Development and Validation of a Serologic Test Panel for Detection of Powassan Virus Infection in U.S. Patients Residing in Regions Where Lyme
Disease Is Endemic
Thomm AM, Schotthoefer AM, Dupuis AP II, Kramer LD, Frost HM, Fritsche
TR, Harrington YA, Knox KK, Kehl SC.
/mSphere/. 2018 Jan 10;3(1). pii: e00467-17. eCollection 2018 Jan-Feb.
Powassan virus (POWV) is an emerging tick-borne arbovirus presenting a
public health threat in North America. POWV lineage II, also known as
deer tick virus, is the strain of the virus most frequently found in
/Ixodes scapularis/ ticks and is implicated in most cases of POWV
encephalitis in the United States. Currently, no commercial tests are
available to detect POWV exposure in tick-borne disease (TBD) patients.
We describe here the development and analytical validation of a
serologic test panel to detect POWV infections. The panel uses an
indirect enzyme immunoassay (EIA) to screen. EIA-positive samples reflex
to a laboratory-developed, POWV-specific immunofluorescence assay (IFA).
The analytical sensitivity of the test panel was 89%, and the limit of
detection was a plaque reduction neutralization test (PRNT) titer of
1:20. The analytical specificity was 100% for the IgM assay and 65% for
the IgG assay when heterologous-flavivirus-positive samples were tested.
On samples collected from regions where Lyme disease is endemic,
seroprevalence for POWV in TBD samples was 9.4% (10 of 106) versus 2%
when tested with non-TBD samples (2 of 100, /P/ = 0.034). No evidence of
POWV infection was seen in samples collected from a region where Lyme
disease was not endemic (0 of 22).
This test panel provides a sensitive and specific platform for detecting
a serologic response to POWV early in the course of infection when
neutralizing antibodies may not be detectable. Combined with clinical
history, the panel is an effective tool for identifying acute POWV
Approximately 100 cases of POWV disease were reported in the United
States over the past 10 years. Most cases have occurred in the Northeast
(52) and Great Lakes (45) regions
(https://www.cdc.gov/powassan/statistics.html). The prevalence of POWV
in ticks and mammals is increasing, and POWV poses an increasing threat
in a greater geographical range.
In areas of the Northeast and Midwest where Lyme disease is endemic,
POWV testing is recommended for patients with a recent tick bite,
patients with Lyme disease who have been treated with antibiotics, or
patients with a tick exposure who have tested negative for Lyme disease
or other tick-borne illnesses and have persistent symptoms consistent
with posttreatment Lyme disease. Testing could also benefit patients
with tick exposure and unexplained neurologic symptoms and chronic
fatigue syndrome (CFS) patients with known tick exposure.
Until now, diagnostic testing for Powassan virus has not been
commercially available and has been limited to patients presenting with
severe, neurologic complications. The lack of routine testing for
Powassan virus in patients with suspected tick-borne disease means that
little information is available regarding the overall prevalence of the
virus and the full spectrum of clinical symptoms associated with
infection. As /Ixodes scapularis/ is the tick vector for Powassan virus
and multiple other tick-borne pathogens, including the Lyme disease
bacterium, /Borrelia burgdorferi/, the clinical presentations and
long-term outcomes of Powassan virus infection and concurrent infection
with other tick-borne disease pathogens remain unknown.
More on Powassan: https://madisonarealymesupportgroup.com/2017/06/28/powassan-can-kill/