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Ehrlichiosis
Human Ehrlichiosis
is a disease caused by rickettsial type organisms that are transmitted
in part by the SAME TICKS that carry Lyme disease. Ehrlichiosis
usually presents with high fever, malaise, headache, myalgia, sweats,
and nausea. Patients diagnosed with Ehrlichia should also be tested for
Lyme disease due to the fact that co-infections have been documented in
several patients.
There are two forms
of the disease caused by the Ehrlichia species: E. chaffeensis
and E. phagocytophilia, which cause the human diseases, Human Monocytic
Ehrlichiosis (HME) and Human Granulocytic Ehrlichiosis (HGE), respectively.
HME has been linked to the bites of Amblyomma Americanum (Lone
Star Tick) and HGE has been closely linked to the bites of Ixodes Scapularis
and Ixodes Pacificus. The Dermacentor Variabilis (dog tick)
has also been suggested in the transmission of both. Seroconversion usually
occurs between two and four weeks after infection.
| HME: |
First described
in 1987 and confirmed in 30 states, predominately in the southeast
and mid-atlantic states. HME has also been found in Europe and Africa. |
| HGE: |
Originated in
Minnesota and was first described in 1994. HGE has been found in the
upper midwestem states, northeastern states, and northern California.
|
IgG/IgM Antibody
Tests: Titer levels for IgG and IgM antibodies are given individually
for HME and for HGE.
| Interpretation: |
<1:40 |
Negative for
IgG and IgM antibody |
|
1:40–1:160 |
May indicate
progression of disease and/or treatment |
|
>1:160 |
May suggest disease
states |
Ehrlichia PCR
Tests
The PCR-based diagnostic
assays that detect Ehrlichia are highly sensitive and specific to HGE
and HME DNAs. The four steps, direct from serum, are:
- Hybridization/Selection
Step —
This step specifically removes the “common PCR inhibitors” from
serum and, at the same time, selects and purifies the DNA fragment of
interest.
- PCR Amplification
— The purified Ehrlichia fragments are PCR amplified with
Ehrlichia specific primers. A primer is a synthetically produced nucleic
acid sequence that by design and selection contains Ehrlichia specific
nucleotide sequences. The specific sequence “hybridizes” or
binds specifically to Ehrlichia, therefore only Ehrlichia
specific DNA is amplified.
- Detection of Ehrlichia
Specific Amplified Products —
The PCR amplified Ehrlichia DNA fragment is detected by agarose
gel electrophoresis. Thus the “right size” amplified product
detected by agarose gel electrophoresis would be Ehrlichia specific.
- Confirmation
— Any sample that
is positive for Ehrlichia will be confirmed by a second PCR either
for HGE or HME:
- HGE Confirmation
PCR will be performed with HGE specific primers
- HME Confirmation
PCR will be performed with HME specific primers
| Test
# |
Test
Description |
Specimen
|
Collection
and Shipping |
| 203 |
Human
Monocytic Ehrlichiosis (HME) IgG & IgM Antibody |
0.5
ml Serum |
For
all tests:
Collect in red top tube, separate serum and send at room temperature,
OR collect in SST tube, spin and send at room temperature. |
|
750 |
HME
PCR Test |
1.0
ml Serum |
| 206 |
Human
Granulocytic Ehrlichiosis (HGE) IgG & IgM Antibody |
0.5
ml Serum |
| 755 |
HGE PCR Test |
1.0 ml Serum |
| 148 |
Tick Test by PCR |
Tick(s) |
IGeneX,
Inc.
795 San Antonio Rd., Palo Alto, CA 94303 USA
Tel. 650.424.1191 / 800.832.3200 Fax. 650.424.1196
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