were positive for E. chaffeensis-reactive antibodies. This site-specific geographic association between A. americanum and the presence of E. chaffeensis-reactive antibodies in deer provides strong evidence that A. americanum is a natural vector of E. chaffeensis or a closely related species among white-tailed deer.

Ehrlichiosis in a golf-oriented retirement community

BACKGROUND

Ehrlichiosis due to Ehrlichia chaffeensis usually occurs sporadically or in small clusters, with an annual incidence estimated at 3 to 5 cases per 100,000 population in areas of endemic disease. The putative principal vector is the Lone Star tick (Amblyomma americanum). We investigated an outbreak of ehrlichiosis that occurred in June 1993 among members of a golf-oriented retirement community (community A) in Tennessee. The community is densely wooded and borders a wildlife-management area where deer are numerous.

METHODS

We conducted a case-control study, using medical-history reviews, serologic testing, and testing with the polymerase chain reaction for E. chaffeensis infection. We also surveyed a sample of 10 percent of the households in community A and in another golf-oriented community (community B) more than 20 miles (32 km) from the wildlife-management area. Survey participants completed a questionnaire and provided specimens for serologic testing. In both communities, searches for ticks were undertaken.

RESULTS

Eleven cases of symptomatic ehrlichiosis were identified in the case-control study, 10 of which were in community A (attack rate, 330 per 100,000). Of 311 surveyed residents of community A, 12.5 percent had serologic evidence of past E. chaffeensis infection, as compared with 3.3 percent of 92 in community B (relative risk in community A as compared with community B, 3.9; 95 percent confidence interval, 1.2 to 12.2). The risk of infection was associated with tick bites, exposure to wildlife, golfing, and among golfers, retrieving lost golf balls from the rough. Persons who never used insect repellent were more likely to have had infection than persons who did. In community A, thousands of Lone Star ticks were found; in community B, only three ticks were found.

CONCLUSIONS

The high rate of E. chaffeensis infection in community A resulted from its proximity to a wildlife reserve. When outdoor recreational activities are common and concentrations of ticks are high, outbreaks of arthropod-borne zoonoses can be anticipated.

Seroepidemiology of infections due to spotted fever group rickettsiae and Ehrlichia species in military personnel exposed in areas of the United States where such infections are endemic

A prospective, seroepidemiologic study of spotted fever group rickettsiae (SFGR) and Ehrlichia infections was done among 1194 US military personnel exposed in a heavily tick-infested area of Arkansas in 1990. Seroconversion (4-fold) and seroprevalence rates were determined by indirect immunofluorescent antibody assays. Seroconversions to SFGR occurred in 30 persons (2.5%), whereas seroconversion to Ehrlichia species occurred in 15 (1.3%). The majority of seroconverters did not report symptoms (22/30 [73%] of SFGR seroconverters; 10/15 [67%] of Ehrlichia species seroconverters). History of tick attachment was associated with seroconversion to SFGR (relative risk [RR] = 4.3, P < .001) and Ehrlichia species (RR = 3.6, P < .05). Use of permethrin-impregnated uniforms significantly decreased risk of infection (P < .01); use of bed nets increased risk by 4-fold. Tickborne infections represent a significant threat to military personnel training in areas in which these infections are endemic.

Antibodies against Rickettsiaceae in dogs of Setúbal, Portugal

An indirect fluorescent antibody test was performed on sera collected from dogs housed in the municipal kennel of Setúbal to assess the prevalence of antibodies to Ehrlichia canis, the causative agent of canine ehrlichiosis and to Rickettsia conorii, agent of boutonneuse fever in humans. Two other members of the family Rickettsiaceae, Coxiella burnetii and Rickettsia typhi, were included in the serosurvey. Of the 104 dogs tested, 85.6% had antibodies to R. conorii, 50% to E. canis, 26.9% to R. typhi, and 4.8% to C. burnetii. These high seroprevalence rates of dogs with antibodies all year around against Rickettsiaceae suggest that physicians, public health officers and veterinarians should more frequently consider the diagnosis of these infections in Portugal.

Experimental transmission of Ehrlichia chaffeensis (Rickettsiales: Ehrlichieae) among white-tailed deer by Amblyomma americanum (Acari: Ixodidae)

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.

Temporal association of Amblyomma americanum with the presence of Ehrlichia chaffeensis reactive antibodies in white-tailed deer

From 1981 through 1993, tick infestations and serum antibodies reactive to Ehrlichia chaffeensis, the causative agent of human ehrlichiosis, were monitored among white-tailed deer (Odocoileus virginianus) at Whitehall Experimental Forest, Clarke County, Georgia (USA). Neither ticks nor E. chaffeensis antibodies were detected during the first two years of the study. Infestations of the lone star tick (Amblyomma americanum), a suspected vector of E. chaffeensis, first were noted on deer in 1983. Prevalence and intensity of A. americanum sharply increased from 1985 to 1989, and prevalence was 100% from 1990 to 1993. Antibodies reactive to E. chaffeensis were first detected in 7% of deer sampled in 1986. Antibody prevalence increased to 21% in 1987 and was 100% from 1988 to 1993. This temporal association between the establishment of A. americanum and the appearance of E. chaffeensis antibodies provides evidence to support the concept that A. americanum could be a natural vector of E. chaffeensis. The high prevalence of antibodies among all age classes of deer also reaffirms that white-tailed deer may be sensitive natural sentinels for monitoring the distribution of E. chaffeensis.

Susceptibility of white-tailed deer (Odocoileus virginianus) to infection with Ehrlichia chaffeensis, the etiologic agent of human ehrlichiosis

Although more than 320 cases of human ehrlichiosis have been diagnosed in 27 states since 1986, the reservoir host or hosts remain unknown. Since antibodies reactive to Ehrlichia chaffeensis, the etiologic agent of human ehrlichiosis, have been found in white-tailed deer (Odocoileus virginianus), we experimentally evaluated the susceptibilities of four white-tailed deer to infection with E. chaffeensis and Ehrlichia canis, a closely related species. A fifth deer served as a negative control. Isolation and nested PCR amplification results from peripheral blood indicated that E. chaffeensis circulated for at least 2 weeks. The deer developed antibodies to E. chaffeensis by day 10 after inoculation, but there was no indication of clinical disease. Immunohistochemical staining identified E. chaffeensis within macrophage-type cells in lymph nodes. The deer inoculated with E. canis did not become infected and did not seroconvert. These results indicate that white-tailed deer can support an E. chaffeensis infection with resulting rickettsemia of at least 2 weeks. The resistance to infection and the absence of seroconversion upon exposure to E. canis indicate that antibody responses previously detected among wild deer are not E. canis cross-reactions. The role of deer as competent reservoirs in the life cycle of E. chaffeensis remains to be explored with suspected tick vectors.

Dose effects of seeds placement deviations from pre-planned positions in ultrasound guided prostate implants

The effects of random (drifting) errors in actual seed placement during prostate implants have been evaluated by using geometrically optimized implants of I-125 and Pd-103 seeds. Results indicate that small random deviations in the seeds placement from the preplant position may affect the planned dose and beam profiles significantly.

Human ehrlichiosis in the United States, 1985 to 1990

OBJECTIVE

To describe the epidemiology, clinical features, laboratory manifestations, response to therapy, and factors related to morbidity and mortality in a large group of patients with ehrlichiosis.

DESIGN

Case-series.

SETTING

Laboratory-based surveillance in the United States.

PATIENTS

237 patients whose serum had a fourfold increase or decrease in antibodies to Ehrlichia canis or E. chaffeensis.

MEASUREMENTS

Epidemiologic, clinical, laboratory data, hospitalization, duration of illness, complications, and treatment response.

RESULTS

From 1985 through 1990, 237 case-patients were identified in 21 states; rates exceeded 1 per 100,000 per year in only 5 counties. Incidence rates increased with age and were higher among men. Most case-patients had nonspecific illness and were not suspected of having a rickettsial infection. Many patients (60.8%) were hospitalized. Leukocyte and platelet counts typically decreased and liver function tests typically increased through day 7. Three (6.1%) of 49 outpatients treated only with tetracycline were hospitalized compared with 35 (92%) of 38 outpatients treated only with antibiotics other than tetracycline or chloramphenicol (P < 0.001). Among hospitalized patients, recovery was faster for those initially treated with tetracycline (median, 16 days) or chloramphenicol (median, 12 days) than for those initially treated with other antibiotics (median, 27 days; P = 0.03 for both comparisons). In a logistic regression analysis, severe illness or death was more probable among case-patients 60 years or older (odds ratio [OR], 4.60; 95% CI, 1.87 to 11.2) and among those who did not receive tetracycline or chloramphenicol until 8 or more days after symptom onset (OR, 4.38; CI, 1.36 to 14.0).

CONCLUSIONS

The findings of this study are primarily representative of more seriously ill patients with human ehrlichiosis. Although rates are low, ehrlichiosis is found in many areas of the United States. Patients with a history of tick exposure, acute febrile illness, decreasing leukocyte counts, and decreasing platelet counts may have ehrlichiosis. Prompt treatment with tetracycline or chloramphenicol markedly decreases the morbidity.

White-tailed deer as a potential reservoir of Ehrlichia spp

We determined the antibody prevalence to Ehrlichia spp., in white-tailed deer (Odocoileus virginianus) and the geographic distribution of seropositive animals in 84 counties in Alabama, Arkansas, Florida, Georgia, Illinois, Kentucky, Louisiana, Maryland, Massachusetts, Mississippi, Missouri, North Carolina, South Carolina, Tennessee, Texas, Virginia, and West Virginia (USA). Using an indirect fluorescent antibody test we detected antibodies (> or = 1:128) to this bacterium in 544 (43%) of 1269 deer. Presence of antibodies to Ehrlichia spp. was related to a southerly latitude, low elevation, and resulting milder climatic conditions. It appears that white-tailed deer were naturally infected with Ehrlichia spp.; the infection was widely distributed throughout the southeastern United States. Based on these data, we propose that white-tailed deer play a role in the natural history of Ehrlichia spp. infection in the United States.

Ehrlichia chaffeensis and Rochalimaea antibodies in Kawasaki disease

Sera from 38 patients with Kawasaki disease were tested for immunofluorescent antibodies to Ehrlichia chaffeensis, Rochalimaea henselae, and R. quintana Oklahoma. Only 2.5% of the patients tested positive for E. chaffeensis, and 5% were positive for R. henselae and R. quintana Oklahoma. Our data suggest that Ehrlichia and Rochalimaea spp. do not play a unique role in the etiology of Kawasaki disease.

Human ehrlichiosis: hematopathology and immunohistologic detection of Ehrlichia chaffeensis

Human ehrlichiosis is a recently described zoonosis caused by a rickettsia that infects leukocytes. Most patients have fever, headache, chills, and myalgias and develop leukopenia, thrombocytopenia, anemia, and elevations in serum hepatic aminotransferases. The cause of the peripheral leukopenia and thrombocytopenia is not known. We studied peripheral blood smears, bone marrow aspirates, and bone marrow biopsy specimens from patients with serologically proven ehrlichiosis to characterize the pathologic changes associated with leukopenia or thrombocytopenia, to detect the presence of immunohistologically demonstrable ehrlichiae, and to establish the infected host target cell(s). Specimens were obtained from 12 patients, and immunohistology for Ehrlichia chaffeensis was performed on tissue sections, aspirated bone marrow, and peripheral blood smears. Mean leukocyte and platelet counts available for nine patients were white blood cell count 3,300/microL (range, 1,100 to 10,300/microL) and platelets 61,000/microL (range, 40,000 to 82,000/microL). Findings included myeloid hyperplasia (eight cases), megakaryocytosis (seven cases), granulomas (eight cases), marrow histiocytosis (one case), myeloid hypoplasia (one case), pancellular hypoplasia (one case), and normocellular marrow (two cases). Morulae of E chaffeensis were detected in four of 10 cases examined by immunohistology. Most ehrlichiae were detected within histiocytes, although morulae were rarely present within lymphocytes. Leukopenia, thrombocytopenia, or pancytopenia apparently most often results from peripheral sequestration or destruction; however, hypoplasia of marrow elements is present occasionally. Immunohistologic demonstration of E chaffeensis offers a direct means for establishing the etiologic diagnosis. These observations show the relatively frequent occurrence of bone marrow granulomas and suggest that infection of cells of the reticuloendothelial system may participate in the pathogenesis of human ehrlichiosis.

Human endothelial cells as an alternative to DH82 cells for isolation of Ehrlichia chaffeensis, E. canis, and Rickettsia rickettsii

Ehrlichia chaffeensis, etiologic agent of human ehrlichiosis, and Rickettsia rickettsii, etiologic agent of Rocky Mountain spotted fever (RMSF), are both tick-borne agents that cause nonspecific symptoms that may be indistinguishable from each other early in the course of infection. E. canis is a canine pathogen closely related to E. chaffeensis and was initially suspected of being the causative agent of human ehrlichiosis. If a febrile illness is reported, after tick exposure, neither ehrlichiosis nor RMSF can be immediately ruled out. When attempts are made to isolate the agent from blood, a very limited amount of blood is often available; we, therefore, sought a tissue-culture cell line that would support the growth of both R. rickettsii and E. chaffeensis. A newly established human microvascular endothelial immortal cell line (CDC/EU.HMEC-1) was evaluated for supporting the growth of both agents. Our results demonstrate that HMEC-1 supports the growth of R. rickettsii, E. chaffeensis, and E. canis and may be a useful tool for the isolation of these agents.

Identification of Ehrlichia chaffeensis morulae in cerebrospinal fluid mononuclear cells

We report a case of ehrlichiosis in a 72-year-old man who developed extreme lethargy, acute renal failure requiring hemodialysis, and respiratory insufficiency requiring intubation. Lumbar puncture performed on the second day of hospitalization revealed significant cellular pleocytosis. Ehrlichia morulae were tentatively identified in mononuclear cells in routinely processed Wright-stained cytospin preparations of cerebrospinal fluid (CSF). Identification was confirmed by a specific immunocytochemical staining procedure. Subsequent identification specifically as Ehrlichia chaffeensis morulae was established by polymerase chain reaction analysis, which revealed E. chaffeensis-specific DNA in CSF, bone marrow, and blood samples; by indirect fluorescent-antibody analysis, the patient developed an antibody titer of 32,768 against E. chaffeensis antigen. The patient responded to intravenous therapy with doxycycline and dexamethasone. Subsequently, neurologic, hematologic, renal, and pulmonary status had returned to baseline at follow-up 12 weeks after admission. To our knowledge, this is the first identification of E. chaffeensis morulae in CSF cells in an infected patient.

Susceptibility of dogs to infection with Ehrlichia chaffeensis, causative agent of human ehrlichiosis

Ehrlichia chaffeensis, the newly recognized agent of human ehrlichiosis, is closely related to E canis, the causative agent of canine ehrlichiosis. Eight pups were inoculated IV with E chaffeensis-, or with E canis-infected DH82 cells, or organisms released from these host cells. Two additional pups served as nonexposed controls. Marked thrombocytopenia was observed in the E canis-infected pups, but not in those infected with E chaffeensis. Homologous serologic response was observed in the E chaffeensis-exposed pups by postinoculation day (PID) 14 and in the E canis-exposed pups by PID 21. Ehrlichia chaffeensis and E canis were reisolated from the respective inoculated pups on each of 8 attempts from PID 7 to 26. One E chaffeensis-exposed pup that was challenge exposed with E canis via blood transfusion, developed fever, anorexia, and thrombocytopenia, suggesting lack of cross protection against E canis.