This chapter first gives a brief history of human monocytotropic ehrlichiosis (HME), which is a zoonotic disease. From this brief history of HME, it is clear that rapid progress in understanding this newly emerged tick-borne zoonosis was facilitated both by its successful cultivation and by experimental studies of ticks linked to field observations. Epidemiological studies were furthered through the use of molecular techniques, and knowledge of HME expanded rapidly in the early to mid-1990s. Next, the chapter talks about biology of the etiologic agent. In the eastern United States, Ehrlichia chaffeensis is maintained in an epizootic cycle involving the lone star tick (Amblyomma americanum) as the principal vector and the white-tailed deer (Odocoileus virginianus) as a major vertebrate reservoir. This critical vector-host association places these two species at the core of E. chaffeensis epizootiology and strongly influences its geographic distribution and seasonality of transmission. HME caused by E. chaffeensis is endemic to the United States, with residents in the southeastern and south-central states at highest risk. The clinical recognition of HME can be difficult, since the spectrum of manifestations is broad and nonspecific, ranging from asymptomatic infection to mild self-limited symptoms to rapidly fatal disease. HME typically presents as an uncomplicated, acute, nonspecific febrile illness that resolves rapidly if treated with doxycycline, characteristic of many rickettsial infections. The chapter ends with a discussion on laboratory diagnosis, treatment and prevention of HME.

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.

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 deer 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.

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.

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.

Journal of Veterinary Internal MedicineVolume 12, Issue 5 p. 389-393 Open Access Morphologic and Molecular Evidence of a Dual Species Ehrlichial Infection in a Dog Presenting with Inflammatory Central Nervous System Disease James H. Meinkoth, Corresponding Author James H. Meinkoth Department of Anatomy, Pathology and Pharmacology, Oklahoma State University, Stillwater, OK Department of Anatomy, Pathology and Pharmacology, Oklahoma State University, Stillwater, OK 74078; e-mail: [email protected]Search for more papers by this authorSidney A. Ewing, Sidney A. Ewing Department of Infectious Diseases and Physiology, Oklahoma State University, Stillwater, OKSearch for more papers by this authorRick L. Cowell, Rick L. Cowell Department of Anatomy, Pathology and Pharmacology, Oklahoma State University, Stillwater, OKSearch for more papers by this authorJaqueline E. Dawson, Jaqueline E. Dawson Viral and Rickettsial Zoonoses Branch, Centers for Disease Control and Prevention, Atlanta, GASearch for more papers by this authorCynthia K. Warner, Cynthia K. Warner Viral and Rickettsial Zoonoses Branch, Centers for Disease Control and Prevention, Atlanta, GASearch for more papers by this authorJohn S. Mathew, John S. Mathew Department of Infectious Diseases and Physiology, Oklahoma State University, Stillwater, OKSearch for more papers by this authorMary Bowles, Mary Bowles Department of Medicine and Surgery, Oklahoma State University, Stillwater, OKSearch for more papers by this authorAmy E. Thiessen, Amy E. Thiessen Department of Anatomy, Pathology and Pharmacology, Oklahoma State University, Stillwater, OKSearch for more papers by this authorRoger J. Panciera, Roger J. Panciera Department of Anatomy, Pathology and Pharmacology, Oklahoma State University, Stillwater, OKSearch for more papers by this authorCarl Fox, Carl Fox Department of Infectious Diseases and Physiology, Oklahoma State University, Stillwater, OKSearch for more papers by this author James H. Meinkoth, Corresponding Author James H. Meinkoth Department of Anatomy, Pathology and Pharmacology, Oklahoma State University, Stillwater, OK Department of Anatomy, Pathology and Pharmacology, Oklahoma State University, Stillwater, OK 74078; e-mail: [email protected]Search for more papers by this authorSidney A. Ewing, Sidney A. Ewing Department of Infectious Diseases and Physiology, Oklahoma State University, Stillwater, OKSearch for more papers by this authorRick L. Cowell, Rick L. Cowell Department of Anatomy, Pathology and Pharmacology, Oklahoma State University, Stillwater, OKSearch for more papers by this authorJaqueline E. Dawson, Jaqueline E. Dawson Viral and Rickettsial Zoonoses Branch, Centers for Disease Control and Prevention, Atlanta, GASearch for more papers by this authorCynthia K. Warner, Cynthia K. Warner Viral and Rickettsial Zoonoses Branch, Centers for Disease Control and Prevention, Atlanta, GASearch for more papers by this authorJohn S. Mathew, John S. Mathew Department of Infectious Diseases and Physiology, Oklahoma State University, Stillwater, OKSearch for more papers by this authorMary Bowles, Mary Bowles Department of Medicine and Surgery, Oklahoma State University, Stillwater, OKSearch for more papers by this authorAmy E. Thiessen, Amy E. Thiessen Department of Anatomy, Pathology and Pharmacology, Oklahoma State University, Stillwater, OKSearch for more papers by this authorRoger J. Panciera, Roger J. Panciera Department of Anatomy, Pathology and Pharmacology, Oklahoma State University, Stillwater, OKSearch for more papers by this authorCarl Fox, Carl Fox Department of Infectious Diseases and Physiology, Oklahoma State University, Stillwater, OKSearch for more papers by this author First published: 05 February 2008 https://doi.org/10.1111/j.1939-1676.1998.tb02140.xCitations: 18AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL References 1 Stockham SL, Schmidt DA, Tyler JW. Canine granulocytic ehrlichiosis in dogs from central Missouri: A possible cause of polyarthritis. Vet Med Rev 1985; 6: 3– 5. 2 Maeda K., Markowitz N., Hawley RC, et al. Human infection with Ehrlichiu canis, a leukocytic rickettsia. N Engl J Med 1987; 316: 853– 856. 3 Dawson JE, Ewing SA. Susceptibility of dogs to infection with Ehrlichia chaffeensis, causative agent of human ehrlichiosis. Am J Vet Res 1992; 53: 1322– 1327. 4 Dawson JE, Biggie KL, Warner CK, et al. Polymerase chain reaction evidence of Ehrlichia chaffeensis, an etiologic agent of human ehrlichiosis, in dogs from southeast Virginia. Am J Vet Res 1996; 57: 1175– 1979. 5 Dawson JE, Warner CK, Baker B., et al. Ehrlichia-Wke 16S rDNA sequence from wild white-tailed deer (Odocoileus virginianus). J Parasitol 1996; 82: 52– 58. 6 Mathew JS, Ewing SA, Barker RW, et al. Attempted transmission of Ehrlichia canis by Rhipicephalus sanguineus after passage in tissue cell culture. Am J Vet Res 1996; 57: 1594– 1598. 7 Meinkoth JH, Hoover JP, Cowell RL, et al. Ehrlichiosis in a dog with seizures and nonregenerative anemia. 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Philadelphia , PA : WB Saunders; 1990: 404– 414. 14 Ewing SA, Roberson WR, Buckner RG, et al. A new strain of Ehrlichia canis. J Am Vet Med Assoc 1971; 159: 1771– 1774. 15 Anderson BE, Greene CE, Jones DC, et al. Ehrlichia ewingii sp. nov., the etiologic agent of canine granulocytic ehrlichiosis. Int J Syst Bacteriol 1992; 42: 299– 302. 16 Harvey JW. Ehrlichia platys infection (infectious cyclic thrombocytopenia of dogs). In: CD Greene, ed. Infectious Diseases of the Dog and Cat. Philadelphia , PA : WB Saunders; 1990: 415– 418. 17 Kakoma I., Hansen RD, Anderson BE, et al. Cultural, molecular, and immunological characterization of the etiologic agent for atypical canine ehrlichiosis. J Clin Microbiol 1994; 32: 170– 175. 18 Lewis GE, Huxsoll DL, Ristic M., et al. Experimentally induced infection of dogs, cats, and nonhuman primates with Ehrlichia equi, etiologic agent of equine ehrlichiosis. Am J Vet Res 1975; 36: 85– 88. 19 Johansson KE, Pettersson B., Uhlen MU, et al. Identification of the causative agent of granulocytic ehrlichiosis in Swedish dogs and horses by direct solid phase sequencing of PCR products from the 16S rRNA gene. Res Vet Sci 1995; 58: 109– 112. 20 Greig B., Asanovich KM, Armstrong PJ, et al. Geographic, clinical, serologic, and molecular evidence of granulocytic ehrlichiosis, a likely zoonotic disease, in Minnesota and Wisconsin dogs. J Clin Microbiol 1996; 34: 44– 48. 21 Ewing SA, Dawson JE, Panciera RJ, et al. Dogs infected with a human granulocytotropic Ehrlichia spp. (Rickettsiales:Ehrlichieae). J Med Entomol 1997; 34: 710– 718. 22 Barlough JE, Madigan JE, DeRock E., et al. Protection against Ehrlichia equi is conferred by prior infection with the human granulocytotropic ehrlichia (HGE agent). J Clin Microbiol 1995; 33: 3333– 3334. 23 Madigan JE, Richter PJ, Kimsey RB, et al. Transmission and passage in horses of the agent of human granulocytic ehrlichiosis. J Infect Dis 1995; 172: 1141– 1144. 24 Ewing SA, Fox JC, Johnson EM, et al. Canine ehrlichiosis: Differences between granulocytic and agranulocytic agents (abstr), Prog Abstr 69th Ann Meet Conf. Res. Work. Anim. Dis. 1988; 40 (abstract). 25 Greene CE, Burgdorfer W., Cavagnolo R., et al. Rocky Mountain spotted fever in dogs and its differentiation from canine ehrlichiosis. J Am Vet Med Assoc 1985; 186: 465– 72. 26 Hildebrandt PK, Huxsoll DL, Walker JS, et al. Pathology of canine ehrlichiosis (tropical canine pancytopenia). Am J Vet Res 1973; 34: 1309– 1320. 27 Harkess JR, Stucky D., Ewing SA. Neurologic abnormalities in a patient with human ehrlichiosis. South Med J 1990; 83: 1341– 1343. 28 Eng TR, Harkess JR, Fishbein DB, et al. Epidemiologic, clinical, and laboratory findings of human ehrlichiosis in the United States, 1988. JAMA 1990; 264: 2251– 2258. 29 Maretzki CH, Fisher DJ, Greene CE. Granulocytic ehrlichiosis and meningitis in a dog. J Am Vet Med Assoc 1994; 205: 1554– 1556. Citing Literature Volume12, Issue5September 1998Pages 389-393 ReferencesRelatedInformation

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.

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.

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.

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.

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.

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).

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.

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.

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.

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.

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.