Foley JE, Lerche NW, Dumler JS, Madigan JE.
A simian model of human granulocytic ehrlichiosis.
Am J Trop Med Hyg 1999 Jun;60(6):987-93
Abstract: Following intravenous inoculation
with horse blood-infected with the agent of human granulocytic ehrlichiosis
(HGE) from a human fatality, two rhesus macaques (Macaca mulatta) exhibited
pyrexia and lethargy on days 4-12 postinfection (PI). Hematology revealed
neutropenia, thrombocytopenia, and anemia, with ehrlichial morulae in monocytes
and neutrophils on days 4-12. Blood was polymerase chain reaction (PCR)-positive
on days 4-12 and bone marrow was PCR-positive on day 11. There was a minor
increase in gamma-glutamyl transpeptidase on day 12 and serum interferon-gamma
levels increased by day 18. Seroconversion occurred on day 20 PI to a titer
of 100 by day 22. Western blot bands characteristic of HGE included 25-,
44-, 80-, 94-, 105-, and 125-kD bands. There was generalized lymphohistiocytic
infiltration in the liver, spleen, lymph nodes, and other tissues. The
liver had focal hepatocyte apoptosis. There was HGE DNA (by PCR) only in
the spleen. Comparable findings were not observed in a monkey that received
uninfected horse blood as a control. This animal model of human disease
is important for further studies of HGE diagnosis, management, and pathogenesis.
Joon-seok Chae, Janet Foley, J. Stephen Dumler, John
E. Madigan
Genetic comparison among naturally occurring Ehrlchia equi and
Human Granulocytic Ehrlichiosis (HGE) agent isolates from northern California
based on the nucleotide sequences of 16S rRNA, 444 Ep-ank and groESL
Heat Shock Operon Genes.
International Conference on Rickettsiae and Rickettsial Disease
& American Society for Rickettsiology 14th sesquiannual joint meeting
at Marseille on June 13 - June 16, 1999.
Abstract: We examined the DNA sequences
of three genes to determine the diversity among 11 naturally occurring
isolates of Ehrlichia equi in horses (n=11) and granulocytic ehrlichiosis
agent (n=2) in humans acquired from clinical cases in California, USA.
Ehrlichia
equi isolates were obtained from Sierra (n=6), Mendocino (n=3), Sonoma
(n=1) and Marin (n=1) counties in California and human granulocytic ehrlichiosis
(HGE) agent isolates were obtained from Humboldt county (n=2) in California,
USA. These isolates were analyzed by determining the sequences following
polymerase chain reaction using specific primers for 16S rRNA, 444 Ep-ank
and groESL heat shock operon genes. All three genes were amplified
from 13 clinical samples. The nucleotide sequences of 16S rRNA genes
were identical among two human HGE isolates (CAHU-HGE1 and CAHU-HGE2) from
Humboldt county and two horse E. equi isolates (CAMEBS and CAMAWI)
from Mendocino and Marin counties. The 16S rRNA gene sequence differed
in a single nucleotide, positions 34 and 180, in the E. equi isolates from
Sierra (CASITL) and Sonoma (CASOLJ) counties respectively, and the other
E.
equi isolates. The sequences of 444 Ep-ank fragment which
included the region encoding the four ankyrin repeats were identical among
all E. equi and two HGE agent isolates. These sequences when
compared to the same gene sequences of a HGE agent isolate from the eastern
United States (BDS and USG3 strains) had two and sixteen differences at
nucleotide positions, respectively. When the groESL heat shock
operon gene sequences were compared, one HGE agent isolate (CAHU-HGE1)
and three E. equi isolates (CASITL, CAMEBS; Mendocino and CAMAWI;
Marin counties) had identical sequences. The other isolates had differences
in two and four nucleotide positions, 1,483 and 1,546 between CAHU-HGE1
and CAHU-HGE2 isolates and 347, 1,303, 1,448 and 1,496 between CAHU-HGE1
and CASOLJ isolates, respectively. However, the translated amino
acid sequences of groESL gene fragments were identical among E.
equi, HGE agent and E. phagocytophila except that from the CASOLJ
isolate. The results of translated amino acid sequence of 444 Ep-ank
from CA isolates were different from the eastern United States (BDS and
USG3 strains). These results suggest that E. equi and the
HGE agent found in California are similar or identical, but may differ
from the isolates of equine and human origin found in the eastern US.
Nicola Pusterla, Jon B. Huder, Christian M. Leutenegger, Ueli Braun,
John
E. Madigan, and Hans Lutz
Quantitative Real-Time PCR for Detection of Members of the Ehrlichia
phagocytophila Genogroup in Host Animals and Ixodes ricinus Ticks.
Journal
of Clinical Microbiology, May 1999, p. 1329-1331,
Vol. 37, No. 5
Janet E. Foley, Jeffrey E. Barlough, Robert B. Kimsey, John
E. Madigan, Elfriede DeRock, and Amy Poland.
Ehrlichia spp. in Cervids from Clifornia.
Journal of Wildlife Disease. 1998.
34 (4):731-737.
Abstract: Blood samples from six mule deer (Odocoileus
hemionus hemionus), 15 black-tailed deer (O. h. columbianus), and 29 elk
(Cervus elaphus nannodes) were assayed for human monocytic and human granulocytic
ehrlichiosis (HGE) by polymerase chain reaction (PCR), DNA sequencing,
and serology to determine whether cervids are involved in the maintenance
of these potential human pathogens in California, USA. The deer were sampled
in August to October. The 29 tule elk from Point Reyes National Seashore
were sampled in August. All deer were seronegative for antibodies to HGE/Ehrlichia
equi, while the E. equi
seroprevalence among elk was 17%. The 16S rDNA PCR prevalence in deer
was 38% (in mule deer and black-tailed deer) for Ehrlichia-like sp. of
white-tailed deer, 5% (one black-tailed deer only) for E. equi, and 0%
for E. chaffeensis. The PCR prevalence in elk was 0% for Ehrlichia-like
sp. of white-tailed deer, 31% for E. equi, and 0% for E. chaffeensis. The
E. equi from two positive elk samples was successfully propagated in HL-60
cell cultures. DNA sequencing confirmed that the Ehrlichia-like sp. sequences
from California deer were closely related to sequences reported from white-tailed
deer from Oklahoma and Georgia. The E. equi strain from deer and elk resembled
other E. equi strains from California. These results suggest that cervids
may be important in the natural maintenance of E. equi in California.
Pusterla, N; Weber, R; Wolfensberger, C; Schär, G; Zbinden, R;
Fierz, W; Madigan, JE; Dumler, JS; Lutz, H.
Serological evidence of human granulocytic ehrlichiosis in Switzerland.
European Journal of Clinical Microbiology and Infectious Diseases,
1998
Mar, 17(3):207-209.
Abstract: To investigate whether human granulocytic
ehrlichiosis (HGE) is prevalent in Switzerland, 1515 human serum samples
from individuals with different risks for tick exposure were tested for
antibodies to Ehrlichia phagocytophila, a surrogate marker of the agent
of HGE. The distribution of titres showed marked differences between
sera of individuals with no or low risk for tick exposure and those with
a high risk. The results of serological testing provided evidence of HGE
in Switzerland as well as evidence of two types of coinfections: those
with the agent of HGE and Borrelia burgdorferi, and those with the agent
of HGE and the central European tickborne encephalitis virus.
Jeffrey E. Barlough, Gerhard H. Reubel, John E.
Madigan, Larisa K. Vredevoe, Paul E. Miller, and Yasuko Rikihisa.
Detection of Ehrlichia risticii, the Agent of Potomac Horse
Fever, in Freshwater Stream Snails (Pleuroceridae: Juga spp.) from Northern
California.
Appl. Environ. Microbiol. 1998. 64:2888-2893.[Abstract][Full
Text]
Gerhard H. Reubel, Robert B. Kimsey, Jeffrey E. Barlough, and John
E. Madigan.
Experimental Transmission of Ehrlichia equi to Horses through
Naturally Infected Ticks (Ixodes pacificus) from Northern California.
Journal of Clinical Microbiology, July 1998,
p. 2131-2134.
Abstract: We report the experimental transmission of
Ehrlichia
equi from naturally infected Ixodes pacificus ticks to horses.
Three weeks after exposure to ticks, two of three horses developed clinical
signs compatible with E. equi infection, while one horse remained
asymptomatic. 16S rRNA gene PCR of blood leukocyte lysates was positive
for all horses at various time points; two horses seroconverted.
The 16S rRNA gene sequences amplified from tick-exposed horses showed more
than 99% homology to corresponding fragments of the 16S rRNA genes of E.
equi, Ehrlichia phagocytophila, and the human granulocytic ehrlichiosis
agent.
Gerhard H. Reubel, Jeffrey E. Barlough, and John
E. Madigan.
Production and Characterization of Ehrlichia risticii, the
Agent of Potomac Horse Fever, from Snails (Pleuroceridae: Juga spp.) in
Aquarium Culture and Genetic Comparison to Equine Strains.
Journal of
Clinical Microbiology, June 1998, p. 1501-1511.
Magnarelli, LA; Ijdo, JW; Anderson, JF; Madigan,
JE; Dumler, JS; Fikrig, E.
Antibodies to Ehrlichia equi in dogs from the northeastern
United States.
Journal of the American Veterinary Medical Association, 1997
Nov 1, 211(9):1134-7.
Astract: OBJECTIVE: To determine whether dogs living
in tickinfested areas of the northeastern United States had been exposed
to Ehrlichia equi, an etiologic agent of granulocytic ehrlichiosis.
DESIGN: Analyses of dog sera. ANIMALS: 106 ill dogs and 12 clinically normal
dogs. PROCEDURE: Antibodies to E equi were detected by indirect fluorescent
antibody taining methods and western blot analyses. RESULTS: 10 of 106
(9.4%) sera tested from ill, privately owned dogs living in tick-infested
areas of Connecticut and New York state had antibodies to E equi, a member
of the E phagocytophila genogroup. Titration end points ranged
from 1:80 to 1:1,280. Immunoblots revealed antibodies to proteins of E
equi having molecular masses of predominantly 29, 40, 44, 105, 120, and
160 kd. There was good agreement between results of serologic testing methods,
but use of the human isolate (NCH-1 strain) in western blot analyses detected
2 additional seropositive dogs found to be negative by indirect fluorescent
antibody staining methods with the MRK strain. CLINICAL IMPLICATIONS: Dogs
living in areas where ixodes scapularis is abundant may be exposed to multiple
pathogens, such as E equi or Borrelia burgdorferi. Although mild or subclinical
infections with E equi may develop, dogs with marked leukopenia, thrombocytopenia,
or anemia should be viewed as possibly having ehrlichiosis. Laboratory
diagnosis should include examinations for morulae in granulocytes or monocytes
in addition to serologic analyses.
Asanovich, KM; Bakken, JS; Madigan, JE;
Aguero-Rosenfeld, M; Wormser, GP; Dumler, JS.
Antigenic diversity of granulocytic Ehrlichia isolates from humans
in Wisconsin and New York and a horse in California.
Journal of Infectious Diseases, 1997
Oct, 176(4):1029-34.
Abstract: The agent of human granulocytic ehrlichiosis
(HGE), Ehrlichia phagocytophila, and Ehrlichia equi are very
similar. HGE is of variable severity. Genetic and antigenic differences
among 3 human isolates (Webster, Spooner, and NY-8) and 1 horse isolate
(MRK) were evaluated. The 16S rRNA gene sequences were identical in all
human isolates. By use of 5 homologous antisera from these 3 humans and
1 horse and an additional 5 antisera in heterologous reactions, the immunodominant
antigens of each isolate were noted to differ in molecular size: 43 kDa
in the Webster (Wisconsin) isolate, 46 kDa in the Spooner (Wisconsin) isolate,
42 and 45 kDa in the NY-8 (New York State) isolate, and a 42 kDa doublet
in the E. equi MRK isolate from California. Two sera from a Wisconsin patient
reacted weakly or not at all with the NY-8 isolate. Antigenic structural
diversity exists among otherwise indistinguishable granulocytic ehrlichial
isolates.
Barlough, JE; Madigan, JE; Kramer, VL;
Clover, JR; Hui, LT; Webb, JP; Vredevoe, LK.
Ehrlichia phagocytophila genogroup rickettsiae in ixodid
ticks from California collected in 1995 and 1996.
Journal of
Clinical Microbiology, 1997 Aug, 35(8):2018-21.
Barlough, JE; Madigan, JE; Turoff, DR;
Clover, JR; Shelly, SM; Dumler, JS.
An Ehrlichia strain from a llama (Lama glama) and Llama-associated
ticks (Ixodes pacificus).
Journal of
Clinical Microbiology, 1997 Apr, 35(4):1005-7.
Barlough, JE; Rikihisa, Y; Madigan, JE.
Nested polymerase chain reaction for detection of Ehrlichia risticii
genomic
DNA in infected horses.
Veterinary Parasitology, 1997 Mar,
68(4):367-73.
Abstract: A nested polymerase chain reaction was developed
for amplifying a 529-bp segment of the 16S ribosomal RNA gene of Ehrlichia
risticii from equine buffy coat cells. Confirmation of identity of
the amplified bands was accomplished by Southern hybridization and DNA
sequencing. The study indicated a detection limit of > 10 copies of the
target gene, and specificity for E. risticii as based on a panel
of test rickettsiae. Ticks (Ixodes pacificus) collected in an area of northern
California enzootic for equine monocytic ehrlichiosis were found to be
negative for E. risticii DNA.
Barlough, JE; Madigan, JE; DeRock, E; Bigornia,
L.
Nested polymerase chain reaction for detection of Ehrlichia equi
genomic DNA in horses and ticks (Ixodes pacificus).
Veterinary Parasitology, 1996 Jun,
63(3-4):319-29.
Abstract: A nested polymerase chain reaction for detecting
Ehrlichia
equi in horses and ticks (Ixodes pacificus) was developed. A major
second-round PCR product of 928 bp could be readily visualized in ethidium
bromide-stained agarose minigels. An internal probe was used to verify
the identity of the amplified product by non-radioactive (digoxigenin-based)
Southern blotting; additional confirmation was provided by DNA sequence
analysis. A dilution study testing the sensitivity of the PCR indicated
that DNA derived from < = 7.6 but > 3 infected neutrophils was sufficient
to generate a PCR signal. The specificity of the PCR was examined using
a panel of rickettsiae, of which only E. equi and the closely-related human
granulocytotropic ehrlichia produced PCR bands. In an in vivo infection
study, E. equi DNA was detected in blood buffy-coat cells of an experimentally-infected
horse on days three through 14 post-inoculation. In a separate study, three
of six adult I. pacificus that as nymphs had been fed on an experimentally
infected horse were found to be PCR-positive for E. equi.
Munderloh, UG; Madigan, JE; Dumler, JS;
Goodman, JL; Hayes, SF; Barlough, JE; Nelson, CM; Kurtti, TJ.
Isolation of the equine granulocytic ehrlichiosis agent, Ehrlichia
equi, in tick cell culture.
Journal of Clinical Microbiology, 1996
Mar, 34(3):664-70.
Abstract: The equine granulocytic ehrlichiosis agent,
Ehrlichia equi, is closely related or identical to the human granulocytic
ehrlichiosis (HGE) agent. Both are suspected of being transmitted by ticks.
We have successfully isolated E. equi in a cell line, IDE8, derived from
a putative vector, the tick Ixodes scapularis. Peripheral blood leukocytes
from an experimentally infected horse were inoculated onto IDE8 monolayers.
Cultures were incubated in a candle jar at 34 degrees C in tick cell culture
medium with NaHCO3 and an organic buffer [3-(N-morpholino)-propanesulfonic
acid] (MOPS). Within 2 weeks, infected cells were detected in Giemsa-stained
culture samples, and the organisms subsequently spread to uninfected cells
in the cultures. E. equi was passaged serially by transferring a portion
of an infected culture to new cell layers every 2 to 3 weeks. The identity
of the organisms was confirmed by PCR using oligonucleotide primers specific
for E. equi and the HGE agent and by immunocytology. Homologous equine
antibodies and human anti-HGE convalescent serum recognized E. equi grown
in tick cell culture. Electron microscopy revealed electron-lucent and
-dense ehrlichia-like forms developing within host cell endosomes. E. equi
passaged twice in tick cell culture retained infectivity and pathogenicity
for the equine host, as demonstrated by intravenous inoculation of a suspension
of infected tick cells and subsequent reisolation from peripheral
blood, in fulfillment of Koch's postulates.
The horse developed severe clinical signs, i.e., fever, inappetence,
thrombocytopenia, icterus, and limb edema, typical of granulocytic equine
ehrlichiosis, within 1 week.
Madigan, JE; Barlough, JE; Dumler, JS;
Schankman, NS; DeRock, E.
Equine granulocytic ehrlichiosis in Connecticut caused by an agent
resembling the human granulocytotropic ehrlichia.
Journal of Clinical Microbiology, 1996
Feb, 34(2):434-5.
Abstract: The first recognized cases of equine granulocytic
ehrlichiosis in New England are described. The DNA sequence of the 16S
rRNA gene of the causative ehrlichia was found to be identical to that
of the human granulocytotropic ehrlichia, the agent of human granulocytic
ehrlichiosis.
Goodman, JL; Nelson, C; Vitale, B; Madigan, JE;
Dumler, JS; Kurtti, TJ; Munderloh, UG.
Direct cultivation of the causative agent of human granulocytic
ehrlichiosis
[see comments] [published erratum appears in N Engl J Med 1996 Aug
1;335(5):361]
New England Journal of Medicine, 1996
Jan 25, 334(4):209-15.
Abstract: BACKGROUND. Human granulocytic ehrlichiosis
is a potentially fatal tick-borne infection that has recently been described.
This acute febrile illness is characterized by myalgias, headache, thrombocytopenia,
and elevated serum aminotransferase levels. The disease is difficult to
diagnose because the symptoms are non-specific, intraleukocytic inclusions
(morulae) may not be seen, and the serologic results are often initially
negative. Little is known about the causative agent because it has never
been cultivated. METHODS. We studied three patients with symptoms and laboratory
findings suggestive of human granulocytic ehrlichiosis, including unexplained
fever after probable exposure to ticks, granulocytopenia, and thrombocytopenia.
Peripheral blood was examined for ehrlichia microscopically and with use
of the polymerase chain reaction (PCR). Blood was inoculated into
cultures of HL60 cells (a line of human promyelocytic leukemia cells),
and the cultures were monitored for infection by Giemsa staining and PCR.
RESULTS. Blood from the three patients, only one of whom had inclusions
suggestive of ehrlichia in neutrophils, was positive for human granulocytic
ehrlichiosis on PCR. Blood from all three patients was inoculated into
HL60 cell cultures and caused infection, with intracellular organisms visualized
as early as 5 days after inoculation and cell lysis occurring within 12
to 14 days. The identity of the cultured organisms was confirmed by immunofluorescence
microscopy, PCR analysis, and DNA sequencing. DNA from the infected cells
was sequenced in regions of the 16S ribosomal gene reported to differ between
the agent of human granulocytic ehrlichiosis and closely related species,
including Ehrlichia equi and E. phagocytophila which cause infection in
animals. The sequences from all three human isolates were identical and
differed from the strain of E. equi studied in having guanine rather than
adenine at nucleotide 84. CONCLUSIONS. We describe the cultivation of the
agent of human granulocytic ehrlichiosis in cell culture. The ability to
isolate this organism should lead to a better understanding of the biology,
treatment, and epidemiology of this emerging infection.
Richter, PJ Jr; Kimsey, RB; Madigan, JE;
Barlough, JE; Dumler, JS; Brooks, DL.
Ixodes pacificus (Acari: Ixodidae) as a vector of Ehrlichia
equi (Rickettsiales: Ehrlichieae).
Journal of Medical Entomology, 1996
Jan, 33(1):1-5.
Abstract: Ehrlichia equi, a rickettsia described
from horses in California 30 yr ago, causes equine granulocytic ehrlichiosis
throughout the Americas and possibly Europe. Here, we report experimental
transmission of E. equi from infected to susceptible horses through bites
of western blacklegged ticks, Ixodes pacificus (Cooley & Kohls). In
preliminary field studies, only I. pacificus consistently infested horses
and vegetation at 3 locations with contemporary cases of equine ehrlichosis,
and in particular, I. pacificus was the only species found attached to
all of the infected horses. Exposure to bites of ticks in the genus Ixodes
poses previously unrecognized and serious health risks to humans and animals.
Madigan, JE; Rikihisa, Y; Palmer, JE; DeRock,
E; Mott, J.
Evidence for a high rate of false-positive results with the indirect
fluorescent antibody test for Ehrlichia risticii antibody
in horses.
Journal of the American Veterinary Medical Association, 1995
Dec 1, 207(11):1448-53.
Abstract: OBJECTIVE--The original objective was to determine
seroprevalence of Ehrlichia risticii antibody among horses in California.
On the basis of the unexpected results of the survey, an investigation
into the accuracy and reproducibility of results of the indirect fluorescent
antibody (IFA) test for E risticii was carried out. DESIGN--Prospective,
seroprevalence study. ANIMALS--Healthy horses (n = 655) and horses with
clinical signs of equine monocytic ehrlichiosis (EME; n = 514) from various
regions of California. PROCEDURE--The IFA test was performed. Results were
compared with results of an ELISA and with results of western immunoblot
analysis. RESULTS--Overall, 104 of 655 (15.9%) healthy horses had evidence
of an antibody response. However, 84 of 514 (16.3%) horses with clinical
signs of EME also had positive test results, and of the 8 seropositive
diseased horses for which paired (acute and convalescent) samples had been
submitted, only 1 had a rise in antibody titers between the acute and convalescent
samples. Comparison of results for the IFA test, ELISA, and western immunoblot
analysis revealed a high rate of false-positive results for the IFA test.
Subsequent studies suggested that routine vaccination of horses with non-E
risticii vaccines may have contributed to the false-positive reactions.
CLINICAL IMPLICATIONS--The data failed to provide conclusive evidence of
E risticii infection among California horses. Owing to the high percentage
of false-positive test results, caution is advised when using the IFA test
to diagnose EME in horses or to determine the necessity for E risticii
vaccination.
Barlough, JE; Madigan, JE; DeRock, E; Dumler,
JS; Bakken, JS. Protection against
Ehrlichia equi is conferred by prior infection with the human
granulocytotropic Ehrlichia (HGE agent).
Journal of Clinical Microbiology, 1995
Dec, 33(12):3333-4.
Abstract: A Thoroughbred filly that developed clinical
signs of equine granulocytic ehrlichiosis following inoculation with the
human granulocytotropic ehrlichia was shown to be resistant to challenge
with Ehrlichia equi, a closely related agent. This result further substantiates
the close and potentially conspecific relationship between these two granulocytotropic
ehrlichiae.
Madigan, JE; Richter, PJ Jr; Kimsey, RB;
Barlough, JE; Bakken, JS; Dumler, JS.
Transmission and passage in horses of the agent of human granulocyticehrlichiosis.
Journal of Infectious Diseases, 1995
Oct, 172(4):1141-4.
Abstract: The human granulocytotropic ehrlichia and Ehrlichia
equi produce similar diseases in their respective host species (humans,
horses). Currently, the phylogenetic and biologic relationships of these
2 uncultured pathogens remain unclear. Previous studies have revealed nucleotide
sequence similarity approaching identity at the level of the 16S ribosomal
RNA gene. To investigate the biologic similarities of these 2 ehrlichiae,
the susceptibility of horses to the human agent was tested by intravenous
inoculation of infected human blood. The results demonstrate that the human
granulocytotropic ehrlichia produces a disease in the horse indistinguishable
from that caused by E. equi, providing biologic evidence that these 2 organisms
are highly related and potentially conspecific. It is possible that cases
of human illness now attributed to human granulocytotropic ehrlichia may
in fact be caused by 1 or more strains of an ehrlichia known chiefly as
an equine pathogen.
Dumler, JS; Asanovich, KM; Bakken, JS; Richter, P; Kimsey, R; Madigan,
JE.
Serologic cross-reactions among Ehrlichia equi, Ehrlichia
phagocytophila, and human granulocytic Ehrlichia.
Journal of Clinical Microbiology, 1995 May,
33(5):1098-103.
Abstract: Homology in the 16S rDNAs shows that the agent
of human granulocytic ehrlichiosis (HGE) is closely related to the veterinary
pathogens Erlichia equi and Erlichia phagocytophila. After HGE, patients
develop antibodies reactive with E. equi and E. phagocytophila; thus, we
hypothesized that these species are closely related and share significant
antigenicity. Antisera from humans, horses, dogs, and cattle were tested
by indirect fluorescent-antibody assay (IFA) for antibodies reactive with
E. equi and other ehrlichiae and tested by immunoblot to identify the specific
reactions with E. equi. All convalescent-phase sera from human patients
with HGE and from animals infected or immunized with E. equi or E. phagocytophila
had antibodies reactive with E. equi by IFA; no reactions with Ehrlichia
chaffeensis occurred with these sera, and only one horse naturally infected
with E. equi had a serologic reaction against Ehrlichia sennetsu. Human
and animal sera obtained after infection or immunization with other Ehrlichia,
Rickettsia, and Bartonella species did not react with E. equi by IFA. E.
equi immunoblots revealed as many as 19 bands with equine anti-E. equi
serum. All HGE agent, E. equi, and E. phagocytophila antisera tested reacted
with a 44-kDa antigen of E. equi, while other anti-Ehrlichia spp. sera
reacted with this antigen rarely or not at all. HGE agent, E. equi, and
E. phagocytophila antisera but not other sera also reacted occasionally
with 25-, 42-, and 100-kDa antigens. Most sera reacted with antigens between
approximately 56 and 75 kDa, probably heat shock proteins. The HGE agent,
E. equi, and E. phagocytophila share significant antigenicity by IFA and
immunoblot.
jchae@ucdavis.edu
