Scientists Prove Ticks
Harbor Heartland Virus, a Recently Discovered Disease in the United States
Scientists
have for the first time traced a novel virus that infected two men from
northwestern Missouri in 2009 to populations of ticks in the region, providing
confirmation that lone star ticks are carrying the recently discovered virus
and humans in the area are likely at risk of infection. The findings were
published online in the American Journal of Tropical Medicine and
Hygiene.
EDITOR'S NOTE: Lone star ticks are found in Charlestown. I know because I've been bitten by one. It's a tick bite that actually hurts.
Dubbed
Heartland virus or HRTV, the infection causes fever, headaches, and low white
blood cell and platelet counts. The two men infected in 2009, who live about 70
miles apart, were sufficiently ill to require hospitalization.
They eventually recovered, and no other cases have been reported. Disease experts anticipate, however, that more people could become infected. The Missouri Department of Health and Senior Services is working with the US Centers for Disease Control and Prevention (CDC) to identify additional cases and determine the role of this novel virus as a human pathogen.
"Ten
samples of ticks tested positive for the Heartland virus, nine of which were
collected from the property of one of the patients and one that came from
conservation lands nearby," said Harry M. Savage, PhD, a research
entomologist at CDC in Fort Collins, Colorado and the lead author of the paper.
"It's pretty strong evidence that the virus is persisting from season to
season in tick populations and that these ticks play an important role in
disease transmission."
There
is no treatment available for HRTV. Unlike other tick-borne diseases like Lyme,
ehrlichiosis and Rocky Mountain spotted fever, HRTV is a virus and thus does
not respond to antibiotics.
Disease Hunting
HRTV
was discovered when a doctor at the hospital treating the two infected men, who
had reported being bitten by ticks, sent blood samples to a CDC laboratory in
Atlanta for testing. All involved assumed the tests would reveal ehrlichiosis,
the tick-borne disease that is most common in the area.
Instead, the tests
revealed a virus that had never been recognized. Subsequent analysis showed
that HRTV belongs to a group of viruses known as phleboviruses, which can be
carried by sandflies, mosquitoes or ticks. Savage said there is a separate team
of researchers conducting tests with animals in the area in an effort to
identify the "reservoir hosts" that are carrying the virus and
passing it along to ticks.
Since
the HRTV discovery, which was reported in August 2012 in the New
England Journal of Medicine, scientists have been combing the area for the
source of the infection. Savage and his team, which included investigators from
Missouri Western State University, collected 56,428 ticks from April to August
of 2012.
They employed a variety of collection methods. Flannel pads used in
infant bedding were mounted to bamboo poles to act as a sort of fly-paper for
ticks. Plastic food containers were "baited" with dry ice, which
emits carbon dioxide -- a natural attractant for the ticks. Researchers even
removed ticks from horses and dogs.
"Finding
a virus in ticks requires the collection and testing of large numbers of
ticks," Savage said. The virus infection rate in nymph stage ticks from
one farm owned by a patient was about one in five hundred over the study
period. Humans are likely to become infected when they are bitten by a tick
carrying the virus. Savage said one of the HRTV patients recounted pulling
dozens of ticks off his body each night before bed.
According
to Savage, the ticks that carry the virus -- known as lone star ticks for the
single white spot found on females -- are common in the area and in many other
parts of the country as well. Currently, there are no reports of HRTV in any
other tick populations aside from those isolated in northwestern Missouri. He
said it's hard to predict where the virus might be located in the US and if the
virus will spread.
HRTV
appears to be related to another new disease recently discovered in China, a
life-threatening virus called severe fever with thrombocytopenia (SFTSV). SFTSV
also appears to be tick-borne, though there is evidence of person-to-person
transmission as well.
"This
research illustrates the ever-changing world we live in and why we must sustain
our nation's investment in research into these types of diseases that the
majority of Americans will never hear of," said David H. Walker, MD,
president of the American Society of Tropical Medicine and Hygiene, whose
research has included a focus on tick-borne diseases.
"It is only by
getting trained experts into the field and doing the necessary work of
collecting and testing thousands of specimens, as these scientists did, that we
can be one step ahead of what could become another serious health threat
carried by ticks."
To
prevent Heartland virus and other diseases spread by ticks, CDC recommends
taking the following steps:
- Wear repellent
- Check for ticks daily
- Shower soon after being outdoors
- Call your doctor if you get a fever or rash
Story Source:
The
above story is based on materials provided by American
Journal of Tropical Medicine and Hygiene, via EurekAlert!, a service of AAAS.
Note: Materials may be edited for content and length. For further
information, please contact the source cited above.
Journal Reference:
1.
Harry M. Savage, Marvin
S. Godsey, Jr., Amy Lambert, Nickolas A. Panella, Kristen L. Burkhalter,
Jessica R. Harmon, R. Ryan Lash, David C. Ashley, and William L. Nicholson.First
Detection of Heartland Virus (Bunyaviridae: Phlebovirus) from Field Collected
Arthropods. Am J Trop Med Hyg, July 22, 2013 DOI: 10.4269/ajtmh.13-0209
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American Journal of Tropical Medicine and Hygiene (2013, July 22).
Scientists prove ticks harbor Heartland virus, a recently discovered disease in
the United States. ScienceDaily. Retrieved July 23, 2013, from
http://www.sciencedaily.com/releases/2013/07/130722202920.htm