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.

Molecular characterization of carrier rabies isolates.

We compared the genomes of nine dog rabies virus isolates using two molecular methods. The viruses used in the comparison included three Ethiopian rabies strains from carrier dogs, a street strain from a rabid dog from the same geographic area, two saliva isolates made from an experimentally infected carrier dog, the virus isolated from the tonsil of this carrier dog at necropsy, and two laboratory strains. We produced overlapping polymerase chain reaction (PCR) segments spanning 97% of the genome. Restriction analysis of these PCR products with AvaII, Bcll, and BamHI detected 39 variable sites representing 668 nucleotides (nt) or 5.5% of the genome. We also compared the DNA and the deduced peptide sequences of a 200-nt segment of the 3' end of the rabies nucleoprotein gene. Previous work with these Ethiopian carrier viruses and the endemic street strain had failed to show any differences among them. Both restriction mapping and sequence analysis of 200 nt of the nucleoprotein gene allowed us to individually identify these isolates. Phylogenetic analyses of these data sets showed only the two saliva isolates of the experimentally infected carrier dog to be identical. Each of the viruses in this study, including the one isolated from the tonsil of the experimentally infected carrier dog, could be distinguished by these techniques.

Comparisons of nucleotide and deduced amino acid sequences of the glycoprotein genes of a Chinese street strain (CGX89-1) and a Chinese vaccine strain (3aG) of rabies virus.

We analyzed the glycoprotein gene sequences of a Chinese street rabies virus strain (CGX89-1) and a Chinese human rabies vaccine strain (3aG). The complete glycoprotein gene sequence of each strain has 1575 nucleotides and encodes a polypeptide of 524 amino acids. The overall nucleotide homology of these glycoprotein genes is 84.5%, and the deduced amino acid homology is 89.5%. Twenty-one percent of the base changes result in amino acid substitutions. Comparison of the homologies of the glycoprotein genes showed that the most conserved region is the ectodomain, whereas the most variable regions are the transmembrane and cytoplasmic domains. The overall nucleotide homologies of the 3aG glycoprotein and the CGX89-1 glycoprotein compared with the Pasteur virus glycoprotein are 91.2% and 84.1% respectively. The glycoprotein gene sequences presented here, the first from isolates of Chinese origin, provide insights into the biologically significant regions of this rabies gene.

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.

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.

Laboratory investigation of human deaths from vampire bat rabies in Peru.

In the spring of 1996, multiple cases of an acute febrile illness resulting in several deaths in remote locations in Peru were reported to the Centers for Disease Control and Prevention (CDC). The clinical syndromes for these cases included dysphagia and encephalitis. Because bat bites were a common occurrence in the affected areas, the initial clinical diagnosis was rabies. However, rabies was discounted primarily because of reported patient recovery. Samples of brain tissue from two of the fatal cases were received at CDC for laboratory confirmation of the rabies diagnosis. An extensive array of tests on the formalin-fixed tissues confirmed the presence of both rabies viral antigen and nucleic acid. The virus was shown to be most closely related to a vampire bat rabies isolate. These results indicate the importance of maintaining rabies in the differential diagnosis of acute febrile encephalitis, particularly in areas where exposure to vampire bats may occur.

Procedures for reproducible detection of rabies virus antigen mRNA and genome in situ in formalin-fixed tissues.

Procedures allowing the reproducible in situ detection of rabies virus antigen and RNAs (both genome and message) in formalin-fixed tissue are described. These procedures can be used on sequential tissue sections and thereby permit comparison of results from tests detecting both antigen and RNA in the same tissue. This antigen-detecting procedure has also been used to identify both the phylogenetically distant rabies viruses from silver-haired bat and vampire bat and the rabies-related viruses Mokola, Duvenhage, and Lagos bat. One of the critical steps in these procedures is the digestion (and the resulting exposure of the target molecules) with proteinase K. These methods may be useful for the identification of other viruses of public health importance. Because in many situations only formalin-fixed tissue is available for postmortem diagnosis, the technical ability to identify a virus antigen and nucleic acid in such tissues greatly extends potential diagnostic capabilities.

A comparative study of the fluorescent antibody test for rabies diagnosis in fresh and formalin-fixed brain tissue specimens.

Many diagnostic methods have been used to detect rabies virus antigen. The preferred method for routine diagnosis of rabies in fresh or frozen brain tissues is the fluorescent antibody test (FAT). In this study, the FAT was used to evaluate the rabies status of fresh/frozen brain specimens from more than 800 rabies-suspected cases, in more than 14 different species of animals. A comparable brain specimen from each case was fixed in 10% buffered formalin and examined by the FAT. The evaluation of rabies status between fresh and formalin-fixed tissues was in agreement in more than 99.8% of the cases. When fresh tissue is not available for testing, these results validate the use of this procedure for routine diagnosis of rabies in formalin-fixed brain tissues.

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.

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.

Relationships of patient satisfaction with experience of system performance and health status.

This article investigates the relationship between three types of measures obtained from consumer surveys: satisfaction, health status, and report of systems performance. Analyses demonstrate that patient reports of the quality of processes of care or system performance (such as receiving results of tests or receiving conflicting information from staff members) are significantly related to satisfaction independently of perception of health status. Since dissatisfaction is known to be associated with disenrollment, patient reports of system performance are of great interest to health plans.

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.

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.

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.

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.

Peer review in quality assurance.

Peer review can be an effective tool for quality assurance. Many methods are available for a group of clinicians to use to evaluate the care that they deliver. Successful review often depends on the support of a nonjudgmental environment. When the goal of the review is problem identification and problem solving, not blaming, peer review can result in true quality improvement.