Chester County Medicine Summer 2021 - 21

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Figure 2: Adult female (A), male (B), and nymph (C) of
A. americanum. Notice the characteristic white spot on the
female's dorsal shield. Image courtesy of James Occi.
Obviously, the entire field of TBDs is simply too big for a single
article to cover. So, for purposes of this article, we have chosen to
focus on just one of the newest and least considered TBDs occurring
here in the US, viz, the Heartland virus.
Heartland virus (HRTV) is a phlebovirus of the Bornyaviridae
family of viruses. Reflecting the Spring and Summer active " questing "
of the nymph and adult ticks, most clinical cases have occurred
between April and September, but flu-like symptoms have been
reported into December. Systemic symptoms have included: fever,
fatigue, anorexia, headache, arthralgia, myalgia, nausea and diarrhea.
Lab tests show leukopenia, thrombocytopenia, and some elevation
of liver transaminases.
Believed to be transmitted by ticks, HRTV was first detected in
Missouri in 2009, and only described as a human pathogen in 2012
when two area residents became ill following multiple tick bites.
Subsequent field and lab work by state and local health departments
and the CDC identified the highly aggressive Amblyomma americanum,
a.k.a. " The Lone Star Tick " as a vector for this virus. No
other ticks tested positive. The initial population study, centering
around Missouri, showed that 19% of those tested had evidence
of acute HRTV infection; 1% had had a past infection; and 80%
were negative. Those with acute infections were residents of seven
(7) states (MO, AR, IN, KY, OK, KS, NC), indicating that by the
time the first cases were recognized, the pathogen-carrying ticks had
already spread to seven states.. Additional cases diagnosed in 2014
saw the area of distribution expanded to include another state (TN).
By 2018, the human case totals exceeded 35.
Thus, in 2013, the CDC implemented a national protocol to
evaluate patients throughout the nation for HRTV and better define
its distribution, clinical spectrum, and epidemiology. However, there
have not been a lot of journal articles on this specific topic after
2018. One might conjecture that other issues (e.g., the COVID-19
pandemic) have rightfully pre-empted a lot of clinical research
interest, leaving little time or resources to follow the natural history
of this relatively new and seemingly regional disease.
Figure 3: Nymph (A), male (B), female (C), partiallyengorged
female (D) and two fully-engorged adults (E) of
A. americanum. Image courtesy of James Occi.
However, past epidemiological experience would indicate that
whenever Mother Nature introduces a new pathogen into new
immunologically naive populations (in this case, both the humans
and the vectors) it would be only a matter of time before that disease
begins to show rapid, if not exponential, growth, restricted primarily
by the extent of overlap of both populations' distribution ranges,
exposure and infectivity rates, and such things as replication indices.
Another thing to consider would be the variety and numbers of
potential reservoir host animals on which the tick vectors can feed.
A recent report from Boston University ( February 2021) indicates
that studies have now shown high seroprevalence rates for HRTV
in northern raccoons, white tailed deer, horses, coyotes and moose,
a finding which adds to the possibility, and probability, that HRTV
will continue to spread.
At this point, the best treatment for HRTV disease is to prevent it.
Otherwise treatment is supportive. Many patients have required
hospitalization, but with supportive care most people have fully
recovered. However, " a few older patients with comorbidities have
died. " There is no specific routine testing available for HRTV, but
protocols are said to be in place to allow testing for evidence of
HRTV RNA, IgM, and IgG antibodies. The CDC has advised
healthcare providers to consider HRTV testing for patients who
have otherwise unexplained fever (>/= 100.4 F or or 38.0 C),
leukopenia (WBC <4500 per cu.mm), and thrombocytopenia (<
150,000 per cu mm) and who have tested negative for Ehrlichia and
Anaplasma infection or have not responded to doxycycline therapy.
CDC advises physicians to contact their state health department
if they have a patient with an acute illness which may be compatible
with Heartland Virus Disease.
Dr. Maher is a retired Public Health Physician, former
County Health Director, and a long time member of the
CCMS Board of Directors. He has made free use of internet
websites for the information used in this article. A list of
references can be made available upon request.
SUMMER 2021 | CHESTER COUNTY Medicine 21
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Chester County Medicine Summer 2021

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